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Posted At: November 29, 2007 @ 10:46 AM

Posted By: Reed Timmer

As a strong upper trough moves across the Rockies by Saturday, a deep surface low will intensify over the Central Plains before moving rapidly northeastward across the Great Lakes Region by Sunday.  Given a strong anticyclone (~1030-1046 mb) in its wake, strong winds and a well-developed deformation zone to the northwest of the surface low track will result in blizzard conditions from NE, SD, Northwest IA, southern MN, and northern WI Saturday-Sunday.  An intense lake effect event will then develop as the cold air behind the system filters across the relatively warm waters of the Great Lakes by late in the weekend through early next week.   Since this potentially major winter weather event is still a few days out, the forecast track of the surface low still could change significantly.  Right now, it looks like the heaviest snow will fall over the above region, and the recent model runs have been relatively consistent with this forecast.  Shown below is the 60 hr total precip valid next Monday morning, with the dark blue coloring representing > 0.50" liquid equivalent precip, and the purple representing > 1.50", equating to well over a foot of snowfall.  Stay tuned for updates!  If this system appears strong enough, we may be heading north to document the extreme winter conditions!

Posted At: November 27, 2007 @ 2:18 PM

Posted By: Reed Timmer

Lake effect snow warnings have been issued over parts of Northern Lower Michigan, as intense northwesterly flow lake effect bands have developed in the wake of a strong cold front that moved across the Great Lakes earlier today.  Shown below is a graphical display of the warnings and advisories in place for this event:

During cold northwesterly flow events, Northern Lower Michigan often receives the brunt of the snowfall since the cold air "picks up" moisture from both Lake Superior and Lake Michigan, resulting in especially intense snowbands over Northern Lower.  As seen in the composite reflectivity loop below from this afternoon, a single intense snowband stretches from central Lake Superior, across the Upper Peninsula, and across Lake Michigan into the Northern Lower Peninsula!  Given the increased fetch over the relatively warm waters of both lakes, any locations under this snow band in the Northern Lower Peninsula will see especially intense snowfall rates, with up to a foot or more of snow likely by tomorrow morning! 

Posted At: November 26, 2007 @ 10:44 AM

Posted By: Reed Timmer

Here is a summary of the SW Texas Winter Storm, with the snowfall data and pictures obtained from the Midland NWS website.  As can be seen in the snowfall graphic, measurable snow was reported as far south as the Rio Grande River! -- Although I bet there were some higher amounts in the mountains of northern Mexico as well.  Interestingly, these type of events are most common during El Nino years, when an abnormally strong subtropical jet stream transports huge amounts of Pacific moisture into the region.  However, this event occurred during a rapidly strengthening La Nina event! 

Posted At: November 25, 2007 @ 10:48 AM

Posted By: Reed Timmer

As a surface low pressure center slowly intensifies along the Louisiana Gulf Coast this afternoon, a warm front will drift northward from the Gulf of Mexico, providing surface based instability for the already-established band of convection moving eastward across the Central Gulf Coast.  Any storms that can root along the warm front today will have a chance to produce brief tornadoes given the backed winds and enhanced helicities along the boundary.  The SPC has issued an MD for the area, as shown below:

The RUC cape analysis shows the position of the warm front well as of 1900 UTC, with 2000+ J/kg values in the warm sector over the Gulf of Mexico.  Any cells that can become surface based along or to the south of the warm front will quickly become supercells, and may even produce tornadoes as the cross the front.  Any supercells that do form will likely be of the HP variety, given the embedded nature of the storms, and thus any tornadoes will likely be rain-wrapped.

Posted At: November 24, 2007 @ 8:54 PM

Posted By: Reed Timmer

The intense snow band over SW Texas continues to intensify and expand this evening, as strong low-level warm advection intensifies ahead of the  trough over the Southern Rockies/Mexican Plateau.  The SPC has issued a Mesoscale Discussion for the area, with the mention of 1-2" per hour snowfall rates within the band over  Pecos, Crane, and Upton Counties!

Posted At: November 24, 2007 @ 5:22 PM

Posted By: Reed Timmer

Two interesting winter storms, based on very different meteorological processes, highlighted the weather today in northern Lower Michigan and southwest Texas, respectively.  The former was a unique lake effect snow event over a very localized area of extreme northern MI near the Straits of Mackinac, caused by cold southwesterly flow ahead of a subtle shortwave trough.  A persistent band of very heavy snow pounded rural areas of northern Emmet County, including Mackinaw City.  8-12 inches of snow fell in localized areas where the band remained the longest.  A radar loop from earlier this afternoon shows this incredible, yet localized event:


Meanwhile, a much more widespread, synoptic-scale storm system has been impacting Southwest Texas today with very heavy snow, especially along the I-20 corridor west of Abilene.  The heavy snow is expected to continue through Sunday morning over this region, with 8-12 inches of snow likely in localized areas of the Hill Country, Pecos Valley, and the Guadalupe Mountains near El Paso.  Below is the watch/warning summary map from the Storm Prediction Center, showing the lake effect snow warning for Emmet County, Michigan, and the Snow Advisories and Heavy Snow Warnings in Southwest Texas.


The Special Weather Statement discussing the heavy snow situation in Texas can be viewed using the following link:

http://kamala.cod.edu/tx/latest.wwus84.KMAF.html

Here is a radar loop from this afternoon-early evening from Southwest Texas, showing the precipitation shield with this early season winter storm.  If any visitors to the blog are from this region, we'd greatly appreciate any pictures of the snowfall! 

Posted At: November 23, 2007 @ 2:24 AM

Posted By: Reed Timmer

Here is video from the lake effect snow event downwind of Lake Michigan from Thanksgiving Day.  When we left Grand Rapids (~30 miles inland), it appeared that the massive lake effect snow band would move well inland near the Holland, MI area, and a lake effect snow advisory was issued for most of southwest Lower Michigan.  However, the band remained largely offshore due to the development of a land breeze (surface winds shifted towards the thermal low pressure over the warm lake waters), and we only experienced light snow showers along the shoreline.   Here is a radar loop from about 3:30 pm  to 5:30 pm EST while we were intercepting the snowband:

Posted At: November 21, 2007 @ 11:11 AM

Posted By: Reed Timmer

A snowstorm will be likely from the northern MS River Valley through the Great Lakes Region this evening through Thanksgiving Day, as a low pressure center gradually strengthens along a strong baroclinic zone stretching across the central U.S.  3-6 inches of snow will be common, especially across southern WI, southern and central MI, and southeast Ontario by Thursday afternoon.  The national radar loop from Wednesday afternoon is shown below, with the deformation zone (wrap-around) precip clearly evident across Iowa.


Loops of WRF forecast MSLP and surface temperature from Wednesday afternoon through Thursday morning are provided below, with the surface baroclinic  zone clearly evident from Michigan southwest to Oklahoma.  Cyclogenesis is currently underway across the Southern Plains, with a slowly strengthening low pressure system moving from Northeast OK into MO at this time.  As an upper-level trough impinges on the Plains, this low-pressure system will intensify and move northeastward towards the Ohio Valley by tonight.  As the cold front continues to move southward, the rain currently over the Great Lakes Region will change over to snow by this evening.  Given slantwise convective instability in place, there will be substantial mesoscale banding within the deformation zone precipitation, thus some locations will receive heavy snow tonight across southern WI, central MI, and southeast Ontario. 


Based on the WRF forecast precip for Thursday night, a broad area of 3-6 inches will fall across most of the central and northern Great Lakes Region, with the higher amounts falling where mesoscale bands can remain over the same areas.  I'm currently located in Grand Rapids, MI, where a snow advisory is in effect tonight.  I'll be documenting this event from start to finish, and will post video updates as the heavy snow commences.  Stay tuned for updates!

Posted At: November 19, 2007 @ 12:28 PM

Posted By: Reed Timmer

The first significant cold-snap of the winter season is expected to invade the entire U.S. this week, just in time for Thanksgiving and major holiday traveling.  Previous model runs have also been hinting at a major snowstorm for the central U.S., but this morning's model runs have backed off that solution, but are still indicating the potential for a Nor'easter impacting New England by late week.  The GFS forecast MSLP for the evening of Thanksgiving shows the massive Arctic air mass in place, with the developing cyclone in the Canadian Maritimes.  Shortly after this time period, this low is expected to "bomb out" just off the coast of Newfoundland, bringing heavy snow and strong winds to Canada and possibly New England.  I'm still holding out hope of a snowstorm for here in the central U.S. with the strong baroclinic zone draped from the Great Lakes southwest to the Southern Plains by Midweek -- hopefully we can get a low pressure system to develop along the temperature gradient and move northeast towards the Ohio Valley before the energy is transferred to the East Coast system.  If this scenario occurs, then I'll be at ground zero here in Michigan!  Stay tuned for updates.

Posted At: November 17, 2007 @ 12:42 PM

Posted By: Reed Timmer

Here are some INCREDIBLE lightning shots from Mike O'Neill of Darwin, Australia...You can find more of his work at his website, StormscapesDarwin.com.  The Tropics of Northern Australia probably have some of the best lightning displays in the world during the rainy season(s), as the Inter-Tropical Convergence Zone sags south to through the area.  Australia also averages around two category 5 tropical cyclones per year!  Enjoy the pictures!

Posted At: November 16, 2007 @ 12:07 PM

Posted By: Reed Timmer

Check out this video of a water spout just off the coast of Oran, Algeria.  Toufik Tidjane shot this video on October 30, 2007.  It's difficult to tell if it's a supercell tornado or a non-supercell water spout.  Any thoughts?

Posted At: November 15, 2007 @ 10:52 AM

Posted By: Reed Timmer

Tropical Cyclone Sidr has maintained its intensity over the last 24 hours, with maximum sustained winds currently estimated at 130 knots with gusts to 160 knots as of 12z Thursday.  The storm is expected to make landfall over the next few hours over Southwest Bangladesh, and the impacts will be catastrophic.  A storm surge of 20+ feet can be expected just to the east of the center at landfall, especially along the numerous river mouths that feed into the Bay of Bengal, which will leave very few structures left standing anywhere in the vicinity of the coast.  This is a very bad situation for Bangladesh, and will likely go down as one of the most devastating natural disasters in the country's history.

The updated forecast track map from the Joint Typhoon Warning Center is shown below, which is a worst-case scenario for Bangladesh as most of the major river mouths will be located just to the east of the center at landfall.  Thus, strong, persistent southerly flow will "pile-up" the water in these inlets, and the swampy low-lands will be covered in 20+ feet of water.  Thankfully, evacuations have been underway in this region for the past 24-48 hours, with residents near the coast being moved well inland as quickly and efficiently as possible.  Stay tuned for updates on this dangerous situation.  Here are some links to news stories about Sidr:

http://news.xinhuanet.com/english/2007-11/15/content_7083396.htm 

http://www.thedailygreen.com/environmental-news/blogs/hurricanes-storms/cyclone-sidr-47111211

http://www.cnn.com/2007/WORLD/asiapcf/11/14/bangladesh.cyclone.ap/index.html

http://www.msnbc.msn.com/id/12784349/

Posted At: November 14, 2007 @ 10:44 AM

Posted By: Reed Timmer

Tropical Cyclone Sidr, with maximum sustained winds currently estimated at 130 knots with gusts to 160 knots, is heading straight for the populated and storm surge-prone Southeast India/western Bangladesh Coast, including the city of Calcutta, India.   The satellite image below from the Joint Typhoon Warning Center shows the textbook tropical cyclone in the center of the Bay of Bengal, where water temperatures are some of the warmest in the world!


Wave heights are estimated to be around 10 m (33 ft) in the vicinity of the eye, setting the stage for a potentially catastrophic storm surge at landfall in about 36 hours, especially immediately east of the eye.  Compounding the severity of the situation, the mouths of the Ganges and Padma Rivers are located in this region, which will likely experience a 20 foot wall of water if located immediately east of the eye, as 100+ knot southerlies will "pile-up" the water within these inlets.   Shown below is the official track map of the Joint Typhoon Warning Center, which shows the storm making landfall shortly before 00z on Nov 16.  Stay tuned for updates on this dangerous situation.

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

Posted By: Reed Timmer

High wind warnings have been issued by EC for southeast Alberta and most of southern Saskatchewan, with winds forecasting to decrease by evening.  If anyone has any pictures or video of this incredible event, please email them to me so I can post them on the blog! 

Posted At: November 11, 2007 @ 2:25 PM

Posted By: Reed Timmer

Summary:
With 850 total severe wind, hail, and tornado reports, April 2 was the most active severe weather day during the 2006 season.  The most significant tornadoes occurred over Northeast Arkansas, Southeast Missouri, and Western Tennessee, with a single long-track supercell producing two F3 tornadoes that severely damaged the communities of Marmaduke, AR; Caruthersville, MO; and Newbern, TN.  66 tornadoes were produced over 7 states, but most of these were weak and brief in nature in eastern IA or associated with the linear convective system that evening in IL.  Sadly, 29 fatalities occurred from this outbreak, with most associated with the long-track tornadic supercell that developed in Northeast AR and tracked into western TN.

Shown below is a loop of the national radar mosaic with severe weather watches overlaid from 18z to just after 00z on April 2, 2006.  As can be seen in the loop, severe thunderstorms developed very early in the day in southeast IA and central MO in a very highly sheared environment with marginal instability.  Much of this convection was linear in nature, with embedded mini-supercells.  As mentioned above, several weak, brief tornadoes were produced in southeast IA just east of the surface with these storms.  Later in the day, strong supercell thunderstorms developed in southeast MO and northeast AR along the cold front in an environment that was also highly sheared, but also had extreme instability.  Surprisingly, none of the watches issued by the SPC were of the PDS variety.



Weather Analysis Maps:           
RUC analysis maps for 2300 UTC April 2, 2006 for 500 mb, 850 mb, and the surface are displayed below, which is around the time of the significant tornadoes in the central MS River Valley.  At first glance, the optimal forecast target for tornadoes south be in southeast IA and northeast MO just east of the surface low along the warm front, where surface winds would be extreme backed and the nose of the LLJ would exist.  Here, you would expect a NNE moving supercell to experience favorable storm-relative low-level shear with easterly winds at the surface, but as can be seen in the 850 mb map (upper right), the LLJ was likely too veered to generate a textbook hodograph for significant tornadoes...this could have been the reason why most of the tornadoes were weak and brief in nature (even though the instability was low, there was zero CIN and low LCLs in this region).  I'd like to see a more southerly if not SSE-ly LLJ in this region, which was not the case.  Most storm chasers on this day selected the northern mode on this day, and missed the significant tornadoes further south.  If we were chasing, we may have done the same!  However learning from events such as this are what prevent future busts.


As is typical with massive severe weather outbreaks, they are usually "bi-modal" in nature, which means that the severe weather reports are often focused in two main areas: one to the north in the vicinity of or just to the east of the surface low, and further south where instability is maximized but wind shear is still sufficient for tornadoes.  The southern mode of this event was obviously over Northeast AR, Southeast MO, and western TN, but there are several reasons why this area might be overlooked at first glance for tornadoes.  First, the cold frontal boundary is oriented more southeast to northeast further south, which might make it difficult for storms to move off the boundary and remain discrete with an advancing cold front.  However, it can clearly be seen from the 500 mb map above that upper-level winds are just north of due-westerly over this region, so supercell storm motions should be easterly if not ESE-ly for a right-mover.  Thus, any supercells that develop along the cold front in this region should easily move off the front, preventing any undercutting action or rapid transitions to a linear convective modes.  One might also think that the LLJ is too veered in this region, with WSW-ly 850 mb flow at 40+ knots.  However, this favors the development of strong tornadoes with an ESE-ly or even southeasterly moving supercell.  Still though, hodographs must be diligently analyzed to see if ample storm-relative low-level shear can be attained.  Another positive aspect of the southern mode is the much deeper moisture and high instability, which is usually the case. 


One key development as late afternoon progressed into evening over the central MS River Valley was the backing of the surface winds over the southern mode region.  Earlier in the day, surface winds were predominantly out of the southwest if not WSW just east of the cold front, likely due to strong mixing of the westerly momentum air down to the surface with afternoon heating.  These veered surface winds initially limited the low-level shear and the tornado potential.  Correspondingly, the supercells over this region were initially non-tornadic and rather high-based, but as the anvil shadows decreased surface heating and mixing, and as peak heating passed, the surface winds backed to a more SSW-ly direction in the storm environment, which created plenty of low-level shear for strong tornadoes.

Reports and Damage Surveys:
Ignoring the tornado reports in central IL that were associated with bow echos and embedded supercells in a linear convective system, the bi-model structure of this outbreak can be seen clearly in the tornado reports.  The distinct west-to-east lines of several tornado reports in northeast AR eastward clearly show that there were two long-track, prolific tornado producing supercells there.



Shown below is a damage survey map produced by the Memphis NWS office for the April 2 supercells in their CWA.  The northern tracks were the most damaging tornadoes that passed through the communities of Marmaduke, AR; Caruthersville, MO in the Bootheel; and Newburn TN.  Photos of this tornado can be found at the following website:

http://www.srh.noaa.gov/meg/events/April2006/index.php





Radar Loops:
Shown below are radar loops depicting the evolution of the Marmaduke - Caruthersville - Newburn supercell. 




Any comments or discussions about this incredible severe weather outbreak are much encouraged!  The plan during the "off-season" during periods of boring weather is to post more unique case studies on the blog so that we can learn from these events and improve our knowledge as storm chasers and weather enthusiasts.  I hope you enjoyed the case study!

Associated Youtube Videos:

 
  

Posted At: November 10, 2007 @ 12:35 PM

Posted By: Reed Timmer

I'm sure many of you have seen this video...but I thought I'd post it for those who haven't.  I believe this tornado occurred on April 2, 2006, a day that we definitely should have been chasing but I was out of town and couldn't chase. 

Our plan for the blog during periods of uneventful weather is to post  blog entries for "events remembered"...where model data, forecast products, reports, and video will be shown for historical severe weather outbreak days.  It will not only help us relive previous events, but will also help those learn and discuss forecasting topics and chase strategies.

Posted At: November 8, 2007 @ 8:43 PM

Posted By: Reed Timmer

A strong, vertically-stacked low pressure system is drifting southward across western Scandinavia, with 50-70 mph northerly winds to the west of the cyclone across the entire North Sea.   These persistent northerlies are "piling-up" water along the western and southern boundaries of the North Sea, resulting in a storm surge of historic proportions along the eastern UK and Northwest European Coastlines. 

Holland will experience the brunt of the storm surge, with the highest values above sea level recorded since 1953.  According to Cors, a native of Holland the most recent data is showing a surge of 310 cm above sea level at New Amsterdam.  As conditions continue to worsen, a levee breach is unlikely, but not out of the question.  Check out the URL below for the recent storm surge data from Holland:

http://www.svsd.nl/index.cfm?page=waterstandgrafieken.denhelder&load=denhelder.H10

Here is a story from CNN focusing on the storm surge in southeast England:

http://www.cnn.com/video/#/video/weather/2007/11/08/connery.uk.flood.warning.itn?iref=videosearch
Thanks to Cors for keeping us continually updated on this dangerous situation.

Posted At: November 7, 2007 @ 6:54 PM

Posted By: Reed Timmer

The final episode of "Storm Chasers" will air tonight on Discovery Channel at 9:00 pm Central.  Click the link below for a description of the episode.  Since the tornado event dates seem to be scattered throughout the entire series, with no apparent chronological order, it's difficult to speculate which event will be featured in this episode.  The description states they intercepted a tornado near Woodward that developed earlier than expected...I'm guessing this is the May 6, 2007 event, where an HP tornadic supercell developed near Woodward and produced a low-contrast tornado just north of the KS/OK border.  Feel free to post your opinions on the show here!

http://dsc.discovery.com/tv-schedules/series.html?paid=1.14593.25317.16420.1

Posted At: November 7, 2007 @ 12:57 AM

Posted By: Reed Timmer

Heavy lake effect snow showers continue to the lee of Lakes Superior, Ontario, and Erie tonight, with over a foot of wet snow reported in parts of the Upper Peninsula of Michigan over the last 24-36 hours.  6-12 inches of snow has also fallen over the higher elevations of western NY, with the Tug Hill Plateau likely to receive the heaviest amounts.  Shown below are some radar loops from the U.P. of Michigan and western NY respectively:



Early in the winter season when the lake waters are still very warm, CAPE values of 1000+ J/kg are often achieved over the Great Lakes when Arctic air-masses move in.  Thus, thunder and lightning are quite common with the more intense lake effect showers.  Our plan later this winter is to document some intense lake effect snow bands downwind of Lakes Erie and Ontario, where snowfall rates can exceed 5 inches per hour!

Posted At: November 5, 2007 @ 12:30 PM

Posted By: Reed Timmer

A strong trough centered over the Great Lakes Region and an associated cold front moving across the central U.S. will provide the possibility for severe weather this afternoon over western TN and KY.  As expected for this time of year, instability will be lacking over the area, with CAPEs mainly below 1000 J/kg at peak heating.  Low-level shear will be favorable for tornadoes, but storms will likely have problems remaining discrete along the cold frontal boundary.  The result is the smallest Slight Risk area of the year.  Stay tuned for updates!

Posted At: November 4, 2007 @ 12:50 AM

Posted By: Reed Timmer

A strong extra-tropical cyclone, that was once Hurricane Noel only a few days ago, is pounding New England and the Canadian Maritimes with strong winds gusting over 50 mph, heavy rain, and even heavy snow in northwestern Maine and southeast Quebec.  The minimum surface pressure of the cyclone was 975 mb as of 0600 UTC, which is very low for a mid-latitude cyclone.  Shown below is a regional radar loop from 2330 UTC to 0500 UTC, with blue representing snow and pink representing rain/snow mix.


The surface map from this region as of 0600 UTC shows maximum wind gusts in the mid 40s mph mainly along the coastal areas, with heavy snow falling in parts of Quebec just north of Maine.  The higher elevations of northwestern ME are likely experiencing very heavy, wet snow and gusting winds tonight, with power outages a certainty. 

Posted At: November 2, 2007 @ 12:55 PM

Posted By: Reed Timmer

The low-lying Mexican state of Tabasco, which lies on the Gulf of Mexico Coast to the west of the Yucatan Peninsula, is currently being slammed by catastrophic floods caused by very heavy rains last week.  70% of the state, and 80% of the capital city, Villahermo, are under water as rivers in the region have flooded their banks, resulting in one of the worst natural disasters in history for Mexico.  Here is video from Reuters:

Posted At: November 1, 2007 @ 1:00 AM

Posted By: Reed Timmer

The 3rd Episode of "Storm Chasers", a documentary featuring the Tornado Intercept Vehicle (TIV), will air tonight at 9:00 pm Central on the Discovery Channel, followed by a second documentary about the science of storm chasing.  Please post your opinions here!  Here is the description of the 3rd Episode:

Storm Chasers
Episode 3
TV-PG

Five weeks into their storm chasing season, IMAX filmmaker Sean Casey and meteorologist Josh Wurman are under the gun to intercept a tornado. Conflict between Josh and Sean reach new heights, and Sean begins to trust his instincts over Josh's science.

Click below for a schedule and description of the shows:

http://dsc.discovery.com/tv-schedules/series.html?paid=1.14593.25317.16420.1