Ramblings of a Graduate Student

Deviating from the cold theme of the past two days (mainly because I just got back from a walk and am freezing…), today’s map deals with severe thunderstorms and tornadoes.

Every year the National Weather Service’s (NWS) Storm Prediction Center (SPC) issues approximately 850 severe thunderstorm and tornado watches combined.  Greg Carbin, the Warning Coordination Meteorologist (WCM) at the SPC, put together a graphic that contains the number of watches issued per county during 2009 (valid through October).

A couple of things stand out about the geographic distribution of this year’s convective watches.

1. Central Oklahoma had the most watches (~35) of anywhere in the United States.
2. There are few watches issued west of the Continental Divide.
3. East of the Continental Divide, only four areas did not record a single convective watch: far western Texas (El Paso area), far southern Texas (Brownsville area), east central Wisconsin (Green Bay area), and eastern Maine (Portland and Jonesport areas).
4. There is a relative minimum in watches from southwest to north central Kansas – right in the middle of theVORTEX II domain.
5. There is a relative maximum in watches from northeast Colorado into eastern Wyoming and western Nebraska – several of which were issued during VORTEX II.  (VORTEX II’s only significant tornado intercept occurred nearLa Grange, Wyoming, near the border of Wyoming and Nebraska.)
6. The lack of repeated land-falling tropical systems resulted in no coastal areas having a pronounced maximum.

(Image courtesy of the NWS SPC.)

Well, it’s over.  VORTEX II has ended for 2009.  (It actually ended on 13 June 2009, but due to an incredibly hectic last few days, I was unable to blog about it until now.)

VORTEX II 2009 intercepted only one tornado this year, but a lot of good data was collected on non-tornadic thunderstorms.  These “null” datasets (ones without tornadoes) are just as important as tornadic datasets in that it allows researchers to develop numerical prediction models that have to produce tornadoes when the atmosphere would produce tornadoes, and not produce tornadoes when the atmosphere wouldn’t produce tornadoes.  I know this sounds pretty basic and trivial, but it is a crucial distinction to make.  At this time most of our numerical models of supercell thunderstorms result in tornadoes.  However, an overwhelming majority of supercell thunderstorms do not produce tornadoes.  However, it would be nice if next year we can get more tornadic datasets.

In other news, the night of 12 June (34th day of VORTEX II) will be one I won’t forget anytime soon.  An EF1 tornado struck Norman, OK less than 1.5 miles from where I live.  This tornado developed from a thunderstorm that was approximately 30 minutes old, which is extremely fast for a thunderstorm to produce tornadoes.  Furthermore, this tornado struck the “meteorology Mecca” and the sirens did not sound until 10 minutes after the tornado lifted.  Needless to say there is quite a controversy brewing in Norman.  The text of the Public Information Statement about the damage survey is below.

000
NOUS44 KOUN 131717
PNSOUN

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE NORMAN OK
1217 PM CDT SAT JUN 13 2009

...TORNADO IN NORMAN FRIDAY EVENING...

METEOROLOGISTS FROM THE NATIONAL WEATHER SERVICE FORECAST OFFICE IN
NORMAN CONDUCTED A SURVEY OF DAMAGE THAT OCCURRED IN NORMAN ON
FRIDAY EVENING. THE SURVEY DOCUMENTED THAT A WEAK TORNADO OCCURRED
AROUND 1030 PM ON FRIDAY JUNE 12 ALONG A 2 MILE PATH EXTENDING FROM
NEAR SOUTHEAST 24TH AVENUE AND ALAMEDA STREET TO SOUTHEAST 48TH
STREET AND LINDSEY STREET. CURRENT INDICATIONS ARE THAT THE TORNADO
WILL BE RATED A LOW-END EF1 TORNADO. ALL OF THIS INFORMATION IS
PRELIMINARY AND SUBJECT TO CHANGE AS THE INVESTIGATION CONTINUES.

THIS IS THE FIRST TORNADO TO OCCUR WITHIN THE CITY LIMITS OF NORMAN
SINCE MARCH 13 1990 WHEN TWO TORNADOES OCCURRED IN NORMAN. ON THAT
DAY...AN F2 TORNADO DEVELOPED 1 MILE WEST OF CRINER IN MCCLAIN
COUNTY AND CAUSED DAMAGE IN NOBLE BEFORE DISSIPATING WITHIN THE
SOUTHEASTERN PORTION OF NORMAN AT A POINT 5 MILES NORTHEAST OF
NOBLE. A SECOND TORNADO /AN F1/ MADE A 5 MILE PATH THROUGH EAST
NORMAN NEAR AND NORTH OF LAKE THUNDERBIRD.

AN EF0 TORNADO ON MAY 7 2008 OCCURRED JUST SOUTH OF THE NORMAN CITY
LIMITS MOVING FROM JUST SOUTHEAST OF GOLDSBY TO NEAR 36TH AVENUE
SOUTHEAST AND POST OAK ROAD.

$$

SPEHEGER/SMITH/ANDRA

Well, today didn’t produce the tornadoes that we thought were certainly possible, but it was a very valuable data nonetheless.  The armada spent the night before in Kearney, NE (again).  The rationale was that by doing so they could either play eastern Nebraska or western Nebraska.  During the conference call, it was decided to target the storms in eastern Nebraska, since they held the most promise for tornadoes (or at least this is what we thought).

The armada left fairly early for Beatrice, NE, and while enroute decided to retarget to Auburn, NE.  Around the time they arrived in Auburn, the first thunderstorm of the day developed in eastern, northcentral Kansas.  This thunderstorm quickly became a supercell.  To its southeast, another thunderstorm developed and this one also quickly became a supercell.  The armada watched both of these storms very closely and decided to target (rightfully so) the southeastern storm.

The armada targeted this storm the from around 5PM CDT until sunset (~9 PM CDT).  It had all the characteristics of a tornadic supercell (hail 4.5″ and larger included!), but for some reason struggled to produce a tornado.  Near Amity, MO, one of the Dopplers on Wheels observed a brief “tornado-like vortex” that knocked a few branches down onto the road.  While officially a tornado, this is certainly not the type of tornado that the VORTEX II crew envisioned targeting.  However, even though the armada didn’t observe a classic tornado, this dataset is invaluable because of it being a great “null case”.  In my opinion, the data collected today is more valuable than the data collected in Wyoming on the tornado.  Ths is because on both days the forecast called for tornadoes.  The Wyoming day produced a tornado, while the Missouri day did not.  Examining the Missouri dataset might help us understand what was different in the environment and help us forecast tornado outbreak days better in the future.

I can’t wait to see the results from this!

The armada drove a long way last night to reach their hotels in Kearney, NE because they believed the best target for supercells and / or tornadoes today would be in southeast Nebraska and southwest Iowa.  However, during the morning briefing, the talk transitioned to heading back west and playing possible storms in western Nebraska.  The thought was that while the better tornado potential might exhist in Iowa, the road network and terrain made deployments difficult and the better chances of catching a workable storm were out west.

Without going into too many details, the armada intercepted a tornado warned thunderstorm that briefly appeared like it might produce a tornado, but never did.  This makes today a first for VORTEX II…consecutive days with a tornado warned thunderstorm!  This storm was moving quickly so the armada only got one chance at a deployment on it.  When it moved past, they targeted a new storm to the southwest of the old storm.  They armada hustled into place south of North Platte and got in position to watch the storm completely collapse.

There weren’t really any other targetable storms, and the armada was closing in on nightfall, so operations were ended around 8:21 PM CDT.

Tomorrow looks like a potentially tornadic day across places in the plains.  Hopefully, if a tornado does occur, the VORTEX II armada is on it.

As I mentioned in yesterday’s post, it finally happened.  The VORTEX II armada captured a tornado.  They started out the day in Sterling, KS and were faced with the decision of staying in the same general area / heading slightly SE or heading up NE of the Cheyenne ridge.  Field coordinator David Dowell and myself gave passionate arguments for targeting Wyoming which helped turn the tide…and this is what the armada did.

They started out by heading to Kimball, NE (which is in the far southwest county of the NE panhandle) and watched thunderstorms develop to their west.  As the thunderstorms moved closer to the armada, it became clear that the southern most storm had developed supercellular characteristics.  After a brief discussion, the armada decided to make this the target storm and they deployed on it.  As they approached the storm from the east, the National Weather Service office in Cheyenne, Wyoming issued a tornado warning on the storm.  While the storm was not producing a tornado at that precise moment, the storm certainly looked like it was getting ready to produce one.  The Weather Channel broke in to their regularly scheduled program began streaming live video of the supercell thunderstorm.

As the armada sent probes 1, 2, and 3 into the region of the thunderstorm that was about to produce the tornado, very large hail began to fall on the vehicles.  In fact, probes 1 and 3 received so much hail that the damage forced them to abandon all other missions for that day.  They were forced to stay behind the armdada and have their windows repaired.

While the probes were being pelted by hail greater than 4.50″  (softball size), the supercell began to develop a rapidly rotating wall cloud that went on to produce a tornado (carried live by the Weather Channel).  The storm was sampled from start to finish by the armada (and The Weather Channel).

Once the tornado dissipated, the armada tried to reposition themselves to try and observe any additional tornadoes that might develop.  This proved a difficult task due to the poor road network and storm motion.  Fortunately for the armada, the storm did not produce an additional tornado, so they didn’t miss one due to poor roads.

When operations where finally called off, the armada had a long drive back to their hotel (Kearney, NE).  To make matters worse, the storms they had been targetting all day had grown together and formed what is known as a Mesoscale Convective System (MCS; really just a really big cluster of thunderstorms interacting and aiding one another).  This MCS repeatedly had transient rotational signatures, extremely large hail, and damaging winds that tracked all along the roads the armada needed to travel in order to reach their hotel.  Because of this, I kept the VORTEX II Operations Center open until after 1 AM CDT.  I’m happy to report that every vehicle made it back safely…except probes 1 and 3 which were forced to stay in Cheyenne for repairs.

The tornado was preliminarily rated an EF-1 on the Enhanced Fujita scale.  For more information, including pictures of the tornado, please visit the NWS Weather Forecast Office in Cheyenne, WY

[Show as slideshow]

[View with PicLens]

It finally happened.  VORTEX II intercepted a tornado.  I’m still in the middle of operations, so I can’t write a post, but suffice to say the drought is over.

For more information about the intercept, please visit The Weather Channel, the VORTEX II Facebook page, and / or search on YouTube.

I’ll try to post more tomorrow.

The armada spent the night in Colby, KS.  This morning the decision that faced them was to either target storms that might develop in the northern Texas panhandle and then move south, or to target the storms in NE CO / SE WY and which would move southeast.  Being in Colby, KS and the realization that the severe weather threat tomorrow afternoon and evening appeared to be better over the northern target than the southern one, the armada chose to target the northern choice.  The feeling was while the meteorology was slightly better to the south, the driving down there to chase storms away from where they would need to be the next day it wasn’t worth it.

The armada headed to Byers, CO with the intent of chasing storms that might develop in and around the Denver area.  Enroute to this target, the armada realized that the low clouds and storms already developing by lunch time would probably spell doom for any threat of supercells.  Based on this they headed to Greeley, CO and waited for the next wave of thunderstorms.  Unfortunately, the next wave of thunderstorms also developed too early and left a rain-cooled atmosphere in its wake.  This cool air ruined any chance for supercells in this area, so the armada set its sights on storms developing north of Cheyenne.

These new thunderstorms were slowly becoming supercells and exhibited transient mesocyclone features.  By the time they got up to Cheyenne, WY and headed east on I80, these storms were bonified supercells (albeit weak ones).  The armada set up a deployment and collected some data as the storm moved into Nebraska.  Interestingly, while not a true supercellular tornado, one of the mobile mesonet probes observed a brief landspout tornado!

About the time they armada was going to call it quits for the day, a new thunderstorm developed extremely quickly to their west in the Cheyenne, WY area along colliding outflow boundaries.  This storm quickly became a supercell and tracked through the north and east side of Cheyenne, WY.  The storm exhibited fairly decent low-level rotation but there were no reports of tornadoes.  Several members of the armada experienced golf ball sized hail, but as of this writing, there has not been any damage to the vehicles.

Currently, the armada is experiencing thunderstorms enroute to their hotel.  I’ll be sitting here watching their safety until they reach their destination or the storms have passed.