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#875306 (Received by flhurricane at: 4:52 AM 19.Sep.2016) TCDAT2 TROPICAL STORM KARL DISCUSSION NUMBER 20 NWS NATIONAL HURRICANE CENTER MIAMI FL AL122016 500 AM AST MON SEP 19 2016 Karl continues to have a rather disorganized appearance in satellite imagery. The cloud pattern consists of a relatively small mass of convection northeast of the center, with a separate shapeless cluster of convection farther to the northeast. The initial intensity estimate is held at 35 kt in accordance with the Dvorak CI number from TAFB. Karl`s current poor structure, proximity to an upper tropospheric low near the Lesser Antilles, and large-scale subsidence/convergence over the tropical Atlantic suggest that the storm should only slowly strengthen during the next couple of days. The intensity forecast has been modified downward a bit further to reflect the likelihood of a slower intensification. After 72 hours, a notable increase in moisture, waters of around 30 deg C, and low shear should promote strengthening, perhaps more than indicated in this forecast. The intensity forecast during this time has been increased over the previous one, and is closest to the LGEM model. The initial motion estimate is 270/13. Karl should remain on the south and southwest side of a subtropical ridge the next couple of days, with the flow around this feature steering the cyclone westward and then west-northwestward. From days 3-5, Karl will encounter a weakness in the ridge over the west-central Atlantic, which should cause the cyclone to turn northwestward and northward with a substantial decrease in forward speed. The new track forecast is nudged to the south of the previous one through 48 hours, with more emphasis put on the weaker GFS solution. The track forecast from days 3-5 has been adjusted to the east of the previous one, and is consistent with the expectation of stronger cyclone as depicted in the ECWMF solution. FORECAST POSITIONS AND MAX WINDS INIT 19/0900Z 18.2N 47.7W 35 KT 40 MPH 12H 19/1800Z 18.6N 49.7W 35 KT 40 MPH 24H 20/0600Z 19.1N 52.1W 40 KT 45 MPH 36H 20/1800Z 19.9N 54.6W 45 KT 50 MPH 48H 21/0600Z 21.0N 57.1W 50 KT 60 MPH 72H 22/0600Z 24.0N 62.2W 60 KT 70 MPH 96H 23/0600Z 27.0N 65.2W 75 KT 85 MPH 120H 24/0600Z 29.5N 65.7W 85 KT 100 MPH $$ Forecaster Kimberlain |