Ramblings of a Graduate Student

I have had a difficult time trying to write tonight’s blog. Normally I have this problem because there is nothing really “exciting” to write about. Tonight the problem is I don’t know what to write without creating a dissertation! As I hinted at last night, almost every meteorologist in the southern plains is focused on the exact evolution of the southern plains winter storm. There were close to 70 National Oceanic and Atmospheric Administration (NOAA) and University of Oklahoma (OU) meteorologists in attendance at today’s Hazardous Weather Testbed (HWT) map discussion. I’m sure tomorrow we’ll have even more.

The official precipitation forecast from the National Weather Service’s (NWS) Hydrometeorological Prediction Center (HPC) continues to have over 2.5-3″ of liquid equivalent (the amount of rain or water from melted ice/snow) falling across portions of Oklahoma, western Arkansas, and northern Texas.  Generally speaking, almost all of today’s numerical weather prediction (NWP) models are in excellent agreement with this HPC forecast.  Where the models differ – between each other and also with different simulations of the same model – is in the form that this precipitation will fall.  Hopefully by the end of this post someone will have an idea as to what will happen…

The culprit for the soon-to-be winter storm is easily identified in current satellite imagery.  In the image above, the shortwave trough (upper low) that is the batch of white clouds off the southwest coast of California.  Over the next 24 hours the upper low should track south-east into northern Mexico.

Sometime during the 24-36 hour time-frame the upper-low should begin to turn more toward the east and then northeast.  When this turn to the northeast happens is crucial for determining precipitation types and duration across portions of the Texas Panhandle, Oklahoma, and western Arkansas.  One reason why where the turn occurs is important, is that it will have a direct impact in where several important features of the cyclone will become established.

Above is the 700mb (~10,000 feet above ground level) chart from the 00Z (6PM CST) North American Model (NAM).  The 700mb chart is important for winter weather forecasting because a lot of important features are easily identified on it.  Below, I’ve annotated the same chart as displayed above.  The red arrows represent initially warm, moist air (moving in the direction of the arrows), whereas the blue arrow represents initially cold,dry air (also moving in the direction of the arrow).  The red arrow is often referred to as the “Warm Conveyor Belt” and the blue arrow is often referred to as the “Dry Slot”.

In the warm conveyor belt, warm moist air from near the surface flows northward into the developing cyclone.  As it flows northward, it tends to encounter colder, drier air at the surface.  Warm, moist air is less dense then cold, dry air so the warm, moist air flows up and over the cold air.  So, in addition to the warm, moist air flowing northward, it is also flowing upward (from the ground).  As warm, moist air reaches higher altitudes, it encounters lower atmospheric pressure and begins to expand.  This expansion of the warm, moist air causes the temperature of the warm, moist air to cool, condensate, and eventually precipitate.

Depending on the strength of the developing cyclone, the warm conveyor belt will either continue to develop ahead of the (weak) cyclone or a portion of the warm conveyor belt will get wrapped around the backside of the cyclone…typically near and north of the 700mb low.  When the warm conveyor belt wraps around the cyclone, the cyclone takes on the typical “comma” shape often seen on satellite imagery and in text books.  This conveyor of warm, moist air aids in the development of clouds and precipitation on the backside of the low.  Precipitation resulting from this process is often referred to as “wrap-around” precipitation because it has wrapped all the way around the low.  Because this is occurring on the backside of the low, the surface temperatures are often falling as the surface cold front has most likely passed through.  Thus, in winter, snow is often found in the “wrap-around” precipitation.

Equally important in the life-cycle of a cyclone is the “Dry Slot”.  Unlike the warm conveyor belt that starts near the surface, the dry slot originates in the upper portion of the troposphere.  Here, cold, dry air begins to get entrained into the mid-level cyclone.  As mentioned above, cold, dry air is more dense than warm, moist air – which is typically found near the surface.  Thus, the cold, dry air aloft attempts to sink toward the surface.  As it does this, the cold, dry air encounters air at a high pressure and is forced to compress.  This sinking and compressing results in a relative warming and substantial drying.  This drying out of the atmosphere tends to supress precipitation development which also aids in the development of the comma shape often seen.  The dry slot is often found just south of the track of the 700mb low.

So what do the warm conveyor belt and dry slot have to do with when the storm turns north?  Well, the earlier the upper-low makes the northward turn, the farther north the 700mb low will track and a good portion of southern Oklahoma into western Arkansas will be “dry slotted” at the same time the temperature become cold enough to support snow.  Places that are dry slotted, in turn, would receive considerably less snow than places that remain in the warm conveyor belt.

So, based on the images above, what does the NAM forecast?

Southern Oklahoma and western Arkansas dry slot…

With this said, the warm conveyor belt is producing so much precipitation ahead of the dry slot that Oklahoma and Arkansas should still see over 2.5-3″ of liquid equivalent…before the dry slot overtakes them.  For Oklahoma, surface temperature would support much of this falling as freezing rain and sleet (to the tune of over 0.5″ of ice and 2-4″ of sleet!) while west-central Arkansas would see mainly rain (with a brief opportunity for some ice toward the end of the precipitation).  As for the places remaining in the warm conveyor belt?  This run of the NAM predicts over a foot of snow in a wide area from Tulsa westward to Edmond, Enid, Woodward, etc.

Remember, this is just one run of one computer model.  The forecasts continue to change as we learn more about the approaching short-wave trough (upper low).  The above scenario should be taken as 1 possibility out of many others.  In fact, another model run at the same time as the NAM predicts much more sleet across the aforementioned area, and does have as pronounced of a dry slot.

Only time will tell with this storm.  Please refer to your local National Weather Service office for more details for your specific area.

The course in the title of the post is the School of Meteorology’s “tie it all together” course for its seniors.  This is a 4 credit hour course (that actually meets for 8 hours a week).  This year the course instructor is Professor Kevin Kloesel (who also serves as Associate Dean for the College of Atmospheric and Geographic Sciences).  I have the privilege of serving as one of the two TAs for the course, as well as guest instructor for the times Prof. Kloesel has been (will be) out of town.

This is the course I’ve wanted to TA since my being at OU; this is also the course I would want to teach every year if I were a professor in a school or department of meteorology.  It’s the course that deals with tying together all the equations and pieces of knowledge that students have acquired during their studies at OU via looking at actual weather maps and data.  To me, there is something rewarding about looking at weather maps on a daily basis and developing an understanding – and appreciation – of what is on going in the atmosphere.

This year’s synoptic class has 54 students in it.  This is by far the largest undergraduate synoptic class – ever.  Because of the size of the class, Prof. Kloesel is trying something different this year.  There are no prepared exams; Mother Nature prepares a daily examination.  Book-based assignments do not have a due date (except the end of the semester); there simply might not be enough time to get the assignments done because of Mother Nature’s daily examinations.  Map analysis occurs on almost a daily basis.  In short, there is no predefined curriculum of what is going to occur on a given day.  Prof. Kloesel and I wake up every morning, take a look at what opportunities and teachable moments the atmosphere has presented, and then attempt to create a daily lesson based on that day’s opportunity.

So far this semester the students have worked very hard.  On the very first day of class, the students were given a blank surface map and given 30 minutes to analyze it.  (This turned out to be an all class period assignment.)  The students also were given a blank skew-t diagram and the raw data and told to plot the sounding by hand.  All the while trying being expected to analyze the 500mb and 250mb maps.  On day three, students were given 10, 500mb charts (24 hours apart) that had the dates and times removed and were expected to put the charts back in order.  (Oh, by the way, the charts were given to them in-order to start with…).  Day four yielded a discussion about a tropical system in the western Atlantic and their first “proficiency evaluation”.  Following weeks have yielded discussions on how to identify whether a trough will dig (move equator-ward)or lift (move pole-ward) – Meeker’s method – or if they will intensify (deepen) or weaken (fill) – using 1000-500mb thickness charts.  A guest lecture by the Storm Prediction Center’s (SPC) Warning Coordination Meteorologist (WCM), Greg Carbin, yielded a discussion about doing composite charts via pencil and paper – which promptly led to a “proficiency evaluation” on that very topic the following day.

This is the fourth week of class and all of the students have worked hard – and come a long way, although they can’t see it.  However, Prof. Kloesel and I can.  The students should be proud of how hard they have worked and how far they have come, but the journey for them is just beginning – not ending.  There are a lot of exciting things still to come.  Beginning next week, students will be expected to give a quick map briefing in front of their peers.  This map briefing will focus on four questions that are usually left out of the forecast process:

1. What has happened?
2. Why did it happen?
3. What is happening?
4. Why is it happening?

Notice the absence of anything related to a “forecast”.  We aren’t there yet.  Students need to be able to understand the analysis process if they have any chance at being able to produce a coherent forecast.  That’s what these briefings will focus on the next couple of weeks.

As part of this upcoming emphasis on preparing coherent map briefings (not discussion), I am going to try to post a blog every day addressing these 4 questions.  It is my hope that some of the students will stumble across these posts via this blog or via Facebook (which posts snippets from this blog whenever I post).

Now, where did I put that 500mb hand analysis…

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.

Today started the new semester at one of the two universities at which I’m teaching this spring. Yes, you read that right, two universities.  In fact, I’m teaching (or co-teaching) four classes, in three disciplines, at two universities.  The classes are

• Ordinary Differential Equations (Mid-America Christian University)
• Mathematical Modeling (Mid-America Christian University)
• Intermediate Analysis of Political Data (The University of Oklahoma)
• Introduction to Meteorology II Laboratory (The University of Oklahoma)

In addition to teachings these classes, I’m chair of the Student Affairs Committee (SAC) at the School of Meteorology, preparing for my role as a nowcaster in the meteorological field project, VORTEX II, and beginning my preparation to take the qualifying exam.

…I’m in for a busy semester…