[Tropical] Tropical Cyclone Discussion

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WTNT41 KNHC 171457
TCDAT1

HURRICANE EDOUARD DISCUSSION NUMBER  25
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL062014
1100 AM AST WED SEP 17 2014

Edouard is maintaining two concentric rings as indicated in the
latest visible satellite images and recent NOAA Hurricane Hunter
aircraft wind data.  Even though the central pressure is rather low,
958 mb, the pressure gradient is spread out over the large area
comprising the two rings, leading to a lower peak wind than a
typical cyclone would have. Flight-level and SFMR winds still
support an intensity of about 80 kt, which is unchanged from the
previous estimate.

Edouard is accelerating northeastward with a motion of 045/20 kt.
The hurricane is being steered by mid-latitude flow between the
subtropical ridge and a broad trough over the western Atlantic
Ocean.  This pattern should force Edouard to move faster toward the
east-northeast by late tonight, and eastward by late tomorrow.   In
a couple of days, Edouard (or its remnants) should turn southward
to the west of the Azores around a large trough over the eastern
Atlantic Ocean.  The track guidance remains tightly clustered for
the first 48 hours but continues to show some divergence during
the post-tropical phase.  The ECMWF has remained consistent on a
sharper southward turn, while the GFS is showing a more gradual
equatorward motion.  Because of the consistency of the ECMWF during
the past few runs, the latest NHC track is staying on the southwest
side of the model envelope at long range, roughly halfway between
the model consensus and the ECMWF.

Edouard is moving quickly toward the northeast and should pass over
waters cooler than 26C in less than 12 hours.  Only a gradual
weakening is shown during the first 24 hours due to cooler waters
and moderate shear.  All of the global models show a sharp increase
in shear after that time while the cyclone is moving over much
colder water.  Thus a more rapid weakening is shown beginning late
tomorrow, which is similar to a blend of the previous NHC forecast,
the Florida State Superensemble, and the intensity consensus.  The
cyclone is expected to become post-tropical in 2 or 3 days, which
is in good agreement with the global models.  Although Edouard is
expected to traverse warmer waters by the end of the forecast
period, strong northwesterly shear is anticipated to hinder any
redevelopment potential.


FORECAST POSITIONS AND MAX WINDS

INIT  17/1500Z 36.4N  53.3W   80 KT  90 MPH
 12H  18/0000Z 38.3N  49.9W   75 KT  85 MPH
 24H  18/1200Z 39.8N  44.7W   70 KT  80 MPH
 36H  19/0000Z 40.1N  40.7W   55 KT  65 MPH
 48H  19/1200Z 39.7N  38.7W   40 KT  45 MPH
 72H  20/1200Z 39.4N  35.8W   35 KT  40 MPH...POST-TROPICAL
 96H  21/1200Z 37.5N  33.5W   30 KT  35 MPH...POST-TROPICAL
120H  22/1200Z 34.5N  33.0W   30 KT  35 MPH...POST-TROPICAL

$$
Forecaster Blake



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