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Talking the Tropics With Mike: Isaias makes landfall near the S./N. Carolina border

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*** Low pressure/tropical wave ’92-L’/‘Potential Cyclone Nine’ was upgraded to tropical storm Isaias Wed. evening while over the Eastern Caribbean.... moved over Eastern Dominican Republic Thu. afternoon then offshore & quickly reorganized becoming the 2nd hurricane of the Atlantic season a little before midnight. Isaias quite literally fell apart Sat. afternoon while crossing Andros Island of the Bahamas & the mid & low level centers have pretty much been disjointed ever since. But at the last minute, Isaias strengthened into a hurricane Mon. evening, Aug. 3rd before coming ashore about 11:15EDT near Ocean Isle Beach, NC with max sustained winds near 85 mph & min central pressure of 988mb/29.18″. It’s the fifth season in a row with 2 or more U.S. landfalls & the earliest on record to have 5 named storms hit the U.S. breaking the record of 5 Aug. 18, 1916. Isaias was the 5th July named storm over the Atlantic which ties the record for the month set in 2005. And it marks the fastest to ‘I’ beating the previous record set by “Irene” in - when else - 2005.

LOCAL JACKSONVILLE/NE Fl./SE Ga.:

Isaias moved northward well east of the Fl. coast Sun. night through Mon. morning with virtually all the “weather” - strongest winds & heaviest rain - north & east of the center. The track of the center was ~75-100+ miles east of NE Fl./SE Ga. & Jacksonville.

On this track, impacts locally were not been severe & conditions will continue to improve:

* Rain amounts were mostly less than an inch. In fact, afternoon storms this week will drop more rain than Isaias did.

* a dangerous rip current risk at area beaches along with rough seas & surf will slowly improve but beware of scouring in the sand at the beaches from the recent heavy wave action that may induce additional rip currents.

* water levels will recede but ocean water will take a while to completely escape so tides will still be a little above avg. through at least Tue. There will also be some astronomical boost with the full moon Monday/Tue. Forecast tides * here *.

* Winds quickly diminish & are offshore (out of the west).

FORECAST DISCUSSION & REASONING:

Isaias remained reasonably well organized after traversing the rugged terrain of the Dominican Republic Thu. missing some of the highest mountainous peaks. Moving at more than 20 mph, Isaias did not stay over land for much more than 8-10 hours. However, Isaias struggled mightily Sat. afternoon while passing over the N. Andros Island of the Bahamas. At one point, the center was completed exposed & mostly void of convection. But then there was a big burst of t’storms near & north of the center Sat. evening which then gave way to the ongoing west/southwest shear followed by another burst Sunday morning that likewise eventually did succumb to the shear. Vigorous t’storm activity has become persistent since Sunday afternoon but with two centers on radar imagery - a low level circulation closer to the coast & a midlevel circulation to the northeast. The two centers finally “hooked up” allowing for intensification early Mon. evening.

Isaias will now race northeast across Chesapeake Bay to near New York City Tue. then to Western New England Tue. night/early Wed. as the storm accelerates northeast while coming under the influence of an upper level trough approaching from the west.

Isaias is essentially “shooting the gap”. The approaching upper level trough moving into the Eastern U.S. provided an alleyway to steer Isaias more north/northeast then northeast up the eastern seaboard & just inland.

Spaghetti plots:

Water vapor imagery shows the continental dry air rushing east underneath/south of Isaias:

NOAA WaveWatch III “Significant Wave Height” forecast:

Rainfall forecast:

The path of Isaias in red vs. Floyd, 1999/Matthew, 2016/Dorian, 2019. It should be noted that Floyd, Matthew & Dorian were considerably stronger & larger tropical cyclones....

The graph & map below - the next 2 images - courtesy Dr. Phil Klotzbach:

Meanwhile... a tropical wave has some potential to develop some over the Central Atlantic while moving northwest. Early indications are that this will turn more north with time staying east of the U.S. & north of the Caribbean & Greater & Lesser Antilles but then stall.

And t.d. #10 formed just off the coast of Africa Fri. over the far E. Atlantic but has dissipated.


Saharan dust.... Tropical waves continue to “fester” along the south edge of the dust & have the potential to thrive once away from the dust.

2020 names..... “Josephine” is next on the Atlantic list (names are picked at random by the World Meteorological Organization... repeat every 6 years... historic storms are retired (Florence & Michael last year) & Dorian is certain to be retired from the ’19 list....


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 is extreme over the NW Caribbean:

Sea surface temp. anomalies:

SE U.S. surface map:

Surface analysis centered on the tropical Atlantic:

Surface analysis of the Gulf:

Caribbean:

Global tropical activity: