IDALIA INTENSIFIES…HURRICANE WARNINGS ISSUED FOR THE FLORIDA GULF COAST…FORECAST SYNOPSIS…ISSUED AUG. 28, 2023…2:50 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.

The following is my outlook forecast for the 2023 Atlantic Hurricane Season:
STORM W SEASONAL FORECAST
TOTAL NAMED STORMS: 11– 14
TOTAL HURRICANES :       5 – 6
MAJOR HURRICANES:       2 – 3

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

SEASON TOTALS
NAMED STORMS:          9
HURRICANES:                2
MAJOR HURRICANES: 1

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.

Satellite loop imagery this morning show IDALIA still trying to get its act together.  IR imagery indicates deep convection pulsing and moving around the system.  However, recent visible imagery indicates the LLC had been exposed, but has now moved to a position under the very northern edge of the deep convection.  Water Vapor loop imagery shows IDALIA may be having a slight problem with dry air, and close analysis of the visible channel tends to indicate this.
WEATHERNERDS GOES 16 SATELLITE LOOP IMAGERY IDALIA



As of the 2:00 p.m. EDT advisory from the NHC, the following information was available on IDALIA:
1:00 PM CDT Mon Aug 28
Location: 21.2°N 85.1°W
Moving: N at 8 mph
Min pressure: 987 mb / 29.15 in
Max sustained: 70 mph
PLEASE REFER TO THE FOLLOWING FOR WATCHES, WARNINGS, and VERY IMPORTANT STORM INFORMATION:
https://www.nhc.noaa.gov/text/refresh/MIATCPAT5+shtml/281753.shtml?

The most recent satellite and recon fixes indicate IDALIA is now moving to the north.  Based on current steering layers mean and water vapor loop imagery, a mid level shortwave trof is over the central GOMEX,  and the current setup should allow IDALIA to continue moving northward, for about the next 24 – 36 hours.  As this trof passes, another trof is forecast to move into the central and eastern U.S.  This should begin the more NNE track for IDALIA.  Based on current and forecast steering maps, this appears to be the case at the moment.  However, this will all depend on how quickly IDALIA becomes more organized, and how quickly she strengthens.  The stronger the system, the higher up in the atmosphere is the steering mean.  Currently, she is being steered at the 850 – 500 mb mean.  If she intensifies to 60 knots, she will be steered by the next layer up, 850 – 400 mb mean
CURRENT STEERING LAYER MEAN

850 – 400 MEAN

Based on my analysis, and the tight cluster of the track guidance models, I agree with the NHC forecast track at the moment.  Based on this, landfall appears to be close to Cedar Key, FL.
12Z TRACK GUIDANCE

NHC TRACKING MAP

Keep in mind, THIS IS NOT WRITTEN IN STONE and any shift in track could rpesent a whole new set of conditions!  Again, once this clears the Yucatan Channel, Yucatan Peninsula and Cuba, strengthening should begin to occur, and model guidance information should become more accurate.  One factor in the lolly gagging around is IDALIA has been under the influence of alcohol…just kidding.  She has been under the influence of the parent circulation of embedded within the CAG (Central American Gyre), as shown in recent 850 mb vorticity maps

The recent reported intensity from the NHC is 70 mph.  Bear in mind, we went from 45 mph yesterday evening, up to 65 mph earlier this morning.  Based on current conditions from CIMSS, the radial shear pattern has shifted west somewhat and is located over the Yucatan Peninsula.  This is allowing for some moderate shear over the system, which would explain the center being just under the northern edge of the deep convection.  The 200 mb outflow has become somewhat less defined but strong around the southern periphery.  However PWAT is still high, and IDALIA will be traversing very warm water and moderate to high OHC (Ocean Heat Content).
CIMSS UPPER LEVEL

WIND SHEAR

PWAT

I still have no change yet in my forecast reasoning in that both the ECMWF and GFS models still indicate improving conditions for IDALIA once she fully enters the GOMEX, and is inline with the 11:00 a.m. NHC forecast discussion:
Although there is still some moderate northwesterly shear over the storm, intensification seems likely during the next 12-18 hours, and Idalia is forecast to become a hurricane during that time. By Tuesday, the environment over the eastern Gulf of Mexico is expected to become more conducive for strengthening. Steady to rapid intensification is predicted beginning Tuesday while Idalia traverses the warm waters of the eastern Gulf and the upper-level environment becomes more favorable. The NHC intensity forecast again calls for Idalia to reach major hurricane strength before landfall along the Gulf coast of Florida.
This is still indicated by both the ECMWF and GFS.  I am only using the ECMWF graphics, except for mid level RH, which was unavailable:
SHEAR

PWAT

200 MB

GFS MID LEVEL RH

IRT the 200 mb streamline pattern, there is very good diffluence shown, and the storm will be under the influence of the right rear entrance region of a 200 mb jetstreak NNE of the system.  This will aid in creating divergence aloft:
JETSTREAK INFORMATION
https://www.theweatherprediction.com/habyhints2/601/

Based on the information I have analyzed, I still believe once IDALIA moves into the GOMEX and clears the surrounding land masses, she should begin rapid intensification.  While intensity guidance models have changed this morning on the 12Z update, only indicating a high end category 2 storm, I cannot safely rule out the possibility of a minimal category 3 system prior to landfall.  As I think back to last season, the forecast conditions seem pretty similar to what was forecast for IAN.  In fact, upon analyzing real time info as far as shear and upper pattern, conditions did not appear extremely favorable, however look at how quickly he intensified to CAT 4 – 5.  Given this, I cannot rule out the NHC intensity forecast:
INIT 28/1500Z 20.8N 85.2W 55 KT 65 MPH
12H 29/0000Z 22.0N 85.2W 65 KT 75 MPH
24H 29/1200Z 23.9N 85.1W 75 KT 85 MPH
36H 30/0000Z 26.4N 84.6W 90 KT 105 MPH
48H 30/1200Z 29.2N 83.5W 100 KT 115 MPH
60H 31/0000Z 31.9N 81.2W 55 KT 65 MPH…INLAND
72H 31/1200Z 33.6N 78.0W 50 KT 60 MPH…OVER WATER
96H 01/1200Z 34.6N 71.2W 50 KT 60 MPH
120H 02/1200Z 34.5N 67.0W 50 KT 60 MPH

Hurricane warnings have been issued along the west coast of Florida.  Since I have been working on this since about 11:00 a.m., in order to save time, please click on all the graphics for IDALIA from the NHC website:
NHC GRAPHICS PAGE:
https://www.nhc.noaa.gov/refresh/graphics_at5+shtml/175343.shtml?3-daynl

Please use the following LOCAL STATEMENTS page by clicking the bold blue headings under each column:
LOCAL STATEMENTS
https://www.nhc.noaa.gov/text/refresh/index_hls5+shtml/281810.shtml?

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

WSI 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)
I will have another update sometime tomorrow afternoon.

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

Have a blessed evening!

T. F. “STORM” WALSH III
GMCS, USCG (ret)
METEOROLOGIST / HURRICANE SPECIALIST /SEVERE WEATHER SPECIALIST
MEMBER WEST CENTRAL FLORIDA AMS