DORIAN REMNANT (INVEST 91L) SPECIAL FORECAST SYNOPSIS…JULY 28, 2013…ISSUED 5:00 P.M. EDT…PHFC

Good evening everyone!

The remnant of Dorian was designated INVEST 91L earlier today.  I will be using these terms interchangeably in the synopsis.

The current STWO (Special Tropical Weather Outlook) from the NHC indicates the remnant is a sharp surface trof as found by reconnaissance aircraft.

NHC GRAPHICAL TROPICAL WEATHER OUTLOOK

ZCZC MIATWOAT ALL
TTAA00 KNHC DDHHMM

SPECIAL TROPICAL WEATHER OUTLOOK
NWS NATIONAL HURRICANE CENTER MIAMI FL
350 PM EDT SUN JUL 28 2013

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

1. DATA FROM AN AIR FORCE RECONNAISSANCE MISSION IN THE REMNANTS OF
DORIAN...LOCATED A COUPLE HUNDRED MILES NORTH OF THE LEEWARD
ISLANDS...INDICATE THAT THE DISTURBANCE DOES NOT HAVE A WELL-
DEFINED CENTER OF CIRCULATION AND CONSISTS OF A SHARP SURFACE
TROUGH.  THE SYSTEM IS PRODUCING WINDS TO GALE FORCE WELL NORTH OF
THE LEEWARD ISLANDS...HOWEVER THE ASSOCIATED SHOWER AND
THUNDERSTORM ACTIVITY HAS WEAKENED DURING THE PAST FEW HOURS.  

ENVIRONMENTAL WINDS ARE EXPECTED TO BE ONLY MARGINALLY CONDUCIVE FOR
REGENERATION DURING THE NEXT COUPLE OF DAYS.  THIS SYSTEM HAS A
MEDIUM CHANCE...30 PERCENT...OF BECOMING A TROPICAL CYCLONE DURING
THE NEXT 48 HOURS AS IT MOVES WESTWARD TO WEST-NORTHWESTWARD AT
AROUND 20 MPH...PASSING NORTH OF THE LEEWARD ISLANDS AND PUERTO
RICO THROUGH MONDAY...AND MOVING OVER THE TURKS AND CAICOS ISLANDS
AND SOUTHERN BAHAMAS ON TUESDAY.  

ADDITIONAL INFORMATION ON THIS SYSTEM CAN BE FOUND IN HIGH SEAS
FORECASTS ISSUED BY THE NATIONAL WEATHER SERVICE...UNDER AWIPS
HEADER NFDHSFAT1 AND WMO HEADER FZNT01 KWBC.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.

FORECASTER BERG

DORIAN FLOATER SATELLITE LOOP IMAGES

Upon my previous forecast, based on the last time I analyzed model data, data at the time did not support any regeneration of Dorian.  Upon researching back, I did notice, the steering layers forecast maps had in fact moved the remnants a little too quickly than what they have actually been moving…in fact, the current run of the steering layers forecast maps has 91L further west than what it actually is at this time.

The current wind shear product from CIMSS, does show a developing upper level anticyclone over the disturbance at the moment.  Another positive factor is, the TUTT to it’s west continues to move W-WNW in tandem with the system, thereby instead of having a negative effect, is just far enough from the disturbance to allow for ventilation over the ex-Dorian.

CIMSS CURRENT WIND SHEAR MAP

The upper level wind diagram does show a fairly robust upper level northern outflow channel, or jet if you will, with modest outflow around the southern periphery of the system.

CIMSS UPPER LEVEL WINDS MAP

CIMSS 850 MB VORTICITY MAP

INVEST 91L seems to have mixed out quite a bit of drier air, and may be able to continue this, as the further west it moves, it will be crossing over some moderate TCHP values, which can help add moisture to the system.

TROPICAL CYCLONE HEAT POTENTIAL (TCHP)

The latest run (12Z) of the GFS Zonal Shear forecast tends to indicate upper level conditions may not remain as hostile as first thought a couple of days ago.  The scenario calls for a waxing and waning of the upper level anticyclone over the next 48 hours, however the average indicates the upper level feature to remain over 91L during the next 48 hours.  Based on latest model guidance track, INVEST 91L should be withing little, to zero zonal shear thereafter.

GFS ZONAL SHEAR FORECAST VARIOUS TIMES

Based on this, I believe ex-Dorian, may have a better than average chance at regeneration over the next 48-72 hours.

Analysis of various satellite loop imagery channels, current and forecast steering layers maps, I tend to concur with the 18Z Dynamic Model Guidance, and prefer the TVCC/TVCN guidance track.  However, based on the forecast steering layers maps, I believe the model guidance may shift right, as the trof that will create the weakness will be slower to lift out than previously forecast.

INVEST 91L 18Z DYNAMIC MODEL GUIDANCE
18zatcfearlyinvest1bestDORIAN

As a precaution…not saying that regeneration is definite…residents of the Florida Peninsula should monitor the progress of this system over the next 72 hours.

I should have another update tomorrow afternoon after my meeting with USCG Air Station Clearwater.

Have a blessed evening!

T. F. “STORM” WALSH III
GMCS, USCG (ret)
METEOROLOGIST / HURRICANE SPECIALIST
MEMBER WEST CENTRAL FL AMS
CERTIFIED SKYWARN OFFICIAL STORM SPOTTER (advanced)
CoCoRaHS OBSERVER

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About palmharborforecastcenter

I am a Tropical Forecast meteorologist, providing hurricane forecasts during the Atlantic Hurricane Season. I retired from the U.S. Coast Guard in July of 2001. Meteorology became my passion in high school, and I have continued my educational background in meteorology since 1996, when I undertook the study of Tropical Meteorology. While working toward my degree, I had to unexpectedly withdraw from college due to my oldest sons medical reasons. I do however, meet the educational criteria of the AMS to be recognized as a meteorologist. Studies include, but are not limited to the Navy Aerographers Mate course, Naval METOC meteorology course, Meteorology 2010 Sophomore level course while attending St. Petersburg College, Clearwater, FL., Basic Forecasting course for operational meteorologists from Rapid WX, meteorology institute, a four month meteorological internship, and extensive research on numerous meteorological topics such as the MJO, NAO, satellite imagery interpretation, etc. I have been forecasting Tropical Weather (Tropical Storms and Hurricanes) since 1996, with my main client being three different Coast Guard Commands.
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10 Responses to DORIAN REMNANT (INVEST 91L) SPECIAL FORECAST SYNOPSIS…JULY 28, 2013…ISSUED 5:00 P.M. EDT…PHFC

  1. originallt says:

    Hi Storm and all, ex-Dorian looks better again this morning on satellite. Waiting to hear your interpretation on it. Thanking you in advance, LT.–PS., hope your morning meeting went well!!

  2. Thanks Storm
    Should this regenerate, does it get a new name as well as a new Invest No.?
    Hope Monty is wrong about MSY and IAH !! We don’t need anything in the GOM unless it degenerates to a BIG FAT RAIN STORM WITH NO W I N D S !!!

  3. Monty says:

    Thanks Storm….looks like models possibly having Dorian (if he should regenerate) heading close to MSY…possibly IAH even…time to start the updates again. I completely trust your synopsis and will take no chances…going out to the gang. Thanks always Storm!!

  4. Jerilyn (jerrob) says:

    Thank you! Will be watching

  5. stuffunee says:

    Thanks Storm. 🙂

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