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HURRICANE EDOUARD DISCUSSION NUMBER  24
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL062014
500 AM AST WED SEP 17 2014

Edouard's presentation on infrared satellite imagery has changed
very little during the past 6 hours, and recent microwave images
indicate that the hurricane still has two well-defined low-level
concentric rings.  A dropsonde released into the southeastern
eyewall just after 0600 UTC during a NASA Global Hawk mission
measured an average wind of 90 kt in the lowest 150 meters, which
equates to an intensity of about 75 kt.  Edouard's initial
intensity is being held at 80 kt under the assumption that the
dropsondes did not sample the maximum winds in the eyewall.
Two dropsondes within the eye measured surface pressures of 960 and
961 mb with some wind, supporting the previous estimated storm
pressure of 959 mb.

Edouard is likely to reach water colder than 26C in about 12
hours or so.  Just as the hurricane reaches the colder water,
vertical shear is expected to increase, and the SHIPS guidance shows
westerly shear of 35 kt in about 48 hours.  With the environment
becoming so hostile, the hurricane is forecast to gradually weaken
during the next 24 hours and then more rapidly lose strength after
that.  The global models continue to show Edouard remaining separate
from nearby frontal zones and not benefiting from baroclinic
support, so the cyclone is likely to become a decaying post-tropical
low by day 3, if not sooner.

Edouard is accelerating northeastward with a motion of 035/17 kt.
The hurricane is becoming partially embedded in faster mid-latitude
westerly flow, and it is expected to continue accelerating for the
next 24 hours or so.  However, the cyclone is forecast to stay
south of the polar jet, and by 48 hours it will turn eastward and
slow down as it moves around a mid-level ridge axis.  Toward the
end of the forecast period, the remnant low should turn southward
before it reaches the main islands of the Azores.  The track
guidance remains tightly clustered for the first 48 hours but then
shows some divergence during the post-tropical phase, with the
ECMWF and HWRF showing the sharpest southward turn.  The updated NHC
track is very close to the multi-model consensus TVCA and not too
far from the previous forecast.

FORECAST POSITIONS AND MAX WINDS

INIT  17/0900Z 35.1N  55.4W   80 KT  90 MPH
 12H  17/1800Z 37.2N  52.3W   75 KT  85 MPH
 24H  18/0600Z 39.3N  47.3W   70 KT  80 MPH
 36H  18/1800Z 40.3N  42.6W   60 KT  70 MPH
 48H  19/0600Z 40.3N  39.6W   45 KT  50 MPH
 72H  20/0600Z 40.1N  36.3W   35 KT  40 MPH...POST-TROPICAL
 96H  21/0600Z 38.5N  33.0W   30 KT  35 MPH...POST-TROPICAL
120H  22/0600Z 35.5N  32.5W   25 KT  30 MPH...POST-TROPICAL

$$
Forecaster Berg

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