Talking the Tropics With Mike: Idalia: WATCHES issued for parts of Fl... Franklin West Atlantic

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***** ALWAYS CHECK & RE-CHECK THE LATEST FORECAST & UPDATES! *****

REMEMBER WHEN A TROPICAL STORM OR HURRICANE IS APPROACHING: Taping windows is *not* recommended & will not keep glass from breaking. Instead close curtains & blinds.

Realize the forecast cone (”cone of uncertainty”) is the average forecast error over a given time - out to 5 days - & *does not* indicate the width of the storm &/or where damage that might occur.

*** LOCAL (Jacksonville/NE Fl./SE Ga.) IMPACTS FROM THE TROPICS:

* Tropical storm “Idalia”: Heavy rain & breezy to windy Tue. afternoon through Wed. into early Thu., isolated tornadoes possible...

* Hurricane Franklin: Rip currents & an easterly swell (waves) at the beaches through Mon./Tue. while 1,000+ miles to the east of Jacksonville

The Atlantic Basin Overview:

Tropical storm “Idalia” will slowly head north and pass through the Yucatan Channel late Monday. The tropical cyclone will be headed for NW Florida &/or Panhandle by midweek as a hurricane.

A Tropical Storm WARNING: Yucatan Peninsula from Tulum to Rio Lagartos, including Cozumel ... Pinar del Rio Cuba. A Storm Surge WATCH: Chokoloskee to Indian Pass Florida, including Tampa Bay... A Hurricane WATCH: Englewood to Indian Pass Florida, including Tampa Bay... A Tropical Storm WATCH: Isle of Youth Cuba ... South of Englewood to Chokoloskee Florida & Dry Tortugas, Florida.

Franklin hit Haiti & especially the Dominican Republic with very heavy rain last Wed. The hurricane is turning northwest with some distant impacts (waves & rip currents) on the U.S. east coast. Franklin will then accelerate to the north/northeast, & there will be some impacts for Bermuda by Tuesday. It now looks like the turn northeast over the NW Atlantic will be sharp enough to keep most impacts east of Canada.

(1) The area of disturbed weather near the Yucatan - Tropical depression #10 - strenghtened into tropical storm “Idalia” late Sunday morning. “Idalia” will first move slowly northward into the Southern Gulf than a turn more northeast - while accelerating - toward Florida with the entire Panhandle & upper west coast susceptible to a landfall. *At this point*... a landfall on the Eastern Panhandle or approximately Big Bend seems to be the area to focus on. The European model continues taking the storm to a landfall north of Tampa - pretty close to Cedar Key - early Wed. - a little faster & stronger than in some previous model output.

The American GFS model - which was late to the “party” - takes a pretty strong hurricane more north with a landfall on the Central Panhandle of Florida early Wed. close to Apalachicola... some 200+ miles to the west of the European model. The Canadian forecast model is similar to the European, just slightly more to the north. The UKMET model is slower & weaker with a landfall just about squarely on the corner of the Big Bend or about half way between the European & GFS landfall points.

Idalia will then turn rather sharply eastward by Wed. night/Thu. moving off the coast of the Carolina’s over the Western Atlantic.

So there’s a big question on exact landfall which will make a for a wide array of possible outcomes & subsequent damage risk. Based on the latest forecast with changes likely:

Track: northward into the Southern Gulf then a turn more northeast toward Florida with the entire Panhandle & much of the west coast susceptible to a landfall. *At this point*... a landfall on the Eastern Panhandle or approximately Big Bend seems to be the area to focus on.

Timing: over the northwest Caribbean through Sun. night... far Southern Gulf by Monday... starting to accelerate to the northeast or N/NE over the Eastern Gulf Tue./Wed. Highest potential impacts on Florida from late Tue. through Wed. evening depending, of course, on the exact track & intensity.

Strength: while sea surface temps. & oceanic heat content are very warm (usually are this time of year but even warmer than avg.), that alone will not necessarily result in a significant storm. Other factors have to be considered, especially wind shear & mid & upper level moisture. So...

(1) moisture - plenty. There’s lots of moisture present. Upon approach to land followed by the landfall, dry continental air will have a tendency to wrap around the underside (south) leaving a tropical cyclone heavily weighted on its north & northeast side at midweek following landfall.

(2) Right now - & through at least Monday - at least moderate shear (30+ mph) out of the west will persist. There will be some decrease in the wind shear by Tue./Wed. as the system approaches land & there will be some upper level ventilation thanks to a nearby trough of low pressure. In addition... Idalia will be moving in line with the mid/upper level wind vector so the effects of the shear should be lessened. And moisture (humidity) remains favorable. A hurricane is forecast at landfall - possibly as strong as a Cat. 2+.

Summary: The forecast is for Idalia to be a hurricane before & at landfall. A midweek strike is probable from the Fl. Panhandle to the upper west coast of Fl. So biggest impacts appear to be from approximately Mexico Beach to the Big Bend to north of Tampa. There will be lots of folks traveling late next week with Labor Day weekend just around the corner so stay up to date on the latest forecasts, but it does appear that t.d. #9 will have cleared the U.S. by at least Fri. though may linger east of the Carolina’s & offshore into the weekend.

Local (Jacksonville/NE Fl./SE Ga.) Impacts (BASED ON CURRENT FORECAST & SUBJECT TO CHANGE):

Rain - An average of 1-2″, locally 3-4″.... heaviest/most widespread from Lake City to Waycross (closer to the forecast track of the center).

Winds - averaging 20-30 mph sustained with gusts 40+ mph *but at this point* would not expect a big or overly strong wind “event”, especially east of I-95. If the European model verifies with Idalia more to the east, sustained tropical storm force winds (39+ mph) with hurricane force gusts (74+ mph) would occur west of I-95... & it’s *possible* hurricane force sustained winds occur from about Waycross to Lake City.

Coast/beaches: windy with winds of 20-30 mph & gusts 40-50+ mph. There will be a high rip current risk largely due to distant hurricane Franklin & an easterly swell. A full moon Wed. evening will also give an astronomical boost to surf. Based on the current forecast, this should not be particularly significant for our beaches. Seas will average 4-8 feet with surf averaging 3-6 feet, locally higher. The peak will be Wed. when seas could reach 8+ feet with surf up to 5+ feet. The best advice is to stay out of the ocean through midweek but if you do insist on going in the water, always swim & surf with a buddy & as close to a lifeguard as possible.

St. Johns River: Based on the latest forecast... strong winds from the south will push water northward to downtown causing potential flooding, the extent of which will depend on how close & how strong the center is to Jacksonville. Once the center of Idalia moves by to the northwest & north, strong winds out of the west will help to “empty” some of the water to the east. All areas along the river & its tributaries - from Putnam Co. through Clay/St. Johns & Duval Co. will be subject to flooding & backwash.

Tornadoes: At least isolated tornadoes are expected late Tue. through late Wed.

Damage: Mostly cosmetic/minor closer to the beach. A few sporadic power outages. Of course, isolated tornadoes could cause very localized more intense damage. If a trend more to the east continues then potential damage would increase too, especially west of I-95 where winds could be much stronger.

REALIZE ALL THESE IMPACTS ARE BASED ON CURRENT FORECASTS... & UNDERSTAND IMPACTS WILL BE MUCH GREATER CLOSER TO LANDFALL (PANHANDLE & UPPER FL. WEST COAST).

REMEMBER THAT THE FORECAST CONE ONLY INVOLVES THE EXPECTED PATH OF THE STORM. DON’T GET FIXATED ON THE CENTER & REALIZE IMPACTS FROM THE STORM WILL EXTEND FAR AWAY FROM THE CENTER.

The 5th image below is the European 500mb (~30-35,000 feet) model forecast for Monday, Aug. 28th. The alleyway for Franklin is clear over the W. Atlantic with the Bermuda high displaced far to the east while a trough of low pressure moves into the Eastern U.S. “Idalia” will have a tendency to get pulled northward given the strong continental high (”heat dome”) over the Central U.S. shifting more west while some semblance of troughing remains over/near the Eastern U.S.

Spaghetti plots including ensemble (instead of running just a single forecast, the computer model is run a number of times from slightly different starting conditions. The complete set of forecasts is referred to as the ensemble, and individual forecasts within it as ensemble members.) “Idalia”:

Peak storm surge forecast in feet above ground level:

The times below correlate with “most likely” arrival time of winds equal to or greater than 39 mph:

Brighter colors indicate higher probabilities of winds greater than or equal to 39 mph. Realize any probability above zero is significant considering most days the probability is zero.

Forecast rainfall in inches:

Water vapor loop. Blue color indicates dry mid & upper level air, white & green indicates high moisture levels:

Sea surface temps. plenty warm:

Mid & upper level wind shear is strong across the Gulf - 30-40+ mph. This will be an inhibitor, at least initially. But once Idalia starts to turn more northeast, it will be moving within the same vector of the shear so strengthening will be “easier”. The shear should also decrease some by midweek.

Oceanic heat content is pretty impressive, especially with a narrow ribbon from Cuba to the Northern Gulf then decreases some with northeastward extent:

Forecast rainfall, European model:

Forecast rainfall, GFS model (is forecasting landfall farther to the west):

(2) “Franklin” (upgraded late last Sunday) over the Northern Caribbean & is now a hurricane east of the Bahamas over the SW Atlantic making the sharp turn to the north/NW. The combination of lessening shear into early next week plus strong upper level diffluence thanks to a trough of low pressure to the north should lead to an eventually strong hurricane over the Western Atlantic with some impacts for Bermuda Tue. into Wed. as the eye moves by to the west & north. It now looks like Franklin will take a sharp enough turn to the east to *not* have direct impacts on Canada. Franklin will also be strong enough - while still well to the east of Florida - to produce an easterly swell at area beaches resulting in a heightened rip current risk all up & down the U.S. eastern seaboard through midweek. A full moon will also add an astronomical boost to seas & surf.

The forecast track is pretty straight forward with a well established alleyway across the Western Atlantic with Franklin accelerating over the next several days while maturing then bending rather sharply to the northeast once at about Jacksonville’s latitude. Franklin should be at about Jacksonville’s latitude but 1,000+ miles to the east late Monday into early Tue.

(3) tropical wave - ‘92-L’ came off the coast of Africa last weekend. This wave appears unlikely to develop now:

(4) And yet another tropical wave is moving west off the coast of Africa. Some gradual development will be possible over the open E. Atlantic.

Check out the upper oceanic heat content (UOHC) [tropical cyclone heat potential/TCHP] across the SW Atlantic, Gulf & Caribbean. The warmth is very deep. But keep in mind warm ocean temps. alone doesn’t necessarily equate to a “big” hurricane season (need other ingredients & factors to be favorable too) but it’s obvious there is a lot of very warm water at great depths over the Caribbean & Gulf of Mexico:

Water vapor loop (dark blue/yellow is dry mid & upper level air):

July tropical cyclone origins:

Averages below based on climatology for the Atlantic Basin for August:

Wind shear:

Saharan dust spreads west each year from Africa by the prevailing winds (from east to west over the Atlantic). Dry air - yellow/orange/red/pink. Widespread dust is indicative of dry air that can impede the development of tropical cyclones. However, sometimes “wanna’ be” waves will just wait until they get to the other side of - or away from - the plume then try to develop if other conditions are favorable. In my personal opinion, way too much is made about the presence of Saharan dust & how it relates to tropical cyclones. In any case, the peak of Saharan dust typically is in June & July.

2023 names..... “Jose” is the next name on the Atlantic list (names are picked at random by the World Meteorological Organization... repeat every 6 years). Historic storms are retired [Florence & Michael in ’18... Dorian in ’19 & Laura, Eta & Iota in ‘20, Ida in ‘21 & Fiona & Ian in ‘22]). In fact, this year’s list of names is rather infamous with “Katrina”, “Rita” & “Wilma” retired from the ‘05 list & “Harvey”, “Irma”,“Maria” & “Nate” from the ‘17 list. The WMO decided - beginning in 2021 - that the Greek alphabet will be no longer used & instead there will be a supplemental list of names if the first list is exhausted (has only happened three times - 2005, 2020 & 2021). The naming of tropical cyclones began on a consistent basis in 1953. More on the history of naming tropical cyclones * here *.

East Atlantic:

Mid & upper level wind shear (enemy of tropical cyclones) analysis (CIMMS). The red lines indicate strong shear:

Water vapor imagery (dark blue indicates dry air):

Deep oceanic heat content over the Gulf, Caribbean & deep tropical Atlantic. The brighter colors are expanding dramatically as we near the peak of the hurricane season.:

Sea surface temp. anomalies:

SE U.S. surface map:

Surface analysis centered on the tropical Atlantic:

Surface analysis of the Gulf:

Caribbean:

GFS wave forecast at 48 & 72 hours (2 & 3 days):

Atlantic Basin wave period forecast for 24, 48 & 72 hours respectively:

East/Central Pacific:

I wrote about “Hilary” near the top after the Atlantic waves. Elsewhere.....

“Irwin” to stay over the open E. Pacific:

West Pacific:

Global tropical activity:

“Damrey” forecast to stay east of Japan:

“Saola” is a formidable typhoon not far from the Philippines while making a loop & moving very slowly & may eventually be a long term - near the middle of the week - threat to Taiwan.