HURRICANE TAMMY FORECAST SYNOPSIS…ISSUED OCT. 20, 2023…11:50 A.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:                 7
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.

Hurricane  TAMMY is being slightly sheared at the moment, due to the radial shear pattern being centered well SW of the LLC.  As of the update at 11:00 a.m. from the NHC, the following was available on TAMMY:
11:00 AM AST Thu Oct 20
Location: 14.1°N 58.6°W
Moving: WNW at 7 mph
Min pressure: 992 mb / 29.29 in
Max sustained: 75 mph

Visible satellite loop imagery indicated that the LLC was displaced slightly to the west of the heavy convection.  This “tilt” is noted in current vorticity maps at 925 and 500 mb respectively.  CIMSS wind shear shows the radial shear pattern, while upper level winds have improved:
TAMMY IR AND VISIBLE LOOP


ADT WIND FIELD



CIMSS WIND SHEAR AND UPPER LEVEL WINDS


I have a slight change in my forecast thinking upon analysis of the current ECMWF and GFS model runs.  based on analysis of the current wind shear forecast, conditions are still forecast to improve slightly during the next 24 hours, with both models indicating the radial pattern to move a little closer toward the LLC, and with the 200 mb forecast indicating and improved outflow indicating a northward out flow channel / jet, and more symmetric PWAT and mid level relative humidity pattern, with increased values.  However, based on analysis of these products, the models indicate TAMMY may begin to feel some slight dry air intrusion, with an increase in wind shear sometime around the Sun. / Mon. time frame.  The 12Z SHIPS diagnostic message and forecast graph information from CIRA multi model diagnostic comparison indicate shear increasing to above 20 knots within the next 60 – 72 hours.  NHC did mention mid level shear may increase below the outflow level, which could be a slight hindrance for strengthening, however analysis of mid level shear so far indicates mid level shear is below 15 kts and has been over the past 24 hours.  Based on this analysis, I expect further gradual strengthening during the next 36 – 48 hours, and TAMMY could be a minimal category 1 hurricane later today.  NOTE: (as I was finishing typing out the synopsis, TAMMY was upgraded to a Category ONE hurricane.) For the time being, I agree with the NHC intensity forecast, which pretty much mimics current intensity forecast guidance:
NHC INTENSITY FORECAST

INIT  20/1500Z 14.1N  58.6W   65 KT  75 MPH
 12H  21/0000Z 15.1N  59.8W   70 KT  80 MPH
 24H  21/1200Z 16.4N  60.9W   75 KT  85 MPH
 36H  22/0000Z 17.9N  61.9W   75 KT  85 MPH
 48H  22/1200Z 19.3N  62.7W   80 KT  90 MPH
 60H  23/0000Z 20.6N  63.3W   80 KT  90 MPH
 72H  23/1200Z 22.0N  63.3W   80 KT  90 MPH
 96H  24/1200Z 24.4N  61.4W   80 KT  90 MPH
120H  25/1200Z 28.2N  57.7W   75 KT  85 MPH

12Z INTENSITY FORECAST GUIDANCE

SUMMARY OF WATCHES AND WARNINGS IN EFFECT:

The government of France has issued a Hurricane Warning for
Guadeloupe.
The government of Antigua has issued a Hurricane Warning for
Antigua, Barbuda, Montserrat, and St. Kitts and Nevis. 
A Hurricane Warning is in effect for...
* Guadeloupe
* Antigua, Barbuda, Montserrat, St. Kitts and Nevis 
A Hurricane Watch is in effect for...
* Anguilla
* St. Maarten
* St. Martin and St. Barthelemy
A Tropical Storm Warning is in effect for...
* Dominica
* Anguilla
* St. Maarten
* St. Martin and St. Barthelemy
* Saba and St. Eustatius
A Tropical Storm Watch is in effect for...
* Barbados
* Martinique
A Hurricane Watch means that hurricane conditions are possible
within the watch area, in this case within the next 24 to 36 hours.

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 could be required later today.

For storm information specific to your area, please monitor
products issued by your national meteorological service.

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/201458.shtml

CENTRO NACIONAL DE HURACANES AVISO PUBLICO
https://www.nhc.noaa.gov/text/refresh/SJUTCPAT5+shtml/201507.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  approaching a weakness in the ridge, caused by a deep layer trough.  This should allow TAMMY to begin the NW motion later today.  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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