POSSIBLE SUB-TROPICAL STORM FORMATION FORECAST SYNOPSIS…ISSUED MAY 01, 2015…12:00 NOON EDT

SEVERE WEATHER RISK:  NONE
TROPICAL STORM FORMATION:  NONE

ALL forecasts contained on this site,  are based on my analysis and knowledge of various forecast tools, including information contained in NHC products, and are not copies from any other entity.

During the Hurricane Season “Pre Season” time frame, given my limited forecast time due to my part time employment, Severe Weather forecasts will be suspended in order to focus on any probable mischief in the tropics.  Should conditions warrant, I will try to include Severe Weather, however it would be appreciated if subscribers refer to the Storm Prediction Center site.

Good day everyone,

Upon completing my analysis of the most recent run of Global models, and Regional DGEX solutions, save any erroneous model errors, or GIGO (Garbage In…Garbage Out), it is the professional opinion of this forecaster that either a baroclinic or sub-tropical storm should begin to develop IVO the northern Bahamas within the next 5 days.  As of my analysis this morning, the most widely use Global models show this solution, and have been in a run to run consistency over the past 4 -5 days, with the only major differences being strength,  track, and  of this supposed system.  The GFS, NAVGEM, and the regional DGEX keep the entity far enough offshore, indicating no real affect to the U.S. East Coast.  The European model (ECMWF) and the Canadian Model (CMCGGEM) indicate a sub-tropical storm making landfall over the southern portion of North Carolina, and the FIM 9 south of OBX.  The following maps indicate this morning’s model solutions, and my synopsis is posted below these maps.

GFS 165 HOUR FORECASTGFS.165
ECMWF 192 HOUR FORECAST
ECMWF 192
CMC 162 HOUR FORECAST
CMC 162
NAVGEM 144 HOUR FORECAST
NAVGEM 144
FIM 9 174 HOUR FORECASTwind_10m_f174

DGEX 144 HOUR FORECAST
DGEXseast.eta.10mw144
SSEC GEOSTATIONARY SATELLITE

Now, one may ask, “Are the SST’s warm enough for development”?  The answer to the question is…YES.  Another common question is usually concerning wind shear.  Well, a sub-tropical system is a little different critter, in that the SST’s only need to be at 23C, vice 26.5C for Tropical Storm formation.  Reason being is, these usually begin as cold core and transition to shallow warm core after being over the warmer water, relative to the surrounding atmosphere and environment in which the system is embedded.  Second, wind shear for the most part doesn’t affect a subtropical system as much as a pure tropical system.  Development and slow strengthening can occur, in such case as this probability, if the system is located to the east of the mid – upper level trof, and will develop in wind shear values >10 m/s -1.

Analysis of the CURRENT SST maps, and forecast wind shear from both the GFS and CMC this morning, indicate a somewhat favorable environment for a system to develop, and possibly strengthen slowly…as wind shear is forecast to relax somewhat around the specified forecast time frames.  I know thee wind shear maps can be confusing, so an easy way to remember what’s favorable, and what isn’t…BLUE – GREEN mean GO…DEEP YELLOW – RED mean STOP.

CURRENT SST MAP
natlanti.c
GFS WIND SHEAR FORECAST
GFS.850200shear25

CMC WIND SHEAR FORECAST
CMC.850200shear28

As far as track and strength…currently I have only ONE forecast steering layer map to rely on, which is from the GFS at the PSU e-WALL site, which keeps this away from the U.S. coast.  Based on this unfortunate glitch, this will have to be dealt with in real time if and when development occurs.  However, to give some idea, the ECMWF as a rule of thumb, usually outperforms the GFS as far as track (most of the time).  I have noticed in my forecasting over the past few hurricane seasons, that the CMC, albeit goes crazy a lot, it has had a decent track record on steering.  Based on this, and given modeling pretty much indicates some ridging in the forecast once this begins, along with 500 mb height rises north of the area indicated in the NCEP 500 mb anomaly departure forecast maps (would keep the system from escaping to the east), I have to side with the ECMWF, CMC, and FIM 9 models as far as track at this time. 

NCEP ESRL 500 MB ANOMALY DEPARTURE
z500nanom_f192_usbg

z500nanom_f216_usbg

I will be monitoring this during the course of the beginning of next week, and will be updating on my time off from work.

Elsewhere, Tropical Storm formation is not expected.

Have a blessed day!

T. F. “STORM” WALSH III GMCS, USCG (ret)
METEOROLOGIST / HURRICANE SPECIALIST / SEVERE WEATHER SPECIALIST MEMBER WEST CENTRAL FLORIDA AMS
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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4 Responses to POSSIBLE SUB-TROPICAL STORM FORMATION FORECAST SYNOPSIS…ISSUED MAY 01, 2015…12:00 NOON EDT

  1. originallt says:

    Thanks, Storm. Just looked at Sunday’s 12Z GFs(5-3-15) and it still shows a very weak system off the GA./S.C. coast by may7-8. Much weaker than the Euro.or CMC

  2. dellamom says:

    Thank you for your time and expertise, Storm. I hope the system plays with the fishes, but know that you will sound the alarm if people need to take action. God bless you and yours.

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