703
WTNT45 KNHC 210846
TCDAT5

Hurricane Erin Discussion Number 40
NWS National Hurricane Center Miami FL AL052025
500 AM EDT Thu Aug 21 2025

Erin's satellite presentation currently shows the low-level center
embedded beneath a 90 n mi-wide Central Dense Overcast. Outer
convective bands extend a couple of hundred miles away from the
center, but there has recently been some erosion of the clouds
within the southwestern part of the circulation, which likely
signals an increase in shear. On the last transect through the
storm, the Air Force Reserve Hurricane Hunters measured 700-mb
flight-level winds of 100 kt, and found that the central pressure
had risen to 945 mb. The current intensity is estimated to be 90
kt, although it should be noted that some of the satellite intensity
estimates are lower.

Erin has made its closest approach to the North Carolina coast and
is now moving north-northeastward (020 degrees) at 15 kt. There is
no change in the forecast reasoning of the future track. Erin
should continue to accelerate and turn east-northeastward by Friday
as it becomes increasingly embedded within the mid-latitude
westerlies. The new NHC track forecast is a bit faster than the
previous prediction, showing Erin racing across the north Atlantic
with a peak forward speed of about 35 kt in 72 hours.

The prospects for strengthening appear to be coming to a close,
particularly with the atmosphere becoming more stable and shear
increasing during the next 12-24 hours. Only slow weakening is
forecast during the next 36 hours, but steady weakening is likely
after that time. Erin's transition to a post-tropical cyclone has
been moved up to 60 hours in the official forecast, but some of the
latest guidance indicate it could happen as soon as 36-48 hours
from now. The global models, including the GFS and ECMWF, are also
trending toward keeping the post-tropical cyclone big and strong
while it moves across the north Atlantic, and the NHC wind radii and
intensity forecasts have been adjusted upward accordingly.


KEY MESSAGES:

1. Erin will continue to produce life-threatening surf and rip
currents along the beaches of the Bahamas, much of the east coast of
the U.S., Bermuda, and Atlantic Canada during the next several days.
Beachgoers in those areas should follow advice from lifeguards,
local authorities, and beach warning flags.

2. Storm surge flooding and tropical storm conditions will continue
on the North Carolina Outer Banks today. The storm surge will be
accompanied by large waves, leading to significant beach erosion and
overwash, making some roads impassible.

3. Tropical storm conditions are expected today along the Virginia
coast. Wind gusts to tropical storm force are likely along
portions of the remainder of the U.S. Mid-Atlantic and southern New
England coasts today through early Friday.

4. Tropical storm conditions are possible on Bermuda this afternoon
through early Friday. Gusts to gale force are possible along the
coast of Nova Scotia on Friday and the Avalon Peninsula of
Newfoundland on Saturday.


FORECAST POSITIONS AND MAX WINDS

INIT 21/0900Z 34.2N 72.1W 90 KT 105 MPH
12H 21/1800Z 35.8N 70.3W 90 KT 105 MPH
24H 22/0600Z 37.8N 66.7W 85 KT 100 MPH
36H 22/1800Z 39.6N 62.1W 85 KT 100 MPH
48H 23/0600Z 41.4N 56.2W 75 KT 85 MPH
60H 23/1800Z 43.6N 48.7W 65 KT 75 MPH...POST-TROP/EXTRATROP
72H 24/0600Z 46.7N 40.2W 60 KT 70 MPH...POST-TROP/EXTRATROP
96H 25/0600Z 53.0N 26.7W 55 KT 65 MPH...POST-TROP/EXTRATROP
120H 26/0600Z 56.8N 21.7W 45 KT 50 MPH...POST-TROP/EXTRATROP

$$
Forecaster Berg


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