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#875778 (Received by flhurricane at: 5:10 AM 24.Sep.2016) TCDAT2 TROPICAL STORM KARL DISCUSSION NUMBER 40 NWS NATIONAL HURRICANE CENTER MIAMI FL AL122016 500 AM AST SAT SEP 24 2016 Data from an Air Force Reserve reconnaissance aircraft this morning indicate that Karl has made the much anticipated turn toward the northeast, and that the center has also reached its closest point of approach to Bermuda. The strongest 825-mb flight-level wind measured thus far has been 66 kt and the highest SFMR surface wind measured has been 49 kt. The central pressure of 994 mb is based on a recent dropsonde report. An earlier dropsonde report indicated that the flight-level center was tilted to the northeast of the surface center. Based on these data, the initial intensity is being maintained at 55 kt. The initial motion estimate is 035/15 kt. Karl is now coming under the influence of deep southwesterly steering flow in advance of an approaching strong mid-latitude trough and surface cold front. This flow pattern should keep Karl moving northeastward away from Bermuda and steadily increase its forward speed to 40-45 kt by 36-48 hours. The new forecast track is similar to but slightly to the left of the of the previous advisory track, and lies down the middle of the tightly clustered track guidance. Karl appears to have entrained some dry air in the mid- and low- levels of the atmosphere based on reconnaissance data. However, the cyclone is forecast to remain over SSTs of at least 27 deg C for the next 24 hours or so within an environment of moderate vertical wind shear. This should allow Karl to strengthen to a hurricane in about 24-36 hours. After that, the cyclone is forecast to undergo extratropical transition as it merges with the cold front, and this should be complete by 48 hours, if not sooner. The cyclone is expected to be absorbed by a larger extratropical low between 48-72 hours. The new intensity forecast is similar to the previous advisory and lies close to the consensus model IVCN. FORECAST POSITIONS AND MAX WINDS INIT 24/0900Z 31.7N 64.3W 55 KT 65 MPH 12H 24/1800Z 33.5N 61.2W 60 KT 70 MPH 24H 25/0600Z 36.7N 54.9W 65 KT 75 MPH 36H 25/1800Z 41.6N 45.6W 70 KT 80 MPH 48H 26/0600Z 47.6N 36.4W 65 KT 75 MPH...POST-TROP/EXTRATROP 72H 27/0600Z...DISSIPATED $$ Forecaster Stewart |