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Tropical Storm GONZALO Forecast Discussion Number 5

2014-10-13 16:52:30| National Hurricane Center (Atlantic)

Issued at 1100 AM AST MON OCT 13 2014 000 WTNT43 KNHC 131452 TCDAT3 TROPICAL STORM GONZALO DISCUSSION NUMBER 5 NWS NATIONAL HURRICANE CENTER MIAMI FL AL082014 1100 AM AST MON OCT 13 2014 An Air Force Reserve reconnaissance aircraft investigating Gonzalo this morning found 850 mb maximum flight-level winds of 64 kt along with reliable SFMR surface winds near 55 kt in the northeastern quadrant, plus a central pressure of 992 mb. In addition, the Antigua-Barbuda Meteorological Service recently reported a sustained wind of 58 kt and a gust to 76 kt. Based on these data, the intensity has been increased to 55 kt. Reports from the aircraft radar and Antigua-Barbuda also indicate the center of Gonzalo passed over Antigua between 1300-1400 UTC. The initial motion estimate is 290/9 kt. Gonzalo is expected to continue to move west-northwestward today, and turn toward the northwest after 24 hours when the cyclone clears the northern Lesser Antilles. After that, the mid-level ridge to the north of Gonzalo is expected to break down as a strong mid-latitude trough moving off of the U.S. east and southeast coasts approaches the area north of Puerto Rico and Hispaniola in about 72 hours. The weakening ridge will allow Gonzalo to move slowly northward, and then turn toward the northeast and accelerate on Days 4 and 5. The latest NHC model guidance appears to have stabilized and has no longer made any eastward shifts, so the official forecast track is just an update of the previous advisory track, which lies close to a blend of the GFEX and TVCN consensus models. The satellite presentation of Gonzalo has continued to improve, and radar data from Guadeloupe indicates that a small but intense vortex may have passed over Antigua earlier this morning. Overall, the improvement in the horizontal and vertical structure of Gonzalo the past several hours, along with weak vertical wind shear and SSTs greater than 29C, should allow for at least steady strengthening of the cyclone through the next 96 hours. By 120 hours, southwesterly wind shear of around 20 kt is expected to affect Gonzalo, which should induce a slow weakening trend. The NHC intensity forecast is similar to the previous forecast and the SHIPS intensity model. Gonzalo is forecast to be reaching hurricane strength by the time it passes near the British Virgin Islands, and so a hurricane warning is in effect there. Although hurricane conditions are not currently expected in the U.S. Virgin Islands, only a slight deviation to the left of the forecast track, or a more rapid strengthening of the storm, would result in the need to extend the hurricane warning into those areas. Interests in the hurricane watch area are reminded that the watch means that hurricane conditions are possible...and in this case within 24 hours. FORECAST POSITIONS AND MAX WINDS INIT 13/1500Z 17.2N 61.9W 55 KT 65 MPH 12H 14/0000Z 18.0N 63.3W 60 KT 70 MPH 24H 14/1200Z 19.4N 65.0W 70 KT 80 MPH 36H 15/0000Z 20.8N 66.4W 75 KT 85 MPH 48H 15/1200Z 22.4N 67.5W 80 KT 90 MPH 72H 16/1200Z 24.8N 68.0W 90 KT 105 MPH 96H 17/1200Z 27.4N 66.9W 95 KT 110 MPH 120H 18/1200Z 31.7N 64.0W 90 KT 105 MPH $$ Forecaster Stewart

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Tropical Storm FAY Forecast Discussion Number 14

2014-10-13 16:39:59| National Hurricane Center (Atlantic)

Issued at 1100 AM AST MON OCT 13 2014 000 WTNT42 KNHC 131439 TCDAT2 TROPICAL STORM FAY DISCUSSION NUMBER 14 NWS NATIONAL HURRICANE CENTER MIAMI FL AL072014 1100 AM AST MON OCT 13 2014 Fay is well on its way to becoming a post-tropical cyclone or even dissipating within a frontal zone. Satellite images and surface observations indicate that a cold front is located just to the west of Fay, and cold air stratocumulus clouds are wrapping around the western side of the system. In addition, deep convection is now displaced well to the northeast of what passes for a low-level center. The Florida State University cyclone phase evolution analyses indicate that Fay has a warm core, which is the reason why it is still designated as a tropical storm, but it won't be one for much longer. The initial wind speed is lowered slightly to 50 kt, following the decrease in the satellite intensity estimates. The storm is moving quickly eastward at about 25 kt as it is embedded in the mid-latitude westerly flow. Assuming it maintains a closed circulation, a continued eastward motion at a slightly slower forward speed is expected. The NHC track forecast is similar to the previous one and lies near the middle of the guidance envelope. FORECAST POSITIONS AND MAX WINDS INIT 13/1500Z 34.1N 52.2W 50 KT 60 MPH 12H 14/0000Z 33.7N 48.7W 45 KT 50 MPH...POST-TROP/EXTRATROP 24H 14/1200Z 32.9N 44.6W 45 KT 50 MPH...POST-TROP/EXTRATROP 36H 15/0000Z 32.2N 40.9W 40 KT 45 MPH...POST-TROP/EXTRATROP 48H 15/1200Z 31.8N 37.0W 35 KT 40 MPH...POST-TROP/EXTRATROP 72H 16/1200Z 32.0N 29.5W 30 KT 35 MPH...POST-TROP/EXTRATROP 96H 17/1200Z...DISSIPATED $$ Forecaster Cangialosi

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Tropical Storm GONZALO Forecast Discussion Number 4

2014-10-13 11:00:31| National Hurricane Center (Atlantic)

Issued at 500 AM AST MON OCT 13 2014 000 WTNT43 KNHC 130900 TCDAT3 TROPICAL STORM GONZALO DISCUSSION NUMBER 4 NWS NATIONAL HURRICANE CENTER MIAMI FL AL082014 500 AM AST MON OCT 13 2014 The satellite presentation of Gonzalo has gradually improved overnight with increased banding features seen in both infrared satellite images and Guadeloupe radar. The small inner core has also become a little better defined in the radar imagery. Dvorak data T-numbers from SAB and TAFB are 3.0 and 3.5, respectively, and the initial wind speed has been increased to 50 kt. An Air Force Reserve Hurricane Hunter aircraft is scheduled to investigate the cyclone in a few hours, which should provide a better assessment of Gonzalo's intensity and size. Although some mid-level dry air is noted to the west of the cyclone, low shear and warm water should favor strengthening during the next several days. The NHC intensity forecast calls for steady intensification and Gonzalo is forecast to become a hurricane in 24 to 36 hours. The updated intensity forecast is close to the SHIPS model and is very similar to the previous advisory. The initial motion estimate is 280/9 kt. Gonzalo is forecast to turn west-northwestward, then northwestward during the next day or so, while it moves around the southwestern periphery of a mid-level ridge over the central subtropical Atlantic. Most of the track guidance has again shifted slightly eastward during the first 48 hours, and the NHC forecast track has been nudged in that direction. The NHC forecast is along the southern edge of the guidance envelope during the first couple of days and is close to the GFS and ECMWF models. After that time, Gonzalo is forecast to turn northward then north-northeastward ahead of a deep-layer trough that approaches the east coast of the United States in about 4 days. Although the track guidance is in general agreement on this scenario, there remains large differences in the forward speed of the cyclone later in the period. The GFS, UKMET, and HWRF showing more north-northeastward acceleration than the ECMWF. The updated NHC track forecast is near the GFS/ECMWF consensus, which is faster than the previous advisory. FORECAST POSITIONS AND MAX WINDS INIT 13/0900Z 16.8N 60.9W 50 KT 60 MPH 12H 13/1800Z 17.4N 62.5W 55 KT 65 MPH 24H 14/0600Z 18.6N 64.3W 60 KT 70 MPH 36H 14/1800Z 20.2N 65.8W 70 KT 80 MPH 48H 15/0600Z 21.5N 67.0W 75 KT 85 MPH 72H 16/0600Z 23.8N 68.1W 85 KT 100 MPH 96H 17/0600Z 26.0N 67.5W 95 KT 110 MPH 120H 18/0600Z 29.0N 65.5W 90 KT 105 MPH $$ Forecaster Brown

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Tropical Storm FAY Forecast Discussion Number 13

2014-10-13 10:48:37| National Hurricane Center (Atlantic)

Issued at 500 AM AST MON OCT 13 2014 000 WTNT42 KNHC 130848 TCDAT2 TROPICAL STORM FAY DISCUSSION NUMBER 13 NWS NATIONAL HURRICANE CENTER MIAMI FL AL072014 500 AM AST MON OCT 13 2014 A series of microwave images indicate that Fay has begun extratropical transition. The cloud pattern has become quite asymmetric and the remaining central deep convection, situated well to the northeast of the center of circulation, is decreasing. An earlier AMSU-B overpass showed significant erosion of the southern flank of Fay due to intruding cold, dry, low to mid-level air associated with an approaching strong baroclinic frontal zone. Furthermore, the GFS model-forecast cyclone phase diagram shows Fay completing transition to an asymmetric cold core system in 12 hours or so. A compromise of the objective and subjective satellite intensity estimates keeps the initial intensity at 55 kt for this advisory. Although the cyclone is expected to remain generally in warm water south of the Gulf Stream's north wall, strong, persistent, vertical shear is forecast to further weaken Fay through the 72 hr period. Afterward, the post-tropical cyclone should continue to decay and open up into a trough of low pressure within the aforementioned frontal boundary and dissipate over the northeastern Atlantic. Based on a consensus of the global models, an adjustment to the length of the official forecast has been made, and it now postpones dissipation until day 4. The tropical storm is gradually accelerating eastward and is now moving at 23 kt within the mid-latitude westerlies. Fay is forecast to slow a bit during the next 24 hours, in response to interaction with the cold front, and track eastward to east-southeastward until dissipation. The NHC forecast is close to the TVCA multi-model consensus and the post-tropical cyclone forecast guidance from the Ocean Prediction Center. FORECAST POSITIONS AND MAX WINDS INIT 13/0900Z 34.3N 55.3W 55 KT 65 MPH 12H 13/1800Z 34.3N 51.2W 50 KT 60 MPH...POST-TROP/EXTRATROP 24H 14/0600Z 33.7N 47.2W 40 KT 45 MPH...POST-TROP/EXTRATROP 36H 14/1800Z 32.7N 43.2W 35 KT 40 MPH...POST-TROP/EXTRATROP 48H 15/0600Z 32.1N 39.5W 30 KT 35 MPH...POST-TROP/EXTRATROP 72H 16/0600Z 32.0N 32.0W 25 KT 30 MPH...POST-TROP/EXTRATROP 96H 17/0600Z...DISSIPATED $$ Forecaster Roberts

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Tropical Storm FAY Forecast Discussion Number 12

2014-10-13 04:35:26| National Hurricane Center (Atlantic)

Issued at 1100 PM AST SUN OCT 12 2014 000 WTNT42 KNHC 130235 TCDAT2 TROPICAL STORM FAY DISCUSSION NUMBER 12 NWS NATIONAL HURRICANE CENTER MIAMI FL AL072014 1100 PM AST SUN OCT 12 2014 Fay's cloud pattern has rapidly deteriorated in organization since this afternoon due to strong southwesterly vertical wind shear. Microwave and last-light visible satellite imagery indicate that the low-level center has become exposed to the southwest of a large mass of very cold-topped convection. The same satellite data also indicate that the center has become increasingly deformed, making the initial position more uncertain than normal. This uncertainty has resulted in a large scatter in Dvorak intensity estimates. The initial intensity is lowered to 55 kt, in agreement with the latest Dvorak estimate from SAB, which was closest to the estimated center position. Even stronger west-southwesterly shear should affect Fay during the next couple of days. Meanwhile, much drier and more stable air behind a cold front impinging on the storm from the northwest should become entrained within Fay's circulation. The combination of these factors should lead to additional steady weakening, with global models showing extratropical transition occurring in about 24 hours (or perhaps sooner). The NHC intensity forecast is similar to the previous one and in excellent agreement with the latest statistical- dynamical model consensus. The exposed center in the last few visible images was south of previous estimates, and as a result the initial motion estimate is now more sharply toward the east, or 080/21. Fay is expected to continue racing eastward or east-southeastward at the base of a potent shortwave trough moving through eastern Atlantic Canada and the north Atlantic. The NHC track forecast has been adjusted toward the right of the previous one, based primarily on the new center position and motion. FORECAST POSITIONS AND MAX WINDS INIT 13/0300Z 34.1N 58.2W 55 KT 65 MPH 12H 13/1200Z 34.4N 53.6W 50 KT 60 MPH 24H 14/0000Z 33.9N 48.0W 45 KT 50 MPH...POST-TROP/EXTRATROP 36H 14/1200Z 33.4N 42.6W 35 KT 40 MPH...POST-TROP/EXTRATROP 48H 15/0000Z 33.0N 37.0W 30 KT 35 MPH...POST-TROP/EXTRATROP 72H 16/0000Z...DISSIPATED $$ Forecaster Kimberlain

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