Talking the Tropics With Mike: Once powerful Lee struggling against some shear & dry air

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*** LOCAL (Jacksonville/NE Fl./SE Ga.) IMPACTS FROM THE TROPICS: None through this weekend but building seas & surf by Monday & especially through mid & late next week with an escalating rip current risk...

The Atlantic Basin Overview:

** “Lee” was upgraded to a tropical storm Tue. afternoon & to a hurricane Wed. afternoon & intensified to a Cat. 4 Thu. afternoon & to a Cat. 5 late Thu. evening!... but has struggled recently but will be “on the field” through at least next weekend.

** The strong tropical wave - ‘96-L’ was upgraded to tropical depression #14 Thu. morning & “Margot” Thu. afternoon - should stay far out to sea over the E. then Central Atlantic.

** Another strong tropical wave moving west off the coast of Africa...

(1) The strong tropical wave - ‘95-L’ - that moved off the coast of Africa this past weekend and was upgraded to tropical depression #13 Tue. morning then to tropical storm “Lee” Tue. afternoon & then to a hurricane Wed. afternoon. The hurricane rapidly intensified Thu. becoming a Cat. 4 Thu. afternoon then a Cat. 5 later Wed. night. It’s the first Cat. 5 since Ian briefly reached Cat. 5 intensity over the Southeast Gulf late last Sept. Lee will move steadily west/northwest through the weekend while gradually slowing down & will be a textbook long track (mostly) major hurricane (Cat. 3+). I would not be surprised to see an annular hurricane at times once Lee is mature. Hurricane hunter aircraft will be investigating Lee daily through next week.

Lee’s track will move well north of Puerto Rico over the weekend then a veer more northwest east of the Bahamas while slowing its forward speed. The the hurricane goes far to the east of Fl. next week as Lee is likely to turn northward through a weakness - alleyway - over the Western Atlantic that’s become well established. Lee is the third major (Franklin & Idalia so far) hurricane of the Atlantic season ... the third hurricane of the Atlantic season develops - on average - Sept. 7 (4 so far this year) while the 2nd “major” hurricane average date is Sept. 19.

While fluctuations in intensity will occur due to structural changes such as eyewall replacement cycles from the weekend into much of next week, Lee should be a major hurricane for many days. There is some dry mid & upper level air just west/southwest of Lee which is occasionally eroding the western portion of the circulation & Lee may occasionally ingest some of that dry air but overall Lee should remain an intense island all to its own. It appears Lee may move over the cooled wake from Franklin by the middle of next week which could cause at least some weakening in addition to potential upwelling underneath a slower moving Lee from Sunday through about Wed. Some moderate mid & upper level shear is also impinging on the hurricane & looks to persist through at least Sunday. This shear + the nearby dry air seems to eating away a bit at the overall structure of Lee.

It looks like Lee will increase its forward speed again by mid to late next week as it fully rounds the west side of the Bermuda high & starts to feel the “pulling” effects of an approaching upper level trough. This is where the forecast track becomes more problematic & possibly - ultimately - a threat for a landfall..

If Lee is truly a threat for any of the U.S. lower 48, it would appear to be well north of Jacksonville on or near the upper U.S. east coast (New England) &/or some of the eastern provinces of Canada... & it’s possible it could stay east of the entire eastern seaboard but way too early to know definitively. The forecast models are in remarkably good agreement showing Lee not reaching Jacksonville’s latitude until next Thu. through early Fri. while 1,500+ miles to the east (the GFS has generally been about 12-24 hours earlier than the European). An easterly swell, rough seas & surf will impact our local beaches for much of next week with a high rip current risk. There’s the potential for 5-7+ foot breakers along the NE Fl. & SE Ga. coast next Wed. through Fri.

There continues to be at least some signal in the forecast models - albeit very inconsistent - for potential direct impacts from Lee for New England by late next week into the following weekend a well as Nova Scotia & Newfoundland. This part of the forecast track is the most uncertain but should come into clearer view by early next week. The European model has generally been more west than the GFS & has been leaning toward a track that would be of great concern for New England by next weekend. Lee would likely be anywhere from a Cat. 1 to Cat. 3 by then but would also be a much more expansive storm.

The Bermuda High remains anchored rather far north & east which is favorable for an early turn north of the intense hurricane. But once Lee has rounded the western edge of the Bermuda high while an upper level trough is moving through the Central & Eastern U.S., Lee will make a turn more north & possibly even northwest later next week which could bring into “play” New England & Eastern Canada as an upper level trough moves eastward toward the NW Atlantic possibly drawing Lee a little more northwest for a time as the tropical cyclone interacts with the trough.

(2) The very strong tropical wave - ‘96-L’ - was upgraded to t.d. # 14 Thu. morning over the far Eastern Atlantic & to tropical storm “Margot” late Thu. This tropical cyclone is likely to stay far to the east over the Eastern & Central Atlantic but should eventually become a hurricane once in a more favorable environment by at least the early to middle part of next week & may ultimately be another ‘major’ hurricane.

(3) A strong tropical wave is emerging off the coast of Africa & has the potential to develop but not until the longer range (beyond the next week to 10 days) while moving westward on roughly the same path as Lee & farther south than Margot. Models have been inconsistent with when & if this wave might try to develop. But earlier development would probably mean an earlier turn to the north (which is what we’ll root for!).

The image below is from University of Wisconsin-Milwaukee & shows the top 10 analog tracks for where Lee developed (only one of the analogs has hit Florida)....

“Margot” - East Atlantic:

The map below is the 500 mb (~30,000 feet) forecast for next Tue. (09/12) from the European model. The Bermuda High is weaker & shifted a little northeast while a trough of low pressure dives into the Eastern U.S. This combination should help Lee turn northward to the east of Florida but an eventual turn more north or northwest is still possible in the long range once north of Florida’s latitude.

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 stretching eastward all the way into the Central Atlantic:

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..... “Nigel” 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.: