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| #723796 (Received by flhurricane at: 10:38 PM 12.Oct.2014) TCDAT3 TROPICAL STORM GONZALO DISCUSSION NUMBER 3 NWS NATIONAL HURRICANE CENTER MIAMI FL AL082014 1100 PM AST SUN OCT 12 2014 The circulation of Gonzalo, which has shown some signs of inner-core features, is apparent in radar imagery from Guadeloupe, but the cyclone's overall convective pattern is somewhat disorganized in satellite imagery. A small area of central convection is noted near the center, along with a rather linear convective band in the eastern semicircle. Little deep convection is noted west of the center, perhaps due to westerly shear of around 10 kt and some dry air in the mid and upper levels seen in radiosonde data from St. Maarten. The initial intensity remains 40 kt based on the earlier aircraft data and a blend of the latest Dvorak data-T numbers from TAFB and SAB. The SHIPS model shows the shear weakening in 12 to 18 hours, and most of the intensity guidance shows Gonzalo reaching hurricane status in about 36 hours. Additional intensification is forecast after that time in a low-shear environment over warm waters. The new NHC intensity forecast is largely an update of the previous one and is close to the IVCN consensus through the period. The initial motion estimate is 275/10, as Gonzalo is being steered by a mid-level ridge to its northeast. During the next 36 to 48 hours, the cyclone will gradually turn northwestward as it moves around the western periphery of this ridge. Overall, the guidance envelope has shifted a little to the right through the first 2 days, and the NHC forecast has been adjusted in that direction but lies south of the multi-model consensus and close to the ECMWF. After that time, most of the guidance shows the cyclone turning northward into a weakness in the ridge and then accelerating northeastward ahead of a mid-latitude trough by day 5. There is still a large amount of along-track spread at these time ranges, with the GFS, HWRF, GFDL, and GEFS ensemble mean showing a faster northeastward acceleration, and the slower ECMWF showing the trough missing Gonzalo and leaving the cyclone moving slowly northeastward by the end of the period. At days 3 through 5, the NHC forecast is faster and shows more of a northeastward motion compared to the previous one, but is much slower than the GFS and south of the consensus out of respect for the ECMWF model. FORECAST POSITIONS AND MAX WINDS INIT 13/0300Z 16.6N 60.2W 40 KT 45 MPH 12H 13/1200Z 16.9N 61.9W 50 KT 60 MPH 24H 14/0000Z 17.7N 63.8W 55 KT 65 MPH 36H 14/1200Z 18.8N 65.3W 65 KT 75 MPH 48H 15/0000Z 20.0N 66.5W 70 KT 80 MPH 72H 16/0000Z 22.5N 68.0W 85 KT 100 MPH 96H 17/0000Z 24.5N 68.0W 95 KT 110 MPH 120H 18/0000Z 27.0N 66.0W 90 KT 105 MPH $$ Forecaster Brennan |
