Talking the Tropics With Mike: Cuba still slowing Fred’s reorganization... T.D. #7 forms

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Potential local - Jax/NE Fl./SE Ga. impacts from“Fred” BASED ON CURRENT FORECAST.... it is way too early to determine IF there will be impacts to the local area from t.d. #7 soon-to-be “Grace”:

* increase in tropical moisture late in the weekend into early next week

* multiple heavy bands of showers & t’storms Sunday / Mon. Rainfall totals through Mon. shoulda average 1-2″, locally 3″+.

* isolated waterspouts & tornadoes

* a little breezy - winds on average 10-15 mph w/ a few higher gusts within/near rain bands but widespread strong winds *not* expected

* heightened rip current risk at area beaches - swim or surf with a buddy & as close to a lifeguard as possible

* no storm surge

* CHECK BACK FOR UPDATES!!

The strong tropical wave entered the NE Caribbean Tue. & was upgraded south of Puerto Rico to tropical storm “Fred” Tue. evening - the 6th named storm of the Atlantic season & about 2 1/2 weeks ahead of the avg. date of Aug. 28th. The avg. date for the first hurricane is Aug. 10th but Elsa briefly became a hurricane in early July. Fred weakened to a tropical depression over the mountainous terrain of Hispaniola Wed. evening & has struggled since with more land interaction with the coast of Cuba. Overall... forecast models have come into decent agreement on the track & speed of Fred though there are important/subtle differences in the longer range.

Fred has taken it on the chin after tangling with Hispaniola & Cuba. Any center that might reform could have a tendency to “jump around” a bit given the interaction with land not to mention the lack of a decent inner core. I suspect the center will try to emerge near any strong bursts of convection. In any case, Fred will slow through the weekend as the system rounds the western edge of the expansive Bermuda High stretching from the U.S. to the Central Atlantic.

One of the greatest complicating factors has been - & will be - the land interaction. There is a good deal of westerly shear though overall conditions appear to become more favorable by the weekend save the continued potential for land interaction. The poorly organized center did miss Puerto Rico Tue. night but spent nearly 24 hours over the Dominican Republic & Haiti then near or over the Cuban coast through Fri. night. Both the GFS & European have been initializing well & bring the system through the Florida Straits & to the Eastern Gulf of Mexico over the weekend with similar timing taking Fred into the Central Panhandle by Monday but overall slower & more west in recent model cycles. The overall gradual shift to the west within the model suite is somewhat concerning & likely a product of a stronger Bermuda High. The more west Fred gets, the longer over warm Gulf water, less land (Florida) interaction & generally more optimal conditions for more strengthening than currently indicated. Point being - current forecasts may be underdone on the strength over the Gulf then ultimately at landfall which looks to be Monday between New Orleans & the Fl. Panhandle.

The GFS has had a right/east bias the last couple of weeks with tropical cyclones over the E. Pacific, but the model was a clear “winner” during Elsa 4-5 weeks ago. A stronger ridge seems to be the most logical forecast right now given how stout the ridge has been since essentially May. As such, at least a somewhat more westward track - before turning more north - seems to me to be the way to go right now.... & as mentioned above, is the direction the models are trending. The UKMET is generally a compromise between the GFS & European but takes a more westward track in the short term followed by a sharper move north in the longer range ending up close to where the GFS & European are but a little slower - arriving at the Gulf coast Mon. night-Tue. Given all the land interaction in the short term, it would seem any window for significant strengthening would hold off until at least Sunday. But given the time of year & more than warm enough ocean water, we must remain vigilant on a storm that might try to intensify rather quickly IF given the opportunity (away from land, lower shear, humid air) which is something that could happen if Fred takes longer to turn north which seems to be very realistic at this point.

Everyone along the Gulf coast should stay up to date on the latest trends & forecasts!

So.... improving conditions for Puerto Rico & Hispaniola while gusty squalls will impact Cuba into Saturday.

Expect heavy rain & gusty winds for much of the Florida Peninsula at one time or another over the weekend into Monday beginning with South Fl. & the Keys as early as Fri. night then progressing northward through the weekend into Monday extending as far west as at least Mobile & Pascagoula.

Stay tuned & stay up to date on the latest forecasts!

Spaghetti plots including ensemble forecasts for Fred:

South Fl. Water Management District:

Some dry air in the vicinity of the disturbance but more moisture with time to the northwest:

A half foot or more of rain will accompany Fred causing areas of flooding, especially considering the wet ground due to a wet last 6-7 weeks:

A “zone” of strong shear is gradually shrinking & weakening:

500 mb (~30,000 feet) GFS forecast - the Bermuda High will be critical! It appears the high will break down some & shift a little east/northeast by Sun./Mon. thereby allowing the northward/NW turn by Fred. How strongly the ridge builds back in next week will be key for the movement of what will likely be “Grace”.

Elsewhere - tropical wave ‘95-L’ has become tropical depression #7 & is steadily & quickly moving west/northwest. The track appears to be very similar - at least initially - to Fred. As Fred departs to the north next week, a high pressure ridge should have a tendency to build underneath which may - ultimately - steer ‘95-L’ (Grace?) more westward. Forecast models are at great odds regarding the longer range movement & intensity of this probable tropical cyclone. The GFS model has been particularly “bullish” with a stronger system possibly impacting the U.S. east coast but has had some pretty wild swings while other forecast models are weaker & more south & west (likely driven by the trade winds since depicting a more shallow system + the strengthening ridge).

Meanwhile... yet another wave is coming off the coast of Africa & moving westward.

We’re now less than 4 weeks from the peak of the hurricane season (Sept. 10), so just from a climatological point, we should see an uptick in Atlantic activity. But there are also other indications of a more active period or “burst” with the MJO, seasonally warm sea surface temps. & rather impressive deep oceanic heat content.

Sea surface temps. across the Atlantic are now near to above avg. across much of the basin (2nd image below) & - even more importantly - deep oceanic heat content is becoming impressive & the “equivalent oceanic heat content” - namely depth averaged temperature in the upper 300 m (~984 feet) - is even more impressive all the way from Africa to the Gulf of Mexico. Such an ocean water temp. pattern is conducive to long track deep tropical Atlantic tropical cyclones & can lead to a more favored regime for rapid intensification cycles. From an AMS research paper in ‘08 Mainelli, DeMaria, Shay, Goni: “Results show that for a large sample of Atlantic storms, the OHC variations have a small but positive impact on the intensity forecasts. However, for intense storms, the effect of the OHC is much more significant, suggestive of its importance on rapid intensification. The OHC input improved the average intensity errors of the SHIPS forecasts by up to 5% for all cases from the category 5 storms, and up to 20% for individual storms, with the maximum improvement for the 72–96-h forecasts. The statistical results obtained indicate that the OHC only becomes important when it has values much larger than that required to support a tropical cyclone.” More recent research continues to indicate similar correlations.

Saharan dust. Dry air - yellow/orange/red/pink. Widespread dust is most common earlier in the hurricane season & 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 the plume then try to develop if everything else happens to be favorable.

2021 names..... “Grace” 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). Last year - 2020 - had a record 30 named storms. 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 twice - 2005 & 2020). 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 continues to increase across the Gulf, Caribbean & deep tropical Atlantic & has become pretty impressive from the Central/NW Caribbean into the Gulf of Mexico: