September 20, 2020

Tropical Storm Debby

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THERE HAS BEEN A SIGNIFICANT CHANGE IN THE FORECAST TRACK WITH THIS

ADVISORY. THE OFFICIAL FORECAST NO LONGER BRINGS DEBBY WESTWARD

ALONG THE NORTHERN GULF OF MEXICO AND INSTEAD KEEPS THE CYCLONE

MEANDERING OVER THE NORTHEASTERN GULF FOR THE NEXT 3 TO 4 DAYS.

THIS FORECAST IS A COMPROMISE BETWEEN THE CONSISTENT EASTWARD

SOLUTION PROVIDED BY THE GFS FOR THE PAST SEVERAL DAYS AND THE NEW

TWIST OF THE ECMWF. THE ECMWF MODEL…WHICH HAS BEEN

FORECASTING DEBBY TO MOVE WESTWARD ALONG THE GULF OF MEXICO… NOW

HAS THE CYCLONE MEANDERING FOR THE NEXT 3 DAYS OVER THE

NORTHEASTERN GULF. SINCE THESE TWO RELIABLE MODELS ARE IN

MARGINALLY BETTER AGREEMENT…I AM A LITTLE MORE CONFIDENT…BUT

NOT COMPLETELY…THAT DEBBY IS NOT GOING TO TURN WESTWARD OVER THE

GULF. HOWEVER…NEW OFFICIAL TRACK REMAINS A LOW-CONFIDENCE

FORECAST.

 

DEBBY IS A SPRAWLING SYSTEM…WITH MOST OF THE THUNDERSTORM ACTIVITY

IN A CURVED BAND WELL REMOVED FROM THE CENTER.  DATA FROM THE

RECONNAISSANCE PLANE A FEW HOURS AGO INDICATE THAT THE INITIAL

INTENSITY REMAINS 50 KNOTS. THE SHEAR IS NOT EXPECTED TO CHANGE

MUCH FOR THE NEXT DAY OR SO…BUT BECAUSE DEBBY IS FORECAST TO

REMAIN OVER WATER…THERE WILL BE SOME OPPORTUNITY FOR A SLIGHT

STRENGTHENING BEFORE THE CENTER MOVES INLAND. HOWEVER…THE CYCLONE

WILL LOCATED BE NORTH OF THE AREA OF HIGH OCEANIC HEAT CONTENT AND

THE UPWELLING COULD HALT THE INTENSIFICATION.

 

Rob Lightbown of Crown Weather said at 11:18am Sun Jun 4

According to recon reports this morning, the center of Tropical Storm Debby was located to the northeast of the NHC official position. The reason for this is because the center of the storm seems to be constantly moving underneath the deeper convection. This fact, plus a change in the overall guidance, has caused me to seriously doubt the forecast track towards Texas. Very frustrating to the say the least!! Additionally with thunderstorms trying to develop on the western side of this storm and the fact that wind shear values are decreasing, Debby is likely to strengthen over the next couple of days and become a hurricane.

The latest track guidance has gone against my thinking and have converged on a track onshore somewhere between the Florida Panhandle and southeastern Louisiana.

The big problem in the forecast track is the fact that the overall steering winds around Debby will be extremely weak over the next few days and the storm sits in between two big high pressure ridges. One ridge of high pressure will be located over the southern Plains while the other is sitting over the western Atlantic. In the middle is a departing trough of low pressure moving out of the northeastern United States.

The 10 million dollar forecast question is whether this trough of low pressure will be strong enough to pull Debby northeastward or will the trough miss the storm and allow the ridge of high pressure over the Southern Plains states build to the north and turn it westward.

This change in the overall guidance has really put me at odds on what to do. I had a couple of questions this morning to answer: The first is should I maintain a Texas track, but shift it northward up the coast. The second question is should I shift the forecast track dramatically and risk the error of having the track be totally wrong. One thing that I noted was that the European ensembles show a large spread in the possible tracks ranging from central and south Texas to Tampa.

So, it is of my opinion and of total frustration that I am shifting the forecast track for Debby to an area between Mobile Bay and Apalachicola. With that said, the overall steering around Debby is extremely difficult to forecast and that Texas scenario is still possible. I want to point out that I have a serious concern that the turn towards the west turn may actually occur as the storm is coming inland and travel right along the coast from the Florida panhandle westward to southern Louisiana. If this should come to pass, then much of the northern Gulf coast would be raked by strong winds, heavy rainfall & surge concerns.

All interests along the northern Gulf coast should continue to monitor the progress of Debby very closely.

 

For more up to date information on Debby go to:

www.crownweather.com/

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