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Talking the Tropics With Mike: Distant Gaston joins powerful Fiona...Trop. wave headed for Caribbean

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REMEMBER WHEN A TROPICAL STORM OR HURRICANE IS APPROACHING: Taping windows is *NOT* helpful & will not keep glass from breaking.

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 damage that might occur.

** FIRST ALERT! ** - Anyone living in - or traveling to - the Caribbean, Gulf of Mexico, Yucatan Peninsula &/or the U.S. Gulf Coast should stay up to date on the latest forecast for a storm likely to develop over the Caribbean then a possible move over the Gulf of Mexico **

** No *inland* impacts from Fiona for Jacksonville/NE Fl./SE Ga.... beaches to be affected by easterly swells, somewhat rough seas/surf & a high rip current risk through late week augmented by onshore flow Fri. into the weekend.... & no impacts from Gaston over Central Atlantic **

Atlantic Basin:

Tropical wave - ‘96-L’ was upgraded to tropical depression #7 Wed. morning then to tropical storm “Fiona” Wed. evening & to a hurricane Sun. morning with a Cat. 1 (85 mph winds) landfall Sunday afternoon about 3:20pm EDT along the southwest coast of Puerto Rico near Punta Tocon followed by another landfall (Cat. 1/90 mph winds) early Mon. at 3:30am EDT along the coast of the Dominican Republic near Boca de Yuma. The hurricane strengthened into a Cat. 2 late Mon. then to a ‘major’ hurricane early Tue. - the first major hurricane of the Atlantic season. The avg. date for such an occurrence is Sept. 1.

Fiona’s steering currents are pretty straight forward & locked in (hence, a narrow forecast cone). The strongest shear is now oriented north & east of the eye & Fiona will remain on the western edge of the westerly shear thereby allowing for further strengthening over very warm ocean water with high humidity. While still restricted some over the western portion of the tropical cyclone, upper level outflow has improved dramatically & all signs point to a powerful Cat. 3+ hurricane for much of the rest of this week. Of note - the center moving a little south of due west into the face of the shear - as was the case last Wed./Thu. & parts of Fri. - has led to eventually powerful hurricanes that had a similar trend. And indeed Fiona followed suit. As Fiona moves away from the Caribbean, a sharper turn north is occurring while moving away from the Bahamian Islands to near Bermuda by Thu. night then a turn back north, even a little NW over the N. Atlantic.


* Puerto Rico/U.S. Virgin Islands/nearby Caribbean islands: Improving weather & seas through but river flooding will last longer.

* Most intense impacts for Hispaniola are easing, but the Dominican Republic will still have to deal with flooding rains/mudslides into Wed... Haiti escapes most of the wind & rain.

* Impacts to the Southeast Bahamas, especially the Turks & Caicos Islands - in the form of strong winds, heavy rain & rough seas/surf - will diminish through Wed. Most of the Bahamas - central & northwest islands - will get through Fiona unscathed.

* Impacts for Bermuda Thu. night/Fri. - wind/rain/rough seas/surf.

* Impacts for Nova Scotia & Newfoundland this weekend (becoming large/strong post-tropical ocean storm) - very heavy rain, strong winds, high seas, very rough surf.

* Increasing swells/seas/surf + dangerous rip currents for virtually all of the U.S. east coast through this week (but Fiona well offshore)

Forecast models briefly trended more west Thu. but have trended back east recently which is why one should not become too obsessed with individual model runs. Some of the real time aircraft dropsonde data was used Thu. in the 18Z (2pm) GFS model run *but not* in the 00Z (8pm) model run which is probably why the GFS had a “hiccup” in the 18Z Thu. run showing a track much more west. I bemoan when real time data is not consistently used within the models as it usually causes inconsistency within the models. Either use it with reach run as long as it’s available or don’t use it at all. The good news is that Gulfstream G-IV research aircraft started consistently flying Sat. & will continue the next several days with the data gathered from the atmospheric environment in & around Fiona then can be used to initialize the GFS for each run. Good clustering & consistency of the models continues keeping Fiona well east of the U.S. mainland. The GFS remains a little faster & bit more east than the European model.

Tip of the hat to the GFS model for pretty much winning the model battle on Fiona.

The steering influences for Fiona are distinct & pretty much locked in place in the form of an upper level trough moving to New England then the NW Atlantic while the Bermuda high is well to the east providing the distinct alleyway across the W. Atlantic for Fiona. The upper level trough then captures Fiona by this weekend bending the transitioning to a post-tropical low to the north & northwest late in the week/next weekend which has big implications for Nova Scotia & Newfoundland as the low will remain a powerful ocean storm even after losing tropical characteristics.

So to recap: Fiona is turning northward ... impacts will ease for the far east & SE Bahamas with a close pass by Bermuda - just to the west & northwest - late Thu. into Fri. morning. Then there will be the bend back to the north or even a little northwest over the N & NW Atlantic late in the week.

Elsewhere... a couple of active tropical waves are over the Central/Eastern Atlantic with the potential for development.

Here’s an early heads-up! for the Caribbean & U.S. Gulf Coast anywhere from Fl. to Texas as well as the Yucatan Peninsula. The primary concern for the Caribbean will be late this week/weekend into early next week & mid to late week into the following weekend for the Gulf of Mexico. The deets:

(1) A more southern latitude wave that moved off of Africa last week is steadily approaching the SE Caribbean with an increase in t’storm activity albeit disorganized. This is a classic wave in that it formed from a complex of intense storms over Africa... encountered hostile conditions (shear & dry air) for days before finding more favorable conditions. Both the GFS & European global models have jumped on this wave now with potential development over the Caribbean by at least the weekend. The GFS is faster to develop the wave vs. the European but both models eventually show a hurricane if not over/near the Caribbean then over the Gulf of Mexico. There may some interaction with the north coast of S. America the next couple days which could limit overall organization but once the wave gains some latitude, it would appear most ingredients are in place for the development of a tropical cyclone over the Caribbean.

It looks like this disturbance will stay south of recently hard hit Puerto Rico & Dominican Republic. The time table - *for right now* is Central/Eastern Caribbean through the weekend: near/south of Jamaica late in the weekend/early next week... the NW Caribbean/Southern Gulf by the middle of next week... into/over the Gulf of Mexico through late next week. Still very early on the path & strength of this *potential* storm. There will be changes, stay up to date!

(2) The combination of a low pressure area/tropical wave over the Central Atlantic has quickly organized & was upgraded to tropical depression #8 Tue. morning then to tropical storm “Gaston” Tue. afternoon. The depression is far to the east of Bermuda & southwest of the Azores will move more north then slowly northeast so no chance to move across the Atlantic, but Gaston will have some impact on the far Western Azores.


The alleyway for Fiona is well established as the Bermuda high shifts east & a series of upper level troughs move to the U.S. east coast & NW Atlantic:

Despite the eye of Fiona moving away, some heavy distant rain bands well to the southeast of the center are still streaming northward across Puerto Rico where rainfall totals will exceed 2 1/2 feet on some parts of the islands!:

Water vapor loop shows some dry air near wave ‘96-L’, but it’s more moist than past days:

A zone of shear - on the order of 20-30+ mph - remains east/west just north of Fiona. Forecast models gradually take Fiona to the edge then west of the strongest shear.

Hurricane hunter aircraft snapshot of the eye of Fiona early Tue.!:

Sunday morning:

Friday night recon mission:

Thursday recon mission:

September origins:

Averages below based on climatology for the Atlantic Basin through September. This season so far is well below avg.:

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, we’ve had several large dust plumes spread west to the Caribbean & Gulf with the peak of Saharan dust typically in June & July.

2022 names..... “Gaston” 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]). In fact, this year’s list of names is rather infamous with “Charley”, “Frances”, “Jeanne” & “Ivan” retired from the ‘04 list (all hit Fl.) & “Matthew” was retired in 2016. The WMO decided - beginning last year - 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:

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:

Updated Atlantic seasonal forecast from early Aug. - NOAA & CSU:

The East Pacific:

West Pacific:

Global tropical activity: