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Tropical Storm KARL Forecast Discussion Number 37
2016-09-23 16:45:24| National Hurricane Center (Atlantic)
Issued at 1100 AM AST FRI SEP 23 2016 000 WTNT42 KNHC 231445 TCDAT2 TROPICAL STORM KARL DISCUSSION NUMBER 37 NWS NATIONAL HURRICANE CENTER MIAMI FL AL122016 ISSUED BY THE NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1100 AM AST FRI SEP 23 2016 A NOAA P3 flight continued to fly through Karl for a few hours after the release of the last advisory, and while it didn't find winds higher than 50 kt, dropsonde data did indicate that the minimum pressure had fallen to 992 mb. Microwave data indicate that Karl is still under the influence of 15-20 kt of south- southeasterly shear. The convective pattern has continued to improve, however, with an elongated curved band extending to the northeast and east of the central convection. With sea surface temperatures running between 29-30C for the next 24 hours and vertical shear expected to decrease slightly, it seems likely that Karl will continue to strengthen during the next couple of days. The intensity guidance is in fairly good agreement on the intensification trend, and in fact most of the models are showing Karl reaching a strength between 60 and 65 kt in about 24 hours. Therefore, the updated official forecast now shows Karl reaching hurricane intensity at that time. Continued strengthening is likely after that time, and the peak intensity shown in the official forecast is slightly higher than the previous forecast at 48 hours, which is in line with the latest guidance. Karl will be in the process of extratropical transition at that time, but the global models fields only agree that the transition will be complete by 72 hours. Karl should then be absorbed by a larger extratropical low by day 4. The last fix from the NOAA P3 was a little east of the previous Air Force fixes, so it's possible that Karl's center has begun to move east of due north. Until we know for sure, the initial motion is set to be northward, or 360/10 kt. Karl is located near the western edge of the subtropical ridge axis, and it should become increasingly embedded in the mid-latitude westerlies during the next couple of days. Therefore, the cyclone is forecast to turn northeastward and begin accelerating within the next 24 hours, with the motion becoming even faster by 72 hours. The spread among the track models is extremely tight on this forecast cycle, and very little change was required from the previous advisory. The new official forecast lies very close to the TVCN multi-model consensus. Since Karl is now forecast to become a hurricane by 24 hours while the center is passing just to the east of Bermuda, the Bermuda Weather Service has elected to issue a Hurricane Watch for the island. FORECAST POSITIONS AND MAX WINDS INIT 23/1500Z 28.6N 64.8W 50 KT 60 MPH 12H 24/0000Z 30.2N 64.8W 55 KT 65 MPH 24H 24/1200Z 32.3N 62.7W 65 KT 75 MPH 36H 25/0000Z 34.9N 57.8W 70 KT 80 MPH 48H 25/1200Z 38.9N 49.8W 75 KT 85 MPH 72H 26/1200Z 50.7N 29.0W 60 KT 70 MPH...POST-TROP/EXTRATROP 96H 27/1200Z...ABSORBED BY A LARGER EXTRATROPICAL LOW $$ Forecaster Berg/Sullivan/Gerhardt/Schichtel
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