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Tropical Storm GONZALO Forecast Discussion Number 3

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

Issued at 1100 PM AST SUN OCT 12 2014 000 WTNT43 KNHC 130235 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

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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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Hurricane FAY Forecast Discussion Number 11

2014-10-12 22:34:26| National Hurricane Center (Atlantic)

Issued at 500 PM AST SUN OCT 12 2014 000 WTNT42 KNHC 122034 TCDAT2 HURRICANE FAY DISCUSSION NUMBER 11 NWS NATIONAL HURRICANE CENTER MIAMI FL AL072014 500 PM AST SUN OCT 12 2014 After 1200 UTC, subjective T-numbers from and TAFB and objective numbers from the University of Wisconsin-CIMSS indicate that Fay has reached hurricane status with an initial intensity of 65 kt. This coincided with the presence of a closed mid-level eye feature in microwave imagery and a center surrounded by very deep convection. Fay is the fifth hurricane of the 2014 Atlantic hurricane season. Given the strong shear and the expected interaction with a cold front, Fay will probably weaken below hurricane status during the next few hours and begin the expected extratropical transition. Fay is already embedded in the fast mid-latitude westerlies and is moving toward the east-northwest or 070 degrees at 22 kt. Fay should accelerate even further and turn more to the east. The NHC forecast is in the middle of the guidance envelope, and is a blend of the previous forecast and the Ocean Prediction Center input. FORECAST POSITIONS AND MAX WINDS INIT 12/2100Z 34.7N 60.7W 65 KT 75 MPH 12H 13/0600Z 35.6N 56.0W 60 KT 70 MPH 24H 13/1800Z 36.0N 50.0W 55 KT 65 MPH...POST-TROP/EXTRATROP 36H 14/0600Z 35.0N 43.5W 45 KT 50 MPH...POST-TROP/EXTRATROP 48H 14/1800Z 33.5N 40.0W 40 KT 45 MPH...POST-TROP/EXTRATROP 72H 15/1800Z...DISSIPATED $$ Forecaster Avila

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Tropical Storm GONZALO Forecast Discussion Number 1

2014-10-12 19:55:23| National Hurricane Center (Atlantic)

Issued at 130 PM AST SUN OCT 12 2014 000 WTNT43 KNHC 121755 TCDAT3 TROPICAL STORM GONZALO SPECIAL DISCUSSION NUMBER 1 NWS NATIONAL HURRICANE CENTER MIAMI FL AL082014 130 PM AST SUN OCT 12 2014 An Air Force Reserve reconnaissance aircraft investigating the low pressure system east of the Leeward islands found SFMR surface winds of tropical storm force, and based on this information the low has been upgraded to Tropical Storm Gonzalo. The initial motion estimate is an uncertain 270/09 kt. Due to a strong ridge to the north of Gonzalo, the cyclone is expected to move generally westward at around 10 kt for the next 24 hours or so, followed by a gradual turn to the west-northwest in the 36-72 hour time frame. After that time, a deep-layer trough moving off of the U.S. east coast is expected to erode the ridge, causing Gonzalo to move slowly northwestward to northward. The NHC track forecast closely follows the consensus model TVCN. The small size of Gonzalo, combined with low shear conditions less than 10 kt and SSTs of at least 29C, argue for at least steady strengthening throughout the forecast period. There will likely be occasional intrusions of dry mid-level air that may briefly slow the intensification process, but those occurrences should generally be short-lived. The intensity forecast closely follows the SHIPS intensity model. NOTE: Data from the reconnaissance aircraft has been received by the NHC, but telecommunications problems are preventing the dissemination of these data. FORECAST POSITIONS AND MAX WINDS INIT 12/1730Z 16.4N 58.4W 35 KT 40 MPH 12H 13/0000Z 16.4N 59.5W 35 KT 40 MPH 24H 13/1200Z 16.5N 61.7W 45 KT 50 MPH 36H 14/0000Z 17.2N 63.8W 55 KT 65 MPH 48H 14/1200Z 18.2N 65.5W 65 KT 75 MPH 72H 15/1200Z 20.5N 67.5W 75 KT 85 MPH 96H 16/1200Z 22.0N 68.0W 85 KT 100 MPH 120H 17/1200Z 24.0N 68.0W 85 KT 100 MPH $$ Forecaster Stewart

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Tropical Storm FAY Forecast Discussion Number 10

2014-10-12 16:35:24| National Hurricane Center (Atlantic)

Issued at 1100 AM AST SUN OCT 12 2014 000 WTNT42 KNHC 121435 TCDAT2 TROPICAL STORM FAY DISCUSSION NUMBER 10 NWS NATIONAL HURRICANE CENTER MIAMI FL AL072014 1100 AM AST SUN OCT 12 2014 The cloud pattern associated with Fay has become more symmetrical, and microwave data also reveal that the inner core structure is better than 12 hours ago, including the presence of a closed mid-level eye feature. I was tempted to classify the system as a hurricane, but the consensus of the Dvorak T-numbers still support an initial intensity of 60 kt. No significant change in strength is anticipated, but only a 5-kt increase in the winds will bring Fay to hurricane status. A strong cold front is rapidly approaching the cyclone, and extratropical transition will most likely occur in about 24 hours. Fay has turned to the right as anticipated, and the best estimate of the initial motion is toward the northeast or 055 degrees at 21 kt. Fay should accelerate even further and turn more to the east while embedded in the fast mid-latitude westerly flow. The NHC forecast is in the middle of the guidance envelope, and is a blend of the previous forecast and the Ocean Prediction Center input. FORECAST POSITIONS AND MAX WINDS INIT 12/1500Z 34.0N 62.8W 60 KT 70 MPH 12H 13/0000Z 35.5N 59.0W 60 KT 70 MPH 24H 13/1200Z 36.0N 52.5W 55 KT 65 MPH...POST-TROP/EXTRATROP 36H 14/0000Z 36.0N 46.0W 45 KT 50 MPH...POST-TROP/EXTRATROP 48H 14/1200Z 34.0N 42.0W 40 KT 45 MPH...POST-TROP/EXTRATROP 72H 15/1200Z...absorbed by a front $$ Forecaster Avila

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