STATUS: 8 March 2018

Status: GO for Saturday IOP

Teams are enroute, or will soon be, to the Monroe LA subdomain of VORTEX-SE. This is one of two subdomains we will use this year, depending on the forecasted weather.

A narrow mid-tropospheric jet is forecast to be advancing toward Louisiana from the west-northwest on Saturday. To the north of this jet, lift will be strong, likely leading to quite a bit of precipitation and low-level cooling. To the south, the air will be sinking which should enhance the “lid” and possibly limit convection. Between these two regions, there should be a narrow goldilocks zone of sufficient CAPE and strong shear that could support some low-level rotation. Of course, many things can go wrong (and usually do, to the benefit of the general public) with this scenario and any convection may be non-rotating.

We will deploy one mobile C-band “SMART-Radar” from OU to pair with the U. Louisiana-Monroe S-band research radar, and ULM mobile sounding teams. The NOAA P-3 aircraft will likely take off midday Saturday and head toward Louisiana, if this forecast holds up. They will make radar observations of the most interesting storms, and will focus on storms over the ground radar domain near Monroe when storms are present there.

There is a slim chance that there will be tornado potential in the Georgia/N Florida area on Sunday. Although we don’t have a ground subdomain there, the P-3 aircraft may fly a mission to observe storms in that region.

Thereafter, we expect quiet conditions until the following weekend.

One more time with the caveat: forecasting conditions for a field observing program are very different than forecasting for more general purposes. We are generally fine with a “busted forecast”, especially if we are able to obtain data to tell us why we busted. Learning what processes reduce tornado potential are almost as interesting as catching tornadic events. Because tornadoes are rare, we have to observe most everything that comes along with even a little potential. And this spring, our focus is not so much on the physical processes in the atmosphere in the Southeast, but learning how to make much better observations in this difficult region.

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Spring 2018 observations begin

This spring, we are taking a breather from the style of experiments we conducted in 2016 and 2017. This is intended to give researchers some time to study data we have already collected, and to use new insights to improve our scientific questions and use of resources in future years.

However, the NOAA P-3 Hurricane Hunter aircraft will be used in VORTEX-SE this spring. This aircraft has a Doppler radar with a pair of antennas in the tail so that we can do analysis of the precipitation and winds in Southeast storms. One antenna looks slightly forward of the aircraft and the other slightly rearward. As the plane flies by a storm, along-beam velocities measured in these two separate “look angles” can be combined to give us the complete velocity at millions of points.

We have a huge challenge in VORTEX-SE owing to the terrain and vegetation to produce the kinds of mobile radar analyses that have been obtained comparatively routinely in the Great Plains. Until we can tackle this problem, we will not be able to do the sorts of detailed storm studies that can tell us how a particular tornado formed, and how the parent storm might have behaved differently than the fairly well-understood Great Plains cousins. So in addition to the NOAA P-3, we will be deploying three-radar networks consisting of University of Oklahoma SMART-Radars (dual-polarization mobile C-band radars) and either the U. Alabama-Huntsville C-band dual-polarization Doppler radar at Huntsville (known as ARMOR), or the U. Louisiana-Monroe S-band dual-polarization Doppler radar at Monroe. We want to know if such deployments of combined surface/airborne Doppler radars can be used to produce higher quality storm airflow analyses than other combinations of radars, and whether/not we can do a better job piecing together the airflow patterns in the crucial near-ground layer that is so important to tornado formation and longevity. Then, using this assessment, we can more effectively plan future observations to address VORTEX-SE science questions.

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STATUS: 7 MARCH 2018

STATUS: IOP Watch

We are anticipating a possible IOP on Saturday and Saturday night.

A trough will deepen across the northern High Plains late Friday, causing an acceleration of the flow in the upper atmosphere across OK on Saturday. This trough will consolidate somewhat as it approaches MO/AR, and a surface low will deepen fairly rapidly somewhere in the region centered near Memphis.

The developing southerly flow should bring Gulf moisture back into the Arklatex region Friday night, although the confidence in the “quality” of this moisture is not high. A series of runs of the operational GFS show a subtle decrease with time in the forecasted dewpoints across the region on Saturday, and an associated decrease in CAPE. We expect that drier air will remain in place across GA, and perhaps parts of AL, because the pattern and fast-moving wave will not allow moisture to return to those areas. So any complex of storms that develop in the Arklatex region Saturday will eventually run out of juice as they race east.

Another question (seemingly always a major issue in VORTEX-SE) is the likelihood, timing, and effect of an MCS in the Gulf of Mexico. These systems are probably associated with subtle waves in the jet stream, and those waves may not be well forecast until within 24 hours of passage because prior to that time they are somewhere out over the Pacific.

The current best guess is that storms will form in far east Texas on Saturday, with at least some tornado potential, and roll east across Louisiana in the evening, and perhaps into MS/AL during the night. We expect that our most likely subdomain for combined airborne and surface radar observations will be the U. Louisiana-Monroe subdomain.

Bear in mind when reading these discussions that we are forecasting conditions required for successful research operations. We have a very high tolerance for erroneous forecasts of possible tornadoes; they are a rare phenomenon and it is a lot more painful to miss an observing opportunity than it is to be operating and nothing happens.

A final IOP decision will be made Thursday afternoon, 8 March.

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