NewsNew LIVE CHAT feature implemented!
Posted At: July 30, 2007 @ 1:14 PM
Posted By: Reed Timmer
Related Categories: General
Thanks to Jason, the new LIVE CHAT feature has been implemented! To enter the chat, just click on the **Live Chat** link on the menu bar, and enter your alias. Keep in mind this is a beta version, and we plan on initiating many security features in the near future, including moderators to keep spammers away from the chat. If spammers become a problem, please log off of the chat, and return at a later time, or wait until the security measures are enabled.
We've been having problems with impersonators, etc, so all chat entries from the TornadoVideos.net team WILL BE DISPLAYED IN RED.
The chat will also be operational during chases, so you can chat with the storm chasers live while they're in the field. Hopefully this will be a useful tool in the reporting/spotting process as well. We also plan to implement high-quality streaming video in time for next chase season, so the chat will compliment that feature well. ENJOY!
We've been having problems with impersonators, etc, so all chat entries from the TornadoVideos.net team WILL BE DISPLAYED IN RED.
The chat will also be operational during chases, so you can chat with the storm chasers live while they're in the field. Hopefully this will be a useful tool in the reporting/spotting process as well. We also plan to implement high-quality streaming video in time for next chase season, so the chat will compliment that feature well. ENJOY!
Tornado photos from near Drayton Valley, AB on July 29!
Posted At: July 29, 2007 @ 11:41 PM
Posted By: Reed Timmer
Related Categories: Tornadoes
Here are some photos of a tornado/funnels that touched down near Drayton Valley, AB earlier this evening (July 29), shot by local storm chasers Brandon Brown, Dale K., and Kenny A. TEXTBOOK structure!
Supercells ongoing northwest and southwest of Edmonton!
Posted At: July 29, 2007 @ 5:18 PM
Posted By: Reed Timmer
Related Categories: Tornadoes
Supercells have already initiated northwest and southwest of Edmonton, with the two most intense cells just north of Whitecourt and just west of Drayton Valley, AB. Given sufficient wind shear and instability just to the east of these storms, they do have a tornado potential as the move ENE at 30 mph. Severe thunderstorm warnings have been issued for these storms, but I would not be surprised if they will be upgraded to tornado warnings at any time. Stay tuned for updates.
Supercells likely once again in Alberta!
Posted At: July 29, 2007 @ 10:57 AM
Posted By: Reed Timmer
Related Categories: Tornadoes
Supercells will develop once again along the foothills of Alberta later this afternoon and evening, especially west of Edmonton and Drayton Valley, AB, where instability is forecast to be maximized. Shown below are some selected WRF forecast panels from this morning (500 mb and CAPE, respectively).
As shown above, a large trough is digging into the western Canada today, with 35+ knots at 500 mb across all of Alberta. The positive vorticity advection from this trough, along with upslope low-level flow will initiate convection over the foothills by around 5:00 pm MT. With CAPE values of 3000+ J/kg from the foothills eastward across the adjacent plains, along with ample deep-layer shear, supercells will be the primary mode of convection and will have no problem sustaining over the weakly capped plains. Stay tuned for updates as this severe weather event unfolds!
As shown above, a large trough is digging into the western Canada today, with 35+ knots at 500 mb across all of Alberta. The positive vorticity advection from this trough, along with upslope low-level flow will initiate convection over the foothills by around 5:00 pm MT. With CAPE values of 3000+ J/kg from the foothills eastward across the adjacent plains, along with ample deep-layer shear, supercells will be the primary mode of convection and will have no problem sustaining over the weakly capped plains. Stay tuned for updates as this severe weather event unfolds!
Textbook LP supercell west of Edmonton, AB this evening!
Posted At: July 28, 2007 @ 8:32 PM
Posted By: Reed Timmer
Related Categories: General
An LP supercell developed earlier this afternoon over the foothills west of Edmonton, Alberta, and has since tracked east across the adjacent plains, producing loonie size hail at times. Several severe thunderstorm warnings have been issued for this storm, and a classic rear flank downdraft/forward flank downdraft gust front signature has been evident on radar for several scans. Here is the radar image from around 5:30 pm MT when the storm was at peak intensity:
Yellowhead county near Evansburg, Wildwood and MacKay
6:30 PM MDT Saturday 28 July 2007
Severe thunderstorm warning for
Yellowhead county near Evansburg, Wildwood and MacKay continued
At 6:30 PM an intense thunderstorm was near chip lake. The thunderstorm is tracking east at 25 km/h. Hail near loonie size has been reported with this storm.
Thunderstorms have developed along the foothills. These thunderstorms will move to the east at about 30 km/h. Some of these thunderstorms may become severe giving large hail
Yellowhead county near Evansburg, Wildwood and MacKay
6:30 PM MDT Saturday 28 July 2007
Severe thunderstorm warning for
Yellowhead county near Evansburg, Wildwood and MacKay continued
At 6:30 PM an intense thunderstorm was near chip lake. The thunderstorm is tracking east at 25 km/h. Hail near loonie size has been reported with this storm.
Thunderstorms have developed along the foothills. These thunderstorms will move to the east at about 30 km/h. Some of these thunderstorms may become severe giving large hail
Tornado in Iceland yesterday!
Posted At: July 28, 2007 @ 10:21 AM
Posted By: Reed Timmer
Related Categories: Tornadoes
This tornado occurred yesterday in a desert region of Iceland called the Skeidararsandur, which is located near the coast between two glaciers. Based on soundings from the area, this appeared to be a "cold-core" setup. These photos were taken by Malfridur Omarsdottir.
Based on these photos, this tornado appears to be a land spout, but there looks to be a low cloud base above the hose. Cold-core setups should be quite common in Iceland, given the strong, occluded, and vertically-stacked low pressure systems that move across the North Atlantic towards England. Back in North America today, the morning model runs are showing some small potential just west of the central Lake Region of Manitoba, but the cap looks to be VERY strong..and convective initiation appears unlikely at this time.
Based on these photos, this tornado appears to be a land spout, but there looks to be a low cloud base above the hose. Cold-core setups should be quite common in Iceland, given the strong, occluded, and vertically-stacked low pressure systems that move across the North Atlantic towards England. Back in North America today, the morning model runs are showing some small potential just west of the central Lake Region of Manitoba, but the cap looks to be VERY strong..and convective initiation appears unlikely at this time.
Mysterious chunks of ice up to 50 lbs in weight falling from the sky in northeast Iowa!!?!!
Posted At: July 27, 2007 @ 1:12 PM
Posted By: Reed Timmer
Related Categories: General
Check out this CNN article:
http://www.cnn.com/2007/US/07/27/falling.ice.ap/index.html?eref=rss_us
Supposedly chunks of ice, some up to the size of a basketball and weighing 50 lbs, have been falling from the sky near Dubuque, IA!! Authorities are theorizing they either fell from a passing plane or originated naturally in the upper atmosphere (which does not seem feasible to me!). Here is a picture of one of the chunks from cnn.com
http://www.cnn.com/2007/US/07/27/falling.ice.ap/index.html?eref=rss_us
Supposedly chunks of ice, some up to the size of a basketball and weighing 50 lbs, have been falling from the sky near Dubuque, IA!! Authorities are theorizing they either fell from a passing plane or originated naturally in the upper atmosphere (which does not seem feasible to me!). Here is a picture of one of the chunks from cnn.com
Severe storms likely today in Ohio River Valley, Central MS River Valley, and Great Lakes Regions
Posted At: July 27, 2007 @ 11:45 AM
Posted By: Reed Timmer
Related Categories: General
Pictures of a waterspout on Mobile Bay this morning!
Posted At: July 26, 2007 @ 1:53 PM
Posted By: Reed Timmer
Related Categories: Tornadoes
Here are pictures of a waterspout that formed over Mobile Bay this morning just north of Dauphin Island, AL, courtesy of Brian Jones, a local marine biologist.
Severe weather possible today over the Upper MS River Valley
Posted At: July 26, 2007 @ 10:41 AM
Posted By: Reed Timmer
Related Categories: General
Severe storms will develop this afternoon/evening along an advancing cold front and old outflow boundaries from the previous night's convection in southern MN, WI, northern IA, southeast SD, and extreme northeast NE. The WRF is forecasting a 30 kt low-level jet to develop at 00z in extreme southeast MN, southern WI, and northeast IA, so any discrete storms in this region will have a chance to rotate, given the moderately strong northwesterly flow aloft. Selected panels from this morning's WRF run for 7:00 pm CDT are displayed below:
Pictures from the severe tstorm in Winnipeg
Posted At: July 25, 2007 @ 11:12 PM
Posted By: Reed Timmer
Related Categories: General
Severe thunderstorms developed in an EXTREMELY unstable environment this evening, with CAPE values of over 10,000 J/kg by 4:00 pm CDT over much of southern Manitoba (see RUC analysis from 21z below). Consequently, Winnipeg was pounded with very heavy rain and strong straightline winds today. Here are some pictures courtesy of Tim Wilson from the Winnipeg storm today:
Here is the RUC analysis for CAPE as of 21z (4:00 pm CDT) earlier today (thanks for the image PB). Never have I seen CAPEs this high! However, these analyzed values are likely the result of intense evapotranspiration over the vast farmland of southern Manitoba, and a very shallow layer of 80+ deg F dewpoints. The mixed-layer CAPE values would have been a much better measure of the instability today east of the cold front.
Here is the RUC analysis for CAPE as of 21z (4:00 pm CDT) earlier today (thanks for the image PB). Never have I seen CAPEs this high! However, these analyzed values are likely the result of intense evapotranspiration over the vast farmland of southern Manitoba, and a very shallow layer of 80+ deg F dewpoints. The mixed-layer CAPE values would have been a much better measure of the instability today east of the cold front.
Severe thunderstorm watch issued for southern MB!
Posted At: July 25, 2007 @ 2:42 PM
Posted By: Reed Timmer
Related Categories: General
A severe thunderstorm watch has been issued by Environment Canada for portions of southern Manitoba this afternoon and evening for the warm sector south and east of an advancing cold front. Please report any severe weather in MB today/tonight to Environment Canada using the following phone number: 1-800-239-0484
The best chance for severe thunderstorms will be in extreme southern and southeast Manitoba, south and east of the cold front depicted in the figure below. Instability in the warm sector is EXTREME this afternoon, with RUC-analyzed CAPE values exceeding 8000 J/kg in spots! Despite marginal wind shear, if a storm initiates in this highly unstable environment it will rapidly become severe. Given this instability, there is a small chance of tornadoes with any storms south and east of the cold front, but the low-level wind shear is very marginal at this time.
Even with the marginal 0-1 km wind shear, the excessive CAPE values are producing fairly impressive 0-1 km EHI values of 4+ in extreme southern MB near the North Dakota border. These EHI values are sufficiently high for tornadic supercells, if storms can initiate.
The best chance for severe thunderstorms will be in extreme southern and southeast Manitoba, south and east of the cold front depicted in the figure below. Instability in the warm sector is EXTREME this afternoon, with RUC-analyzed CAPE values exceeding 8000 J/kg in spots! Despite marginal wind shear, if a storm initiates in this highly unstable environment it will rapidly become severe. Given this instability, there is a small chance of tornadoes with any storms south and east of the cold front, but the low-level wind shear is very marginal at this time.
Even with the marginal 0-1 km wind shear, the excessive CAPE values are producing fairly impressive 0-1 km EHI values of 4+ in extreme southern MB near the North Dakota border. These EHI values are sufficiently high for tornadic supercells, if storms can initiate.
Severe weather possible today in southern Manitoba
Posted At: July 25, 2007 @ 10:35 AM
Posted By: Reed Timmer
Related Categories: General
A slow-moving cold front will advance across southern Manitoba today, bringing a good chance of severe thunderstorms south and east of the lake region today. While low-level flow will be marginal for tornadoes, deep-layer shear will be sufficient for supercells especially over the north and east part of the red-shaded area above. As seen below, instability will once again be extreme, with CAPEs of over 3000 J/kg throughout the warm sector. Stay tuned for updates.
Storms exploding in southeast SK!
Posted At: July 24, 2007 @ 11:32 PM
Posted By: Reed Timmer
Related Categories: General
Severe storms and possible supercells have exploded from just east of Regina, through Yorkton, and up to Swan River, SK tonight, as the low-level jet has increased convergence along the advancing cold front. I just got off the phone with storm chasers who are tracking the cell northeast of Yorkton (shown above), and they have reported possible wall clouds and even potential funnels with this storm near Kamsack. It still remains to be seen if this cell is or can remain to be surface based. Stay tuned for updates!
Tornado warnings in Alberta today!
Posted At: July 24, 2007 @ 9:35 PM
Posted By: Reed Timmer
Related Categories: Tornadoes
A long-track tornadic supercell developed once again today in the mountains of Alberta and tracked east across the adjacent plains this evening, possibly producing tornadoes near Drumheller, AB between 6:30 and 7:00 pm MDT. Here is the radar image as the storm was just east of Drumheller:
Meanwhile, in Saskatchewan, a strong cap has suppressed convection for the entire day, with EXTREME instability in place across the southeast part of the province east of the advancing cold front. Convective initiation is still a small possibility here, and any storms that do develop will quickly become severe. The 8:00 pm CDT RUC analysis for CAPE is shown below...note the large area of 5500+ J/kg!!! However, it appears that this instability will likely not be realized.
Meanwhile, in Saskatchewan, a strong cap has suppressed convection for the entire day, with EXTREME instability in place across the southeast part of the province east of the advancing cold front. Convective initiation is still a small possibility here, and any storms that do develop will quickly become severe. The 8:00 pm CDT RUC analysis for CAPE is shown below...note the large area of 5500+ J/kg!!! However, it appears that this instability will likely not be realized.
Severe weather, isolated tornadoes possible today in southeast SK/southwest MB
Posted At: July 24, 2007 @ 1:33 AM
Posted By: Reed Timmer
Related Categories: Tornadoes
The same trough responsible for yesterday's supercells in Alberta will be moving across the central Canadian Prairies today (Tuesday), providing the necessary ingredients for supercells and even isolated tornadoes across the red-shaded area above. A rather strong cap will be in place today over this region, so there is a chance that storms will not initiate in the best environment for tornadoes. However, if an isolated storm develops in southeast Saskatchewan or southwest Manitoba (later in the evening and overnight) tomorrow, there will be a chance for tornadoes. Stay tuned for updates!
INCREDIBLE supercells/shelf clouds across Alberta on Monday!
Posted At: July 23, 2007 @ 10:31 PM
Posted By: Reed Timmer
Related Categories: General
Pictures of a beautiful LP supercell just north of Red Deer, Alberta taken by Elaine Cripps:
Pictures of a shelf cloud taken near Edmonton, AB by Dale from late Monday evening:
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Pictures of a shelf cloud taken near Edmonton, AB by Dale from late Monday evening:
Pictures of the Edmonton storm courtesy of Mike M:
(Mike reported 60-90 km/hr winds with this line of storms!)
(Mike reported 60-90 km/hr winds with this line of storms!)
Severe weather likely central Plains/Missouri River Valley Today
Posted At: July 23, 2007 @ 1:12 AM
Posted By: Reed Timmer
Related Categories: Tornadoes
An interesting severe weather event will occur over the Central U.S. today, with northeasterly flow at mid- to upper-levels around the western periphery of a large ridge over the Eastern U.S. Given the expected southwesterly storm motion, helicity values will be quite high over eastern NE, western IA, central KS, and even central OK (see below right) -- exceeding 200 m2/s2. A shortwave will be embedded in this northeasterly flow aloft, providing the trigger for convection over these areas, with the WRF forecasting widespread storms from Iowa SSW to Oklahoma. Given the impressive helicity values, supercells and even isolated tornadoes will be possible, especially from eastern NE/western IA through central KS.
Severe weather possible Tuesday for Saskatchewan
Posted At: July 23, 2007 @ 12:45 AM
Posted By: Reed Timmer
Related Categories: Tornadoes
A strong upper-trough and associated cold front will traverse the central Canadian Prairies on Tuesday and Tuesday night, bringing a chance for severe weather in east-central Saskatchewan extending into extreme west-central Manitoba overnight. Low-level and deep-layer shear will be sufficient for supercells and isolated tornadoes with any isolated storms that develop where the greatest instability and strong LLJ are co-located.
Comparing the 850 mb forecast above with the CAPE (instability) forecast below, it can be seen that the low-level jet will be slightly displaced to the east of the best instability. This displacement is very common in the model forecasts of Canadian severe weather setups, and often times, the low-level jet verifies further west closer to the advancing cold front, especially during the evening as the lower atmosphere begins to cool after peak heating. If the LLJ is further west, then the tornado threat will be higher over east-central Saskatchewan, but if the WRF model verifies, then the threat will mainly be large hail and strong straight-line winds. Stay tuned for continuous updates!
Costa Rican tornado video!
Posted At: July 22, 2007 @ 12:05 PM
Posted By: Reed Timmer
Related Categories: Tornadoes
Check out this video of a tornado in Costa Rica. This video was added to Youtube in June 2007, so I'm assuming the tornado occurred this year. You can see what appears to be a condensation funnel towards the end of the video clip. I'll be adding a post tonight about the severe chances tomorrow in Iowa, as well as in Saskatchewan/Manitoba on Tuesday!
Line of severe storms moving across southeastern SK!
Posted At: July 21, 2007 @ 4:21 PM
Posted By: Reed Timmer
Related Categories: General
As of 4:00 pm CDT, a north-south oriented line of severe thunderstorms was moving eastward across southeast Saskatchewan south of Yorkton. The line was beginning to take on "bow-echo" characteristics, so strong, damaging straight-line winds are likely with these storms. Further development is anticipated northeast of Estevan, in the extreme southeast corner of SK later this afternoon. These storms will have the possibility of developing into supercells, with a very small tornado threat. Shown below is a graphical summary of the current watches/warnings. As of 4:00 pm CDT, all warnings were severe thunderstorm warnings, with no tornado warnings in effect.
Conditional Severe Wx Threat Today for northwest ND, eastern SK, and western MB
Posted At: July 21, 2007 @ 9:36 AM
Posted By: Reed Timmer
Related Categories: General
Despite extreme instability, a strong capping inversion will limit thunderstorm development for most, if not all, of the day in northwest ND, eastern SK, and western MB. However, if storms can initiate, they will likely be severe, producing very large hail and strong straight-line winds. The region with the conditional severe wx threat today is shown in the red shaded area in the selected model forecasts shown here. As seen below, the low-level jet is forecast to be relatively weak, with only around 20-25 knots at best along the instability axis at 850 mb. This weakness should limit the tornado threat, if storms can break through the capping inversion.
As shown in the 12 hr accumulated precipitation forecast by the WRF model for 7:00 pm this evening, the storm coverage is predicted to be rather sparse, due to the strong capping inversion. Still though, the WRF predicts storms will initiate in northwest North Dakota and southeast Saskatchewan by early evening. I would not be surprised to see storms initiate further north between Saskatoon and the Manitoba Border as well, where slightly better wind shear exists. Given the extreme instability, and ample deep-layer shear, these storms will likely be supercells, but with a rather limited tornado threat as mentioned. Stay tuned for updates!
Several water spouts reported yesterday near New Orleans!
Posted At: July 20, 2007 @ 10:51 AM
Posted By: Reed Timmer
Related Categories: Tornadoes
Severe thunderstorms continuing in AB/SK
Posted At: July 19, 2007 @ 10:23 PM
Posted By: Reed Timmer
Related Categories: General
Severe thunderstorms are continuing in central and eastern Alberta, but Edmonton and Calgary have been spared today. A dryline/Pacific cold front swept east of the Foothills today, with storms developing from southeast AB NNW to east of Edmonton, and also west and northwest of Edmonton. Several of the storms exhibited classic supercell structure, but were mainly in remote areas where reports were lacking. However, the storms in southeast AB and also west and northwest of Edmonton easily could have produced tornadoes. Thankfully, the major urban corridor was spared today, and the extreme shear and instability for the most part was not realized as a dryline/front pushed well east of the foothills. Displayed above is the radar as of 9:10 MDT, showing the weakening severe storms as they move into extreme western SK. Here is a graphical summary of the warnings as of 9:00 pm MDT:
Storms intensifying rapidly in Alberta!
Posted At: July 19, 2007 @ 6:04 PM
Posted By: Reed Timmer
Related Categories: General
As seen above, storms are intensifying rapidly all around Edmonton, AB, with the best looking storm just west of Edson, AB. This storm is showing some supercellular characteristics, and poses the highest tornado threat at this time. This storm should track just west of Whitecourt, AB over the next few hours. Meanwhile, storms are initiating on a boundary/dryline southeast of Edmonton as well, southwest of Wainwright...even though these storms are east of the best dynamics, they will also have a chance to become severe. Stay tuned for updates!
Initiation of supercells expected over the next 2-3 hours!
Posted At: July 19, 2007 @ 5:00 PM
Posted By: Reed Timmer
Related Categories: Tornadoes
The latest RUC model is still predicting convective initiation over the next 2-3 hours over the Foothills of Alberta, moving into the Plains by evening. Initation will likely occur west and northwest of Calgary, and west of Edmonton. The upper disturbance can be seen on satellite moving across the Rockies of British Columbia, and this disturbance should help initiate the storms.
Severe thunderstorm watch issued from Calgary to Edmonton and surrounding areas!
Posted At: July 19, 2007 @ 2:35 PM
Posted By: Reed Timmer
Related Categories: Tornadoes
A severe thunderstorm watch has been issued by Environment Canada for the areas outlined in yellow below. I'm very surprised this isn't a tornado watch, since the instability and shear are more than adequate for tornadoes once storms develop in a few hours. It will likely be upgraded later this afternoon and evening. As soon as storms begin showing up on radar, I'll post another blog entry. STAY TUNED!!
1:11 PM MDT Thursday 19 July 2007
Severe thunderstorm watch for
Drayton Valley - Devon - Rimbey - Pigeon Lake continued
Thunderstorm watch in effect.
This is an alert to the potential development of severe thunderstorms with large hail and damaging winds.
Monitor weather conditions..Listen for updated statements. If threatening weather approaches take immediate safety precautions.
A developing north south frontal zone from just west of Edmonton south to west of Red Deer has begun to pool moist unstable air. It is expected that thunderstorms could begin to trigger near this boundary after 3 PM and well into the evening hours. Storms which develop are expected to move northeastwards. It is possible this watch may be extended southeastwards towards Medicine Hat as the day progresses.
Watches
Drayton Valley - Devon - Rimbey - Pigeon Lake1:11 PM MDT Thursday 19 July 2007
Severe thunderstorm watch for
Drayton Valley - Devon - Rimbey - Pigeon Lake continued
Thunderstorm watch in effect.
This is an alert to the potential development of severe thunderstorms with large hail and damaging winds.
Monitor weather conditions..Listen for updated statements. If threatening weather approaches take immediate safety precautions.
A developing north south frontal zone from just west of Edmonton south to west of Red Deer has begun to pool moist unstable air. It is expected that thunderstorms could begin to trigger near this boundary after 3 PM and well into the evening hours. Storms which develop are expected to move northeastwards. It is possible this watch may be extended southeastwards towards Medicine Hat as the day progresses.
Severe weather outbreak likely in Alberta today
Posted At: July 19, 2007 @ 12:34 AM
Posted By: Reed Timmer
Related Categories: Tornadoes
As a strong shortwave trough ejects northeastward across the Canadian Rockies today (Thursday), the ingredients are coming together for a significant severe weather outbreak across Alberta for the Foothills and the adjacent Plains in the region highlighted in red on the selected model plots below:
Shown above is the WRF forecast CAPE (instability) for 6:00 pm MT this evening. CAPE values of 3000+ J/kg are widespread across the entire Foothills and adjacent Plains of Alberta, given the very high moisture values and relatively cold air aloft. Southeast portions of the province have very high instability, but a strong capping inversion will be in place, which could suppress storm development for much of the day. However, if a storm initiates in southeast AB (outside of the red shaded area), it will still rapidly become severe and will pose a tornado threat. However, the best dynamics are located to the north of this region in the red shaded area. Shown below is the forecast 12-hr accumulated precipitation ending at 6:00 pm MT. This shows widespread thunderstorm development from north of Calgary through Edmonton, and northwest along the Foothills/high plains. These storms will likely be supercellular.
There is one negative on the tornado potential for tomorrow -- fairly unidirectional flow between 700 mb and 500-300 mb -- as seen below in the WRF forecast wind panels. For the tornado chances to be maximized, the wind should veer to a more westerly direction with height (which is not the case here), because this results in greater storm motion-relative wind shear. For tornadoes to occur tomorrow, right-turning supercells will be necessary. If there were more directional shear forecast between low-upper levels, then today would likely be a much more significant tornado outbreak. But...tornadoes are still very possible with any storms that deviate right of the upper-level flow. Stay tuned for updates...I plan on posting SEVERAL blog entries as this volatile severe weather situation unfolds!!
Shown above is the WRF forecast CAPE (instability) for 6:00 pm MT this evening. CAPE values of 3000+ J/kg are widespread across the entire Foothills and adjacent Plains of Alberta, given the very high moisture values and relatively cold air aloft. Southeast portions of the province have very high instability, but a strong capping inversion will be in place, which could suppress storm development for much of the day. However, if a storm initiates in southeast AB (outside of the red shaded area), it will still rapidly become severe and will pose a tornado threat. However, the best dynamics are located to the north of this region in the red shaded area. Shown below is the forecast 12-hr accumulated precipitation ending at 6:00 pm MT. This shows widespread thunderstorm development from north of Calgary through Edmonton, and northwest along the Foothills/high plains. These storms will likely be supercellular.
There is one negative on the tornado potential for tomorrow -- fairly unidirectional flow between 700 mb and 500-300 mb -- as seen below in the WRF forecast wind panels. For the tornado chances to be maximized, the wind should veer to a more westerly direction with height (which is not the case here), because this results in greater storm motion-relative wind shear. For tornadoes to occur tomorrow, right-turning supercells will be necessary. If there were more directional shear forecast between low-upper levels, then today would likely be a much more significant tornado outbreak. But...tornadoes are still very possible with any storms that deviate right of the upper-level flow. Stay tuned for updates...I plan on posting SEVERAL blog entries as this volatile severe weather situation unfolds!!
Supercells initiating shortly in western Alberta!
Posted At: July 18, 2007 @ 3:20 PM
Posted By: Reed Timmer
Related Categories: Tornadoes
MAJOR derecho event expected today across IA-northern IL!
Posted At: July 18, 2007 @ 10:40 AM
Posted By: Reed Timmer
Related Categories: General
A major derecho or long-lived linear mesoscale convective system (MCS) event is expected today from eastern IA through northern IL from late afternoon through late evening, respectively. Extreme instability and good deep-layer shear in a classic northwesterly-flow situation will prevail over this region today. While the initial storm mode will likely be supercells over central IA, with the threat of VERY large hail, strong straight-line winds, and isolated brief tornadoes, the cells should quickly congeal into a monster MCS, which will rapidly propagate southeastward towards northern Illinois by late evening. Stay tuned for updates!
Supercells AGAIN in Alberta!
Posted At: July 17, 2007 @ 4:27 PM
Posted By: Reed Timmer
Related Categories: Tornadoes
Low-precipitation (LP) supercells have initiated in the upslope flow along the Foothills of the Rocky Mountains in western Alberta this afternoon. Given the rather weak, meridional upper-level flow, these storms will likely not move much off the mountains until later this evening, when the cap may lead to their demise. Here is the Calgary radar as of 3:30 pm MT.
Consequently, a severe thunderstorm watch has been issued for parts of western Alberta along the Foothills and adjacent Plains this afternoon/evening, and a severe thunderstorm warning has been issued for the supercell identified above. Hail to the size of quarters has already been reported with this storm. A tornado watch is also in effect for parts of northeast AB and northwest SK for brief funnels that have been reported under weak thunderstorms/cumulus clouds...these seem to happen often up there!
Consequently, a severe thunderstorm watch has been issued for parts of western Alberta along the Foothills and adjacent Plains this afternoon/evening, and a severe thunderstorm warning has been issued for the supercell identified above. Hail to the size of quarters has already been reported with this storm. A tornado watch is also in effect for parts of northeast AB and northwest SK for brief funnels that have been reported under weak thunderstorms/cumulus clouds...these seem to happen often up there!
Low-level jet magic possible in IA this evening?
Posted At: July 17, 2007 @ 2:50 PM
Posted By: Reed Timmer
Related Categories: Tornadoes
Shown above is the RUC forecast 850 mb flow for 7:00 pm and 10:00 pm for the central U.S. Note how the low-level jet is forecast to increase from ~25 knots to 35+ knots from 00z to 03z this evening! Given a forecast storm motion of SSE, this wind direction for the LLJ generates a favorable hodograph for tornadic supercells this evening. If storms can remain discrete, the tornado potential could be locally enhanced in northeast IA, where 6000 J/kg CAPE is forecast to develop.
The Storm Prediction Center has issued a mesoscale discussion for this area for elevated hail-producing storms developing. However, if the instability can develop as forecast, a tornado watch may be needed for this area later this evening. Stay tuned for updates!
Repeat situation today in northern Iowa -- Supercells likely!
Posted At: July 17, 2007 @ 10:43 AM
Posted By: Reed Timmer
Related Categories: Tornadoes
Here are some selected RUC forecasts for 7:00 pm CDT this evening:
CAPE values will be extreme along the IA/MN border into northeast IA and extreme northwest IL later this afternoon and evening, with values approaching 5000 J/kg (purple values in upper-left map) over northeast IA. Low-level shear will be adequate for tornadoes over this region, with WSW flow at 850 mb of 20-30 knots. These supercells will be moving in SE and SSE direction along the instability axis, and will quickly become high-precipitation (HP) monsters as the evening progresses. VERY large hail and strong straight-line winds will be the main threat, but as mentioned, an isolated tornado cannot be ruled out. Shown below are the SPC storm reports for yesterday, which was a very similar setup. One tornado was reported in Washington County, IA just before 4:00 pm CDT, 7 miles west of Haskins. I have not seen any pictures of the tornado yet, but the couplet was intense on radar at the time of the tornado. Stay tuned for updates!
CAPE values will be extreme along the IA/MN border into northeast IA and extreme northwest IL later this afternoon and evening, with values approaching 5000 J/kg (purple values in upper-left map) over northeast IA. Low-level shear will be adequate for tornadoes over this region, with WSW flow at 850 mb of 20-30 knots. These supercells will be moving in SE and SSE direction along the instability axis, and will quickly become high-precipitation (HP) monsters as the evening progresses. VERY large hail and strong straight-line winds will be the main threat, but as mentioned, an isolated tornado cannot be ruled out. Shown below are the SPC storm reports for yesterday, which was a very similar setup. One tornado was reported in Washington County, IA just before 4:00 pm CDT, 7 miles west of Haskins. I have not seen any pictures of the tornado yet, but the couplet was intense on radar at the time of the tornado. Stay tuned for updates!
Insane weather video from Amsterdam!
Posted At: July 16, 2007 @ 8:20 PM
Posted By: Reed Timmer
Related Categories: Tornadoes
Here is video of what appears to be a beautiful shelf cloud approaching Amsterdam, Netherlands, provided by Cors of insaneweather.com. The straited, laminar appearance is created as colder, relatively dense outflow surges rapidly along the ground under the warmer, less dense ambient air. The striations represent moisture/temperature variations in the vertical.
Severe weather again in Alberta today!
Posted At: July 16, 2007 @ 2:04 PM
Posted By: Reed Timmer
Related Categories: Tornadoes
Despite relatively weak low-level wind shear, extreme instability and sufficient deep-layer shear will be in place just east of the Rocky Mountains in central/southern Alberta today for supercells. Very large hail and strong straightline winds will be the main threat, but an isolated brief tornado cannot be ruled out with any boundary interactions that occur.
Joel and I will be watching the evening model runs closely, and will likely make a decision this evening on whether we will make the trip to AB for greater tornado chances later in the week (especially Thursday). Stay tuned for updates!
Pictures of the Red Deer, AB supercell!
Posted At: July 15, 2007 @ 11:41 PM
Posted By: Reed Timmer
Related Categories: Tornadoes
Here are some pictures of the tornadic supercell that developed west of Red Deer, Alberta Sunday afternoon and tracked southeastward towards Olds, AB, taken by Canadian storm chaser Brandon Brown of Red Deer. Thanks to Brandon for allowing me to post these incredible pictures! Congrats on a very successful chase.
Note the suspicious lowering above directly under the striated tower. This was likely an occluded circulation, with a new circulation further to the right where the RFD gust-front met the foward flank gust-front. Also see the crisp towers along the flanking line feeding into this intense supercell tower. This cell was tornado-warned for much of the evening, and exhibited a textbook hook echo on radar.
Note the suspicious lowering above directly under the striated tower. This was likely an occluded circulation, with a new circulation further to the right where the RFD gust-front met the foward flank gust-front. Also see the crisp towers along the flanking line feeding into this intense supercell tower. This cell was tornado-warned for much of the evening, and exhibited a textbook hook echo on radar.
Two Alberta supercells tracking southeastward SW of Red Deer, AB
Posted At: July 15, 2007 @ 4:50 PM
Posted By: Reed Timmer
Related Categories: Tornadoes
Warnings
Mountain View county near Sundre3:31 PM MDT Sunday 15 July 2007
Severe thunderstorm warning for
Mountain View county near Sundre issued
At 3:20 PM radar indicates two severe thunderstorm cells one west of Sunchild and another west of caroline. There have been reports of some storm rotation and loonie sized hail near caroline. These storms are expected to continue tracking slowly southeastwards for the next hour.
A hot and humid airmass persists over south and central Alberta. An approaching jet stream from the bc interior is expected to trigger thunderstorms along the foothills this afternoon and track east northeastwards. Should these thunderstorms form there is a good chance they will produce severe weather. Remember some severe thunderstorms produce tornadoes.
Severe weather likely again today for Alberta!
Posted At: July 15, 2007 @ 11:04 AM
Posted By: Reed Timmer
Related Categories: General
Thunderstorms will once again initiate over the Rocky Mountains of western Alberta, and will become severe as they move eastward over the adjacent Plains where substantial moisture and instability will prevail. The tornado threat should be minimal today, since the best dynamics and wind shear will be just to the west of the instability axis. Shown below are some selected RUC forecasts for this evening.
The yellow shading in the CAPE map above depicts values of 2500 J/kg or greater, which is forecast to exist from just south of Edmonton northward along the Plains adjacent to the mountains. The dewpoints are forecast to mix out over southern Alberta, including the Calgary area, limiting the instability there. As can be seen below in the 500 mb forecast for this evening, the jet streak will be just west of the instability axis as of 6:00 pm MT, so the best deep-layer shear will still be west of the area at least before 7:00 pm. Consequently, the low-level shear will also be lacking over this area before 7:00 pm, and the threat for tornadic supercells should be limited...although a brief spin-up cannot be ruled out. After 7:00 pm MT, when the jet streak is forecast to overspread the instability axis, wind shear will be on the increase, and supercells will be more likely with any discrete storms.
The yellow shading in the CAPE map above depicts values of 2500 J/kg or greater, which is forecast to exist from just south of Edmonton northward along the Plains adjacent to the mountains. The dewpoints are forecast to mix out over southern Alberta, including the Calgary area, limiting the instability there. As can be seen below in the 500 mb forecast for this evening, the jet streak will be just west of the instability axis as of 6:00 pm MT, so the best deep-layer shear will still be west of the area at least before 7:00 pm. Consequently, the low-level shear will also be lacking over this area before 7:00 pm, and the threat for tornadic supercells should be limited...although a brief spin-up cannot be ruled out. After 7:00 pm MT, when the jet streak is forecast to overspread the instability axis, wind shear will be on the increase, and supercells will be more likely with any discrete storms.
Today is the 7-year anniversary of the Pine Lake, Alberta F-3 tornado!
Posted At: July 14, 2007 @ 3:23 PM
Posted By: Reed Timmer
Related Categories: Tornadoes
On July 14, 2000, a powerful wedge tornado destroyed the Green Acres Camp Ground on the southwest side of Pine Lake in Alberta, 90 miles north of Calgary. The tornado was up to a mile wide at times, and struck the camp ground at around 6:30 pm local time, destroying over a dozen homes. Debris from the camp ground was scattered across the lake in an adjacent subdivision. Sadly, 11 people lost their lives from this tornado, and hundreds were injured. Here is a video clip from The Weather Network coverage of this tornado on July 15, 2000:
Pictures of a Michigan gustfront and sunset
Posted At: July 12, 2007 @ 10:00 PM
Posted By: Reed Timmer
Related Categories: General
With very cold air aloft, a band of convection that developed over northern Wisconsin moved rapidly southeastward through western Lower Michigan just before sunset, producing a beautiful gust front/shelf cloud, waterspouts along the Lake Michigan shoreline, and 45 mph winds. Here are some pictures from Grand Rapids, MI as the gust front was moving through:
Severe storms exploding across the Central/Southern Plains!
Posted At: July 12, 2007 @ 2:22 PM
Posted By: Reed Timmer
Related Categories: Tornadoes
Severe thunderstorms have been developing along a W-E boundary across northern Nebraska this afternoon, with several severe thunderstorms warnings and a watch in effect for the area (see below). These storms will likely be multi-cellular in nature, and marginal severe wind and hail will be the main threat.
Meanwhile, instability has been building all day across northwest OK, southwest KS, southeast CO, and the northern Texas Panhandle, with CAPEs exceeding 3000+ J/kg as of early afternoon. 0-1 km helicity values of 100-150 m2/s2 also exist across the area of maximum instability, yielding favorable conditions for supercells later this afternoon and evening. Shown below is the RUC analysis from 1:00 pm CDT showing the CAPE and CIN over the Southern Plains.
Meanwhile, instability has been building all day across northwest OK, southwest KS, southeast CO, and the northern Texas Panhandle, with CAPEs exceeding 3000+ J/kg as of early afternoon. 0-1 km helicity values of 100-150 m2/s2 also exist across the area of maximum instability, yielding favorable conditions for supercells later this afternoon and evening. Shown below is the RUC analysis from 1:00 pm CDT showing the CAPE and CIN over the Southern Plains.
Pictures of a wall cloud near Howe, TX from yesterday
Posted At: July 12, 2007 @ 2:12 PM
Posted By: Reed Timmer
Related Categories: General
Here are some pictures of a wall cloud/low-hanging scud from a severe thunderstorm just south of Sherman, TX yesterday, taken by Erik Burns. The storm briefly exhibited some supercellular characteristics on radar at the time of the photos. If anyone happens to capture any severe weather photos today or in the future, and would like to contribute to the blog, please email them to me at reed@tornadovideos.net and include the watermark you would like on the photo. Thanks!
Heavy rain/flooding AGAIN in central OK!!
Posted At: July 12, 2007 @ 10:11 AM
Posted By: Reed Timmer
Related Categories: General
A weakening mesoscale convective system (MCS) that originated as isolated supercells over the Colorado High Plains, is now pounding central OK with very heavy rain and gusty winds. The ground is EXTREMELY saturated in central OK at present, with widespread standing water and flooding from the heavy rainfall a few nights ago (7+ inches in 12 hours in spots). A flood watch has been issued for this area, with flood warnings a certainty as this heavy rain drifts southward over already flooded areas. Meanwhile, supercells are likely to form again today over the High Plains of NM/CO/TX/OK, and will once again consolidate into a strong MCS by late evening which could hammer the same areas with heavy rain. This summer for central OK and TX could be a 1 in 50 year type event at the least!
Massive MCS forecast to develop over Central High Plains today!
Posted At: July 11, 2007 @ 9:43 AM
Posted By: Reed Timmer
Related Categories: General
Isolated supercells will develop over eastern Colorado today with a subtle jet streak moving across the area embedded in WNW-ly flow. Initially, these discrete cells will have a chance to produce a few tornadoes, despite marginal low-level shear, but VERY large hail will be the initial main threat. The supercells will quickly merge into a large mesoscale convective system near the CO/KS Border, before propagating rapidly southeastward. Widespread severe wind will likely be produced by this MCS.
Severe storms and tornadoes possible for Great Lakes Region today!
Posted At: July 10, 2007 @ 10:47 AM
Posted By: Reed Timmer
Related Categories: Tornadoes
A potent shortwave will move across the northern Great Lakes Region this afternoon/evening, providing the necessary wind shear over an already unstable environment for severe thunderstorms and tornadic supercells. The limiting factors for tornadoes today will be veering surface flow (decreasing low-level shear), and the tendency for storms to become linear given strong linear forcing along the fast-moving cold front. Shown below are some selected forecast fields from the morniing WRF.
A surface warm front/outflow boundary was draped across the northern Great Lakes this morning, with deep tropical moisture to the south, and a modified low-level atmosphere to the north (see below). Winds are more backed to a southeasterly direction to the north of the boundary, and have veered to a SW direction to the south of the boundary. If this front can maintain it's identity through peak heating, the tornado threat could be locally enhanced if storms can remain discrete and interact with this boundary. We will be on standby for this event, and will likely chase it if a tornado threat materializes.
A surface warm front/outflow boundary was draped across the northern Great Lakes this morning, with deep tropical moisture to the south, and a modified low-level atmosphere to the north (see below). Winds are more backed to a southeasterly direction to the north of the boundary, and have veered to a SW direction to the south of the boundary. If this front can maintain it's identity through peak heating, the tornado threat could be locally enhanced if storms can remain discrete and interact with this boundary. We will be on standby for this event, and will likely chase it if a tornado threat materializes.
UPDATE: The latest RUC analysis from around noon EDT shows the best 0-1 km helicity over the northern Lower Peninsula of Michigan WNW across the entire Upper Peninsula of Michigan. Currently, storms are developing along the cold front across north-central WI into the western UP of Michigan, and also over northern Lake Michigan. If discrete supercells can move into the environment shown below, they could produce tornadoes.
Severe storms, including supercells, hammer parts of OK yesterday!
Posted At: July 10, 2007 @ 1:18 AM
Posted By: Reed Timmer
Related Categories: Tornadoes
Storm chaser Michael O'Keeffe shot this great video of a supercell in Overland Park, KS yesterday. Note the textbook lowering and fairly rapid low-level rotation evident in the video!
Here are three pictures, taken by storm chaser Matt Vanevery, of a beautiful supercell that moved over Newcastle, OK late yesterday (Monday) evening. While no tornadoes were officially reported yesterday, large hail and severe straight-line wind reports were very numerous.
Several 70+ mph wind gusts were reported yesterday in Norman, OK with large branches and trees down everywhere! Nicole and Don Guiliano shot some incredible pictures of the damage. Don said that the winds with yesterday's storm were stronger than any RFD he had experienced all year! When the strongest winds arrived, Nicole and Don were parked right next to a large refreshment stand when it was blown over (see picture below).
Here are three pictures, taken by storm chaser Matt Vanevery, of a beautiful supercell that moved over Newcastle, OK late yesterday (Monday) evening. While no tornadoes were officially reported yesterday, large hail and severe straight-line wind reports were very numerous.
Tornadoes possible in Southeast SK/Southwest MB, Canada and northwest ND tomorrow!
Posted At: July 8, 2007 @ 9:35 PM
Posted By: Reed Timmer
Related Categories: Tornadoes
A strong shortwave trough embedded in northwesterly flow will move across the central Canadian Prairies tomorrow (Monday), providing the necessary wind shear and instability for tornadic supercells across southeast Saskatchewan, southwest Manitoba, and northwest/north-central ND by late afternoon. Selected panels from the Sunday evening WRF run are displayed above, with the highest tornado chances in the red-shaded area. Southeasterly surface flow, a southerly LLJ at 30+ kts, and WSW 700 mb flow at ~40 knots will provide SUBSTANTIAL low-level wind shear, with 0-3 helicity values in the 300+ m2/s2 range over southwest Manitoba by 7:00 pm CDT tomorrow evening. As is typically the case with these setups, the LLJ will likely move further west towards the Pacific cold front/dry line/instability axis especially just after 00z as the lower atmosphere decouples (nocturnal inversion forms as surface cools rapidly in the late evening, and LLJ intensifies, often moving west to the previously mixed lower atmosphere). Even if this scenario does not occur, supercells will likely be crossing into the more ideal low-level shear over southwest Manitoba by 7:00-10:00 pm CDT, and thus the tornado threat will be enhanced.
Unfortunately, we will not be chasing this setup, but will definitely be posting updates as the situation materializes. Stay tuned for updates!
Unfortunately, we will not be chasing this setup, but will definitely be posting updates as the situation materializes. Stay tuned for updates!
Massive MCS moving through Northern Great Lakes!
Posted At: July 8, 2007 @ 6:37 PM
Posted By: Reed Timmer
Related Categories: General
MCSs are defined as a large complex of thunderstorms with a scale of 100+ km, and a large contiguous area of cold cloud tops (see infra-red image above). MCSs over the north-central U.S. during mid-late summer often form into derechos, or intense, linear convective systems that often produce widespread wind damage over a large geographical area. The most intense, northern section of the current MCS may form into a derecho as it propagates southeast across northern Lake Michigan.
Flooding will continue over East Texas today and tonight
Posted At: July 6, 2007 @ 1:37 PM
Posted By: Reed Timmer
Related Categories: General
The persistent cut-off low (clearly evident in the visible satellite image above) that has been producing the flooding rains over KS/OK/TX over the past few weeks will continue to meander around the Southern Plains for several more days. The upper-low is now located in extreme northeast TX, with associated heavy thunderstorms from Del Rio ENE to Houston, TX and NNE to Arkansas. The recent models runs forecast the low to drift back northward to Oklahoma over the next few days, bringing more heavy rain and flooding with it. The regional radar image from S. Texas at around 2:30 pm EDT is shown below:
Since this cut-off low is nested within a massive ridge of high pressure, the jet stream is way too far north to transport this system eastward, thus the models are predicting the low to move very little over the next several days. Given the deep tropical moisture in place over this region, latent heat release (occurs as water vapor condenses into rain droplets) within the massive thunderstorm complexes has been immense, resulting in a mesoscale anti-cyclone at upper-levels above the low pressure center. The result is a positive feedback situation, where the low-level cyclone intensifies as a result of the mass divergence aloft with the anticyclone, which enhances low-level convergence and thunderstorm development in association with the low pressure center. This positive feedback is responsible for the rapid intensification of tropical cyclones over water, and the latent heat release results in relatively warm upper-levels of the atmosphere, hence tropical cyclones (and this cut-off low) are termed "warm-core" systems. The factors preventing this cut-off low from intensifying like a tropical cyclone over water are friction with land, and the lack of a continuous heat/moisture flux from a warm (>80oF) body of water. Here are the flood watches and warnings for the region for today/tonight:
Severe storms possible for the Great Lakes Region!
Posted At: July 5, 2007 @ 12:45 PM
Posted By: Reed Timmer
Related Categories: General
Instability and deep-layer shear are sufficient for severe storms over the Great Lakes Region this afternoon and evening, as northwesterly flow prevails over much of the Central and Eastern U.S. The tornado threat will be very low over this region, however, as low-level shear values are very meager. Given a weak capping inversion, the lake breeze fronts should provide the necessary convergence for initiation...here are some select RUC analysis maps from 17z.
The lake breeze front is evident in the CAPE map above by the westerly surface winds along the western side of the lower peninsula of Michigan. Given CAPEs of 1500-2000 J/kg with no cap (blue color indicates convective inhibition or CIN), I would not be surprised if storms initiate along this front in the next few hours, likely along a line three counties east of the lake, and track ESE into southeast lower Michigan. Marginally severe hail and wind will be the main threat with these storms. As can be seen in the map below, the low-level jet will be very weak out of the northwest, and thus storm-relative low-level shear will not be supportive of tornadoes, although a freak boundary incident still could occur somewhere in the Great Lakes/Ohio River Valley.
EDIT: As of 1:42 pm EDT, a storm has already fired along the lake breeze and moved just north of the Lansing area. Latest inspection of echo tops shows that the storm has already started to weaken since it is moving into a more stable environment.
The lake breeze front is evident in the CAPE map above by the westerly surface winds along the western side of the lower peninsula of Michigan. Given CAPEs of 1500-2000 J/kg with no cap (blue color indicates convective inhibition or CIN), I would not be surprised if storms initiate along this front in the next few hours, likely along a line three counties east of the lake, and track ESE into southeast lower Michigan. Marginally severe hail and wind will be the main threat with these storms. As can be seen in the map below, the low-level jet will be very weak out of the northwest, and thus storm-relative low-level shear will not be supportive of tornadoes, although a freak boundary incident still could occur somewhere in the Great Lakes/Ohio River Valley.
EDIT: As of 1:42 pm EDT, a storm has already fired along the lake breeze and moved just north of the Lansing area. Latest inspection of echo tops shows that the storm has already started to weaken since it is moving into a more stable environment.
Severe thunderstorm and tornado warnings in the Mid-Atlantic to Southern Plains and Manitoba!
Posted At: July 4, 2007 @ 6:42 PM
Posted By: Reed Timmer
Related Categories: Tornadoes
Several supercells have developed in the Mid-Atlantic, with nearly 50 large hail (1.5"+ diameter) and severe wind reports this afternoon and evening. A tornado was also reported in Howard County, MD at 4:22 pm EDT with the storm indicated in the radar image below. Radar also indicated 2"+ hail with this storm as it tracked southeastward just northeast of Washington DC.
Tornado watches and severe thunderstorm watches have been issued for the Mid-Atlantic, Ohio River Valley, and portions of the Southern Plains, with large hail and severe straight-line winds the main threat. Supercells have also initiated with the WNW-ly flow regime over southern Manitoba, with one particularly strong supercell moving southward along the southern end of Lake Manitoba. Another strong supercell just recently intensified south of Portage La Prairie, MB. Unfortunately, the radar image could not be saved from the Environment Canada website, thus could not be posted on this update!
Tornado watches and severe thunderstorm watches have been issued for the Mid-Atlantic, Ohio River Valley, and portions of the Southern Plains, with large hail and severe straight-line winds the main threat. Supercells have also initiated with the WNW-ly flow regime over southern Manitoba, with one particularly strong supercell moving southward along the southern end of Lake Manitoba. Another strong supercell just recently intensified south of Portage La Prairie, MB. Unfortunately, the radar image could not be saved from the Environment Canada website, thus could not be posted on this update!
Was the Mobile, AL tornado a supercell tornado??
Posted At: July 4, 2007 @ 11:20 AM
Posted By: Reed Timmer
Related Categories: Tornadoes
Here are some radar images from Mobile, AL from around the time of the tornado (1910-1920z -- 2:10-2:20 pm CDT). After analyzing this radar loop, it appears that an outflow boundary may have merged with the sea breeze front right around Downtown Mobile, allowing for a surface based storm to initiate on this boundary and propagate WSW along it through downtown. It is possible, that the WSW storm-motion enhanced the low-level storm-relative shear, and thus a tornado was produced. It looks from the pictures below that a mini-clear slot may have been wrapping around the tornado.
Here is the official statement from NWS Mobile, which states that winds of 50-55 mph were likely the cause of the damage. It also states that the tornado was a gustnado!!?!! I have seen about 200 gustnadoes and not one of them had a persistent, laminar condensation funnel extending all the way to the ground. From the radar imagery above, it appears that this was actually a supercell tornado and not even a land spout!
Also, by definition, an EF-0 tornado produces winds of 65-85 mph, which is not consistent with the 50-55 mph estimation in the information statement. It is actually incorrectly stated below that an EF-0 tornado has winds of less than 55 mph. This statement either shows lack of knowledge by the author, an honest mistake, or a cover-up since there was no tornado warning or severe thunderstorm warning issued during the entire duration of this storm.
Here is the official statement from NWS Mobile, which states that winds of 50-55 mph were likely the cause of the damage. It also states that the tornado was a gustnado!!?!! I have seen about 200 gustnadoes and not one of them had a persistent, laminar condensation funnel extending all the way to the ground. From the radar imagery above, it appears that this was actually a supercell tornado and not even a land spout!
Also, by definition, an EF-0 tornado produces winds of 65-85 mph, which is not consistent with the 50-55 mph estimation in the information statement. It is actually incorrectly stated below that an EF-0 tornado has winds of less than 55 mph. This statement either shows lack of knowledge by the author, an honest mistake, or a cover-up since there was no tornado warning or severe thunderstorm warning issued during the entire duration of this storm.
PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE MOBILE AL
805 PM CST TUE JUL 3 2007
...SURVEY RESULTS FROM THE MOBILE COUNTY SEVERE WEATHER DAMAGE
OF 3 JULY 2007...
NATIONAL WEATHER SERVICE SURVEY...EYE WITNESS REPORTS...AND RADAR
DATA INDICATE THAT A THUNDERSTORM DOWNBURST OF 50 TO 55 MPH WAS
LIKELY THE CAUSE OF MOST OF THE DAMAGE THAT OCCURRED AROUND 220
PM NEAR THE INTERSTATE-65...DAUPHIN STREET INTERCHANGE.
A SHORT LIVED...GUSTNADO (A VERY WEAK TORNADO ALONG A GUST FRONT)
WITH A RATING OF EF0 (WINDS ESTIMATED LESS 55 MPH) DEVELOPED ALONG
THE LEADING EDGE OF THE OUTFLOW BOUNDARY NEAR THE DAUPHIN WAY BAPTIST
CHURCH JUST ON THE WEST SIDE OF INTERSTATE-65. MINOR TREE DAMAGE
OCCURRED ALONG DAUPHIN STREET NEAR THE CHURCH AND ONE CAR WAS BRIEFLY
LIFTED OFF THE ROADWAY AND DAMAGED WHEN IT WAS BLOWN INTO A TREE. THE
OCCUPANT OF THE CAR WAS WEARING A SEATBELT AND WAS UNINJURED...BUT
THE BACK WINDOW OF THE CAR WAS SHATTERED AND SOME BODY DAMAGE TO THE
VEHICLE OCCURRED. IN ADDITION...A 5 BY 8 FOOT SECTION OF ROOFING
MATERIAL WAS BLOWN OFF THE DAUPHIN WAY BAPTIST CHURCH...RESULTING IN
WATER DAMAGE TO THE CHURCH`S INTERIOR. THE TORNADO QUICKLY DISSIPATED
AFTER THE BRIEF TOUCHDOWN.
THE MOST SIGNIFICANT DAMAGE THEN OCCURRED JUST EAST OF INTERSTATE-65
AT THE SUPER-WALMART ON THE I-65 SERVICE ROAD. EYEWITNESS
REPORTS AND A NATIONAL WEATHER SERVICE STORM SURVEY INDICATE THAT A
THUNDERSTORM DOWNBURST OCCURRED NEAR THE WALMART STORE. A LARGE
SECTION OF THE ROOF AT THE BACK OF THE STORE WAS TORN AWAY AFTER HIGH
WINDS...ESTIMATED TO HAVE BEEN AROUND 55 MPH...BLEW A LARGE AIR
CONDITIONING UNIT OFF THE ROOF. AS A RESULT...SIGNIFICANT WATER
DAMAGE OCCURRED TO THE INTERIOR OF THE STORE. WIND DAMAGE ALSO
OCCURRED IN THE GARDEN SECTION OF THE STORE...WHERE LIGHT WEIGHT
ROOFING MATERIALS AND NUMEROUS OTHER SMALL OBJECTS WERE BLOWN ABOUT
100 YARDS DOWNWIND FROM THE STORE. SEVERAL MINOR INJURIES WERE
REPORTED.
THE OUTFLOW BOUNDARY THAT CAUSED THE DAMAGE AT I-65 MOVED TO THE
SOUTHEAST WHERE SEVERAL PEOPLE SAW A FUNNEL CLOUD NEAR HIGHWAY 90 AND
THE LOOP. THE ONLY DAMAGE THAT COULD BE FOUND IN THIS AREA WAS A TREE
TOP BLOWN OUT AND SEVERAL TRANSFORMERS WERE BLOWN.
Pictures of a landspout tornado in Mobile, AL!
Posted At: July 3, 2007 @ 7:07 PM
Posted By: Reed Timmer
Related Categories: Tornadoes
Here are some pictures of a land spout tornado that touched down near Mobile, AL today, damaging Walmart and sending people to the hospital! This land spout likely formed as an airmass thunderstorm stretched existing vorticity in the vicinity of the sea breeze front. AMAZING!
Huge hail producers likely in southern MN/northern IA/western WI
Posted At: July 3, 2007 @ 10:53 AM
Posted By: Reed Timmer
Related Categories: Tornadoes
Extreme CAPE values and sufficient deep-layer shear for supercells will set the stage for significant hail over the northern Mississippi River Valley. Given CAPEs of 3000+ J/kg and zero CIN over a large area, a widespread severe hail event appears likely. Here are some selected RUC forecasts for 00z this evening:
Forecast 850 mb flow for 00z this evening is shown in the upper-left panel. The low-level flow is very weak prior to this time, but the low-level jet is forecast to intensify ahead of this short-wave by 00z, with up to 30 kts forecast in extreme northeast IA and southeast MN. If supercells can remain discrete until the LLJ intensifies, there will be chance for tornadoes, but very large hail of 2+ inches in diameter will be the main threat. Accordingly, the SPC has indicated the potential for a significant hail event in their Day 1 Outlook:
Forecast 850 mb flow for 00z this evening is shown in the upper-left panel. The low-level flow is very weak prior to this time, but the low-level jet is forecast to intensify ahead of this short-wave by 00z, with up to 30 kts forecast in extreme northeast IA and southeast MN. If supercells can remain discrete until the LLJ intensifies, there will be chance for tornadoes, but very large hail of 2+ inches in diameter will be the main threat. Accordingly, the SPC has indicated the potential for a significant hail event in their Day 1 Outlook:
Supercells possible in western Dakotas today
Posted At: July 2, 2007 @ 11:08 AM
Posted By: Reed Timmer
Related Categories: Tornadoes
After a brief glance at the models, it appears that sufficient CAPE and deep-layer shear will be in place over the Northern High Plains for supercells. Since I'm currently traveling, I haven't had the chance to look at the models in detail, but the SPC has a 5% risk out for tornadoes later this afternoon.
Supercells possible this evening from ND to southern Manitoba!
Posted At: July 1, 2007 @ 12:47 PM
Posted By: Reed Timmer
Related Categories: Tornadoes
Despite a rather strong capping inversion, a slow-moving cold front should provide sufficient low-level convergence for the initiation of supercells later this afternoon/evening from central ND to southern Manitoba. While this appears to be the classic case where the LLJ is displaced slightly east of the instability axis and surface boundary, there does appear to be some overlap along the eastern edge of the instability axis (see diagrams above). Also, after 00z as afternoon mixing ceases, we should see the LLJ develop westward towards the slow-moving cold front. As mentioned, the cap is very strong today, so there is a substantial possibility that storms may not initiate...the models are predicting otherwise, however.
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