Ramblings of a Graduate Student

The image above was taken approximately the same time a tornado was hitting Hammon, OK.  The tornado occurred with the convection associated with the brighter colors in far western Oklahoma.  It was a classic cold core setup, meaning a lot of instability was generated along the eastern edge of the cold-pool aloft associated with the mid-level low.  It so happened that the mid-to-upper level jet streak (cyan color fill below) associated with the mid-level low was positioned such that an area of large scale lift was juxtaposed over the mid-level cold pool.  These two factors, combined with surface convergence along subtle surface boundaries evident on KFDR radar (not attached) enabled thunderstorms to develop in an environment with a lot of environmental vorticity.  At least one thunderstorm this afternoon was able to tap into this environmental vorticity and produce several tornadoes.

Storm season is officially “here”.

After last week was relatively quiet, albeit cold in places, this week is promising to be very active in terms of low pressures, upper-level lows, and precipitation.  Just look at the 5-day precipitation forecasts from the Hydrometeorological Prediction Center posted from a few days ago! One reason for the wet, stormy weather pattern is the number of storm systems (an organized collection of low pressure/height throughout the atmosphere) that are identifiable on water vapor.

In the image below, five upper-level lows are circled – two in yellow and three in red.  I’ve used two colors to distinguish between upper-level lows that have aided in the recent west coast deluge (red) and those that haven’t (yellow).  (Author’s note: It is possible to identify additional upper-level lows, vorticity maximums, and/or short-wave troughs; however, I only circled those “easily identifiable” on a single image – not a loop.)  When analyzed on weather maps, upper-level lows often look like waves with crests (ridges) and troughs (troughs).  When several of these waves line up one after another, similar to box-cars on  a train, meteorologists call it a wave train.  Hence the name of this post.

The eastern (rightmost) upper-low circled in red is currently aiding the development of showers and thunderstorms across the southern plains and will affect a large portion of the central United States on Wednesday.  In fact, Ice Storm Warnings are in effect for a good portion of Iowa and a chance of severe weather is possible across a large portion of the north central Gulf Coast states.

The middle of the upper-lows circled in red moved onshore in southern California this afternoon and resulted in at least three tornado reports along the California coast.  The western (leftmost) upper-low circled in red also came ashore earlier today with a myriad of severe weather associated with it.  I’m uncertainly, but one of these two upper-lows was responsible for a wind gust of 93 mph recorded at Newport Beach Pier.

The parent long-wave trough (giant upper-low) responsible for these short-wave troughs (smaller upper-lows) will remain off the west coast for the next several days.  When this long-wave trough begins to move eastward, a decent severe thunderstorm threat will be possible across a large portion of the southern United States.

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

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

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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.

So much for me being able to do this during the morning.  I guess I’ll just combine posts for the past two days.

Wednesday (Day 4) the armada began the day in Childress, TX with a 9AM conference call to discuss the day before and talk about a forecast for operations that day.  This was a particularly difficult forecast because the better ingredients for tornado development were in northern Missouri, in an area where the armada is not supposed to operate, while in Oklahoma (where the armada can operate) the chance of tornadic storms was considerably less.  During this call it was decided that the armada would reposition in Clintion, OK  by 2PM in anticipation that thunderstorms would develop southwestward into northern Oklahoma along an advancing cold front.  The thought was there might be a chance of collecting data on a storm as it developed, before it “gusted out” and died.

Late in the afternoon, the armada (or, as I’ve heard it called, the “nerd herd”) the field coordinator (FC) decided to move farther north, closer to the advancing boundary.  It was decided to move to Watonga, OK and reevaluate the conditions.  About the time the armada arrived in the Watonga area, the first thunderstorms began developing in Kay county, OK along the Oklahoma-Kansas border.  (It should be noted that this storm went on to produce a very “nice” tornado, in relative open space, that was captured by several news station’s helicopters.)  The armada decided to wait for and play the developing thunderstorms north of them in hopes that this storm on the west end of the cold front would have the best chance to produce tornadoes.  After a few failed attempts to develop into a thunderstorm, convection finally initiated near Fairview, OK.  The armada targeted this storm and attempted to set up a network to collect data.  Unfortunately, this storm would begin to move to the northeast and then develop a new storm to its southwest.  This new cell on the southwest would then get ingested into the original storm and it appeared as if the initial thunderstorm moved south.  This kind of movement (discrete propagation) is indicative of a very strong instability and would normally be a good thing if you are trying to collect data on tornadoes.  However, an overal storm system motion of “south” is extremely difficult to collect data on because the instruments would need to be west of the storm.  The means that the mobile radars would have to try and collect data on any possible tornado by shooting “through” the back side of the storm where heavy rain and hail is falling.  Do this will severe affect the electromagnetic wave and prevent the wave from making it back to the radar.  In a nutshell, this means that you can’t collect any mobile radar data…which is a big portion of this project.

Well, after the radars made an attempt to collect data, the storm motion forced them to have to get south.  Unfortunately, the nearest road option would have taken them into the storm, where falling hail would destroy the $400,000 radars.  This forced most of the radars to head east before being able to head south and at this point the game was essentially over.  The radars were never able to get far enough ahead of the storm to collect really good data and were continually being chased by the storm.  (Ironic, I know!)  Around 8:45 operations were officially called off for the evening as it was dark and the armada’s safety plan does not allow for operations in the dark.  The armada then headed to Yukon, OK for the night.  Ironically, within 30 minutes of calling off operations, the thunderstorm the armada deployed on produced a 12 mile long EF2 tornado that went from Gracemont, OK through Anadarko, OK.  Go figure!

This morning at the 9AM conference call it was decided that severe thunderstorms were not likely across the central United States and no operations would be conducted.  Instead the nerd herd headed toward tomorrow’s target, and as of last check, is resting comfortably in their hotel rooms.  We’ll see what tomorrow holds…