Ramblings of a Graduate Student

During the evening of 23 July 2010, Vivian, South Dakota experienced a severe thunderstorm no homeowner would enjoy; the thunderstorm packed winds estimated to be in the 110-120 miles per hour range. If that wasn’t problem enough, the thunderstorm was also producing hail that measured over 8″ in diameter and 18.5″ in circumference. (Anecdotal reports indicate that the hail was closer to 11″ in diameter when it fell!) Photographs from the region show holes in roofs. Not damaged roofs, but actual holes greater than 5″ in diameter! At least one hailstone was preserved and it officially weighed in at 1.9 pounds — even after substantial melting! You can read more about this thunderstorm, and see pictures of the hailstone(s) here! (Note, I would have blogged about this sooner, but I was waiting for official word that this hailstone is the world record holder, however that will take a while longer.)

If this hail stone is verified as legitimate, and I have no reason to believe it won’t, it will smash the previous record for largest hail stone. That hail stone measured 7″ in diameter and weighed closer to 1.6 pounds. It fell in Aurora, Nebraska on 22 June 2003. Prior to the Aurora, NE hailstone, the world record hailstone was from Coffeyville, Kansas.

Our current understanding of thunderstorms indicates that in order for a thunderstorm to generate a hailstone of this size, several things must come together. First, we need to have a lot of atmospheric instability. This allows for thunderstorms to develop very strong updrafts, which are necessary to suspend the hailstones aloft. Next, we need the freezing level to be relatively close to the ground. When the freezing level is close to the ground, more of the thunderstorm is below freezing. This means that most of the thunderstorm’s moisture is located in a part of the atmosphere that is conducive for ice formation. Lastly, we need the thunderstorm to rotate. This is because a rotating thunderstorm actually acts to make the updraft stronger than it would be if the updraft was not rotating. This allows for the thunderstorm updraft to suspend hailstones even longer, allowing them to become larger.

The radar images above clearly depicts a very strong thunderstorm, known as a supercell, shortly before the town of Vivian, SD experienced the potentially record hailstone. (Vivian is located in the “hook-like” appendage in the bottom-middle of the thunderstorm.) The two images above are both evaluating a height of 15,000 feet above the radar. At this height we can clearly see in the right image that this supercell thunderstorm had very strong rotation!

If we look at around 27,000 feet, we can see what is known as a Bounded Weak Echo Region (BWER) signature in the reflectivity (above/below left). (It looks like a donut-hole. If you are unfamiliar with this signature, the image below is annotated.) This signature is indicative of an extreme updraft. If we examine the velocity image, we see that the thunderstorm is still rotating, albeit, it is more difficult to discern.

The last set of images are a bit different from what I tend to show. Normal radar images depict a quasi-horizontal cross-section through a thunderstorm. These images are actually a vertical cross-section through the thunderstorm (beneath the vertical cross section is a typical radar image!). I’ve annotated a couple of important parts of the thunderstorm in the image below. This thunderstorm had a very strong forward-flank downdraft (which is where most of the heavy rain falls), a very strong rear-flank downdraft (strong winds, moderate rain, and hail¹ are typically found here), and an extremely strong updraft (the largest hail fails around the updraft). At the time of the cross section, Vivian, SD was located almost directly beneath the strong updraft, which helps explain why the largest hail fell there.

Below is from the National Weather Service Forecast Office in Jackson, MS. I thought it important enough for it to be it’s own blog post.  EF4 tornado with a maximum width of 1.75 miles.  Simply amazing…

000
NOUS44 KJAN 260230
PNSJAN

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE JACKSON MS
930 PM CDT SUN APR 25 2010

...PRELIMINARY INFORMATION FROM STORM DAMAGE SURVEYS
TODAY...

FOUR NWS STORM DAMAGE SURVEY TEAMS HAVE BEEN SURVEYING DAMAGE
FROM AROUND THE REGION CAUSED BY THE DEVASTATING STORMS OF
SATURDAY. THE FOLLOWING IS PRELIMINARY INFORMATION REGARDING
THE MAJOR STORM THAT MOVED FROM NORTHEAST LOUISIANA ACROSS
CENTRAL MISSISSIPPI.

NWS SURVEY TEAMS SURVEYED THE PATH OF THE STORM FROM ITS
START WEST OF TALLULAH, LOUISIANA TO AS FAR AS DURANT,
MISSISSIPPI. TORNADO DAMAGE...MUCH OF IT STRONG...WAS FOUND
ALONG THIS ENTIRE PATH...AT LEAST IN THOSE AREAS ACCESSIBLE
BY ROAD.  BASED ON THESE SURVEYS...THIS IS A SUMMARY OF
THE INFORMATION SO FAR:

PATH LENGTH: 97 MILES...THIS LENGTH WILL INCREASE AS MORE
DAMAGE IS SURVEYED EAST OF TODAY`S SURVEY
MAXIMUM WIDTH:  1.75 MILES
RATING: EF4, WITH MAXIMUM WINDS OF 170 MPH
CASUALTIES: 10 TOTAL FATALITIES WITH DOZENS OF INJURIES

A NUMBER OF AREAS OF EF3 DAMAGE WITH ESTIMATED WINDS OF 150 TO 165
MPH WERE FOUND ALONG THE PATH. TWO AREAS OF EF4 DAMAGE WITH MAXIMUM
WINDS OF 170 MPH WERE FOUND...ONE IN YAZOO CITY...AND THE OTHER IN
HOLMES COUNTY.

ANOTHER SURVEY TEAM IS STILL SURVEYING DAMAGE IN CHOCTAW COUNTY
CAUSED BY THE SAME STORM. THIS DAMAGE HAS BEEN DETERMINED TO BE
AT LEAST HIGH END EF3. WHETHER OR NOT THIS IS A PART OF A
CONTINUOUS TORNADO PATH ALL THE WAY BACK TO ITS START IN
NORTHEAST LOUISIANA HAS YET TO BE DETERMINED. NWS SURVEY TEAMS
WILL BE IN HOLMES...ATTALA...AND CHOCTAW COUNTIES AGAIN MONDAY
TO TRY TO DETERMINE THIS...AND WILL ALSO BE ATTEMPTING TO
OBTAIN AERIAL DATA TO HELP CONFIRM A CONTINUOUS PATH.

IT MUST BE STRESSED THAT ALL OF THIS INFORMATION IS PRELIMINARY
AND SUBJECT TO LATER ADJUSTMENT. A TORNADO OF THIS STRENGTH AND
MAGNITUDE REQUIRES A TREMENDOUS AMOUNT OF DAMAGE SURVEYS AND DATA
ANALYSIS. THE NWS WILL CONTINUE TO PROVIDE UPDATES AS ADDITIONAL
INFORMATION IS OBTAINED...AND IS PLANNING TO HOLD A MEDIA BRIEFING
LATER THIS WEEK TO PROVIDE A FULL ANALYSIS OF THE STORM AND THE
DAMAGE SURVEY RESULTS.

THE NWS WOULD LIKE TO THANK ALL OF OUR PARTNERS IN LAW ENFORCEMENT
AND EMERGENCY MANAGEMENT FOR THEIR INVALUABLE ASSISTANCE IN
PERFORMING OUR DAMAGE SURVEYS.

$$

AEG/GRG/SCW/BK

VORTEX II (Verification of the Origin of Rotation in Tornadoes EXPeriment) is scheduled to begin on 10 May and last through 13 June.  I’ll be manning the VORTEX II Operations Center (VOC) here in Norman on a daily basis.  In addition to this, I’m currently writing code (in my spare time) to generate images of model output for use by forecasters in the VOC.  All of this is on top of my current research and school work – which includes making corrections to a journal article and editing a political science paper that needs to be submittd ASAP.  This is certainly a rough end of the semester; and it only goes down hill from there.

Last week a devastating ice storm ravaged parts of the United States; as of this writing, a little under 500,000 customers remain without power.  Three days from now will be the first anniversary of the deadliest tornado outbreak in over 20 years.  May will mark the 10th anniversary of the 3 May 1999 tornadoes in Oklahoma and southern Kansas.  I know most people won’t think anything of these events, however, to me, these events are what either got me interested in meteorology or further my curiosity on the subject.

Synoptic meteorology is a sub-discipline within meteorology that focuses on analysis and prediction of large-scale atmospheric phenomena.  The events mentioned above all stem from synoptic systems.  Unfortunately, meteorology as a science is rapidly moving away from studying and, as a result, teaching synoptic-scale meteorology.  Researchers will argue this is because there is “no money” in studying these topics, and to some degree they are true – money is going to radar research, large supercomputers for running numerical models, and building new satellites.  (Congressmen need to have a large piece of “hardware” or equipment to stand in front of for their photo-op.)  I had hoped when I came to OU that this “Mecca of Meteorology” would be immune to this de-emphasis.  I was sadly mistaken.  Norman is rapidly becoming a radar town.

So, what does this have to do with “map discussions”?  I have had the fortune of being a member of a listserv that is dedicated to synoptic meteorology.  Reading the emails that come across the listserv has been a source of pleasure for me lately, but at the same time, a source of disappointment.  I long to have something of this locally – where students, faculty, and operational meteorologists can argue over the ongoings of the atmosphere.  It is in this setting – where passionate discussion prevails – where learning occurs.  It is also in this setting where the next generation of inspirational meteorologists are born.

I have been told by a great researcher – one whom I respect greatly – that if I wish to see something like this here in Norman, it’s going to take inspired students taking the initiative.  It is my hope and prayer that before I graduate something like this will take hold here in Norman.  I know I’ll do my part.

Tonight was the second installment of Science Cafe Norman.  Tonight’s talk (title is the same as the title of this post) was given by me.  We had a fairly large turnout of around 20-30 people and the talk lasted about an hour.  While I was originally planning on talking more about climate change and less about severe thunderstorms, however the severe thunderstorm portion of the talk took a little longer than expected.  This was fine though, I think everyone enjoyed the talk and learned something new.  Next month the talk is given by my officemate, Melissa Bukovsky, and will focus on regional climate change.  As of right now the talk is scheduled to be on January 8th, but may have to be moved since quite a few people will be at a joint meeting of the mathematical societies and the NCAA College Football National Championship.  Stay tuned!

Tonight I attended the first “Science Cafe” in Norman, OK. Science cafes are live events that involve a face-to-face conversation with a scientist about current science topics. They are open to everyone, and take place in casual settings like pubs and coffeehouses.  The Norman Science Cafe takes place at Hastings (in the coffee shop) on the first Thursday following the first Wednesday of the month at 7PM.  These events are a great way for the general public to understand local research and scientific topics and allows scientists the opportunity to explain their research to a more general audience.  Tonight’s talk was given by Sean Crowell, a mathematics PhD student at the University of Oklahoma.  His talk was titled, “Climate change:  What We Know”.  It was a great first meeting.

I encourage people to check it out!  I give the next talk at the Norman Science Cafe on 4 December 2008 at 7PM.  My talk is titled, “What the Hail?!?  Climate Change and Severe Thunderstorms”.  Check it out!