Posted At: September 29, 2007 @ 12:35 PM

Posted By: Reed Timmer

Based on recent model data, it appears that the best upper dynamics will not eject over the instability axis until very late afternoon or evening, and initiation during daylight hours is a huge uncertainty...especially over the Dakotas and western MN.   Instability will be slightly higher than previously forecast, with CAPE values of 2000+ J/kg from the Dakotas southwestward to northeast CO.  Based on the WRF and RUC models, the best chance for supercells during daylight will be across northeast CO and western NE.  RUC forecast loops for CAPE, 850 mb, and precip are displayed below:


As seen above, instability does not appear to be a limiting factor for severe weather today, with substantial CAPE across the entire warm sector northeast of CO.  However, based on the eastward displacement of the LLJ, there will likely be substantial mixing along the pressure trough/front, increasing cloud-base heights and decreasing low-level shear.  As seen in the 850 mb loop below, the LLJ migrates back westward after 00z (7:00 pm CDT) after daytime mixing ceases, so any discrete cells will encounter enhanced low-level shear after 00z. 

The main limiting factor for diurnal tornadic supercells today will be the late timing of the best upper dynamics ejecting from the upper trough over the western U.S.  Based on the 300 mb and 500 mb forecast, it looks like the primary jet streak will pass over northeast CO/western NE by about 00z, spreading northeastward from there by 03-06z.  The RUC precip forecast is consistent with this, with convective initiation limited to northeast CO and western NE by 00z.  Storms will likely fire across the Dakotas between 00z and 03z, which is coincident with the westward migration of the LLJ around and after sunset, so these storms will have a chance to produce if they can remain discrete. 

The SPC has issued a large 5% area for tornadoes in their Day 1 Outlook, but this is likely for supercells near and after sunset.  Stay tuned for udpates as this severe weather event unfolds.  Good luck to all who are chasing today!

Posted At: September 28, 2007 @ 6:18 PM

Posted By: Reed Timmer

A persistent tornadic supercell has developed in extreme southwest NE and has moved northward across I-80 this afternoon.  So far, no confirmed reports have been received from this storm, but it has looked incredible on radar...absorbing every cell that develops immediately around it.  A severe thunderstorm watch has been in effect this afternoon for northwest KS and western NE, as a jet streak is ejecting out ahead of a large trough over the Western U.S.  RUC analyzed 0-1 km EHIs (below right), are in the 2-3 range ahead of this storm, which is barely sufficient for tornadoes.  EHI is a composite index involving both CAPE and helicity, and is a good measure of the instability and shear in the low-levels of the atmosphere.  Sorry for the late blog update!  I've been away from the computer all day today and just now returned to this insanity!
 

Posted At: September 27, 2007 @ 10:54 AM

Posted By: Reed Timmer

La Nina is the exact opposite of El Nino in the Pacific, with cold sea surface temperature anomalies developing along the Equator in the eastern Tropical Pacific just off the coast of South America, and spreading westward towards the Dateline by December.   The development and intensification of La Nina results from several positive feedbacks within the Pacific Climate System, including an increased surface pressure gradient between the Southwest and Eastern Tropical Pacific, stronger Trade Winds, and increased upwelling of colder deep-waters along the South American Coast. 

If La Nina continues to intensify as forecast, then a cold winter will prevail in the north-central U.S., eastward through the Great Lakes Region and the Northeast.  The Southwest U.S. and southwest Plains will be dry, and likely colder than normal, and the Pacific Northwest will likely experience wetter than normal conditions this winter.  La Nina during late summer and fall is also associated with active hurricane seasons in the Atlantic Basin, which is still yet to be seen.

We're still keeping a close eye on the severe wx chances this weekend...we definitely need more moisture!

Posted At: September 26, 2007 @ 10:37 AM

Posted By: Reed Timmer

The GFS is forecasting a strong trough to plow into the Central/Southern Plains this weekend, bringing the possibility for severe weather from OK to SD on Saturday.  If the current GFS run verifies, a severe weather outbreak would be likely on Saturday, given the strong shear and ample instability over a large region.  If this occurs, we will DEFINITELY be chasing this event! 

Posted At: September 25, 2007 @ 10:34 AM

Posted By: Reed Timmer

At least 11 tornadoes were reported yesterday in the United Kingdom, in association with a massive squall line that roared across the country during the early morning hours.  There tornadoes were either non-supercell tornadoes associated with the "book-end vortices" of bow echoes, or were embedded supercells in the line.  The towns of Farnborough (location of above picture), Nuneaton, Northampton, Luton, and Nottingham reported damage to homes and overturned vehicles, but thankfully, no injuries were reported.  Shown below is a map showing the locations of the reported tornadoes so far, from the London Telegraph:
The links to various news stories concerning this tornado outbreak our listed below, along with a link to the severe weather research group of the UK: Tornado and Storm Research Organization (TORRO).  33 tornadoes are reported annually in the UK, but most of these tornadoes are very small, brief, and weak.  In November of 1981, 105 tornadoes hit the UK in under 6 hours! 

http://www.timesonline.co.uk/tol/news/uk/article2521956.ece

http://www.thewest.com.au/aapstory.aspx?StoryName=421360

http://www.telegraph.co.uk/news/main.jhtml?xml=/news/2007/09/24/ntornado324.xml

http://www.torro.org.uk/TORRO/index.php

A frequent participant in the blog from the UK, Tim Jacobs, posted this great video of the storm yesterday from Lincolnshire, along with some pictures of the tornadoes. 

Posted At: September 24, 2007 @ 10:01 AM

Posted By: Reed Timmer

A strong cold front will continue moving eastward across the central U.S. today, bringing the chance for severe storms from northeast MN southwest to the TX Panhandle.  Once again, low-level shear and instability will be limited, so straight-line winds and marginally severe hail will be the main threat.  The 4km WRF forecast composite reflectivity for this 8:00 pm CDT this evening is shown below. 



http://wwwt.emc.ncep.noaa.gov/mmb/mmbpll/cent4km/v2/

The 4km WRF products (higher resolution than the operational WRF) are experimental, but have been a rather useful tool in predicting initiation and storm mode.  Check out the various precip products at the link above. 

Posted At: September 23, 2007 @ 4:48 PM

Posted By: Reed Timmer

 
Severe thunderstorm watches have been issued by the Storm Prediction Center for central NE north to ND, and by Environment Canada for south-central Manitoba for this afternoon and evening, as a jet streak ejects northeastward through the eastern side of a massive trough.  Straight-line winds and marginally severe hail will be the main threat, since instability and low-level shear will be lacking, esp. for the U.S. watch box.  There will be a small chance for tornadoes further north over extreme southern MB later today, but it is doubtful.  Good luck chasing!

Posted At: September 23, 2007 @ 12:02 PM

Posted By: Reed Timmer

A large trough will move slowly eastward across the Western U.S. today, with a nice southwesterly upper jet stream prevailing aloft across the Northern Plains.  In response to this trough, a 40+ knot low-level jet will also develop across the Plains, but the best flow will remain just east of the instability axis, except maybe in northeast ND and southeast Manitoba.  Another limited factor today will be the lack of moisture, resulting in limited instability as seen in the RUC forecast CAPE for 00z this evening (below left).  Storms will likely develop between 3 and 5 pm today, and could be supercellular, especially in central and northeast ND and southeast Manitoba.
  The SPC has issued a slight risk for today across this region, with straight-line winds and marginally severe hail being the main threats given the LLJ east of the limited instability.  Stay tuned for updates!

Posted At: September 22, 2007 @ 4:06 PM

Posted By: Reed Timmer

With the onset of winter and the end of the fall storm chasing season, we have many exciting new plans for TornadoVideos.net to make it more of a community-involved site, and to increase the value of our website to the public.  Any suggestions on potential products we could implement in the future would be much appreciated.  Here are some of the features we have in the works:

Member-based chat feature:  This will happen soon!

Spotter training page:  Educate new storm chasers and weather enthusiasts on supercell storm structure, severe weather forecasting.

Weather education page:  Provide educational modules on all topics related to meteorology, including severe weather, tropical meteorology, climatology, and forecasting.   These could include video modules, pod-casts, etc.

Weekly photo/video submission page:  Have a photo-sharing page where contributors can share their weather photography and comment on others.

Live, high-quality streaming video:  We've been working on a way to implement broadcast-quality, live video streaming for awhile.  Our plan is to have this up and running by next season.

Storm store:  Web-based store with videos, photos, t-shirts, coffee mugs, etc for sale, as well as donations to natural disaster charity.
Professional video intros:  Here is a video clip, showing the temporary video intro we've created.  Our plan is to add intros to our video that our much more professional looking, and a bit more concise. 

I also want to test out Metacafe, a new video-submission site similar to Youtube, with the clips below.

Thanks in advance for your suggestions!



STORM CHASERS NEARLY HIT BY F4 TORNADO! - Celebrity bloopers here

Posted At: September 21, 2007 @ 11:20 AM

Posted By: Reed Timmer

The NWS in Grand Forks, ND has updated their stats on the August 26, 2007 tornado outbreak in ND/northwest MN, stating that at least 8 tornadoes occurred over this region!  More videos and photos will be added to the page below soon, but video of an INCREDIBLE 1/3 mile wide tornado from 15 miles W of Northwood was just added.  The link for the page dedicated to this event is below, along with the link to the video of the tornado. 

http://www.crh.noaa.gov/fgf/?n=northwood_tor_track

http://www.crh.noaa.gov/images/fgf/news/070826TORs/Aneta/RughLakeTOR_26Aug07_1.mpg

It appears that the tornado in the clip above was different from the Northwood tornado, and interestingly, had a SSW to NNE path despite a ESE storm motion.  The associated tornado cyclone must have been occluding rapidly to produce this path, and is consistent with its relatively short damage path.  A satellite image with the damage path is shown below, from the Grand Forks NWS site.  The Northwood EF4 tornado may have been produced by the storm immediately to the north of this one!  



Here is a radar image that was posted on the blog that night from around 7:30 pm CDT.  I believe the rapidly intensifying storm to the WSW of Grand Forks is the one responsible for the EF3 in the video above, and the storm immediately to its north, moving ESE, eventually produced the Northwood EF4.  The two other supercells to the north also produced tornadoes, although not as large in size.  These storms may have been north of the LLJ core, and may have had less low-level shear to work with, or it could have been due to higher LCLs (cloud bases), or they did produce large tornadoes that just weren't observed.

Every year, there is a prolific tornado-producing event that we seem to overlook and decided not to chase, either because of the long driving distance or the ingredients came together at the last minute and were not forecast well by the models.  This event was one such tornado outbreak that we didn't chase, but it was forecast well by the models and was quite obvious several tornadoes would occur!  I definitely regret not chasing this event...

Meanwhile, a strong trough and associated 40+ knot low-level jet will bring a severe weather chance for the northwest Great Lakes Region today, but the storms will be in terrain not very conducive for storm chasing, with dense forest and even mountains in the western Upper Peninsula of Michigan.  Here is the SPC tornado probability map for their Day 1 Outlook:
In other news, a subtropical depression has developed in the northeast Gulf of Mexico, and is forecast to become a tropical storm in the next 12 hours, before making landfall on the MS Coast on Saturday.  Tropical storm warnings have been issued for the western FL Panhandle westward to the eastern LA Coast.  Stay tuned for updates!  It's an incredible day to be obsessed with weather.

Posted At: September 20, 2007 @ 4:24 PM

Posted By: Reed Timmer

A tornado watch has been issued for parts of central MN mainly W to E along and immediately surrounding a retreating outflow boundary/warm front that has been solidified by elevated convection moving out of the area to the northeast.  Surface-based convection has initiated along this boundary in central MN, and several tornado warnings have been issued based on doppler radar.  Shown below is the watch graphic and MPX radar as of 4:30 pm CDT showing the high-precipitation (HP) supercell.
   
Shown below are the 2100 UTC RUC analysis maps for CAPE and 0-1 km helicity across the region of interest.  The warm front shows up clearly on the CAPE analysis below, stretching NW to SE across central/southern MN.  As can be seen from the surface wind field plotted on this analysis, winds are backed substantially along and to the north of the warm front, enhancing the low-level shear.  However, surface-based instability drops of dramatically north of the boundary as well, so any surface-base storms that develop along the boundary and cross to the north of it will likely become elevated and lose their tornado potential.  The enhanced low-level shear along and to the north of the warm front can be seen in the 0-1 SRH map below (values ~200 J/kg or greater are sufficient for significant tornadoes). 

Convection is also trying to develop further southwest in SW MN and SE SD, but it is unclear whether these towers will break the capping inversion.  Good luck to all the chasers in this area!  Stay tuned for updates.

Posted At: September 20, 2007 @ 10:05 AM

Posted By: Reed Timmer

Here is a video shot by locals in Cape Coral, FL of a water spout that developed over the Gulf of Mexico and came ashore, causing damage to residences and resorts.  An associated press article concerning this tornado is shown below.  Meanwhile, the SPC issued a slight risk for severe weather for today across parts of the Northern Plains...I'll be adding a blog update as this event unfolds.

September 17. 2007 12:56PM

Cape Coral tornado damages 150 homes, injures one

CAPE CORAL -- As many as 150 homes were damaged by a powerful tornado that swept off the Gulf of Mexico and plowed into this southwest Florida city, officials said Monday. Only one person had minor injuries from flying debris.

At least 12 families were displaced after the tornado tossed cars down a street and damaged buildings at about 6:30 p.m. Sunday.

Daniel Noah at the National Weather Service said the tornado started as a water spout over Fort Myers Beach and moved north into Cape Coral. He estimated the winds speeds were between 90 and 110 mph.

Cape Coral's chief inspector, Bill Selvia, told the News-Press of Fort Myers on Monday that the final damage estimate could be in the millions of dollars.

The twister ripped part of the roof off Jessica Gibson's apartment building.

"Water was pouring in through the windows, it soaked everything, everything will be ruined," said Gibson, one of the displaced residents.

At the Silver Sands Resort, the tornado toppled the 1,500-pound tiki bar, knocked over fencing and tore the roof off two units, owner Tom Groves said.

"It threw all the chairs into the pool — just made a general mess," Groves said.

About 3,500 Lee County Electric Cooperative customers lost power in the thunderstorms that spawned the tornado.

Posted At: September 19, 2007 @ 3:14 AM

Posted By: Reed Timmer

According to Dave Carlsen of Environment Canada, recently analyzed home video of the Elie, MB tornado on June 22, 2007 has resulted in an upgrade of the small, yet damaging tornado to F5 intensity -- a first for Canada.  According to the Winnipeg Sun and CBC News, the video of concern shows an "almost-intact house being thrown several hundred metres through the air", and a large van being lofted high into the air.  Here are some links to relevant news stories; the Winnipeg Sun is planning a more extensive article about this story tomorrow.

http://winnipegsun.com/News/Manitoba/2007/09/18/4506223.html

http://www.cbc.ca/canada/manitoba/story/2007/09/18/tornado.html

Contributing to the F5 rating was the very slow motion of the tornado, increasing the residence time of the winds over structures in its path.  The Elie tornado was on the ground for 30 minutes, but had a path length of only 5 km!  Thankfully, no one was killed or injured from this tornado, but 19 people were left homeless in Elie.  This tornado was 1 of 13 "confirmed" violent tornadoes in recorded history for Canada (pers. comm. Simon E.), which is likely far under-estimated, but still more than the 8 that is widely reported by Canadian Media. 

Shown below are some widely-viewed videos of the Elie tornado, mostly from local residents (Sorry to the regular visitors these videos have been posted so many times on previous blog entries!).  The second video below quite possibly could be the video that resulted in the rating upgrade.

Posted At: September 17, 2007 @ 10:42 PM

Posted By: Reed Timmer

Super-typhoon Wipha is closing in on northern Taiwan with maximum sustained winds of 135 knots gusting to 165 knots!  Wipha has been tracking consistently to the WNW and passed just to the south of Ishigaki Jima, where sustained winds of 64 kts with gusts to 88 kts were reported.  This storm is forecast to pass just to north of Taipei by 12z on Sept. 18 with 125 kt winds, and will make landfall in China south of Shanghai by 21z Sept. 19.  James Reynolds is heading to the city of Wenzhou, China (population ~ 5 million) for intercept.  Satellite imagery and the official Joint Typhoon Warning Center track map are displayed below.  Stay tuned for updates from James! 

Posted At: September 17, 2007 @ 12:40 AM

Posted By: Reed Timmer

A synthesis of recent (early September) satellite imagery from the Advanced Synthetic Aperture Radar (ASAR) instrument has revealed some very interesting information -- the ice cover in the Arctic is at its lowest area since satellite documentation began nearly 30 years ago!  In fact, the Northwest Passage (shown in the image below by the blue line), a once impassable sea route between Europe and Asia is now ice free and potentially passable.  The story can be found in its entirety using the link below, and the figure showing the ice cover during early September 2007 is shown below, with the dark gray color representing ice free regions and the green color representing ice.  

http://www.esa.int/esaEO/SEMYTC13J6F_planet_0.html

An update on the severe weather potential tomorrow (Monday) will be displayed on the blog tomorrow morning -- the 00z models tonight (Sunday) look very similar to this morning's runs (described in the previous entry). 

Posted At: September 16, 2007 @ 1:22 AM

Posted By: Reed Timmer

A broad trough with several embedded shortwaves will build over the Western U.S. by Monday, bringing a chance for severe weather and even tornadoes over northwest IA and southwest MN Monday afternoon/evening.  A 30+ knot low-level jet will develop from OK to MN in response to pressure falls over the northern Great Plains, and a pressure trough/front will move across the eastern Dakotas into a  moderately unstable airmass.  Deep-layer shear and instability will be more than sufficient for supercells over the region shaded in red below, and low-level shear could be favorable for tornadoes.  Selected forecasts from Saturday night's WRF run are displayed below:



 
The SPC has issued a slight risk in their Day 2 outlook for the above region, mentioning the potential for tornadic supercells south of the warm front if the cap can be broken.  Stay tuned for updates!

Posted At: September 14, 2007 @ 1:23 PM

Posted By: Reed Timmer

The GFS model has been consistently hinting at a Western U.S. trough developing during the middle to late part of next week.  This could be the start of the Central/Southern Plains fall severe weather season, but the most recent GFS run now forecasts a cut-off system over the Southwest Rockies.  Still though, this cut-off system will likely move eastward with time, bringing increased chances for chase-able setups!

Posted At: September 13, 2007 @ 1:28 AM

Posted By: Reed Timmer

About an hour ago, a special advisory was issued by the NHC upgrading Humberto to a hurricane, based on reconnaissance aircraft data.  A hurricane warning has also been issued for the northeast TX/southwest LA Coast, with maximum sustained winds estimated at 70 knots!  The center of Humberto can be seen clearly on Houston, TX radar, which shows a fairly compact but intense storm.  Shown above is a loop showing the landfall of Humberto.  Shown below is the special advisory issued by the NHC:

WTNT44 KNHC 130534

TCDAT4
HURRICANE HUMBERTO SPECIAL DISCUSSION NUMBER   4
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL092007
115 AM EDT THU SEP 13 2007

THIS SPECIAL ADVISORY IS BEING ISSUED TO UPGRADE HUMBERTO TO A
HURRICANE.  BOTH THE INITIAL AND 12-HOUR INTENSITY FORECAST HAVE
BEEN INCREASED...AND A HURRICANE WARNING HAS BEEN ISSUED.  THE
UPGRADE IS BASED ON DATA RECEIVED FROM AIR FORCE RECONNAISSANCE
AIRCRAFT AND NOAA NWS DOPPLER RADAR. 

THIS SPECIAL ADVISORY SUPERSEDES THE INTERMEDIATE ADVISORY...WHICH
WOULD HAVE BEEN ISSUED AT 0600 UTC. 

FORECAST POSITIONS AND MAX WINDS

INITIAL      13/0515Z 29.4N  94.4W    70 KT
 12HR VT     13/1200Z 30.1N  93.9W    55 KT...INLAND
 24HR VT     14/0000Z 31.6N  92.7W    30 KT...INLAND
 36HR VT     14/1200Z 32.5N  91.2W    25 KT...INLAND
 48HR VT     15/0000Z 32.5N  90.0W    20 KT...REMNANT LOW
 72HR VT     16/0000Z...DISSIPATED

$$
FORECASTER MAINELLI/AVILA

Here is a satellite image of Hurricane Humberto from peak intensity, at around 1:30 am CDT.  The Weather Channel reported frequent lightning with the eyewall of Humberto!  It is likely that if Humberto had more time over the warm Gulf of Mexico waters, it could have become a rather significant hurricane.

Posted At: September 12, 2007 @ 12:13 PM

Posted By: Reed Timmer

Tropical Storm Warnings are in effect from the extreme southwest Louisiana Coast to High Island, TX, for an expected tropical storm landfall very early Thursday morning.  The system is currently a tropical depression, with maximum sustained winds of 30 knots, but is expected to intensify into a weak tropical cyclone before landfall.  The NHC believes that TD-9 may already be of tropical storm status, but will know for sure when Reconnaissance Aircraft arrives in the next hour.  Shown below is the official NHC forecast track as of 10:00 CDT:
The satellite presentation looks like what you'd expect for a tropical depression/weak tropical storm, although the convection around the center is quite intense.  The NHC noted weak banding structure on Houston and Corpus Christi radar this morning in the NW and SE quadrants of the storm, indicating that the system was becoming better organized.  The main threats from this storm will be heavy rain (especially if the storm stalls out and is not "picked up" by the westerlies), gusty winds, choppy seas, and even tornadoes in the right-front quadrant near and after landfall.  Stay tuned for updates!

Posted At: September 11, 2007 @ 1:13 PM

Posted By: Reed Timmer

Joost.com is a new website specializing in high-quality internet television broadcast, and has just recently launched their beta version.  Partnering with Thomas Lucas Productions, TornadoVideos.net has provided tornado footage to a channel called SpaceRip, dedicated to topics in space, nature, and aventure.  The current programs featuring TornadoVideos.net footage are Twister Insanity HD and Twister Insanity: Amazing  Chases....each around 15 minutes in length with pure tornado intensity, featuring the May 4, 2007 Ellis Co, OK tornado and the June 23, 2007 Manitoba tornado, as well as highlights from our previous best tornado chases.  Once you download the Joost software, you can use the search tool to find these programs.  Access to the Beta version of Joost is invite only, so you can click on the link below to get an account, and download the software.

https://www.joost.com/presents/gigaom-newteevee/

Our hope is to keep this channel updated continuously throughout each storm season in near real-time, maintaining an internet-based storm chasing reality show.  We'll keep you updated on any new developments regarding this exciting opportunity.   Please let us know what you think!

**Shown below is from a screen capture..showing what the Joost player will look like when you get it working on your computer**
 

Posted At: September 9, 2007 @ 1:14 AM

Posted By: Reed Timmer

Tropical Storm Gabrielle appears to have intensified slightly over the last several hours, as upper-level shear has lessened and the storm remains over the warm waters of the Gulf Stream.  Maximum sustained winds are still estimated at 35 knots as of the 2:00 am EDT advisory, but Gabrielle will likely intensify before passing over the North Carolina Outer Banks early tomorrow afternoon.  The current NHC forecast indicates 45 knot sustained winds with Gabrielle at the time of landfall.  The IR loop as of 2:00 am EDT is displayed below:
The likely center of circulation and outer bands of Gabrielle are well-defined on Morehead City, NC radar, with occasional supercells developing within these bands and near the center.  Heavy rain, isolated tornadoes, and gusty winds will be the main threat as the tropical storm comes ashore, with a 2-3 foot storm surge causing minor beach erosion. 
As is normally the case with recurving tropical cyclones at this latitude, Gabrielle will make a quick transition to an extratropical cyclone as it merges with the jet stream and accelerates to the northeast along the Gulf Stream.  This storm will likely become an intense mid-latitude cyclone over the North Atlantic, and could cause heavy rain and strong winds several days from now somewhere in the UK.

Posted At: September 8, 2007 @ 6:03 AM

Posted By: Reed Timmer

A cold front that has stalled out over central OK, in combination with tropical moisture from the remnants of Hurricane Henrietta that made landfall over Baja Peninsula, Mexico last week, has resulted in flooding rains overnight in north-central Oklahoma.  Nearly 5 inches of rain has fallen in Major County, OK already, with another 1-2+ inches expected over the next few hours as storms continue to train over the same areas.  Shown below is the TLX radar as of 6:00 am CDT:

The Oklahoma Mesonet data below shows the rain that has fallen over central and northern Oklahoma as of 6:00 am CDT!

Accordingly, flood watches and warnings have been issued for much of Oklahoma, southern Missouri, and northwest Arkansas through today and tonight, where several more inches of rain could fall.  Keep in mind that many of the flood warnings in western and north-central OK are not displayed in the map below.  Stay tuned for more updates throughout the day on this potentially dangerous weather situation!

Posted At: September 7, 2007 @ 2:05 PM

Posted By: Reed Timmer

Click the link below for video of a Hurricane Hunter mission into the eye of Category 5 Hurricane Felix early in the morning of September 3.  The best part of the video is during the last few minutes, when still photos of the eye from the aircraft are displayed.  The eye was only 10 miles across at the time of this mission!  More information on this flight is provided at HurricaneHunters.com.

http://www.airshowbuzz.com/videos/view.php?v=9f061057

Posted At: September 6, 2007 @ 11:00 PM

Posted By: Reed Timmer

The severe storms that developed earlier today over the central Plains have congealed into a massive mesoscale convective system (MCS) which has strengthened rapidly over the last few hours at the nose of a 40-50 knot low-level jet.  Several severe thunderstorm and tornado warnings are in effect for this mass of convection in northeast KS, but strong winds and heavy rainfall should be the main threat.  A severe thunderstorm watch remains in effect for the area:
Here is the RUC analysis for 850 mb at 0300 UTC, showing the intense LLJ that has developed to the south and east of the MCS and cold front, which is surging south through Kansas at this time.  This same cold front will finally bring significant rain chances for the Southern Plains tomorrow! 

Posted At: September 6, 2007 @ 12:48 AM

Posted By: Reed Timmer

A strong positively-tilted trough and associated cold front will surge across the Central U.S. tomorrow, bringing the threat for severe thunderstorms from extreme northern KS northward through central NE, eastern SD, and western MN.  Based on the model forecasts Wednesday night, it appears that most of the storms will be linear in nature given the strong linear forcing along the fast-moving cold front, with the best low-level shear southeast of the storms.  If storms can remain discrete along the cold front, however, they will likely be supercellular -- but the tornado threat should be rather low given the limited low-level shear along the cold front.  Selected forecast fields from the 00z WRF model Tuesday night for 00z Wednesday evening are displayed below, followed by a brief synopsis.
 

 
By comparing the WRF forecast surface field/12 hr precip (upper two panels) with the 850 mb forecast (bottom left), it can be seen that the low-level jet will exist well southeast of the cold front and associated storms, with only around 15-20 knots along the front in NE and eastern SD.  The resulting limited low-level shear immediately along the cold front should limit the tornado potential there, and with the strong linear forcing along the front storms will have difficulty remaining discrete/supercellular.  Further north into central MN, the low-level shear immediately east of the cold front is a little more favorable for tornadoes, but still not impressive (not shown).  If a supercell can somehow develop or move into the intense LLJ in southeast NE, then the tornado potential will skyrocket.  The WRF model is hinting at initiation between 00z and 06z in southeast NE at the nose of the LLJ, and if these cells will be discrete and surface-based, then they will likely be tornadic -- although I doubt this can materialize.  If I were chasing tomorrow, I'd likely play central NE, and hope the LLJ verifies further west along the cold front, or hope for storms to remain discrete as they move into the LLJ after 00z.  Or central MN along the cold front could be interesting, especially if the LLJ can intensify after 00z.  Given all these uncertainties for tornadoes, we'll have to sit this one out since I'm trying to graduate while my hairline is still intact!  Although if anyone chases tomorrow and would like to contribute their pictures/video to the blog, please email me!  Stay tuned for updates.

Posted At: September 5, 2007 @ 1:32 AM

Posted By: Reed Timmer

This video was shot by a family in Chalmette, LA, showing how devastating a category 5 storm surge can be.  The water rose from ground level to the roof in only 3 minutes!  Sadly, everyone in this neighborhood lost their homes to the 20+ foot storm surge of Hurricane Katrina.

Similar, if not much worse conditions are likely being experienced in northeast Nicaragua and eastern Honduras after cat 5 Hurricane Felix made landfall last night.  To make the situation worse, 20+ inches of rain fell over the mountainous terrain of Nicaragua and Honduras as Felix weakened over land on Monday, creating devastating mud slides and flash floods.   Below is a link to an article with photos from ground zero:

http://afp.google.com/article/ALeqM5iIG4Rl9AaW-bYPhvI7U_3IcSTZKA

Posted At: September 4, 2007 @ 9:47 AM

Posted By: Reed Timmer

After completing an eyewall replacement cycle, Hurricane Felix strengthened rapidly to a category 5 storm just before landfall on the northeast Nicaragua Coast a few hours ago with sustained winds of 160 mph!  The eye was very small in diameter, and the cloud tops were very cold in the CDO, both consistent with a category 5 hurricane.  As of ~11:00 am EDT, Felix had weakened to category 3 status as it moved over land.  Up to 20 inches of rain is possible over the higher terrain of Nicaragua and Honduras today, causing dangerous mudslides and flash floods.  Thankfully though, Felix is a very small hurricane, with hurricane-force winds only extending ~45 miles from the center, so the impacts should not be as devastating as Hurricane Mitch a few years ago.

Posted At: September 3, 2007 @ 6:16 PM

Posted By: Reed Timmer

Hurricane Felix has weakened slightly today, likely due to eyewall replacement cycles and the entrainment of relatively dry air.   Still though, Felix remains a very dangerous category 4 hurricane with maximum sustained winds of 115 knots as it continues moving westward towards northeastern Nicaragua and eastern Honduras, where hurricane warnings are in effect.  As seen above, the cloud tops have cooled during recent frames of the IR loop, indicating that some strengthening is occurring.  Given the optimum timing of the eyewall replacement cycle with the usual nocturnal intensification, I would not be surprised if Felix strengthens substantially overnight before making landfall tomorrow morning.  Honduras and northern Nicaragua will likely see devastating impacts from this incredible hurricane, which attained category 5 status yesterday faster than any tropical cyclone on record in the Atlantic!  Stay tuned for further updates throughout the night.

Posted At: September 2, 2007 @ 7:10 PM

Posted By: Reed Timmer

"THE HURRICANE HUNTER AIRCRAFT HAD TO ABORT THE MISSION BECAUSE OF 
EXTREME TURBULENCE AND GRAUPEL!!"

000
WTNT31 KNHC 022359
TCPAT1
BULLETIN
HURRICANE FELIX SPECIAL ADVISORY NUMBER  10
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL062007
800 PM EDT SUN SEP 02 2007

...FELIX NOW A CATEGORY FIVE HURRICANE...

REPORTS FROM A NOAA HURRICANE HUNTER AIRCRAFT INDICATE THAT FELIX
CONTINUES TO RAPIDLY STRENGTHEN.

FELIX IS MOVING TOWARD THE WEST-NORTHWEST NEAR 18 MPH...30 KM/HR...
AND THIS GENERAL MOTION IS EXPECTED TO CONTINUE FOR THE NEXT 24
HOURS.

MAXIMUM SUSTAINED WINDS ARE NEAR 165 MPH...270 KM/HR...WITH HIGHER
GUSTS.  FELIX IS A CATEGORY FIVE HURRICANE ON THE SAFFIR-SIMPSON
SCALE.  SOME FLUCTUATIONS IN INTENSITY ARE TO BE EXPECTED OVER THE 
NEXT 24 HOURS.

HURRICANE FORCE WINDS EXTEND OUTWARD UP TO 25 MILES...35 KM...FROM
THE CENTER...AND TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO 115
MILES...185 KM.

THE LATEST MINIMUM CENTRAL PRESSURE ESTIMATED FROM RECONNAISSANCE
DATA IS 934 MB...27.58 INCHES.

Posted At: September 2, 2007 @ 12:26 PM

Posted By: Reed Timmer

As of noon EDT, Hurricane Felix was exhibiting an incredible satellite presentation, with a well-defined eye and very cold cloud tops through the entire central dense overcast.  The Curacao radar has been showing a very nice eye and eyewall, and has recently been showing a slight wobble to the north.  Check out the radar loop below, beginning at 1500 UTC:

From the visible image below, the eye of Hurricane Felix appears almost entirely cloud-free, with a perfectly symmetric CDO and a nice outflow pattern developing.  Felix is definitely intensifying rapidly, and is taking full advantage of the extremely warm SSTs and weak upper-level shear.  The recent NHC update has maximum sustained winds of 100 mph with Felix, which is definitely underestimating its current intensity.  Based on the satellite presentation, Felix is likely a strong cat 3-cat 4 storm.  The forecast track is unchanged from last night, with a landfall predicted near northern Belize during the day on Wednesday.   Thereafter, Felix will weaken substantially over the Yucatan, and could re-emerge over the southern Gulf of Mexico as a threat to the Texas Coastline.  Stay tuned for updates!

Posted At: September 2, 2007 @ 1:56 AM

Posted By: Reed Timmer

NOAA Hurricane Hunter aircraft has indicated the minimum central pressure of Hurricane Felix has fallen slightly to 987 mb as of the 2:00 am advisory, with conservatively estimated surface winds of 80 mph and a 30 nm wide eye.  Felix continues to look impressive on infra-red, with a faint eye appearing occasionally at the center of the most intense convection.  Here is the satellite image as of 2:00 am EDT:
Felix is forecast to continue moving westward, passing just north of the islands of Aruba, Bonaire, and Curacao in the next 12-24 hours or so, where tropical storm warnings and hurricane watches are in effect.  The GFDL model is predicting the furthest south track -- due west to the northern coast of Honduras by Tuesday, and dissipating over the mountains of Guatemala.   Most of the model forecast tracks are clustered further north, with a projected landfall in northern Belize.  These models show Felix weakening temporarily over the Yucatan, but re-emerging over the southwest Gulf of Mexico as a category 1 hurricane.  The 11:00 pm NHC forecast follows the northern cluster, as shown below:

Given ocean temperatures of nearly 30C in the western Caribbean Sea, and very weak upper-level shear, Hurricane Felix is expected to intensify into a major hurricane before landfall late Wednesday in northern Belize or the southern Yucatan.  While we are considering an intercept of this hurricane, it would have to be an insane storm for us to head down there...since I have my general exam in 2 weeks!  But a last second trip can never be ruled out.  By this time next year we're going to be chasing every single storm on the planet!  AAAAAAAAAAAAAAAAAAAAAA

Stay tuned for frequent updates!

Posted At: September 1, 2007 @ 5:12 PM

Posted By: Reed Timmer

Finally...here is the highlight video for the June 23, 2007 Manitoba chase, showing the entire life-cycle of the tornadic supercell from initiation in southeast Saskatchewan.   Note how the base gradually lowered and increased in size as the supercell moved southeast off the Moose Mountains, SK into the extreme instability.