weatherguy08
(Weather Hobbyist)
Sat May 31 2008 10:05 PM
Re: Tropical Storm Arthur Starts 2008 Atlantic Season

I find it almost scary how accurate the models were on Arthur. I clearly remember all of us talking about the potential for something to develop last Sunday and Monday, then come Saturday, the first named storm of the system has developed. I'm not totally sure if this was an "accident" by the models or if they really caught on to the developing the system, but am not one to believe that all major models would develop a low this early and predict it so well a week out by total accident. This is something we are going to need to remember throughout the season, that we cannot simply right off a system a week before, especially if models are consistently in agreement with each other.

On a related note, this was from the Saturday PM AFD issued by the NWS Office in Lake Charles, LA:

"WITH THE RIDGE OUT OF THE WAY [next weekend]...THIS SCENARIO WILL OPEN
THE GULF TO TROPICAL DISTURBANCES/MOISTURE FROM THE CARIBBEAN. BOTH
THE GFS AND ECMWF...THOUGH DIFFERING FROM RUN TO RUN AND WITH EACH
OTHER...ARE INSISTENT THAT AN AREA OF SFC LOW PRESSURE WILL
EVENTUALLY LIFT OUT OF THE CARIBBEAN INTO THE GULF. WILL CONTINUE
TO MONITOR TRENDS."

The HPC said something similar:

"WHILE TS ARTHUR IS EXPECTED TO DISSIPATE OVER THE YUCATAN
PENINSULA ON WED DAY 4...THE GFS AND ECMWF STILL SHOW AN AREA OF
UNSETTLED WEATHER AND A POSSIBLE LOW CENTER IN THE BAY OF CAMPECHE ON FRI."

After looking at the models, the GFS shows the ridge over the GoM and the CONUS holding through Tuesday. On Tuesday, a low pressure system develops over KS/CO/OK Panhandle area and moves east. Then on Wednesday, a second area of low pressure forms in a similar area then also moves to the east. The combination of these two system results in weakening of the ridge and pressure falls over the GoM, thus "opening the door" for systems to move into the GoM. The ECMWF shows a very similar situation. The ECMWF shows falling surface pressures over the southern GoM in nine to ten days (i.e. Jun 9-10). The GFS only shows a broad area of low pressure over the Gulf, but it does show several consecutive low pressure system moving through the middle part of the CONUS which would "keep the door open" for anything to come up into the Gulf.

In summary, I'm not really saying if anything will develop, but the patterns appear to be in place to allow something to move northwards.



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