Hurricane Isaias Update One

136 

WTNT44 KNHC 010245

TCDAT4

Hurricane Isaias Discussion Number  16

NWS National Hurricane Center Miami FL       AL092020

1100 PM EDT Fri Jul 31 2020

Isaias has a somewhat asymmetrical appearance on satellite images, 

with lots of deep convection over the eastern semicircle and not as 

much over the western part of the circulation.  Reports from an Air 

Force Hurricane Hunter aircraft indicate that the central pressure 

has dropped a few mb, and flight-level and SFMR-observed surface 

wind observations from the aircraft indicate an intensity of near 

70 kt.  The hurricane is experiencing some westerly shear, and this 

is likely to limit intensification.  However, some strengthening is 

still possible on Saturday.  When Isais moves farther north in a 

couple of days, the shear should cause a gradual weakening trend to 

begin.  The official intensity forecast is about the same as the 

previous one, and a little above the model consensus.

The hurricane continues moving northwestward at a bit slower pace, 

or 310/13 kt.  The general track forecast philosophy has not 

changed.  Isais should continue to move northwestward on the 

southwest side of a mid-level ridge through Saturday and begin to 

turn north-northwestward through a weakness in the ridge on Sunday. 

Thereafter, a turn toward the north-northeast and northeast with an 

increase in forward speed is likely during days 3 to 5.  The 

official track forecast is close to the previous one and also very 

close to the latest dynamical model consensus.

The hurricane warning has been extended northward along the Florida 

east coast.

Key Messages:

1. Hurricane conditions and dangerous storm surge are expected in

portions of the Bahamas through Saturday, and Hurricane Warnings

are in effect.

2. Hurricane conditions are expected along portions of the Florida

east coast late Saturday and Saturday night, and a Hurricane Warning

has been issued.  Preparations to protect life and property should 

be rushed to completion.

3. Dangerous storm surge is possible along the Florida east coast

from Jupiter Inlet to Ponte Vedra Beach where water rises of 2 to 4

feet above ground level are possible along the immediate coastline

and adjacent waterways. Residents in these areas should follow

advice given by local emergency officials.

4. Isaias will produce heavy rains and potentially life-threatening 

flash and urban flooding, especially in low-lying and poorly drained 

areas, across South to east-Central Florida, and across the 

Carolinas to the mid Atlantic. Isolated minor river flooding is 

possible across the eastern Carolinas and into Virginia early next 

week.

5. There is a risk of impacts from winds, heavy rainfall, and storm

surge spreading along much of the the U.S. east coast through early

next week, and interests there should monitor the progress of Isaias

and updates to the forecast.

FORECAST POSITIONS AND MAX WINDS

INIT  01/0300Z 23.3N  76.4W   70 KT  80 MPH

 12H  01/1200Z 24.5N  77.8W   75 KT  85 MPH

 24H  02/0000Z 25.9N  79.1W   75 KT  85 MPH

 36H  02/1200Z 27.1N  80.0W   70 KT  80 MPH

 48H  03/0000Z 28.5N  80.5W   65 KT  75 MPH

 60H  03/1200Z 30.2N  80.5W   60 KT  70 MPH

 72H  04/0000Z 33.1N  78.9W   60 KT  70 MPH

 96H  05/0000Z 41.0N  72.5W   55 KT  65 MPH

120H  06/0000Z 47.5N  64.0W   45 KT  50 MPH...POST-TROP/EXTRATROP

$$

Forecaster Pasch

000

FXUS61 KCAR 010111

AFDCAR

Area Forecast Discussion

National Weather Service Caribou ME

911 PM EDT Fri Jul 31 2020

.SYNOPSIS...

A ridge of high pressure will build in from the west overnight

and cross the area Saturday into early Sunday. Low pressure will

approach Sunday afternoon and lift north of the region on

Monday. A cold front will cross the area Monday night. Isaias

will track off southern New England Tuesday and south of our

area Wednesday.........

......LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...

In the long term all eyes will be on Isaias and his eventual

movement along the eastern seaboard. Global models continue to

differ on movement of storm as GFS impacts the state about 18hrs

sooner than EC. For consistency on timing and in collaboration with

GYX hv gone with official fcst from NHC with center of storm in

vicinity of the Gulf of Maine 12z Wed as a post-tropical storm. This

wl likely impact CWA with locally hvy rain, winds and high surf

along with dangerous rip currents off of the Downeast coast.

As Isaias mvs up into the Maritimes expect nw flow to continue in

it`s wake with trof bringing chc for showers thru the end of the

week.

&&