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Tropical Storm CRISTOBAL Forecast Discussion Number 9
2014-08-25 23:16:36| National Hurricane Center (Atlantic)
Issued at 500 PM EDT MON AUG 25 2014 000 WTNT44 KNHC 252116 TCDAT4 TROPICAL STORM CRISTOBAL DISCUSSION NUMBER 9...CORRECTED NWS NATIONAL HURRICANE CENTER MIAMI FL AL042014 500 PM EDT MON AUG 25 2014 Corrected forecast motion through 72 hours Cristobal remains in a moderate shear environment with the low-level center still fully exposed on the north side of the deep convection. A recent Air Force Reserve reconnaissance flight indicated maximum 850 mb flight-level winds of 65 kt in the southeast quadrant where SFMR winds of 51 kt were noted, and the central pressure has remained at 993 mb. Based on these data, the initial intensity has been held at 50 kt. Aircraft fixes indicate that Cristobal is now moving at a more reliable north-northeastward motion of 020/04 kt. There is no significant change to the previous forecast track or reasoning. The latest NHC model guidance continues to be in excellent agreement on the subtropical ridge to the north of Cristobal slowly eroding due to a strong mid/upper-level trough just off the U.S. southeast coast continuing to dig southward as noted in water vapor imagery. The combination of increasing southwesterly flow on the east side of the trough and a building ridge to the south of the cyclone should act to lift Cristobal slowly northeastward over the next 72 hours. After that, Cristobal is forecast to become embedded in deep mid-latitude westerlies and accelerate off to the northeast and east-northeast, becoming a large and powerful extratropical cyclone over the far north Atlantic by 120 hours. The official forecast track is essentially just an update of the previous advisory track, and lies just to the right of the consensus model TVCA. The shear is forecast to ebb and flow over the next 48 hours or so, and the intensity forecast has followed this trend with strengthening indicated during the periods when the vertical shear subsides. Cristobal is still expected to become a hurricane when 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. However, the system is likely to receive a boost from baroclinic effects, remaining as a strong extratropical cyclone. 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. Heavy rainfall is expected to continue across Bermuda through Wednesday ahead of Cristobal. FORECAST POSITIONS AND MAX WINDS INIT 25/2100Z 25.3N 72.5W 50 KT 60 MPH 12H 26/0600Z 26.6N 71.9W 55 KT 65 MPH 24H 26/1800Z 28.9N 71.2W 55 KT 65 MPH 36H 27/0600Z 31.2N 70.4W 60 KT 70 MPH 48H 27/1800Z 33.4N 68.5W 70 KT 80 MPH 72H 28/1800Z 38.1N 60.5W 65 KT 75 MPH 96H 29/1800Z 44.3N 47.3W 60 KT 70 MPH 120H 30/1800Z 51.5N 34.5W 50 KT 60 MPH...POST-TROP/EXTRATROP $$ Forecaster Stewart
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