Talking the Tropics With Mike: Debby weaker-still heavy rain & isolated tornadoes...E. Atlantic wave

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Tropics threats for Jacksonville/NE Florida/SE Georgia: None.

The Atlantic Basin Overview:

(1) “Debby” - The 4th Atlantic named storm of the season strengthened into the 2nd hurricane of the season with the 11pm Sunday, 08/04 advisory. Debby was intensifying right up to landfall but thankfully ran out of time over the warm Gulf water with a 7am EDT landfall at Steinhatchee some 60-70 miles north/northwest of Cedar Key followed by a second landfall as a tropical storm at Bulls Bay, SC early Thu.

Debby has finally been captured by an upper level trough & will accelerate north/northeast as a post-tropical low still capable of producing heavy rain & isolated tornadoes through Saturday from Washington D.C. to Northern New England & Southeast Canada before emerging over the far NW Atlantic.

(2) A couple of active tropical waves are over the Central & Eastern Atlantic. Forecast models have started to catch on to the potential for active couple (at least) of weeks ahead.

The primary first ‘wave of interest’ came off the coast of Africa a few days ago & will continue moving westward then veer west/northwest once about two-thirds west - 45 - 50 degrees W - across the Atlantic. This wave has longer term potential & we may have a tropical cyclone close to the Caribbean &/or SW Atlantic by the middle of next week (Aug. 13th - 15th... & *perhaps* not too far from the U.S. approx Aug. 17th-19th [a week from this weekend]). It’s way too early to determine exact track or any threat to land, but it’s certainly a wave to watch. A faster deepening storm would likely turn northward earlier. And it’s wise to note the European forecast model has had an east bias so far this season.

If there’s a threat to land... it would be appear what could become “Ernesto” will near Puerto Rico by next Tue./Wed... then the Southeast Bahamas a couple of days later. The majority of the long term guidance shows a pretty sharp northward turn, but that’s still more than a week away & anyone of the U.S. east coast should monitor this potential system.

(3) The tropical wave that crossed the Caribbean this week has developed a good deal of convection but is already moving over Central America. There is still some chance for some development over the far SW Gulf of Mexico.

(4) A large upper level low pressure area is spinning over the W. Atlantic while rather quickly lifting N/NE - no surface development is expected.

The velocity potential anomalies map below shows a lot of sinking air (brown lines) - & a lack of convection - over the Atlantic Basin to the far East Pacific while rising air (green lines) is over the Eastern Pacific where strong convection is notable. Often the green areas (MJO pulse) will correlate with increased tropical activity. So it’s the E. Pacific that is active, & this pulse is moving eastward - signs of which we’re already seeing - helping to set off a return to a more active Atlantic through at mid to late August.

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 might occur.

The upper oceanic heat content (UOHC) [tropical cyclone heat potential/TCHP] across the SW Atlantic, Gulf & Caribbean is unseasonably high for this time of year:

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

August tropical cyclone origins (early season breeding grounds are the Gulf &/or Western Caribbean:

Averages below based on climatology for the Atlantic Basin for August (1 hurricane so far, 3 tropical storms):

Wind shear (red - strong shear; green - low shear):

Saharan dust spreads west each year from Africa driven 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* interfere with 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 dust plume then try to develop if other conditions are favorable (we’ve already seen this with Beryl & Debby this year). In my personal opinion, there is way too much “hoopla” 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.

2024 names..... “Ernesto” 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 (the last time this year’s list was used)... 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 because of the ‘04 season when Charley, Frances, Jeanne & Ivan - all retired names - hit Florida within a matter of about 6 weeks. 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 colors will brighten greatly as the water warms to greater depths deeper into the season: