TROPICAL STORM DORIAN…FIRST CAPE VERDE STORM…FORECAST SYNOPSIS…JULY 24, 2013…ISSUED 11:25 A.M. EDT…PHFC

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Good day everyone!

ENTER…THE CAPE VERDE SEASON

Overnight,  INVEST 98L had acquired enough persistent convection near the center to be classified a Tropical Depression.  Over the past few hours, organization has continued to increase, and T.D. FOUR has strengthened to Tropical Storm Dorian…our FIRST official Cape Verde Storm.

As of the 11:00 a.m. EDT Advisory from the NHC, the following information was available on Dorian.

11:00 AM EDT Wed Jul 24
Location: 14.3°N 29.9°W
Moving: WNW at 21 mph
Min pressure: 1002 mb / 29.59 in
Max sustained: 50 mph

HURREVAC TRACKING MAP
DORIAN 72

DORIAN 120 FCST

TROPICAL STORM DORIAN SATELLITE FLOATER LOOP IMAGERY

Dorian continues toward the WNW, and I expect this motion to continue for approximately the next 42-48 hours, before more of a bend to the left occurs.  This is in agreement with the current run of the forecast steering layers maps from the PSU e-WALL site.  The current subtropical ridge steering Dorian at the moment, is forecast to continue to slowly shift westward over the next 5 days, and become more elongated.  This places a break in the ridge close to the vicinity of the Northern Bahamas / extreme SE FL. coast by that time.  Should nothing major change in the steering forecast, this system could POSSIBLY be a CONUS threat.  Based on the current and forecast steering maps, I concur with the NHC forecast track, and prefer a blend of the official track (OFCI) and TVCC/TVCN model guidance.

12Z DYNAMIC MODEL GUIDANCE
12zatcfearlyinvest1best.DORIAN

Based on the current wind shear map from CIMSS, the storm is under an upper level anticyclone at this time near 13.0N…30.0W.  Based on the 06Z run of the GFS Zonal Shear forecast, which has now been consistent run to run for the past 48 hours on this, indicates upper level winds to wane to semi conducive very briefly, but keeping the upper level anticyclone maintained over Dorian for the next 4-5 days.  At the end of the 5 day forecast period, westerly shear is expected to increase, so the system will most likely begin to weaken around that point and time.  Two factors right now will determine how strong Dorian may become, prior to encountering wind shear…cooler sst’s, and dry air just ahead of him.  So far, neither have been a factor, however cooler sst’s should affect Dorian in the next 12 hours or so, and this may arrest any further strengthening for a brief period.  However, save any dry air intrusion, based on the wind shear forecast at the moment, I would look further organization and slow strengthening beginning near 40W longitude.  Based on satellite loop imagery, should Dorian fight off dry air, given the current structure of the storm, albeit slim, I cannot fully rule out our first hurricane of this season SHOULD the storm overcome any of these negating factors, prior to the encounter of westerly shear.  Given the uncertainty and quick forward motion of the storm, I concur at the moment with the NHC intensity forecast.

NHC INTENSITY FORECAST

FORECAST POSITIONS AND MAX WINDS

INIT  24/0900Z 13.9N  28.1W   30 KT  35 MPH
 12H  24/1800Z 14.6N  30.8W   35 KT  40 MPH
 24H  25/0600Z 15.5N  34.4W   40 KT  45 MPH
 36H  25/1800Z 16.2N  37.8W   40 KT  45 MPH
 48H  26/0600Z 16.8N  41.2W   40 KT  45 MPH
 72H  27/0600Z 18.2N  49.0W   40 KT  45 MPH
 96H  28/0600Z 19.3N  56.5W   40 KT  45 MPH
120H  29/0600Z 20.0N  62.0W   40 KT  45 MPH

CIMSS EATL WIND SHEAR

GFS 06Z ZONAL SHEAR FORECAST MAPS

ATLANTIC WATER VAPOR LOOP IMAGERY (DRY AIR IN ORANGE)

I will continue to monitor the progress of Dorian for any significant changes.  I won’t have an update this evening, as I have a prior engagement this evening.

Have a blessed day!

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 TROPICAL STORM DORIAN…FIRST CAPE VERDE STORM…FORECAST SYNOPSIS…JULY 24, 2013…ISSUED 11:25 A.M. EDT…PHFC

  1. originallt says:

    Looking at the storm, it appears real small in size. Smaller than “average”.

  2. Monty says:

    Thanks Storm. I’m going to start sending your synopsis out to the gang. I trust your forecast more than anyone else’s!!

  3. TexasHurricane says:

    Thanks Storm, Any models suggesting where it may go, after it gets to the Carribean area?

  4. Elliot Lisak says:

    Thanks Again,

    Permission to come aboard Sir. You can captain my boat. As usual your on the ball. You should get a Nobel Prize. Clear, concise, and on point …. no bull glitz or fluff. We should clone you.

    Keep it up.

    Elliot

    • Thanks Elliot. Yeah, they won’t hire me cause I don’t have a degree.

      • dellamom says:

        Well, that just indicates that they either lack education or intelligence, not that you do. And the people making those decisions probably do have degrees, but not in anything remotely related to the decisions they are attempting to make. But that’s just me.

  5. originallt says:

    Thanks Storm. I see the NHC forecast strength chart, keeps it fairly weak, but you said it might develop into a Cat 1. I’ll go with you. It’s all ready stronger, at 50mph, than any figure in the chart.

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