Ramblings of a Graduate Student

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.

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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