First Alert Weather

Talking the Tropics With Mike: Tropical depression #13 forms over the E. Atlantic & will become Lee

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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: None through this week...

The Atlantic Basin Overview:

** T.D. #13 has formed & will become “Lee”.

** A large tropical wave is moving off the coast of Africa & - while it is likely to develop - should stay far out to sea over the E. & Central Atlantic.

(1) The strong tropical wave - ‘95-L’ - that moved off the coast of Africa this past weekend has been upgraded to tropical depression #13 & will soon be “Lee”. T.D. #13 will move over the main development region (MDR) through the weekend & appears destined to become a textbook long track hurricane. There *COULD* be a threat to parts of the Caribbean &/or the U.S. in about 6-10 days but plenty of time to see how things - steering currents in particular - play out.

*Current* indications are a close call for Puerto Rico by the weekend then a turn more north a little east of Bahamas & *probably* east of Fl. But folks in Puerto Rico need to closely monitor the latest forecasts as what is likely to be a powerful hurricane will be nearby - to the north & northeast based on the current forecast - Saturday into Sunday. Given weakening shear & warm sea surface temps. + nearly unanimous agreement among the forecast models, the third major (Franklin & Idalia so far) hurricane of the Atlantic season is likely on the way.

If this is a threat for any of the U.S. lower 48, it would appear to be north of Jacksonville... & 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 at the moment showing a powerful hurricane with the GFS generally a little faster with forward movement vs. the European.

The Bermuda High remains anchored rather far north & east which is favorable for a fairly early turn north of a potentially well developed & strong hurricane.

(2) A very strong tropical wave is coming off the coast of Africa & is likely to develop. But this wave is also likely to stay far to the east over the Eastern & Central Atlantic.

The next two images from University of Wisconsin-Milwaukee - the first one is the spaghetti plot... 2nd one is interesting & shows the top 10 analog tracks for where t.d. #13 is located....

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..... “Lee” 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:


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

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

East/Central Pacific:


West Pacific:

Newly formed “Yun-Yeung” is forecast to move just a little east of Japan late this week into the weekend:

Global tropical activity:

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