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#718206 (Received by flhurricane at: 5:05 AM 17.Sep.2014) TCDAT1 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 |