Tropical Storm Isaias

[Taylor Campbell]

This system is staying further south than models initially thought and the forecast track keeps shifting westward.

 

[warneagle]

Yeah, on the one hand you never want to see it hit populated areas, but on the other, if it follows the new cone, it's probably going over Hispaniola and maybe Cuba as well, which will help keep it from strengthening.

 

[Kory]

Yeah, he’s trucking WNW at a very fast clip that is hampering development. Weaker usually means further west and that’s what we’re seeing. A big trough is forecasted to position itself across the Central US and will likely pick it up and shear it to death.

On another note, NCEP should just throw away the GFS server. It is FLAT OUT AWFUL.

 

[Taylor Campbell]

It wouldn’t surprise me short term that this continues to track on the southern end of guidance.

 

[MattW]

Yeah, he’s trucking WNW at a very fast clip that is hampering development. Weaker usually means further west and that’s what we’re seeing. A big trough is forecasted to position itself across the Central US and will likely pick it up and shear it to death.

On another note, NCEP should just throw away the GFS server. It is FLAT OUT AWFUL.

Aside from being something of an eastern outlier, what's wrong with the GFS?

 

[Kory]

Aside from being something of an eastern outlier, what's wrong with the GFS?

Convective feedback issues with nearly every storm. Had Gonzalo remaining intact through most of the Caribbean (it fizzled shortly after passing the Windwards). Had Hanna an open wave 72 hours before it rapidly intensified into a hurricane and made landfall in Texas. Now, it’s correcting itself to a more realistic solution with PTC 9 within the short range. It is an absolutely awful model.

 

[WesL]

BULLETIN
Potential Tropical Cyclone Nine Intermediate Advisory Number 5A
NWS National Hurricane Center Miami FL AL092020
200 PM AST Wed Jul 29 2020

...DISTURBANCE BRINGING HEAVY RAINFALL AND GUSTY WINDS TO THE
LEEWARD ISLANDS...THE U.S. AND BRITISH VIRGIN ISLANDS...AND PUERTO
RICO...


SUMMARY OF 200 PM AST...1800 UTC...INFORMATION
----------------------------------------------
LOCATION...16.2N 64.7W
ABOUT 105 MI...165 KM S OF ST. CROIX
ABOUT 180 MI...285 KM SSE OF SAN JUAN PUERTO RICO
MAXIMUM SUSTAINED WINDS...45 MPH...75 KM/H
PRESENT MOVEMENT...WNW OR 290 DEGREES AT 23 MPH...37 KM/H
MINIMUM CENTRAL PRESSURE...1006 MB...29.71 INCHES

 

[Kory]

This thing is still a mess and has a lot working against it.

 

[akt1985]

We now officially have Tropical Storm Isaias.

 

[WesL]

Nice curves for the Gulf but not so good for East Coast.



Tropical Storm Isaias Advisory Number 9
NWS National Hurricane Center Miami FL AL092020
1100 AM AST Thu Jul 30 2020

...ISAIAS CONTINUES TO PRODUCE LIFE-THREATENING FLASH FLOODING
AND GUSTY WINDS OVER PUERTO RICO...
....HEAVY RAINS AND GUSTY WINDS SPREADING OVER THE DOMINICAN
REPUBLIC...


SUMMARY OF 1100 AM AST...1500 UTC...INFORMATION
-----------------------------------------------
LOCATION...18.1N 68.9W
ABOUT 50 MI...75 KM SW OF PUNTA CANA DOMINICAN REPUBLIC
ABOUT 165 MI...265 KM SE OF PUERTO PLATA DOMINICAN REPUBLIC
MAXIMUM SUSTAINED WINDS...60 MPH...95 KM/H
PRESENT MOVEMENT...NW OR 310 DEGREES AT 20 MPH...31 KM/H
MINIMUM CENTRAL PRESSURE...1003 MB...29.62 INCHES

 

[warneagle]

Isaias is creating some serious flash flooding problems in Puerto Rico.

 

[Kory]

There have been some changes with the trough orientation that will pick up Isaias. It looks to go neutrally tilted over the MS Valley which may allow for a more ventilated upper level pattern instead of a more unfavorable sheared pattern as the storm turns N/NNE.

 

[warneagle]

New NHC forecast does bring Isaias to hurricane strength Saturday morning over the Bahamas.

 

[TornadoFan]

We now have Hurricane Isaias

Hurricane Debby Update Statement

 

[WesL]

Isaias has been upgraded to a Category 1 hurricane, 36 hours sooner than expected (image is from last advisory at 11PM)

 

[gangstonc]

Look like it is starting to intensify quickly!

 

[Kory]

He looks lopsided as SWerly shear and dry air entrainment have pushed convection to the NE side of the circulation. There's a signature dry air entrainment feature racing through the Bahamas on radar...that's outflow from dry air collapsing convection.

Most intensity models say he has peaked intensity wise...but those can be notoriously inaccurate.

 

[WesL]

Hurricane Isaias Advisory Number 14
NWS National Hurricane Center Miami FL AL092020
1100 AM EDT Fri Jul 31 2020

...HURRICANE WATCH ISSUED FOR PORTIONS OF THE FLORIDA EAST COAST...
...SQUALLY WEATHER OVER THE SOUTHEASTERN BAHAMAS AND THE TURKS AND
CAICOS ISLANDS SPREADING INTO THE CENTRAL BAHAMAS...


SUMMARY OF 1100 AM EDT...1500 UTC...INFORMATION
-----------------------------------------------
LOCATION...21.7N 74.5W
ABOUT 365 MI...585 KM SSE OF GREAT ABACO ISLAND
ABOUT 295 MI...470 KM SE OF NASSAU
MAXIMUM SUSTAINED WINDS...75 MPH...120 KM/H
PRESENT MOVEMENT...NW OR 305 DEGREES AT 16 MPH...26 KM/H
MINIMUM CENTRAL PRESSURE...992 MB...29.30 INCHES

 

[Equus]

Hard to believe but recon is finding ~985mb now and Bahamas radar suggests eyewall has quickly fully closed off at beam height at least. Seems to be trying to clear an eye. Until it realizes the extremely dry air to the west, might see some additional deepening

 

[warneagle]

Two fatalities reported in the Dominican Republic.