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| #874710 (Received by flhurricane at: 5:02 PM 12.Sep.2016) TCDAT5 TROPICAL STORM IAN DISCUSSION NUMBER 2 NWS NATIONAL HURRICANE CENTER MIAMI FL AL102016 500 PM AST MON SEP 12 2016 Ian remains poorly organized, with the bulk of the deep convection displaced well to the northeast of the low-level center due to strong vertical shear. The advisory intensity estimate remains at 35 kt in agreement with a Dvorak estimate from TAFB. The global models suggest that some decrease in shear will occur in 36 to 48 hours, when the system moves on the northeast side of a partially cut off upper-level cyclone. This could permit a little strengthening to commence around that time, as reflected in the official forecast. This is slightly above the latest numerical model intensity consensus. By the end of the forecast period, or sooner, Ian should become embedded in a frontal zone over the north Atlantic and be transformed into an extratropical cyclone. Ian has turned to the right, and the initial motion estimate is now about 330/11 kt. The storm continues to move through a break in the subtropical ridge, and in a few days the flow ahead of a mid-tropospheric trough should cause Ian to accelerate north-northeastward to northeastward. The official forecast lies between the latest GFS and ECMWF predictions, and is also close to the dynamical model consensus. FORECAST POSITIONS AND MAX WINDS INIT 12/2100Z 22.9N 50.7W 35 KT 40 MPH 12H 13/0600Z 24.3N 51.7W 35 KT 40 MPH 24H 13/1800Z 26.2N 52.9W 35 KT 40 MPH 36H 14/0600Z 28.5N 54.0W 40 KT 45 MPH 48H 14/1800Z 30.7N 54.5W 45 KT 50 MPH 72H 15/1800Z 35.7N 52.4W 50 KT 60 MPH 96H 16/1800Z 45.0N 42.0W 50 KT 60 MPH 120H 17/1800Z 54.5N 29.0W 50 KT 60 MPH...POST-TROP/EXTRATROP $$ Forecaster Pasch |
