STATUS: 28 Mar 2017


After meeting this morning, the researchers decided to not study the system that will pass through AL on Thursday evening.  There were strong hints in several of our forecasting models that there would be a convective system closer to the Gulf Coast with this wave.  In our experience, this tends to mean a loss of low-level moisture and heat in northern AL.  The reasoning was that we now have some very good data sets on storms that appear to have tornado potential, but fail to produce.  Now we need to skip these “marginal” cases when we can trust our own forecasts.

The pattern remains active, with more systems likely to pass through the domain over the next couple of weeks.  We are a bit worried about a possible increase in the strength of the subtropical jet stream over Mexico and the Gulf of Mexico.  This jet often seems to be associated with coastal convection that depletes water vapor before it can move north in our domain.  Just one more fly in the ointment of VORTEX-SE forecasting.

The next system we will be watching is forecast to affect the Southeast around Monday or Tuesday next week.

Yesterday, we had a very good day of observing.  Over 80 soundings were launched from 12 teams, and combined with data from three profiling systems, we should have a detailed picture of the variations across northern AL that may have contributed to the storm behavior and organization.  We also had a well-planned network of five Doppler radars in the area from Huntsville toward Florence.  The NOAA P-3 was in the air from around 3 to 10 PM.  Add to this the storm intercept teams from Texas Tech and Purdue, and we should have comprehensive data on the two systems we studied.

The first was a band of storms, including a few supercells, that developed in far northwest Alabama in the mid-afternoon.  For a short while, some of these rotated intensely enough aloft that they looked capable of being associated with tornadoes.  After this round of storms passed through and out of the domain, a second quasi-linear convective system moved south into the domain from Tennessee.  This second system was observed for several hours, and produced a couple of bow echoes and some reports of severe hail.

Of course the researchers would prefer to study tornadic storms, but a case like this still is important to the research.  We may be able to determine why the storms with rotation aloft didn’t seem to develop rotation very close to the ground.  We should be able to study the various forms of storm organization and how these were related to variations in the storms’ environments.  And the rich set of surface and upper air observations should provide important data to improve forecasting models, and tools that we use to analyze the airflow in the atmosphere using multiple Doppler radars.

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