Talking the Tropics With Mike: Hurricane Dorian over warm water & near Fl. late in weekend

Aug. 29, 2019 — The "Buresh Bottom Line": Always be prepared!.....First Alert Hurricane Survival Guide... City of Jacksonville Preparedness Guide... Georgia Hurricane Guide.

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DORIAN:

It's still early on this one but POSSIBLE Jacksonville/NE Fl./SE Ga. impacts (primarily later Sun./Mon.) & very dependent on exact location & intensity of Dorian:

* increasing & potentially deadly rip current risk at area beaches (as early as Fri. due to steady onshore flow). Always swim & surf with a "buddy" & as near a lifeguard as possible though best advice is to stay out of the water! Rip current explainer & safety info * here *.

* rough seas & surf... some coastal flooding (accentuated by new moon phase Fri. in addition to heavy rain) + above avg. tides at the coast, St. Johns River & its tributaries.

* breezy winds out of the east/southeast 15-20 mph, higher gusts.... peak wind gusts could reach 50+ mph Sunday into early next week depending on positioning & strength of Dorian.

* several periods of heavy showers & t'storms, but it's not looking like a "washout" for the weekend.... wettest later Sunday into Monday.

* isolated fast-moving tornadoes/waterspouts

Dorian became a hurricane upon approach to Puerto Rico Wed. afternoon with the eye moving a little east & northeast of the island nation sparing Puerto Rico the worst of its wrath but not so for the U.S./ British Virgin Islands. Dorian is still battling against the dry air that's been keeping the storm's intensity in check recently while moving into a lower shear environment. Dorian will now be over the open Southwest Atlantic for at least several days. It is worth noting that Dorian is a generally a compact system - tropical storm force winds extend about 90 miles from the center, but the wind field has been gradually expanding. In any case.... anyone with travel plans to the Caribbean through the week & the Bahamas through the weekend should stay up to date on the latest forecasts. All warnings for Puerto Rico, the Dominican Republic & Virgin Islands have been dropped as conditions quickly improve.

As for beyond the Caribbean..... it looks like Dorian's core has become well established. The positioning of a significant upper level ridge of high pressure - Bermuda high - across the Central Atlantic will be a key factor in the future movement. The upper level high will act as a brick wall stopping the northward movement that virtually all of the models have missed so far likely owing to the an upper level low to the west. The European model has become consistent with Dorian generally strengthening over the SW Atlantic before reaching the Florida coast over the weekend. The GFS model has joined many of the other forecast models in showing a more northwest movement across the SW Atlantic & Bahamas then near or into Florida (depends on the model run) over the weekend or early next week but generally as relatively weaker tropical cyclone. The UKMET model has been showing a similar trend as the European though generally stronger (but has not done particularly well w/ "Erin" - too strong, too far west) but has been lacking consistency. It's not wise to jump on a single model run or even a single model. And there will continue to be changes & updates. The GFS is now the northern outlier & fastest while the European is slower/strongest & the more southern outlier. The conditions over the SW Atlantic & near the Bahamas do appear quite favorable for at least maintaining Dorian if not allowing for strengthening. We need to be aware of the potential for a stronger tropical cyclone in the long term than is currently indicated by models &/or forecasts.

An exiting trough over the Northwest Atlantic this week (helping to steer Erin N/NE) will not be strong enough to pick up Dorian. Instead, high pressure will rebuild in place of & south of the exiting trough turning Dorian back more to the west & northwest & possibly west upon approach to Florida & the S.E. U.S. coast likely in tandem with at least one intensification phase.

So.... the bottom line is stay up to date on the latest forecasts for the Caribbean, Fl. & Southeast U.S. this week into the upcoming holiday weekend. There will be changes in the forecast & impacts in the days ahead! Don't be so foolish as to look at a forecast one day & not return for an update whether it's 1, 3 or 5+ days later.

Spaghetti model plots for Dorian:

Ensemble (An ensemble weather forecast is a set of forecasts that present the range of future weather possibilities) spaghetti plots: (for an in-depth look on ensemble modeling see * this * [Blake/Brennan, NHC])

The GFS model below for the upper levels (500mb) valid Sun. afternoon (09/01) shows the ridge of high pressure/Bermuda high over the Central/Western Atlantic. Dorian will follow the edge of this ridge - path of least resistance - to the west then northwest then north. So..... what I have to figure out is the exact strength & positioning of the ridge to determine exact Dorian movement. As of this moment - very subject to change! (of course).... I favor a strong enough ridge to keep Dorian south of Jacksonville (landfall near Cape Canaveral plus or minus) before a turn NW then north then even NE.

The busy map below helps explains some of what's going on & what's ahead for Dorian. The lines are shear vectors. Brighter lines - yellow & red - stronger shear & the enemy of tropical cyclones. The upper level trough is just west of Dorian helping to nudge Dorian more northwest vs. west. This feature should drop W/SW & weaken in the coming days. When combined with building Bermuda high to the north, Dorian "straightens out"... moves more west.

The solid colors are sea surface temps. show plenty of warm water along Dorian's projected path - 80s & even around 90 degrees near the Bahamas.

And remember what that "cone of concern or uncertainty" means & does not mean. That cone has everything with the historic track error ranging from the moment the forecast was issued all the way out to 5 days when the avg. error is nearly 200 miles!

National Hurricane Center average track error starting with 12 hours & ending at the 120 hour forecast from 2014-'18:

IR satellite:

Tropical wave '98-L' was upgraded to tropical depression #6 late Mon. then to tropical storm "Erin" Tue. night before weakening again to a depression over the Western Atlantic between Bermuda & the U.S. & has since become extra-tropical. Rip currents along area beaches are the biggest threat from the Mid Atlantic to New England as the system accelerates to the N/NE becoming absorbed by an upper level trough.

& a couple of strong waves over the E. Atlantic have at least some potential for gradual development....

An examination of dust over the Central & Eastern Atlantic shows a continuation of a good deal of dust over the Central & Eastern Atlantic as well as parts of the Caribbean. Dorian has been trying to fight off this dry air the last several days.

2019 names..... "Fernand" is next on the Atlantic list (names are picked at random... repeat every 6 years... historic storms are retired (Florence & Michael last year):

East Atlantic:

Mid & upper level wind shear (enemy of tropical cyclones) analysis (CIMMS). The red lines indicate strong shear of which there is plenty across the Atlantic at the moment:

The Atlantic Basin:

Water vapor imagery (dark blue indicates dry air):

Deep oceanic heat content:

Sea surface temp. anomalies show a warm Gulf of Mexico, Central & Northwest Atlantic while the "Main Development Region" (MDR) remain cooler than avg. along with parts of the Central Caribbean.....