Talking the Tropics With Mike: T'storms increase with wave near Bahamas -stays south of Jacksonville

Sept. 2, 2018 — The "Buresh Bottom Line": Always be prepared!.....First Alert Hurricane Survival Guide... City of Jacksonville Preparedness Guide... Georgia Hurricane Guide.

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Local - Jacksonville/NE Fl./SE Ga - impacts from the tropics through the holiday weekend: NONE (but there still will be some rain, heavy at times along with a moderate to high rip current risk at area beaches)......

The Atlantic Basin will be more active during Sept. which, of course, would be climatologically expected...

The Atlantic changes - regarding potential storm development - are underway & should continue into at least the middle of Sept. Tropical waves moving west off Africa are increasing in number & intensity & at least a couple waves are pretty likely to develop.  The uptick in activity coincides with a very persistent pattern of surface & upper level high pressure anchored over or near the N. Atlantic which implies lower pressures to the south (the ol' what goes up, must come down postulate).  The upper level map below for early Sunday shows a strong ridge of high pressure over the Eastern U.S.  This ridge will guide the tropical wave near the Southern Bahamas into the Gulf of Mexico & away from Fl. by mid week.  This upper level ridge will be critical this month as tropical cyclones & waves move westward across the Atlantic.  The orientation, position & strength of the ridge will help determine any possible hits on the Caribbean, U.S. &/or Mexico.

Tropical wave '91-L' - continues to be disorganized but shower & t'storm activity has increased over the Bahamas southward to the Greater Antilles.  The European model seems to have stabilized on a weak tropical cyclone developing over the Gulf of Mexico west of Florida by midweek.  Development fits the pattern overall, & now most global forecast models show at least weak development.   Shear is strong in the area of the wave now partly due to an upper low just east of Jacksonville, & the shear - while not as strong - will still likely be formidable on the backside of an upper level ridge over the Gulf.  So I'll stick to my guns in that there will be no tropical cyclone development hitting Fl. through Monday followed by a gradual attempt at organization Tue. - Thu. over the Gulf as the system moves away from Fl.  If the wave gets farther west over the Gulf (as indicated by the UKMET model) - vs. coming inland near New Orleans - conditions look to be more favorable for more substantial strengthening - less shear + more time over warm ocean.

So I see no changes to the local - Jacksonville/NE Fl./SE Ga. holiday weekend forecast: hot/humid... onshore flow off the Atlantic... scattered overnight/morning/midday convection at the beaches/intracoastal... scattered inland afternoon showers & storms with bands of rain & storms increasing by Monday.  A moderate to high rip current risk at area beaches.

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Tropical storm "Florence" continue over the E. Atlantic.  This system - as the storm becomes stronger/deeper - will turn more northwest over the Central Atlantic then stall - or even move slowly west - as strong high pressure moves across the N. Atlantic next week.  The turn west/northwest &/or stall will be something to watch but indications are that the next upper level trough / surface cold front will then pick up the system again which would lead to a full recurvature, but the pause will be something to monitor & consider.  The European model shows a weaker tropical cyclone which would allow for farther west movement (with the trade winds) while the GFS model shows a sharper & complete recurvature to the north with a stronger tropical cyclone.  The UKMET model is in-between.  I'm not ready to fully bite on any of the scenarios but the slowing of the storm over the Central Atlantic later next week will be a crossroads after which will be the critical move north as Florence is picked up by the next upper level trough OR a miss by the trough which would lead to a storm with a higher potential to get farther west.  Plenty of time to see how things evolve with Florence.  It would seem to me that any impact on the U.S. is at least 10 days away & would be north of Jacksonville IF anywhere on the U.S. coast.

Also of concern.... another wave - possibly two - that will move off the coast of Africa next week.  Either or both of these waves will have the potential to move farther west over the Atlantic as high pressure tries to assert itself across parts of the Central/Northern Atlantic.  Just how strong the Bermuda high is - or is not - will go a long ways in determining whether or not waves/tropical cyclones can move all the way across the Atlantic.

Again - the overall pattern - less shear... a little more moisture... an MJO pulse ..... + approaching the peak of the hurricane season all adds up to staying vigilant in the coming weeks.

The map below shows - in simplest terms - rising (green) & sinking (brown) air.  The green areas - in the tropics - are more favorable for tropical development & this kind of pattern is likely to overspread the Atlantic Basin in the coming weeks.

Note the disorganized showers & storms around Puerto Rico, Hispaniola & the SE Bahamas....

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Forecast model plots for Florence... the wave that moves into the Gulf of Mexico next week... & tropical cyclones over the E. Pacific:

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

The Atlantic Basin....

Caribbean:

Gulf of Mexico:

Water vapor imagery (dark blue indicates dry air):

Deep oceanic heat content continues to increase over the Caribbean & Gulf of Mexico as one would expect now that we're in August.....

Sea surface temp. anomalies show a general recent warming over a good portion of the Atlantic Basin ....

SE U.S. surface map:

Surface analysis centered on the tropical Atlantic:

Surface analysis of the Gulf:

Caribbean:

The E. Pacific remains a busy basin.  Triplets are spread out between Hawaii & Mexico: Miriam (left in the imagery below) is turning sharply north & will weaken while Norman moves west... & a new tropical depression west of Mexico moves westward.  All will stay over open water through the weekend though Norman will be a little northeast of Hawaii by midweek.

Norman:

Olivia:

In the W. Pacific.... once super typhoon "Jebi" is forecast to hit Japan by Tue./Wed. at Cat. 1 or Cat. 2 intensity - leading to heavy rain, strong winds & rough seas.

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