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Tropical Storm GONZALO Forecast Discussion Number 2
2014-10-12 22:54:54| National Hurricane Center (Atlantic)
Issued at 500 PM AST SUN OCT 12 2014 000 WTNT43 KNHC 122054 TCDAT3 TROPICAL STORM GONZALO DISCUSSION NUMBER 2 NWS NATIONAL HURRICANE CENTER MIAMI FL AL082014 500 PM AST SUN OCT 12 2014 The Air Force Reserve reconnaissance aircraft investigating Gonzalo this afternoon has found found 850-mb maximum flight-level winds of 47 kt in the northeastern quadrant along with reliable SFMR surface winds of 39-41 kt. The aircraft also measured a central pressure of 1003-1004 mb and on-board radar indicated that a primitive eye with a diameter of 10 n mi was developing. Based on these data, the initial intensity has been increased to 40 kt, which could be a little conservative. The initial motion estimate is 270/10 kt based on reconnaissance data. There is no significant change to the previous track forecast or reasoning. A strong deep-layer ridge to the north of Gonzalo should keep the cyclone moving westward at around 10 kt for the next 24 hours, followed by a gradual turn to the west-northwest by 36 hours. By 72 hours, a strong mid-latitude trough is expected to move off of the U.S. east coast and act to erode the ridge to the north of Hispaniola, allowing Gonzalo to move slowly northwestward to northward into the weakness in the ridge. The NHC model guidance is in general agreement on this developing track scenario, but there is considerable spread in the model tracks after 36 hours. The GFS and the regional models keep Gonzalo weak until after 48 hours, and take the system well to the east of Puerto Rico and the Virgin Islands. In contrast, the ECMWF and the UKMET show a vertically deep and more robust tropical cyclone moving more westward in deep-layer easterly steering flow. Since the official forecast calls for Gonzalo to become a hurricane within 48 hours, the NHC forecast track lies near the extreme western edge of the model envelope and close to the more robust ECMWF model solution. The combination of the small size of Gonzalo, its precursor eye feature, low vertical wind shear conditions, SSTs at least 29C, and colder than normal upper-tropospheric temperatures support at least a normal rate of intensification throughout the forecast period. Although occasional intrusions of dry mid-level air could briefly disrupt the strengthening process, those occurrences should generally be short-lived due to the strong instability conditions that will be present. In fact, rapid intensification is a very distinct possibility, especially if the aforementioned eye feature continues to develop. The NHC intensity forecast is higher then the consensus models and follows the a blend of the SHIPS and LGEM models. NOTE: Data from the reconnaissance aircraft has been received by the NHC, but telecommunications problems continue to prevent the dissemination of these data. FORECAST POSITIONS AND MAX WINDS INIT 12/2100Z 16.4N 59.5W 40 KT 45 MPH 12H 13/0600Z 16.5N 61.1W 45 KT 50 MPH 24H 13/1800Z 16.9N 63.1W 50 KT 60 MPH 36H 14/0600Z 17.9N 65.0W 60 KT 70 MPH 48H 14/1800Z 19.0N 66.4W 70 KT 80 MPH 72H 15/1800Z 20.9N 67.9W 80 KT 90 MPH 96H 16/1800Z 22.6N 68.3W 90 KT 105 MPH 120H 17/1800Z 24.5N 68.0W 95 KT 110 MPH $$ Forecaster Stewart
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