ZCZC MIATCDAT4 ALL TTAA00 KNHC DDHHMM TROPICAL STORM CRISTOBAL DISCUSSION NUMBER 8 NWS NATIONAL HURRICANE CENTER MIAMI FL AL042014 1100 AM EDT MON AUG 25 2014 Cristobal remains a sheared tropical cyclone with the low-level center fully exposed on the north side of the deep convective cloud mass. Earlier reconnaissance data indicated maximum 850 mb flight-level winds of 61 kt in the southeast quadrant where SFMR winds of near 50 kt were observed. Therefore, the initial intensity has been increased to 50 kt. A NOAA aircraft reported a central pressure of 996 mb, but the dropsonde also reported a 33-kt surface wind. As a result, the central pressure is estimated to be 993 mb. Aircraft fixes indicate that Cristobal is moving erratically north-northeastward or 015/02 kt. Strong northerly shear has been impeding the forward motion of Cristobal for the past several hours by keeping the deep convection displaced to the south of the center, and this is expected to continue through today. On Tuesday, however, a deep trough just of the U.S. east coast is forecast to capture Cristobal and gradually lift out the cyclone to the northeast while the Bermuda-Azores ridge builds westward to the south of the system. The NHC model guidance is in very good agreement on this developing scenario with only minor differences in forward speed. The official track forecast is similar to the previous advisory track, and lies close to a blend of the GFS and ECMWF solutions. The GFS-based SHIPS model indicates northerly shear of 23 kt has been affecting Cristobal. The shear is forecast to gradually subside to around 10 kt during the next 12-24 hours, during which time some slight strengthening could occur. However, by 48-72 hours, the shear is forecast to decrease more significantly, allowing Cristobal to strengthen further, becoming a hurricane as the cyclone passes to the west and north of Bermuda on Wednesday and Thursday. On Days 4 and 5, Cristobal will be passing over much cooler waters and encountering strong southwesterly wind shear as the cyclone becomes embedded in the mid-latitude westerlies, which will result in extratropical transition by 120 hours. Owing to the slow motion of Cristobal, heavy rainfall and possible flooding will remain a threat for the southeastern Bahamas and the Turks and Caicos through Tuesday. FORECAST POSITIONS AND MAX WINDS INIT 25/1500Z 24.6N 72.7W 50 KT 60 MPH 12H 26/0000Z 26.0N 72.2W 50 KT 60 MPH 24H 26/1200Z 27.8N 71.5W 55 KT 65 MPH 36H 27/0000Z 30.0N 70.9W 60 KT 70 MPH 48H 27/1200Z 32.2N 69.7W 65 KT 75 MPH 72H 28/1200Z 36.5N 63.5W 65 KT 75 MPH 96H 29/1200Z 42.7N 50.1W 65 KT 75 MPH 120H 30/1200Z 49.5N 39.0W 60 KT 70 MPH...POST-TROP/EXTRATROP $$ Forecaster Stewart NNNN