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Tropical Depression KARL Forecast Discussion Number 29
2016-09-21 16:49:08| National Hurricane Center (Atlantic)
Issued at 1100 AM AST WED SEP 21 2016 000 WTNT42 KNHC 211443 TCDAT2 TROPICAL DEPRESSION KARL DISCUSSION NUMBER 29 NWS NATIONAL HURRICANE CENTER MIAMI FL AL122016 ISSUED BY THE NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1100 AM AST WED SEP 21 2016 A research flight by the NOAA P3 aircraft earlier this morning had a difficult time closing off a well-defined center of circulation. However, we are able to track what looks like a reasonable center on early-morning visible satellite imagery. Based on the latest satellite images and the P3 data, it does appear that the center has wobbled toward the northwest and slowed down a bit. However, the longer-term 12-hour motion estimate is still west-northwestward, or 295/8 kt. Most of the deep convection remains displaced well to the east of the center, but new convection has recently been developing just to the north and northwest. The initial intensity is held at 30 kt based on earlier reports from the NOAA P3 and a 1254 UTC ASCAT-B scatterometer pass. Karl remains located to the south and southwest of a mid-level high. However, the depression is expected to turn northwestward later today when it begins to move between the high and a mid- to upper-level low located near the Carolina coast. Karl should then turn northward and then accelerate toward the northeast from 48 hours and beyond once it becomes embedded in the mid-latitude westerlies. The track guidance remains in generally good agreement on this scenario, and the main differences appear toward the end of the forecast period when the ECMWF remains much slower than the other models. The new official forecast remains very close to a consensus of the GFS and ECMWF models, which did not require any significant changes from the previous advisory. The distance between Karl and the upper-level low that has been adversely affecting it during the past couple of days appears to be increasing a bit, and the shear vector over the cyclone has become south-southeasterly. Although the global models continue to indicate that the shear will decrease over the next few days, they do not agree on the direction of that shear. In addition, the models do not agree on how much moisture there will be in the mid-level environment around the cyclone. As a result, the intensity forecast is complicated, and confidence is not very high. For continuity's sake, the updated intensity forecast is very similar to the previous forecast during the first 3 days, and then it is a little lower at days 4 and 5 based on the latest guidance. Karl is expected to become extratropical by day 5, which agrees with the latest guidance from the Ocean Prediction Center. FORECAST POSITIONS AND MAX WINDS INIT 21/1500Z 20.8N 57.8W 30 KT 35 MPH 12H 22/0000Z 22.1N 59.6W 30 KT 35 MPH 24H 22/1200Z 24.0N 62.0W 30 KT 35 MPH 36H 23/0000Z 25.7N 63.6W 35 KT 40 MPH 48H 23/1200Z 27.2N 64.8W 45 KT 50 MPH 72H 24/1200Z 31.0N 62.2W 60 KT 70 MPH 96H 25/1200Z 36.0N 52.5W 70 KT 80 MPH 120H 26/1200Z 44.0N 38.5W 60 KT 70 MPH...POST-TROP/EXTRATROP $$ Forecaster Berg/Gallina/Veenhuis
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