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Tropical Depression KARL Forecast Discussion Number 30
2016-09-21 22:43:51| National Hurricane Center (Atlantic)
Issued at 500 PM AST WED SEP 21 2016 000 WTNT42 KNHC 212043 TCDAT2 TROPICAL DEPRESSION KARL DISCUSSION NUMBER 30 NWS NATIONAL HURRICANE CENTER MIAMI FL AL122016 ISSUED BY THE NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 500 PM AST WED SEP 21 2016 The low-level center of Karl appears to have turned toward the northwest with a motion of 305/10 kt based on GOES-East visible imagery, recently tucking underneath the cirrus canopy of developing convection. Though strong at the moment, the deep convection continues to be inconsistent, making the intensity determination a bit muddled. Proximity to NOAA buoy 41044 indicates the circulation appears closed with winds backing from east-northeast to northwest during the past few hours, but there have been no significant pressure falls. ASCAT passes from this morning indicated a broad area of 30-kt winds about 150 n mi to the northeast and east of the center. As such, the initial intensity remains 30 kts at this time. Karl has turned toward northwest as it is being funneled between the southwestern periphery of subtropical ridge and the upper- to mid-level low located north of Puerto Rico and the Virgin Islands. This northwest track should continue through Friday until Karl turns north and rapidly accelerates northeastward, becoming embedded in mid-latitude westerlies. There has been little change in the track guidance, which remains in fairly good agreement through 48 hours. However, differences begin to appear toward the end of the forecast period as the ECMWF continues to be a bit slower. The official forecast remains close to a blend of the GFS and ECMWF but hedges toward the faster GFS solution. This is also in close proximity to the HWRF. Karl's environment continues to gradually improve as the upper low moves westward, reducing vertical wind shear as well supporting a more diffluent upper-level pattern for increased thunderstorm development. However, mid-level moisture values are marginal and may remain as a limiting factor for intensification during the next day or so. Based on the latest intensity guidance, the official forecast now brings Karl back to tropical storm strength over the next day, with intensification continuing through day 4 after the cyclone recurves into the mid-latitude westerlies. Some weakening is possible by the end of the forecast period after Karl's transition to an extratropical cyclone. FORECAST POSITIONS AND MAX WINDS INIT 21/2100Z 21.9N 58.7W 30 KT 35 MPH 12H 22/0600Z 23.3N 60.7W 35 KT 40 MPH 24H 22/1800Z 24.9N 63.0W 40 KT 45 MPH 36H 23/0600Z 26.5N 64.4W 45 KT 50 MPH 48H 23/1800Z 28.2N 65.0W 50 KT 60 MPH 72H 24/1800Z 31.5N 61.8W 65 KT 75 MPH 96H 25/1800Z 36.6N 51.5W 70 KT 80 MPH 120H 26/1800Z 44.5N 38.0W 50 KT 60 MPH...POST-TROP/EXTRATROP $$ Forecaster Gallina/Berg
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