138
WTNT45 KNHC 161433
TCDAT5

Hurricane Erin Discussion Number  21
NWS National Hurricane Center Miami FL       AL052025
1100 AM AST Sat Aug 16 2025

Erin has continued to rapidly strengthen during the past 6 h and is
now a category 4 hurricane.  Reports from Air Force Reserve
Hurricane Hunter aircraft indicate that the central pressure has
fallen to 925 mb inside a 6 nm wide eye, and flight-level winds in
the northern eyewall support surface winds in the 130-135 kt range.
The initial intensity is increased to 135 kt, a 70-kt increase since
24 h ago.  The aircraft, along with land-based radar data from Sint
Maarten, report that an outer eyewall is starting to form. However,
this has yet become apparent in the aircraft wind data.

The hurricane has been moving a bit to the left of the previous
forecast track with the initial motion of 280/15. The track guidance
suggests that Erin will turn back to the west-northwest with a
decrease in forward speed during the next 6-12 h on the south side
of a subtropical ridge. This motion should then  continue through
the weekend, taking the core of Erin to the north of the eastern
Caribbean Islands through Sunday.  After 36 h, the western side of
the ridge is expected to weaken, due to a series of shortwave
troughs moving through the mid-latitude westerlies, and that should
cause Erin to slow further and make a gradual turn to the north. The
track guidance models are in general agreement with this scenario,
but there remain some differences on where, when, and how sharply
Erin makes the northward turn. The new track forecast is shifted to
the south during the first 12-24 h based on the initial position and
motion, and it lies near the southern edge of the guidance envelope.
From 24-72 h there track has been shifted westward due to an overall
shift in the guidance, and the track is similar to the previous
track at 96 and 120 h.

The development of the outer eyewall suggests that rapid
intensification should end during the next several hours.  However,
Erin is expected to reach category 5 status before this occurs, and
the new intensity forecast now calls for a peak intensity of 145 kt.
 After 12 h, the environment becomes a little less favorable, with
increasing northwesterly shear and possible dry air entrainment.
This should lead to gradual weakening of the cyclone through 72 h,
although superimposed on this trend will be fluctuations due to
eyewall replacement cycles.  After 72-96 h, the cyclone is expected
to move into the westerlies where the shear is stronger, and a
faster weakening trend is expected at that time. The new intensity
forecast is at the upper edge of the intensity guidance at 12 h and
near the intensity consensus after that.

Although Erin is a somewhat compact hurricane now, the models are in
strong agreement that the system will grow in size over the next
several days. In fact, by the middle of next week, Erin is forecast
to at least double or triple in size, which will result in rough
ocean conditions over the western Atlantic.


KEY MESSAGES:

1. Heavy rainfall at times through Sunday across the northern
Leeward Islands, the Virgin Islands, and Puerto Rico may lead to
locally considerable flash and urban flooding, along with landslides
or mudslides.

2. Gusts to tropical storm force in Erin`s outer rainbands are
likely in portions of the northern Leeward Islands through tonight
and over portions of the Virgin Islands and Puerto Rico later today
through Sunday. Tropical-storm force wind gusts are possible in the
Turks and Caicos Islands and Southeast Bahamas

3. Erin is expected to produce life-threatening surf and rip
currents along the beaches of the Bahamas, much of the east coast of
the U.S., and Atlantic Canada next week.

4.  Interests in Bermuda should continue to monitor the progress of
Erin since there is a risk of strong winds, heavy rainfall, and high
surf by the middle part of next week.


FORECAST POSITIONS AND MAX WINDS

INIT  16/1500Z 19.7N  62.8W  135 KT 155 MPH
 12H  17/0000Z 20.1N  64.7W  145 KT 165 MPH
 24H  17/1200Z 21.0N  66.8W  140 KT 160 MPH
 36H  18/0000Z 22.3N  68.5W  135 KT 155 MPH
 48H  18/1200Z 23.5N  69.7W  130 KT 150 MPH
 60H  19/0000Z 24.9N  70.4W  125 KT 145 MPH
 72H  19/1200Z 26.4N  70.9W  120 KT 140 MPH
 96H  20/1200Z 30.6N  70.9W  115 KT 130 MPH
120H  21/1200Z 35.7N  66.4W   95 KT 110 MPH

$$
Forecaster Beven