STATUS: 26 Mar 2017

Still blogging from Huntsville….

Yesterday’s mission was interesting.  Although the forecast had looked favorable for Saturday tornadoes in northern AL for a number of days, when we started work yesterday morning, a couple of things had changed.  First, the low level moisture was a bit skimpier than expected.  And the band of storms that started in AR and LA on Friday evening were still alive in eastern MS.  This band was no longer forecast to dissipate, which would have allowed redevelopment later in the day back to the west. So we had no choice but to quickly deploy, and hope the result provided some favorable data.

Some of my colleagues think it’s unusual for an event to look so promising 1-6 days in advance, and then fizzle.  I wonder how often this happens, and how often things look unfavorable but then atmospheric conditions end up supporting tornadoes.  I also wonder if our desire to have storms to study biases us toward believing conditions are more favorable than they are.

If we had been able to heat up for another six hours, and had six more hours of south winds to increase the low-level moisture, Saturday probably would have turned out differently.  But it always seems to be some ingredient that fails, even when the forecast looks promising (yes… scientists are human, have biases, and are not perfectly objective!).

Nevertheless… we had an interesting event that we can learn from.  The band of showers developed one relatively intense cell, with a little lightning, to the southwest of our domain.  Quickly, this cell developed some rotation.  This more intense cell and its rotation persisted all the way across the domain and up into central TN.  At one point, the rotation was tight enough that it appeared there was a tornado threat, but aside from some minor wind damage, no severe weather occurred.  A wave in a convective line like this can be associated with tornadoes, so it will be interesting to look at this case that “almost made it”.

Remember that VORTEX-SE is more concerned with all these very hard-to-forecast tornado scenarios than we are with the big, classic “Great Plains” supercells that are relatively easy to forecast.

This morning, the researchers gathered at 8AM at the UAH SWIRLL facility to talk about the forecast.  First, they decided that today has such low probabilities of storms that VORTEX-SE will not operate.  Tomorrow has a lot of uncertainty.  Some of the operational forecast models are showing supercells at the very northwest corner of AL in the late afternoon.  One experimental model ensemble (an ensemble is a group of computer model forecasts where the starting conditions are changed a little from run to run… to mimic the uncertainty in our measurements of the atmospheric state) shows a band of supercells running generally north-south through AL, at various east-west positions.  Any one of those forecast possibilities would provide us with an opportunity for research.  So given this potential, the researchers decided that we must operate tomorrow.

Yesterday also provided us with a lot of small issues to work on today, such as instrument and communication problems.  This is the way things always go in these field programs… researchers have to solve problems on-the-fly.  We don’t just assume we can go to the field and things will work perfectly every time.

This evening, we will all meet again and start designing the plan for tomorrow’s observations, and then early tomorrow morning we will meet one more time to make sure the plan is the best we can come up with.  Then… back to the field.

So stay tuned.


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