TROPICAL STORM TAMMY FORECAST SYNOPSIS…ISSUED OCT. 19, 2023…2:00 P.M. EDT

ALL forecasts herein are the result of my analysis, (to which you will see me at times, insert excerpts from various agencies due to the nature of the importance of the information) and I am solely responsible for the content.  As ALWAYS, follow the National Hurricane Center, National Weather Service, and your local Emergency Management officials for emergency decisions.  In addition, this is strictly a FORECAST OFFICE.  I CANNOT make decisions regarding travel plans, etc.  My purpose, is to provide you the information, based solely on information I analyze, and the accuracy of the information at hand of the time of analysis, so you may make informed decisions.
(T. F. “Storm” Walsh)

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I will reiterate, my forecasts are based on the available information at the time of analysis, and are only as accurate as the information analyzed and the solutions provided.  Keep in mind, if a forecast doesn’t exactly pan out, remember, the atmosphere is fluid in motion.  When models are being analyzed, that’s just one run, and I have to go with what is presented.  After that, models don’t update again for another 4 – 6 hours, so, what happens between that time is unknown, and forecast conditions can change slightly, to greatly.  This will have an effect on my actual forecast.  Unless otherwise noted, satellite imagery is provided through Weathernerds.org

The following is my outlook forecast for the 2023 Atlantic Hurricane Season:
STORM W SEASONAL FORECAST
TOTAL NAMED STORMS: 14– 16
TOTAL HURRICANES :        5 – 7
MAJOR HURRICANES:        3 – 4

AVERAGE HURRICANE SEASON:
TOTAL NAMED STORMS: 14
TOTAL HURRICANES:         7
MAJOR HURRICANES:        3

SEASON TOTALS:
NAMED STORMS:          19
HURRICANES:                 6
MAJOR HURRICANES:  3

The following are the storm names for the 2023 hurricane season.  As each storm is named, they will be colored in red in order to keep track of the used names in the list:

Arlene Bret Cindy Don Emily Franklin Gert Harold Idalia Jose Katia
Lee Margot Nigel Ophelia Philippe Rina Sean Tammy Vince Whitney

Greetings everyone! 
As a reminder, when forecasting tropical systems, if there are numerous systems to deal with, I always update on the systems that may present an impact or threat to either the U. S. or the Caribbean islands.  Anything far out in the Atlantic or something that may re-curve, take a lower priority as there is more time to deal with them.  Unless we have a system threatening any area, the forecast office will be closed on the weekends.

Tropical Storm TAMMY is being slightly sheared at the moment, due to the radial shear pattern being centered west of the LLC.  As of the 2:00 p.m. intermediate advisory from the NHC, the following was available on TAMMY:
2:00 PM AST Thu Oct 19
Location: 13.5°N 56.4°W
Moving: W at 14 mph
Min pressure: 1002 mb / 29.59 in
Max sustained: 60 mph
Visible satellite loop imagery indicated that the LLC was displaced slightly to the west of the heavy convection:
TAMMY IR AND VISIBLE LOOP


ADT WIND FIELD

I have no change in my forecast thinking other than TAMMY could encounter some drier air in the updated forecast, and based on current TPW analysis, she may be taking in a little dry air at the moment.  Models still indicate some fairly conducive conditions ahead.  Updated runs of the ECMWF and GFS show pretty much the same forecast pattern from yesterday, however the radial shear pattern may not be directly overhead of the storm, but offset slightly west, but not as much as shown in the current CIMSS shear pattern.  Analysis of the 12Z SHIPS diagnostic report, and forecast shear graphs from CIRA, shear is not forecast to appreciably increase for the next 48 – 60 hours.  Analysis of the GFS zonal shear model indicated the GFS shows zero zonal shear within the forecast period out to almost 72 hours.  Based on analyzed forecast conditions, I expect further gradual strengthening during the next 72 hours, and TAMMY could quite be a minimal category 1 hurricane upon reaching the very northern Leeward islands.  While some slight shear may remain, the models call for the upper level pattern to improve providing a little more decent outflow, increase in PWAT, and favorable RH values, though a little drier south of the storm.  In addition, TAMMY will be moving over increasing OHC.  Based on this, the higher OHC and the forecast of an improving upper level pattern should have an offset on any shear, thus my reasoning for the hurricane status.  For the time being, I agree with the NHC intensity forecast
NHC INTENSITY FORECAST

INIT  19/1500Z 13.6N  55.7W   50 KT  60 MPH
 12H  20/0000Z 14.0N  57.4W   55 KT  65 MPH
 24H  20/1200Z 14.8N  59.2W   60 KT  70 MPH
 36H  21/0000Z 16.0N  60.9W   60 KT  70 MPH
 48H  21/1200Z 17.5N  62.1W   65 KT  75 MPH
 60H  22/0000Z 19.0N  62.8W   70 KT  80 MPH
 72H  22/1200Z 20.5N  63.3W   70 KT  80 MPH
 96H  23/1200Z 24.0N  62.8W   75 KT  85 MPH
120H  24/1200Z 28.4N  57.9W   75 KT  85 MPH

SUMMARY OF WATCHES AND WARNINGS IN EFFECT:

A Hurricane Watch is in effect for...
* Guadeloupe
A Tropical Storm Warning is in effect for...
* Guadeloupe

A Tropical Storm Watch is in effect for...
* Barbados
* Dominica
* Martinique
* Antigua, Barbuda, Montserrat, St. Kitts, Nevis, Anguilla, and St.
Barthelemy
* Saba and St. Eustatius
* St. Maarten
* St. Martin
A Hurricane Watch means that hurricane conditions are possible
within the watch area.  A watch is typically issued 48 hours
before the anticipated first occurrence of tropical-storm-force
winds, conditions that make outside preparations difficult or
dangerous.
A Tropical Storm Warning means that tropical storm conditions are
expected somewhere within the warning area within 36 hours.

A Tropical Storm Watch means that tropical storm conditions are
possible within the watch area, generally within 48 hours.

Additional watches and warnings will likely be required later
today.

Please refer to the NHC Public Advisory page for further information on watches, warnings, and hazards.

NHC PUBLIC ADVISORY
https://www.nhc.noaa.gov/text/refresh/MIATCPAT5+shtml/182043.shtml?

Centro Nacional de Huracanes Aviso Publico
https://www.nhc.noaa.gov/text/refresh/SJUTCPAT5+shtml/191501.shtml

There has been no change in my track forecast thinking. Based on analysis of forecast steering maps, and 500 mb geopotential height forecast maps, TAMMY is still on the southern periphery of the subtropical ridge.  In about 24 hours, she should be approaching the western edge of this ridge.  At he same time, an approaching deep layer trough is forecast to create a weakness in the ridge, and should allow TAMMY to turn toward the NW.  The majority of the guidance package indicates this, and I prefer the TVCE and TVCA consensus track.  Based on this, I agree with the NHC forecast track.
12Z TRACK GUIDANCE AND NHC FORECAST TRACK MAP





The following are projected wave heights from the Wavewatch 3 model
WAVEWATCH 3 FORECAST

NHC GRAPHICS PAGE
https://www.nhc.noaa.gov/refresh/graphics_at5+shtml/145301.shtml?3-daynl

The following map will allow to get information from your NWS office.
NWS WATCH / WARNING DISPLAY (LINKED…CLICK MAP, THEN YOUR AREA)

NWS DOPPLER RADAR LOOP (LINKED, CLICK RADAR MAP)

RAP RADAR (CLICK IMAGE THEN RADAR SITE…ONCE YOU CLICK THE SITE, GO TO LOOP DURATION TO CREATE A LOOP)
CARIBBEAN RADAR (CLICK IMAGE)

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