542
WTNT45 KNHC 221439
TCDAT5

Hurricane Erin Discussion Number  45
NWS National Hurricane Center Miami FL       AL052025
1100 AM AST Fri Aug 22 2025

Erin is now well into its extratropical transition.  While there is
some convection that has recently reformed near the center, all of
its other convection has shifted on the left side, with noticeable
frontal features in the northeastern quadrant.  Additionally, the
stratus and stratocumulus clouds off the Mid-Atlantic U.S. coast
continue to suggest that cold air advection is occuring in the
hurricane`s wake.  The initial intensity is kept at 80 kt pending
receipt of the full late-morning scatterometer data, though the
partial pass suggested Erin had grown even larger.

The hurricane is moving faster to the east-northeast, now estimated
at 24 kt.  Model guidance is rapidly accelerating Erin in that
direction over the weekend, reaching a peak speed of up to 40 kt
Sunday.  The powerful extratropical low should slow down and could
undergo a loop over the far North Atlantic early next week as it
becomes a large occluded low.  The new forecast is a bit faster and
south of the previous one, based on the latest corrected consensus
guidance from HCCA and Google Deep Mind.

Current trends and model fields indicate that Erin should complete
extratropical transition by tonight, with perhaps a slight weakening
of the winds on Saturday.  However, Erin is forecast to become an
even larger and stronger system late Saturday into Sunday due to
phasing with a mid-latitude trough, inducing baroclinic
reintensification and even the development of a sting jet on the
back side.  While they disagree on the exact timing, the global
models are all showing a 75-90 kt sting jet on Sunday.  The new NHC
forecast is raised during the extratropical phase for Sunday, and
still could be too low if the latest ECMWF solution is correct.  A
steady weakening is likely to occur early next week as Erin occludes
and loses its upper support south of Iceland.


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. Coastal flooding is expected at times of high tide along portions
of the U.S. Mid-Atlantic and New England coasts through tonight,
making some roads impassable.  Large waves along the coast could
also cause significant beach erosion and overwash.

3. Gale-force wind gusts are possible along the coast of Nova Scotia
today and the Avalon Peninsula of Newfoundland on Saturday.


FORECAST POSITIONS AND MAX WINDS

INIT  22/1500Z 38.8N  63.1W   80 KT  90 MPH
 12H  23/0000Z 40.4N  58.8W   80 KT  90 MPH...POST-TROP/EXTRATROP
 24H  23/1200Z 42.3N  51.4W   75 KT  85 MPH...POST-TROP/EXTRATROP
 36H  24/0000Z 45.5N  41.9W   75 KT  85 MPH...POST-TROP/EXTRATROP
 48H  24/1200Z 49.6N  32.1W   80 KT  90 MPH...POST-TROP/EXTRATROP
 60H  25/0000Z 52.9N  25.9W   80 KT  90 MPH...POST-TROP/EXTRATROP
 72H  25/1200Z 55.9N  22.0W   60 KT  70 MPH...POST-TROP/EXTRATROP
 96H  26/1200Z 58.1N  21.3W   45 KT  50 MPH...POST-TROP/EXTRATROP
120H  27/1200Z 56.5N  18.5W   40 KT  45 MPH...POST-TROP/EXTRATROP

$$
Forecaster Blake