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| #875348 (Received by flhurricane at: 4:49 PM 19.Sep.2016) TCDAT2 TROPICAL STORM KARL DISCUSSION NUMBER 22 NWS NATIONAL HURRICANE CENTER MIAMI FL AL122016 ISSUED BY THE NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 500 PM AST MON SEP 19 2016 Deep convection associated with Karl has increased during the day, and the low-level center is now embedded beneath the convective canopy. Dvorak intensity estimates from TAFB and SAB increased to T2.5/35 kt and T2.0/30 kt, respectively, but these numbers do not yet support an increase in the initial intensity of 35 kt that has been carried in the previous few advisories. SHIPS and UW-CIMSS shear analyses indicate that the southwesterly shear over Karl remains 10-15 kt. However, the guidance shows the shear decreasing, and the improving structure of Karl suggests that this may be already occurring. In addition, moisture in the middle levels of the atmosphere is expected to gradually increase, and SSTs will be between 28-30C for the next five days. All these ingredients suggest that strengthening is likely, and the official forecast continues to show intensification starting slowly at first and then becoming faster after 48 hours. This forecast is very close to a consensus of the SHIPS and LGEM models, and the new official forecast is essentially an update of the previous forecast. The center of Karl jogged northwestward during the day, and the long-term motion estimate is now west-northwestward, or 290/10 kt. A west-northwestward motion is expected to continue for the next couple of days while Karl moves along the southern edge of the subtropical ridge. After that time, Karl is forecast to reach the western edge of the ridge and should turn northward and then northeastward on days 4 and 5. There is still some spread among the track models when this turn is forecast to occur, and as a result there is a lot of uncertainty on how much Karl will affect Bermuda toward the end of the forecast period. Still, the overall guidance envelope has not shifted much, and the updated official forecast is very close to the previous one. This forecast is close to the various consensus models, but it should be noted that the GFS, GFS ensemble mean, and Florida Superensemble all show Karl moving farther west before making the northward turn. FORECAST POSITIONS AND MAX WINDS INIT 19/2100Z 19.3N 49.2W 35 KT 40 MPH 12H 20/0600Z 19.8N 51.1W 40 KT 45 MPH 24H 20/1800Z 20.6N 53.6W 40 KT 45 MPH 36H 21/0600Z 21.6N 56.0W 45 KT 50 MPH 48H 21/1800Z 22.9N 58.4W 50 KT 60 MPH 72H 22/1800Z 25.9N 62.6W 60 KT 70 MPH 96H 23/1800Z 29.0N 65.0W 75 KT 85 MPH 120H 24/1800Z 31.0N 63.0W 85 KT 100 MPH $$ Forecaster Berg/Petersen/Chenard |
