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Tropical Depression KARL Forecast Discussion Number 28
2016-09-21 10:35:15| National Hurricane Center (Atlantic)
Issued at 500 AM AST WED SEP 21 2016 000 WTNT42 KNHC 210835 TCDAT2 TROPICAL DEPRESSION KARL DISCUSSION NUMBER 28 NWS NATIONAL HURRICANE CENTER MIAMI FL AL122016 500 AM AST WED SEP 21 2016 Karl's structure is very difficult to determine this morning. Satellite data indicate that the low-level center moved westward far away from the convection, and currently it is hard to say if Karl possess a closed circulation or not. Assuming that it still does, the maximum winds are estimated generously at 30 kt, since the cloud pattern has become less organized. I would not be surprised if early visible satellite images will reveal that the cyclone has degenerated into a broad area of low pressure. Global models have totally failed so far in forecasting the upper-level winds surrounding Karl. The upper-low near Karl which unanimously all models have been forecasting to weaken is still strong and producing shear over the cyclone. Given such a resilient shear pattern, additional weakening is anticipated today. However, most of the models are still predicting a favorable pattern for intensification, and on this basis as well as continuity, the NHC forecast calls for some strengthening beyond 36 hours while Karl moves away from the hostile tropics. By the end of the forecast period, Karl should be rapidly losing tropical characteristics while it interacts with the mid-latitude flow. The initial motion is also highly uncertain, giving that we have been following the low-cloud swirl defining the alleged center. The best estimate is toward the west or 280 degrees at 12 kt. Karl is approaching the southwestern edge of the subtropical ridge, and this pattern should result in a turn to the northwest and then north during the following two days. After that time, a sharp recurvature is anticipated around the northwestern portion of the subtropical high and ahead of a mid-latitude shortwave. This sharp recurvature is the solution provided by most of the track models, and the NHC forecast is in the middle if the guidance envelope. FORECAST POSITIONS AND MAX WINDS INIT 21/0900Z 20.2N 57.6W 30 KT 35 MPH 12H 21/1800Z 20.9N 59.3W 25 KT 30 MPH 24H 22/0600Z 23.0N 61.5W 30 KT 35 MPH 36H 22/1800Z 25.0N 64.0W 35 KT 40 MPH 48H 23/0600Z 27.0N 65.5W 45 KT 50 MPH 72H 24/0600Z 30.0N 64.0W 60 KT 70 MPH 96H 25/0600Z 35.5N 56.5W 75 KT 85 MPH 120H 26/0600Z 43.0N 42.0W 65 KT 75 MPH...POST-TROP/EXTRATROP $$ Forecaster Avila
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