HURRICANE TAMMY / TROPICAL WEATHER OUTLOOK FORECAST SYNOPSIS…ISSUED OCT. 25, 2023…11:25 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 has strengthened a bit more than what was expected a couple of days ago.  Maximum sustained winds were 105 mph.  The following information was available on Tammy as of the 11:00 a.m. advisory:
11:00 AM AST Wed Oct 25
Location: 26.6°N 59.3°W
Moving: NE at 13 mph
Min pressure: 965 mb / 28.50 in
Max sustained: 105 mph

Visible satellite loop imagery indicated a fairly tight core and ragged eye.
TAMMY IR AND VISIBLE LOOP


The hurricane is under approximately 40 – 45 kts of wind shear.  Mid level shear at the time of analysis was around 25 kts.  A strong upper level, northern outflow channel was present and may be the reason Tammy has been able to strengthen, due to the great upper level divergence.  However, shear at the mid level is below the outflow level and should begin to have an effect.  In fact based on the appearance of the upper pattern, mid level shear, and strong SWLY shear, Tammy may be close to beginning the transition to post tropical / extratropical, as the pattern suggests it may be turning more to a baroclinic state.
CIMSS WIND SHEAR AND UPPER LEVEL WINDS


CIMSS MID LEVEL SHEAR, UPPER LEVEL DIVERGENCE, AND LOWER LEVEL CONVERGENCE



Based on analysis of wind shear forecast maps from both the ECMWF and GFS, along with SHIPS diagnostics, and CIRA shear forecast, wind shear is forecast to remain high over Tammy for almost the next 72 hours.  Based on the very divergent pattern, Tammy could intensify slightly.  However, Tammy should merge with the stalled front to her north and NW later tonight or by early tomorrow.  This will allow for her transition to post – tropical, which according to the NHC, should be completed in about 24 hours, though I believe the process is on the verge of beginning.  Based on my analysis, I agree with the NHC intensity forecast at the moment.
NHC INTENSITY FORECAST

INIT  25/1500Z 26.6N  59.3W   90 KT 105 MPH
 12H  26/0000Z 28.2N  58.8W   85 KT 100 MPH
 24H  26/1200Z 29.8N  59.5W   75 KT  85 MPH...POST-TROP/EXTRATROP
 36H  27/0000Z 30.5N  60.7W   65 KT  75 MPH...POST-TROP/EXTRATROP
 48H  27/1200Z 31.0N  61.8W   60 KT  70 MPH...POST-TROP/EXTRATROP
 60H  28/0000Z 31.2N  62.2W   55 KT  65 MPH...POST-TROP/EXTRATROP
 72H  28/1200Z 31.4N  62.7W   50 KT  60 MPH...POST-TROP/EXTRATROP
 96H  29/1200Z 31.7N  63.0W   45 KT  50 MPH...POST-TROP/EXTRATROP
120H  30/1200Z 31.9N  63.0W   40 KT  45 MPH...POST-TROP/EXTRATROP

WAVEWATCH 3 SIGNIFICANT WAVE HEIGHTS FORECAST

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

Based on analysis of forecast steering products and 500 mb geopotential height animations, TAMMY should begin a more northerly track by later today, and should begin to move toward the NW sometime on Thursday. Thereafter, guidance models indicate a slow westerly motion toward the island of Bermuda, before supposedly being steered away from the island by the forecast steering flow.  Based on this, I currently agree with the NHC forecast track, and tighly clustered track guidance.
12Z TRACK GUIDANCE AND NHC FORECAST TRACK MAP

NHC GRAPHICS PAGE
https://www.nhc.noaa.gov/refresh/graphics_at5+shtml/145611.shtml?3-daynl

Once Tammy makes the transition to post tropical, I will just be monitoring the situation as any watches or warnings issued will be from the Government of Bermuda.

Elsewhere, the ECMWF ensemble and control models, ECMWF, and for the most part the GFS, indicate another possible development.  The models are showing lowering pressures at 500 mb in about 4 – 5 days IVO the central Caribbean Sea.  The ECMWF ensemble members are beginning to indicate low pressure, along with the ECMWF and GFS models indicating the lowering of surface pressures during the period.
ECMWF ENSEMBLE 500 MB ANOMALY FORECAST

ECMWF ENSEMBLE (CONTROL) 500 MB ANOMALY FORECAST

ECMWF DETERMINISTIC

ECMWF ENSEMBLE AVERAGE

GFS 500 MB ANOMALY FORECAST

ECMWF AND GFS MSLP FORECAST


The ECMWF EPS cyclone probability forecast currently indicates a 40% probability of a tropical depression:

I will be monitoring the area closely during the next 72 – 96 hours.

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)

You may direct any questions by contacting me personally, ANYTIME, at: twalsh22000@yahoo.com