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Talking the Tropics With Mike: Fiona speeds past Bermuda... Strong tropical wave over the Caribbean

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** 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 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 augmented by onshore flow Fri. into the weekend.... & no impacts from Gaston over the Northeast Atlantic **

Atlantic Basin:

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 over the weekend into early next week & mid to late week into the following weekend for the Gulf of Mexico. Lots of spread in model forecasts that has only been increasing. The deets:

A more southern latitude tropical wave - ‘98-L’ that moved off of Africa last week is moving over the extreme Southern Caribbean with disorganized t’storm activity. 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. There has been - & will be - some interaction with the north coast of Colombia & Venezuela into Fri. but once the wave gains some latitude through the weekend, it would appear most ingredients are in place for the development of a tropical cyclone over the Central &/or Western Caribbean. A surface low pressure area did emerge Thu. afternoon/evening & has started to pulse with burst of strong thunderstorms. This is likely the genesis of our tropical cyclone.

The global forecast models present a serious conundrum with a wide spray of where the storm might go. However, modeling does at least agree that there will be development. Both the GFS & European models are initializing well which is a positive... the GFS does seem better on the more west & south track the last 24-36 hours, but there may a “jump” of sorts to the north when/if t’storms start to become more numerous & concentrated. Agreement between the models is pretty decent through the weekend with a slowly developing tropical cyclone over the Western &/or Northern Caribbean but the range in the long term - next week is large to say the least - a difference of more than 500 miles! The GFS remains farthest to the west but has seriously shifted east recently. The GFS is now as far east as at least the Fl. Panhandle (close to where the model was a few days ago). The European model on the other hand is much more east & earlier to turn north & continues to trend east. Because of the sharper turn north, the European is earlier to a U.S. landfall - Tue/Wed in or near South Florida. In any case... most ingredients are in place for the development of a tropical cyclone over the Caribbean with very warm water including high oceanic heat content (warm far below the surface of the ocean)... sufficient mid & upper level moisture... low to - at times - moderate shear that will eventually be in concert with the storm’s movement (so less detrimental).

Hurricane hunter aircraft flew across the SE Caribbean & nearby areas Wed. evening & the weather data was ingested into the 00Z GFS model run. However, there are no plans - at least for right now - for that initialization data to be gathered on a steady basis, so - in my opinion - it’s of no help until there is constant surveillance of the surrounding atmosphere that then is incorporated in the analysis data for each model run. I suspect the single run with real-time data is why the GFS had major “hiccups” recently.

Steering currents to consider:

(1) the GFS “won” the forecast battle on Fiona hands down over the European model while the UKMET was consistently out to lunch. Simply based on persistence, it’s very hard to ignore the GFS. (2) there should be some “extra” ridging underneath - to the south of - intense hurricane Fiona. This alone could result in a more westward track for a longer time. But it’s unclear how much ridging will manage to build behind only recently departing Fiona as an upper level trough sweeps across the Eastern U.S. through the weekend. Furthermore... A bit of a weakness or wake trough may linger long enough to allow for the more north then east path. (3) - 98-L should remain rather weak into at least Fri., possibly Sat., so it should be steered more by low level (trade) winds vs. the deep tropospheric flow. (4) a tropical storm/typhoon is forming over the W. Atlantic. A teleconnection says more west for 98-L vs. a sharp turn north (though the ridging over the Pacific does not yet mirror the ridging over the Atlantic) - at least initially (W. Pacific track maps at the bottom). In fact, another & weaker tropical cyclone is to the east of the stronger W. Pacific cyclone.

This disturbance will stay far to the south of recently hard hit Puerto Rico & Dominican Republic. The time table - *for right now* is Central/Western Caribbean through the weekend: near/south & west of Jamaica late in the weekend... near Cuba by early in the week... then somewhere over the Gulf of Mexico mid to late week.... although a faster outcome is possible. Keep in mind that if the European model verifies then impacts to the U.S. will be earlier & primarily to Florida. Still very early on the path & strength of this *potential* storm. There will be changes, stay up to date!

Spaghetti plots for tropical wave ‘98-L’:

What a difference in the models!:

Deep oceanic heat content is impressive across the Caribbean - lots of warm water well below the surface of the ocean:

Strong shear over the far Eastern Caribbean weakens a great deal more to the north & west:

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). Tip of the hat to the GFS for winning the model forecast model - hands down. The steering influences for Fiona are well developed 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. Fiona reaches Jacksonville’s latitude - 700-900 miles to the east Thu. afternoon.

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 reaching Cat. 3 intensity Tue. & a Cat. 4 early Wed.

It’s possible that Fiona may try to become an annular hurricane (strong & steady state with essentially a singular band of intense convection wrapped around a usually rather wide eye) for a time.

FIONA SUMMARY/IMPACTS:

* Puerto Rico/U.S. Virgin Islands/nearby Caribbean islands & Dominican Republic: Improving weather & seas but river flooding will last longer with the typical lag between the end of the heaviest rain & the crest of major rivers.

* Impacts to the Southeast Bahamas, especially the Turks & Caicos Islands - in the form of strong winds, heavy rain & rough seas/surf - have diminished. Most of the Central & NW Bahamas made it through Fiona unscathed.

* Impacts for Bermuda Thu. night/Fri. - wind/rain/rough seas/surf as the eye goes to the west & northwest of the island early Fri. morning, but the wind field continues to expand so still some sustained winds of at least tropical storm force with gusts to hurricane strength.

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

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

Integrated microwave imagery courtesy CIMSS:

Fiona is encountering higher shear again in the coming days, but the hurricane will likely be so well developed... accelerating more or less with the shear... over warm water with plenty of moisture that it’ll create its own favorable “island” to remain intense right up to - & including - the transition to post-tropical:


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

Sunday:

Elsewhere....

Gaston” was upgraded Tue. & will stay over the Central & Northeast Atlantic while completing a clockwise loop as the storm weakens. There are some indications on satellite imagery that Gaston might not be purely tropical, but - in any case - no impacts for the U.S.... rough seas/surf, some rain for the Western Azores where tropical storm WARNINGS have been issued.

And there are a couple of active tropical waves over the Eastern Atlantic. There is the potential for some development with the lead wave slowly moving W/NW... followed by a wave near the African coast that’s should turn rather sharply northward soon. Neither wave is expected to be able to make it all the way across the Atlantic.

Water vapor loop shows plenty of mid & upper level moisture (white & green areas) across a good part of the Atlantic Basin:

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..... “Hermine” 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:

“Newton” has formed over the E. Atlantic & will move - “by law” (LOL) westward away from the Pacific coast of Mexico:

West Pacific:

Global tropical activity:


A tropical storm is impacting Japan with heavy rain & gusty winds as the storm weakens:

A steadily strengthening tropical cyclone will move west across the Northern Philippines through the weekend then west to near Vietnam next week:


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