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Talking the Tropics With Mike: Strengthening Fiona moving away from the Caribbean

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** No *inland* impacts expected from Fiona for Jacksonville/NE Fl./SE Ga.... beaches to be affected by easterly swells, rough seas/surf & a high rip current risk mid through late week.... **

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. with the eye becoming more clear.

Fiona has been battling a narrow - but significant - 30-40 mph - band of westerly shear to its immediate west & northwest but has still managed to organize. 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. 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 Wed./Thu. & parts of Fri. - has led to eventually powerful hurricanes that had a similar trend. And indeed Fiona will become become the first major (Cat. 3+) hurricane of the season for the Atlantic Basin. As Fiona moves away from the Caribbean, a sharper turn north will occur to near & just east of the SE Bahamian Islands Tue... then northeast to near Bermuda by Thu. night then a turn back north over the N. Atlantic.

FIONA SUMMARY/IMPACTS:

* Puerto Rico/U.S. Virgin Islands/nearby Caribbean islands: Improving weather & sea conditions through Tue.

* Most intense impacts for Hispaniola through Mon. night. Strongest winds will impact Dominican Republic along with flooding rains/mudslides... Haiti will escape most of the wind & rain.

* Impacts to the Southeast Bahamas through Tue. night, especially the Turks & Caicos Islands - strong winds, heavy rain & rough seas/surf though the most severe part of the hurricane will stay a little east.

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

* Possible impacts for Nova Scotia this weekend (becoming large/strong post-tropical ocean storm)

* Increasing swells/seas/surf + dangerous rip currents for virtually all of the U.S. east coast during the upcoming 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. This has helped with better initial analysis for models at the beginning of the forecast cycle which would then - in theory - give more accurate output (forecast). Clustering & consistency of the models has improved dramatically keeping Fiona well east of the U.S. mainland. The GFS remains a little faster & bit more east than the European model... the UKMET appears remains out to lunch.

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 should then capture Fiona by next weekend bending the transitioning to a post-tropical low to the north & northwest late in the week/next weekend which has implications for Nova Scotia as the low will remain a powerful ocean storm even after losing tropical characteristics.

Overall - once over the Southwest Atlantic - it looks like conditions (water temps., shear & moisture) will favor strengthening through midweek. There will still be some westerly shear, but Fiona will be moving “with” the shear + may aid from some mid & upper level ventilation courtesy the upper level trough to the NW Atlantic.

Another interesting forecasting tidbit... a typhoon over the W. Pacific is turning sharply to the north & northeast across Japan (track map at the bottom). This typhoon teleconnection might correlate rather well with Fiona over the W. Atlantic this week & the rather sharp turn north & - in time - northeast. This correlation is possible because of the upper level pattern - troughs (dips) & ridges (upside down U’s) in the jet stream - that often (not always) mirror each basin (Pacific & Atlantic). See maps 6 & 7 below.

So to recap: Fiona is leaving the Caribbean ... there will be at least some impacts on some of the Bahamas Tue./Wed. - especially the Turks and Caicos Islands - followed by a move more north & - finally - north/northeast with a close pass to Bermuda 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 at least some potential for development.

(1) A weak low/tropical wave over the Central Atlantic far to the east of Bermuda will move more north so no chance to move across the Atlantic.

(2) A more southern latitude wave that moved off of Africa late last week is now roughly half way between Africa & the Caribbean at a much lower latitude than it predecessors. Both the GFS & European global models have latched onto this wave now with potential development over the Caribbean by the weekend. It’s possible the wave will enter the Gulf of Mexico thereafter. Models had been mostly “ignoring” this wave over the last several days, but this is a wave to keep a close eye on over the next week to 10 days.

Spaghetti plots including the ensemble (faint lines showing all the model runs which gives an indication of uncertainty):

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:

Mountainous terrain over especially the Central & Western portions of Hispaniola with some peaks 10,000+ feet. Fiona missed the highest mountains:

The upper level (about 30,000 feet) teleconnection with troughs & ridges between the Atlantic (steering Fiona) & the Pacific (steering W. Pacific typhoons):

Despite the eye of Fiona moving away, very heavy rain bands well to the east of the center are still streaming northward across Puerto Rico where rainfall totals will exceed 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.

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:

Caribbean:

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:

“Madeline” over the far E. Pacific will slowly peel away to the northwest then west staying well offshore of Mexico & south of the Baja of California:

West Pacific:

Global tropical activity:


“Nanmadol” is weakening after bringing heavy rain & strong winds to much of Japan:


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