TornadoVideos.net

Posted At: August 30, 2007 @ 2:40 AM

Posted By: Reed Timmer

Since there is very little in the way of exciting weather anywhere right now, I thought I'd post an incredible video of the Elie, Manitoba tornado from June 22, 2007 on Youtube.  For those of you that don't know, this tornado was rated an F-4, and happened the day before the tornado we intercepted near Pipestone, MB.

Posted At: August 29, 2007 @ 12:08 AM

Posted By: Reed Timmer

Here is the new TornadoVideos.net logo.  Please let me know what you think.  We'll be adding it to the site, pictures, and video soon...and of course the side of our chase vehicle!  They were created as vector graphics, so the conversion to jpeg distorted the detail a little.  The goal was to keep it very simple and recognizable.


Also, here are some links to an analysis of the Michigan tornado event on August 24, 2007, which included an EF-3 in Howell as well as a few EF-2 tornadoes.  It was a very interesting tornado event since most of the supercells were embedded in a line.  I'm surprised there were such clear pictures of the tornado!

http://www.crh.noaa.gov/crnews/display_story.php?wfo=grr&storyid=9889&source=0

http://www.crh.noaa.gov/crnews/display_story.php?wfo=grr&storyid=9875&source=0

http://www.crh.noaa.gov/crnews/display_story.php?wfo=dtx&storyid=9886&source=0

Posted At: August 28, 2007 @ 2:37 AM

Posted By: Reed Timmer

A lunar eclipse  will be visible tonight across the entire U.S.,  with the central U.S. experiencing the greatest shadow (thanks to Dick M for making us aware of this!).  While I'm not familiar at all with the science of eclipses at all, it appears from the diagram below (from Spaceweather.com),  that the eclipse will be visible from the eastern U.S.  between 9:52 and 11:22 UTC; from the central U.S.  between  11:22 UTC and 12:23 UTC; and along the West Coast shortly thereafter.  Dick McGowan will be photographing the entire evolution of the eclipse, and will be submitting his photos to Spaceweather.com.  Good luck to anyone photographing this!
Here is a time sequence of photographs of a lunar eclipse in October 2004 in Northern California, as seen on Wikipedia.  Clearly, lunar eclipses pose some incredible photo opportunities!

Posted At: August 27, 2007 @ 4:10 AM

Posted By: Reed Timmer

Seven tornadoes were reported over central and eastern North Dakota yesterday, with substantial damage reported in the town of Northwood, ND, in Grand Forks County at around 8:50 pm CDT.  Sadly, there has been 1 fatality reported with the Northwood tornado with multiple mobile homes destroyed.  About 30 minutes earlier, a photogenic stovepipe tornado touched down in Logan County, ND, southeast of Bismark, just north of the town of Napolean.  Shown below is a picture of the tornado taken by local resident, Spike Foster.
Shown below is a radar image of the Logan County storm at the approximate time of the Napolean tornado pictured above.  When the radar loop is played, the textbook hook echo can be seen moving rapidly eastward relative to the storm as the circulation cycled.  This was a classic example of the diurnal low-level jet enhancing low-level shear after 00z sufficiently for large tornadoes to occur.  By evening, mixing in the lower atmosphere had ceased, dewpoints rose 5+ deg F, and the LLJ increased to 40+ knots across all of eastern ND and northwest MN.  This set the stage for a mini-tornado outbreak across the Northern Plains.  More severe weather is expected today across central MN...Stay tuned for updates!

Posted At: August 26, 2007 @ 7:28 PM

Posted By: Reed Timmer

As of 7:30 pm CDT, two incredible tornadic supercells were ongoing in northeast ND, with funnel clouds reported and tornado warnings in effect!  With the low-level jet strengthening rapidly, these cells will have the chance of producing tornadoes over the next hour or two as they move towards extreme northwest MN.  Both cells have been exhibiting strong couplets on storm relative velocity, and textbook hook echoes!  The border crossing at Pembina, ND is directly in the path of the northern supercell, and both cells have turned to the right and are moving to the ESE.

Posted At: August 26, 2007 @ 5:12 PM

Posted By: Reed Timmer

A tornado watch has been issued for eastern ND and extreme northwest MN for this afternoon/evening until 11:00 pm CDT ahead of a strong cold front surging southeastward towards the Red River Valley.  Towering cumulus can be seen on satellite along the front from southeast Manitoba southwestward into central ND.  These towers could develop into supercells over the next few hours.
The 2100 UTC RUC analysis shows CAPE values of 4000+ J/kg from southwest Manitoba into eastern North Dakota, with 0-1 km EHI values of 3+.  Mixing in the lower atmosphere has been strong so far today, reducing the low-level shear values and increasing LCLs.  However, after around 7:00 pm CDT, as the lower atmosphere decouples, a strong low-level jet will develop and dewpoints will increase to around 70F.  If storms initiate, and remain discrete into the evening, then isolated tornadoes will be possible!  Stay tuned for updates.
 

Posted At: August 26, 2007 @ 1:31 PM

Posted By: Reed Timmer

A strong cold front will move rapidly across southern Manitoba and northeast ND this afternoon, and into extreme southwest Ontario and northwest MN by evening, providing the potential focus for severe thunderstorm development after 6:00 pm CDT.  The low-level jet (bottom right panel) will be very strong ahead of the front, with 850 mb flow forecast to exceed 50 knots after 00z.  Deep-layer shear will also be sufficient for supercells.  One negative factor for surface-based storms is the presence of a very strong cap (hatched area in the upper right panel), which will prevent the extreme instability from being utilized most, if not all, of the day.  However, given strong convergence along the cold front, initiation still seems likely especially across southeast MB and southwest Ontario...Although there is some uncertainty as to whether this will be surface based.  Stay tuned for updates!

 

  Meanwhile, the Storm Prediction Center has issued a VERY positive Day 2 outlook for supercells and tornadoes across western MN and extreme eastern SD.  I haven't had a chance to look at the models in detail, but a strong low-level jet and extreme instability will be in place across this region tomorrow! 

Posted At: August 25, 2007 @ 12:53 PM

Posted By: Reed Timmer

Here is a picture of an incredible shelf cloud in the Kansas City area yesterday, taken by Dick McGowan of TornadoLive.com!

Posted At: August 24, 2007 @ 3:46 PM

Posted By: Reed Timmer

A broken line of intense thunderstorms have developed from Michigan southwestward to Oklahoma, with even a few tornado warnings -- one in central Michigan and another in Missouri.  However, the tornado threat does not appear to be high even with the tornado-warned cells.  Hundreds of severe thunderstorm warnings are in effect across the central and eastern U.S., with the strongest cells in the southern Great Lakes Region as expected.  Shown below is a graphic of the severe warnings in effect (blue dots = severe thunderstorm, red dots = tornado warnings).

If anyone captures any good pictures of today's severe weather, and would allow me to post them on the blog for everyone to see, please email them to reed@tornadovideos.net along with the desired copyright watermark.  Stay tuned for updates!

Posted At: August 24, 2007 @ 12:28 PM

Posted By: Reed Timmer

Here are some SPECTACULAR lightning shots from yesterday's storms in the Chicago area, shot by Chris Bray.  If anyone captures any good photos of today's storms, it would be great if I could post them on the blog for everyone to see!




A weak cold front will continue moving slowly southward across the central U.S. today, initiating severe storms from the southern Great Lakes Region southwestward to the TX Panhandle.  CAPE values are forecast to be highest across northern Indiana and northwest Ohio -- ~4000 J/kg (left panel below), with the best wind shear there as well.  Thus, this region will have the best chance for severe weather today.  Still though, all models are forecasting widespread convective development along the entire cold front later this afternoon! (right panel below).
  Accordingly, the SPC has issued a moderate risk for severe storms across central IL, northern IN, northwestern OH, and extreme southern MI, for the likelihood of bow-echo structures and even brief supercells.  Like yesterday, strong straight-line winds will be the main threat.
Shown below is the Storm Reports map for yesterday, August 23.  Nearly 200 severe wind reports were confirmed yesterday, and even a few tornado reports in the Chicago area and central Michigan.  The storm in Michigan looked like a textbook mini-supercell at the time of the tornado, white the Chicago tornado was likely associated with the "book end vortex" of a bow-echo.  Extensive damage was reported in Chicago, with widespread power outages, flooding, downed trees, and even minor structural damage.  Today will be more of the same, but further south by about 50-100 miles.  Stay tuned for updates!

Posted At: August 23, 2007 @ 11:13 AM

Posted By: Reed Timmer

Here is the highlight video from our Hurricane Dean experience in Runaway Bay, Jamaica.  As mentioned, we should have been on the extreme southern peninsula of the island to receive the brunt of the hurricane...but we are still relatively new to chasing hurricanes!  Definitely a learning experience every time.  After landing in Montego Bay, it appeared that Dean was taking a more northerly track, and would move right across the center of the island -- giving the north shore the most intense conditions.  However, the storm wobbled south less than 18 hours before landfall.  In hindsight, we should have waited several more hours at the airport for a more certain forecast track.

Concurrently, typhoon chaser James Reynolds was documenting Typhoon Sepat in Taiwan.  Check out his INCREDIBLE video of ~140 mph winds in the intense eye wall, as well as catastrophic flooding:

Posted At: August 21, 2007 @ 9:00 AM

Posted By: JY

Here is a visible satellite of Cat 3 Dean moving over land:


-----------------------------------------------------------------------------------------------------
Last night:
Dean was officially upgraded to the first Category Five hurricane of the 2007 Hurricane Season


As of the 11pm update with the NHC, Dean has winds of 160 mph, with higher gusts. The winds could actually be higher. We will find out in a couple of hours with the next Hurricane Hunter flight.
This year the Hurricane Hunters have a new instrument called a Stepped Frequency Microwave Radiometer, also known as SMURF. This allows an instantaneous measurement of surface wind speed by measuring sea foam! The radiometer is attached on the wing of the WC-130J's and also measures rainfall rates.
Unlike a dropsonde (the instrument that is manually dropped in the storm to get a vertical profile measurement of the atmosphere) the radiometer stays in place through the flight.

Reed will be back online tomorrow with more Dean updates, included footage from Jamaica!

Posted At: August 19, 2007 @ 11:23 PM

Posted By: JY

Dean is growing after brushing the south side of Jamaica. The storm produced a wind gust in Kingston of 138 mph! Dean is headed toward a favorable environment for intensification! Hurricanes love the Northwest Caribbean! 


Here is a wider view of the Atlantic/Caribbean that shows the location of Dean relative to the Yucatan. Also notice the tropical wave in the Central Atlantic. 


Back in the U.S. there have been MAJOR flooding issues in Minnesota and in Oklahoma. Here is a loop from Saturday night's Erin remnants intensification: 


Reed and Joel will be touring Jamaica tomorrow. Hopefully their internet will be up and running.

Posted At: August 18, 2007 @ 1:23 AM

Posted By: Reed Timmer

Joel and I just booked a ticket to Jamaica, arriving at around noon tomorrow (Saturday), a little more than 24 hours before the projected landfall.  Our plan is to find a safe, sturdy shelter on the south side of the island, capable of withstanding category 4+ winds.  Overnight, Hurricane Dean has intensified into a dangerous category 4 hurricane, with maximum sustained winds of 145 mph.  Shown below is the IR image as of 1:30 am CDT:

Posted At: August 17, 2007 @ 10:46 AM

Posted By: Reed Timmer

Hurricane Dean rapidly intensified overnight and this morning, with a closed eye-wall indicated by the air force hurricane hunter aircraft, and a minimum central pressure of 964 mb!  An enormous outflow pattern and symmetric banding characterize the hurricane this morning,  with estimated maximum sustained winds of 105 knots.   The forecast track is exactly the same as yesterday, with the hurricane crossing the northern Yucatan Peninsula Tuesday morning as a category 4-5 storm!  Here is a visible satellite image of Dean as of 11:00 am EDT, showing a textbook eye developing:
Hurricane Dean likely caused some minor structural damage to the central Lesser Antilles last night; the Martinique Weather Service reported sustained winds of 66 knots with gusts to 90 knots!  However, the worst is still come, as Dean will become a dangerous hurricane over the extremely warm waters of the Caribbean.  Our plan is still book a ticket to Cancun tomorrow, for a flight early Sunday!  Stay tuned for updates!

Posted At: August 16, 2007 @ 1:21 PM

Posted By: Reed Timmer

Hurricane Dean continues to strengthen, with maximum sustained winds currently estimated at 80 knots (conservatively).  A nice central dense overcast is very apparent on IR satellite imagery (see below), with a cloud-filled eye at the center of the most intense convection.   The outflow pattern is VERY impressive, indicating the likelihood of rapid strengthening. 

Most models except for the GFDL predict the hurricane to move over the northern Yucatan Peninsula Monday night/Tuesday morning, very likely as a major hurricane.  The official NHC intensity forecast has maximum sustained winds with Dean at 120 knots by 96 hours!  We are closely monitoring this situation, and are tentatively planning to leave for Cancun by Sunday for intercept!  Stay tuned for updates!

Posted At: August 15, 2007 @ 1:36 PM

Posted By: Reed Timmer

Tropical Depression 5 has been upgraded to Tropical Storm Erin earlier this morning, and is expected to strengthen slightly before making landfall between Brownsville and Corpus Christi, TX in ~48 hours.  The convection around the center of Erin has been extensive, with a very prominent upper outflow pattern.  The main threats with TS Erin will be heavy rain, gusts to 70 mph, and isolated tornadoes in the right-front quadrant in South Texas.  Here is the IR image of Erin as of 1;30 pm CDT.
Shown below is the 3-day forecast track from the National Hurricane Center.  Note the slow re-curve to the north at the end of the forecast period.  This morning's model runs show the cyclone continuing northward across the Southern Plains into the weekend, which could bring tornado chances to TX, OK, and KS if sufficient destabilization can occur!
We are continuing to monitor Tropical Storm Dean as the storm continues moving westward towards the Lesser Antilles.  If the storm follows the forecast track of the NHC, we will be faced with three options: 1.  Intercepting the hurricane in Jamaica, or 2. Waiting for a possible U.S./Mexico landfall, or 3. both.  The storm is still far from the Lesser Antilles, and could very likely move over mountainous Hispaniola, Puerto Rico, and Cuba, which would destroy the storm.  Stay tuned for updates!

Posted At: August 14, 2007 @ 1:51 PM

Posted By: Reed Timmer

This morning, Tropical Depression 4 was upgraded to Tropical Storm Dean, with estimated maximum sustained winds of 40 mph and a minimum pressure of 1004 mb.  As of early afternoon, there was substantial convection near the center of the cyclone, but easterly shear was still preventing explosive strengthening.  The visible image as of around 2:30 pm EDT is shown below:
Dean is forecast to continue a W to WNW movement towards the Lesser Antilles, with gradual strengthening expected as weaker upper-level shear is encountered.  Current models predict that Dean will be nearing major hurricane status with winds exceeding 100 knots as it approaches the Lesser Antilles in 5 days.  Thereafter, the hurricane will either curve slightly to the northwest and make landfall along the U.S. East Coast, or maintain a WNW heading through the Caribbean.  The mountains of Hispaniola and Puerto Rico could also weaken the storm substantially if the hurricane maintains a more southerly course.  Shown below is the official track forecast for Dean issued this morning by the National Hurricane Center:
Meanwhile, Hurricane Flossie continues to be a very strong hurricane as it moves just to the south of Hawaii with maximum sustained winds of 95 knots.  However, huge waves and isolated showers from the outer bands should be the main impacts on southern sections of the Hawaiian Islands.  Here is a visible image of Flossie as of around 3:00 pm EDT:
We are planning to intercept Hurricane Dean, either in the Caribbean before it has the opportunity to interact with land, or somewhere along the U.S. East Coast or Gulf of Mexico Coast.  However, there is still substantial uncertainty in the forecast track of Dean.  Stay tuned for updates!!

Posted At: August 14, 2007 @ 12:00 AM

Posted By: Reed Timmer

Here are pictures of a water spout just south of Pensacola, FL taken by Matt West this weekend.   Water spouts are usually not associated with supercells, but most often occur with even weak thunderstorms or rain showers, as existing rotation in the atmosphere is stretched into a visible vortex.



The pictures below were taken on a research cruise in the Gulf of Mexico by Craig Newton, and are possibly the same water spout.  Note the picture below of the marine radar image from the time of the water spout.  The radar signature looks very similar to the hook echo of a supercell, except on a much smaller scale.

Posted At: August 13, 2007 @ 5:23 PM

Posted By: Reed Timmer

Towering cumulus have persisted for the last few hours along the warm front in central MN, where surface-based CAPE values have been analyzed in the 6000-7000 J/kg range.   However, the cap remains very strong across the region, with the 18z sounding in Minneapolis indicating a 102F convective temperature.  A subtle upper disturbance will be moving across the region, so there still is a very small possibility for initiation.  The Storm Prediction Center has issued the following MD for a tornado watch to be issued shortly:

Based on recent trends in satellite imagery, as well as analysis of the 18z soundings, surface-based initiation seems highly unlikely this evening.  Surface convergence is very weak across the warm front, and 700 mb temperatures are rising above 15C.  However, if storms initiate, they will rapidly become supercellular and will have a high potential of producing tornadoes, given the highly sheared and unstable warm sector.  Here is the satellite image from just before 5:30 pm CDT:

Posted At: August 13, 2007 @ 11:59 AM

Posted By: Reed Timmer

After analyzing the 4km WRF precip forecast last night, we decided that the chase event today in Minnesota had far too many negative factors to make the 15 hour drive to our target area.  Specifically, here are the limiting factors for tornadoes we considered:

1.  WRF and GFS did not forecast precip until after 00z, and the 4 km WRF indicated a large MCS would form at around 8:00 pm.  This indicates that the convection would be forced by the strengthening LLJ and would likely be elevated.

2.  Convective temperatures on most soundings were >100F, and to attain this convective temperature the T/dewpoint spreads would be very high, and conducive to quick transitions to outflow dominance.

3.  700 mb trough moves east and north of the instability axis by peak heating.

4.  In recent forecasts, the warm front has become oriented more north-south, and thus it would be more difficult for a storm to root on the boundary. 

Here are some selected RUC forecast panels confirming the above:
 

  Despite the negative factors listed above, if a storm can become surface-based in the warm sector along or the west and south of the warm front, then the shear and instability are more than sufficient for tornadoes.  There are also storms approaching MN from eastern ND, and these will have a chance to become surface-based and supercellular as they move southeast towards the better instability and weaker cap.  Stay tuned for updates!

Posted At: August 12, 2007 @ 11:47 AM

Posted By: Reed Timmer

A potent shortwave trough embedded in northwesterly flow atop a huge summer anticyclone will bring significant severe weather chances from Fargo, ND ESE to Minneapolis, MN tomorrow (Monday).  Shown below are some selected forecasts from the Sunday morning WRF:
 

  As clearly evident in the CAPE forecast (upper right panel), a strong warm front will extend northwest to southeast across central MN by late afternoon tomorrow, with 4000+ J/kg CAPE along this boundary.  A strong low-level jet (upper left panel) will be induced by the pressure falls associated with this shortwave, giving rise to very high low-level shear values (see helicity in lower right panel) along the warm front in central/northern MN.  Despite a strong cap, the models are consistent in firing convection in this highly unstable and sheared environment by late afternoon/evening.  Given the potential of this setup, we will likely be heading north tonight to position ourselves in northwest MN by initiation.  Stay tuned for updates!

Posted At: August 11, 2007 @ 5:52 PM

Posted By: Reed Timmer

The 21z RUC model has been consistently forecasting convective initiation west of Minneapolis between 6:00 and 7:00 pm.  Tower cumulus in southwest and central MN have been persisting for the last few hours, and could develop into supercells as a subtle shortwave moves through the area.  The low-level wind shear is maximized in southeast MN and western WI, so the storms would have to move into this area to have a chance at producing a significant tornado.

Posted At: August 11, 2007 @ 12:24 PM

Posted By: Reed Timmer

Supercells and isolated tornadoes are likely this afternoon/evening for the Upper Mississippi River Valley, as a strong upper trough moves through Southern Canada.  All models are forecasting a 30+ knot low-level jet to develop by 7:00 pm CDT, with strong westerly flow aloft and extreme instability.  The best 0-1 km helicity is forecast to be in northwest Wisconsin, and extreme southeast Minnesota, collocated with the nose of the low-level jet.  Here are some selected forecasts from the 12z WRF:
 

 

Posted At: August 10, 2007 @ 7:43 PM

Posted By: Reed Timmer

Despite the strong cap and high temperature/dewpoint spreads, supercells have initiated just east of the surface low in north-central SD, and tornado warnings have been issued for these storms.  Until now, the cloud bases have likely been too high for tornadoes, however, anvil shadows appear to be working their magic, and the dewpoints are on the rise rapidly into the upper 60s.  As the lower atmosphere is cooling slightly, winds are beginning to back to a southeasterly direction in the inflow region of the storms. The surface map below, as of 7:50 pm CDT shows the higher dewpoints and backed winds.  In other words, the tornado potential is increasing BIG TIME!   If these storms can remain discrete, large tornadoes are possible given the very high low-level shear values.  HUGE MISTAKE by tornadovideos.net not to be there!!!!!  AAAAAAAAAAAAAAAAAA;lfkajs;dlkfj     We must have lost the edge

Posted At: August 10, 2007 @ 2:13 PM

Posted By: Reed Timmer

Based on the 18z RUC analysis (shown below), the cap is beginning to weaken slightly in north-central South Dakota, as can be seen in the white region of the CAPE/CIN analysis below (blue coloring represents substantial CIN).  As expected, dewpoints have mixed out slightly into the mid 60s over this region, resulting in CAPE values of around 3000 J/kg.  This mixing out of the dewpoints has also resulted in ~30 degree temperature/dewpoint spreads over this region, which is a huge negative factor for tornadoes today, since the storms will have high bases and a tendency to become outflow dominant.  Any storms that initiate in this region must move eastward into a more favorable thermodynamic environment to have a good chance of producing tornadoes, but the cap is much stronger further east.   Right now, it appears that our decision of not chasing this event was the correct move, but several more hours of good heating still remain!

Posted At: August 10, 2007 @ 1:57 AM

Posted By: Reed Timmer

All the necessary ingredients for tornadoes will be in place for the eastern Dakotas tomorrow (Friday), except for one very important thing:  a surface based storm (at least based on Thursday evening's model forecasts).   CAPE values of 4000+ J/kg, a low-level jet of 35+ knots, and backed surface winds along a warm front will exist in this region, but convective inhibition (cap) of 100+ J/kg is forecast across the entire warm sector by the WRF model...which will be an unbreakable capping inversion if this model verifies.  Here are some selected forecasts from the 00z WRF run Thursday evening:
 

 
As seen in the upper-right panel, there is not a single pixel with 0 CIN in the entire warm sector south of the Canadian Border!  This is not only due to seasonably warm temperatures between 850 and 700 mb, but also because the WRF fires several nocturnal mesoscale convective systems from North Dakota SSW to eastern CO (bottom left panel), increasing further the relative temperature at cap level.   However, if the MCSs tonight are less intense than forecast by the WRF, or if the cap is weaker than forecast, then there will be significant potential for tornadic supercells, given the incredible low-level shear (bottom right panel) and immense instability (upper left panel) over the eastern Dakotas.  Because of this insanely strong cap and the likelihood of a clear-sky bust, we have decided not to chase this event..but will be monitoring the new model forecasts and observations closely for any potential of surface-based storm development.  The tornado probabilities map for the Day 1 outlook issued by the Storm Prediction Center at 1:00 am Friday is shown below ...which are a substantial over-estimate if the WRF model cap forecast verifies.  Stay tuned for continuous updates on this potentially active severe weather event.

 

Posted At: August 9, 2007 @ 1:41 PM

Posted By: Reed Timmer

A cold front is currently moving southeastward across central Saskatchewan as of early afternoon, with deep moisture being advected northward ahead of the boundary.  The RUC model is forecasting decent deep-layer shear for southeast SK late this afternoon and evening, but marginal low-level shear.  Still though, with 700 mb flow of 30+ knots, there is a chance for supercells and even a very small possibility of a tornado if storms can remain discrete into the evening!

Moosomin - Grenfell - Kipling - Wawota
12:28 PM CST Thursday 9 August 2007
Severe thunderstorm watch for
Moosomin - Grenfell - Kipling - Wawota issued

Severe thunderstorms are expected to develop over southeastern Saskatchewan this afternoon and evening.

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 trough of low pressure tracking across southeastern Saskatchewan is expected to trigger isolated thunderstorm this afternoon. These storms will have the potential of being severe giving large hail, strong wind gusts, heavy downpours and a slight chance of a tornado.

Posted At: August 9, 2007 @ 9:19 AM

Posted By: Reed Timmer

Several severe thunderstorm warnings have been issued for parts of southeast PA this morning as an intense bow-echo continues to race southeastward towards Philadelphia.  Winds in excess of 60 mph and large hail can be expected with this MCS, and new intense convection is expected to develop on the south side of the line.  A severe thunderstorm watch has been issued for this area, given the weakly capped, moderately unstable airmass downstream.

Posted At: August 8, 2007 @ 5:07 PM

Posted By: Reed Timmer

The website will be down for about 30 mins starting at 5:30 central time (6:30 eastern) for a server upgrade.  Sorry for the inconvenience.  It should be back up by 6:00 central if not sooner.

Thanks!

Jason

Posted At: August 8, 2007 @ 4:52 PM

Posted By: Reed Timmer

Northeast MO Supercell:
A supercell has developed along an outflow boundary in northeast MO, and two tornado warnings have been issued for this storm as of 4:43 pm CDT.  While the storm is relatively far from any radar site, a strong mesocyclone is still very apparent on storm-relative velocity (below right).
 
Northern SD/Southern ND Supercells:
Several supercells with strong mesocyclones have developed in northern SD and southern ND, producing reports of funnel clouds and even brief tornadoes.  The temperature/dewpoint spreads are quite large in this region, so the storms are likely very high based, and thus large tornadoes are very unlikely with these storms.  However, the structure is probably amazing.

Posted At: August 8, 2007 @ 1:27 PM

Posted By: Reed Timmer

Here are some incredible video clips of historical tornadoes, with the first clip featuring an F5 tornado in 1956!  The Andover, KS footage at the bottom has to be some of the most incredible tornado video of all time.

1956 Grand Rapids, MI F5 tornado:

http://youtube.com/watch?v=XnIQmI1BVIA

1979 Wichita Falls, TX F4 tornado:

http://youtube.com/watch?v=tr2nw9qXuG0
Great Bend, KS tornado - year unknown:

http://youtube.com/watch?v=LFxvmbbgg8M

March 13, 1990 Hesston, KS F5 tornado:

http://youtube.com/watch?v=vgbzKF_pSXo

May 6, 1975 Omaha, NE F4 tornado:

http://youtube.com/watch?v=8L2GN4dZ7_w

April 26, 1991 Andover, KS F5 tornado at McConnell Air Force Base:

Posted At: August 7, 2007 @ 1:19 PM

Posted By: Reed Timmer

Since I'm on the road, I haven't had a chance to check out the models in detail, but it was very apparent that wind shear will be lacking over the entire U.S. today.   Still though,  instability will be sufficient over a large part of the central and eastern U.S. for isolated severe storms.  The Day 1 Outlook of the SPC issued at 1630 UTC is displayed above.  It's definitely time for hurricane season.

Posted At: August 6, 2007 @ 11:03 AM

Posted By: Reed Timmer

Extreme instability and marginal low-level and deep-layer shear will be present across eastern SD/NE and western IA today along and south of a quasi-stationary warm front, providing the potential for supercells over this region by late afternoon and evening.  Here are some selected forecasts from the 12z RUC model:
 

  Fig. 1. 12z RUC forecasts for 7:00 pm CDT this evening.

As seen in the lower left panel, surface-based CAPE values from extreme southeast SD, eastern NE, and along the frontal zone in Iowa will be in the 4000-6000 (purple shading) range by 7:00 pm CDT, with intense convective development expected by then as well (lower left panel).  Low-level shear will be a major limiting factor for tornadoes across this region, with <15 knot flow forecast at 850 mb across the entire frontal zone as well as eastern NE.  However, there should be substantial backing of the surface flow along the front, which will enhance the low-level shear from extreme southeast SD, ESE across northern IA...increasing slightly the tornado threat.  The Storm Prediction Center has issued a slight risk for severe storms across this region, with a 5% tornado area.  We have decided not to chase this event, given the absence of good low-level shear over the area as depicted by last night's and this morning's model runs.

 

Posted At: August 5, 2007 @ 12:08 PM

Posted By: Reed Timmer

A subtle shortwave trough embedded in strong zonal flow across the Northern U.S. will move across the Northern Plains region tomorrow, inducing a strong low-level jet in a highly unstable environment across eastern SD extending eastward along the MN/IA border.  Accordingly, the Storm Prediction Center has issued a slight risk in their Day 2 Outlook:

The WRF and GFS models are in disagreement on the strength of this subtle shortwave.  The WRF shows a stronger low-level jet (large area of 30+ knots at 850 mb), and a stronger shortwave trough resulting in a more widespread severe weather event.  The GFS forecasts these features to be much less prominent, and thus the severe threat would be much lower.  

Both models are forecasting a warm front to be in place from the surface low in southeast SD, eastward across the MN/IA border, with 3000+ J/kg CAPE along this front.  Surface winds will be backed along this front, enhancing further the low-level wind shear, and the chances for tornadoes.  If the WRF model verifies, the TornadoVideos.net team will likely be storm chasing this event!  I'll be posting more detailed updates as the model picture becomes clearer this eveing!

Posted At: August 4, 2007 @ 7:05 PM

Posted By: Reed Timmer

Unfortunately, we have been facing significant problems with "spammers" and others with negative intentions on our new live chat feature over the last few days, so we have been forced to temporarily disable our live chat community until we implement a membership system next week.  The membership system is the only viable option to maintain a professional community for weather enthusiasts, meteorologists, and storm chasers.   The membership system will also be in line with our plans of implementing a forum in the very near future, as well as many other networking features that will enable members to share their weather photos, experiences, and knowledge with the world!

Members will have the option of posting on the blog, participating in the live chat and forum, and other advantages.  This system will act to filter out spammers, those looking for a platform to spread misinformation and threats, and anyone else with negative intentions for our community of weather enthusiasts.    

Stay tuned for the membership access this week, as well as the many additional exciting features we plan to add in the near future!

We apologize for the inconvenience!

Posted At: August 4, 2007 @ 6:51 PM

Posted By: Reed Timmer

Convective initiation has finally occurred in the vicinity of the warm front in northwest Iowa, with other storms exploding in a more modestly sheared environment in central NE.  A severe thunderstorm watch has been issued for this area, but with 0-1 km EHI values of 6+ along the warm front in central IA (see second image below), these cells will have a chance to produce tornadoes if they can remain discrete!

Shown below is the RUC analysis for 0-1 km EHI for 6:00 pm CDT for the Missouri River Valley and surrounding area.  A NW to SE oriented warm front extends diagonally across IA, with 0-1 km EHI values of 6+ along and immediately southwest of the warm front in the warm sector.  If the storms in northwest IA can remain discrete and move into this highly sheared environment, they will have the potential to produce large tornadoes.  Negative factors for tornadoes will be the tendency for a linear MCS to form i this area, and warm mid- to upper-level temperatures have resulted in relatively low instability in the warm sector.  Stay tuned for updates on this potentially volatile situation!


It has also been an active day north of the border as well in eastern SK/extreme western MB.  A line of storms and even brief supercells developed in extreme eastern SK, and produced small tornadoes just southwest of the town of La Pas at around 6:15 CDT (see warning statement below).  Additional storms have been trying to develop in extreme southeast SK and southwest MB as well, but have not yet been able to sustain themselves in the strong cap.  Low-level and deep-layer shear over this region is supportive of supercells and even brief tornadoes!





The Pas, cormorant, Westray and Wanless
6:17 PM CDT Saturday 4 August 2007
Tornado warning for
The Pas, cormorant, Westray and Wanless issued

Tornado reported to 911 west of The Pas at 6:15 PM. Tornado was dropping to the ground and lifting repeatedly. This storm will continue to move eastward at 40 km/h.



A strong low pressure system over central Saskatchewan will track towards west central Manitoba this evening. A trough extends southward from this low. A moist and humid airmass combined heating will provide the fuel for strong thunderstorms to develop near the low and along the trough this evening. At 6:30 PM satpix show strong storms moving through the areas.

At approximately 6:15 PM a tornado was reported southwest of The Pas.

Posted At: August 3, 2007 @ 12:40 PM

Posted By: Reed Timmer

Check out this highlight video produced by Dick MacGowan of TornadoLive.com.  This is a sign of things to come in the very near future -- a joint charity project between TornadoVideos.net and TornadoLive.com to help victims of damaging tornadoes as well as keep residents of tornado alley prepared for future tornado disasters.

Posted At: August 3, 2007 @ 10:36 AM

Posted By: Reed Timmer

A subtle shortwave trough embedded in modest WNW flow aloft will move across the Northern U.S. Rockies and through the Northern High Plains today, inducing a strong low-level jet across western Nebraska and the western Dakotas.  Given warm temperatures aloft, as is typical with mid-summer in the U.S., CAPE values will not be extreme, and will peak in the 2000-3000 J/kg range across the slight risk area above.  While a quick transition to a mesoscale convective system is anticipated by the models, there will be a small window this evening for supercells capable of producing large hail and strong winds, and even a small tornado threat if the storms can remain discrete and move into the strong LLJ in the western Dakotas.  Meanwhile, further north where the main jet stream resides, supercells will once again be possible across the Foothills and High Plains of Alberta, where instability and bulk shear values will be supportive of rotating storms.
Fig. 2.  WRF forecast 500 mb flow for 6:00 pm MDT this evening.
Fig. 3.  WRF forecast CAPE for 6:00 pm MDT this evening.

Posted At: August 2, 2007 @ 10:00 AM

Posted By: Reed Timmer

These pictures were taken by typhoon chaser James Reynolds from Nobeoka, Japan as Typhoon Usagi made landfall.  Despite a weakening trend as the typhoon was coming ashore, James sustained a direct hit by the eye.  We'll be keeping you updated on James' chases throughout the remainder of the typhoon season...Last year he even documented a super-typhoon from Vietnam!  Here is a link to those pictures:
http://tornadovideos.decadehost.com/index.cfm/2006/10/2/the-aftermath-of-typhoon-xangsane-in-vietnam

Posted At: August 1, 2007 @ 9:49 AM

Posted By: Reed Timmer

Typhoon Usagi, which is currently producing maximum sustained winds of 115 knots, is forecast to make landfall over southern Japan in ~24 hours by the Joint Typhoon Warning Center.  Given rather cool sea surface temperatures, Usagi is forecast to weaken slightly before making landfall, with sustained winds around 90-100 knots.  Our friend James Reynolds is currently in Japan to document landfall, and will hopefully provide updates soon!

WDPN31 PGTW 011500
MSGID/GENADMIN/NAVPACMETOCCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 05W WARNING NR17//
RMKS/
1. FOR METEOROLOGISTS.
2. 12 HOUR SUMMARY AND ANALYSIS.
   A. TYPHOON (TY) 05W (USAGI) HAS MAINTAINED INTENSITY AT 115 KTS, 
WITH DUAL OUTFLOW CHANNELS COMPENSATING FOR DECREASING OCEAN HEAT
CONTENT. THE SYSTEM CONTINUES TO TRACK NORTHWESTWARD ON THE
SOUTHWESTERN PERIPHERY OF THE SUBTROPICAL RIDGE (STR) ANCHORED EAST
OF JAPAN. ANALYSIS OF WATER VAPOR IMAGERY INDICATES THE UPPER LEVEL
TROUGH WHICH WAS OVER THE KANTO PLAIN YESTERDAY HAS PULLED OUT.
HOWEVER, SYNOPTIC ANALYSIS AT 500 MB SHOWS A BREAK REMAINS BETWEEN
THE STR EAST OF JAPAN AND A SECOND RIDGE WEST OF OKINAWA. 
   B. TYPHOON (TY) 05W (USAGI) IS LOCATED APPROXIMATELY 385 NM
EAST-NORTHEAST OF NAHA, OKINAWA. THE SYSTEM HAS TRACKED NORTHWESTWARD
AT 14 KNOTS OVER THE PAST 06 HOURS. THE CURRENT INTENSITY OF 115 KTS
IS BASED ON DVORAK ESTIMATES OF 6.0/6.5 BY PGTW AND 6.0/6.0 BY RJTD.
3. FORECAST REASONING.   
   A. THE FORECAST REASONING FOR TY 05W HAS NOT CHANGED.
   B. TY 05W WILL CONTINUE TO TRACK NORTHWEST UNDER THE INFLUENCE
OF THE STR TO ITS EAST, MAKING LANDFALL OVER KYUSHU NEAR TAU 24. THE 
AVAILABLE OBJECTIVE AIDS HAVE COLLECTIVELY SHIFTED THE TRACK SLIGHTLY 
BACK TO THE EAST OVER THE PAST TWO WARNING CYCLES, AS THE MODELS ARE 
INDICATING THE STR WILL NOT BUILD AS FAR WEST AS IN PREVIOUS RUNS. 
THE FUTURE STRENGTH OF THE STR MAY BE HINDERED BY A SHORTWAVE TROUGH 
CURRENTLY OVER THE KOREAN PENINSULA. THE STORM WILL MAINTAIN ITS  
INTENSITY IN THE FIRST 12 HOURS OF THE FORECAST AS THE A LOW-LEVEL
ANTICYCLONE TO THE WEST NEAR TAIWAN BEGINS TO WEAKEN THE EQUATORWARD
OUTFLOW CHANNEL. LANDFALL IS FORECAST TO OCCUR NEAR TAU 24 IN EASTERN
KYUSHU, RESULTING IN SIGNIFICANT WEAKENING THROUGH TAU 36. TY 05W IS
FORECAST TO CROSS THE STR AXIS NEAR TAU 36 AND BEGIN ACCELERATING
UNDER THE INFLUENCE OF THE MIDLATITUDE BAROCLINIC ZONE NEAR 40N. THE
AVAILABLE DYNAMIC AIDS ARE IN GOOD AGREEMENT WITH THIS SCENARIO, WITH
EGRR REPRESENTING THE OUTLIER INITIATING THE POLEWARD TURN EARLY AND 
MOVING THE SYSTEM FAST. THIS FORECAST IS BASED ON THE CONSENSUS OF 
THE DYNAMIC AIDS THROUGH TAU 48. 

Posted At: August 1, 2007 @ 9:37 AM

Posted By: Reed Timmer

A cold front will move slowly southward across the Northern Plains and Upper Mississippi River Valley  today, providing the necessary surface convergence for thunderstorm initiation beginning early this afternoon.  Instability is adequate for severe storms, but wind shear will be a huge limiting factor for supercells today.  Here is the SPC Day1 Convective Outlook for today:

Posted At: July 31, 2007 @ 7:05 PM

Posted By: Reed Timmer

Three supercells have developed today west and north of Yorkton, and have already produced hail up to golf ball size according to the warning statements.  The northern most cell split on radar shortly before 7:00 pm CDT, and has hints of an RFD structure on reflectivity.  Despite modest low-level shear, there is some tornado potential with these storms as they track just to the north of Yorkton, SK.  Stay tuned for updates!