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Tropical Storm EMILY Forecast Discussion Number 2

2017-07-31 13:52:45| National Hurricane Center (Atlantic)

Issued at 800 AM EDT Mon Jul 31 2017 000 WTNT41 KNHC 311152 TCDAT1 Tropical Storm Emily Special Discussion Number 2 NWS National Hurricane Center Miami FL AL062017 800 AM EDT Mon Jul 31 2017 This Special Advisory is to upgrade the depression to Tropical Storm Emily, now located just west of Tampa Bay, Florida. A Tropical Storm Warning has also been issued for a portion of the west- central coast of Florida. Doppler velocity data from the NWS Tampa Bay WSR-88D radar indicate average velocities of 48-50 kt on the south side of the circulation center between 4500-6500 ft altitude during the past hour. Using a standard adjustment factor of 80 percent yields an equivalent surface wind of about 40 kt. Therefore, the depression has been upgraded to Tropical Storm Emily. Little change in strength is expected until landfall occurs this afternoon, followed by slow weakening as Emily moves across the Florida peninsula tonight. The initial motion estimate is 095/07 kt. There is no change to the previous forecast track or reasoning. Emily is expected to make landfall along the west-central Florida coast within the warning area by late afternoon, and then continue eastward across the central Florida peninsula tonight, emerging off of the east-central Florida coast Tuesday morning. The primary threat with this system is expected to be locally heavy rainfall across portions of the Florida peninsula during the next couple of days. However, an isolated waterspout will also be possible in the coastal waters within the warning area. This special advisory is being issued in lieu of the standard Intermediate Public advisory. FORECAST POSITIONS AND MAX WINDS INIT 31/1200Z 27.7N 83.2W 40 KT 45 MPH 12H 31/1800Z 27.7N 82.4W 40 KT 45 MPH 24H 01/0600Z 28.3N 80.6W 30 KT 35 MPH 36H 01/1800Z 29.8N 78.6W 35 KT 40 MPH 48H 02/0600Z 31.6N 76.5W 35 KT 40 MPH 72H 03/0600Z 34.5N 72.0W 35 KT 40 MPH 96H 04/0600Z...DISSIPATED $$ Forecaster Stewart

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Tropical Depression SIX Forecast Discussion Number 1

2017-07-31 11:54:10| National Hurricane Center (Atlantic)

Issued at 600 AM EDT Mon Jul 31 2017 000 WTNT41 KNHC 310954 TCDAT1 Tropical Depression Six Special Discussion Number 1 NWS National Hurricane Center Miami FL AL062017 600 AM EDT Mon Jul 31 2017 Radar imagery from the NWS Tampa Bay WSR-88D indicates that shower and thunderstorm activity associated with the small low pressure area over the eastern Gulf of Mexico have persisted and become better organized overnight. Earlier ASCAT data showed that the system has a well-defined circulation and winds of at least 30 kt over a small area to the north and northwest of the center. Based on these data, advisories are being initiated on a 30-kt tropical depression. The depression is currently embedded within an area of moderate to strong northwesterly shear. Although the upper-level winds could become a little more favorable for strengthening, the depression is expected to move inland over the west-central Florida peninsula later today, and no significant change in wind speed is predicted. After the depression moves over the western Atlantic, increasing westerly shear is forecast to prevent intensification. This scenario is in agreement with the GFS and ECMWF models, which show the system weakening and likely dissipating in 3 to 4 days, or perhaps sooner. The depression is moving eastward at about 7 kt. The cyclone is embedded within the southern portion of a deep-layer trough that extends southwestward along the U.S. east coast. This pattern should steer the system eastward today, then northeastward with some increase in forward speed through dissipation. The track guidance is in relatively good agreement on this scenario, although there are some differences in how fast the system will accelerate northeastward. For now, the NHC forecast lies between the faster HWRF and GFS solutions, and the slower ECMWF. The primary threat with this system is expected to be locally heavy rainfall across portions of the Florida peninsula during the next couple of days. Due to the uncertainty in the intensity forecast, a Tropical Storm Watch has been issued for a portion of the west- central coast of Florida. FORECAST POSITIONS AND MAX WINDS INIT 31/1000Z 27.7N 83.5W 30 KT 35 MPH 12H 31/1800Z 27.7N 82.4W 30 KT 35 MPH 24H 01/0600Z 28.3N 80.6W 30 KT 35 MPH 36H 01/1800Z 29.8N 78.6W 30 KT 35 MPH 48H 02/0600Z 31.6N 76.5W 30 KT 35 MPH 72H 03/0600Z 34.5N 72.0W 30 KT 35 MPH 96H 04/0600Z...DISSIPATED $$ Forecaster Brown

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Tropical Storm Irwin Forecast Discussion Number 36

2017-07-31 10:40:26| National Hurricane Center (East Pacific)

Issued at 200 AM PDT Mon Jul 31 2017 000 WTPZ45 KNHC 310840 TCDEP5 Tropical Storm Irwin Discussion Number 36 NWS National Hurricane Center Miami FL EP102017 200 AM PDT Mon Jul 31 2017 Irwin finally appears to be suffering from the effects of cooler water. Deep convection associated with the cyclone has decreased in coverage overnight, but the convection that remains is organized in a band over the eastern portion of the circulation. Dvorak T-numbers have started to decrease, and a blend of the various T- and CI-numbers yields an initial wind speed estimate of 50 kt. Irwin will be moving over SSTs of 22 to 23 deg C during the next 12 to 24 hours, which should cause the cyclone to quickly weaken. In fact, Irwin is likely to degenerate to a remnant low in about 24 hours, when the deep convection dissipates. The global models suggest that the low will dissipate in about 72 hours. Irwin is moving north-northwestward at about 11 kt. The cyclone is expected to continue on a north-northwestward heading today, then slow down and turn northwestward on Tuesday as it moves around the remnant circulation of Hilary. The latest track guidance is in good agreement and no significant change from the previous NHC track forecast was needed. FORECAST POSITIONS AND MAX WINDS INIT 31/0900Z 20.7N 126.7W 50 KT 60 MPH 12H 31/1800Z 22.4N 127.5W 40 KT 45 MPH 24H 01/0600Z 24.7N 128.7W 30 KT 35 MPH...POST-TROP/REMNT LOW 36H 01/1800Z 26.5N 130.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 48H 02/0600Z 27.8N 131.2W 20 KT 25 MPH...POST-TROP/REMNT LOW 72H 03/0600Z...DISSIPATED $$ Forecaster Brown

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Tropical Storm Irwin Forecast Discussion Number 35

2017-07-31 04:34:42| National Hurricane Center (East Pacific)

Issued at 800 PM PDT Sun Jul 30 2017 000 WTPZ45 KNHC 310234 TCDEP5 Tropical Storm Irwin Discussion Number 35 NWS National Hurricane Center Miami FL EP102017 800 PM PDT Sun Jul 30 2017 Irwin is one resilient tropical storm. Amazingly, the cloud pattern has improved during the past few hours, with deep convection forming and rotating around the center even though the cyclone is now over sea surface temperatures colder than 25 deg C. A 0002 UTC SSMIS microwave pass revealed a small ring of deep convection that was partially open on the east side, but it also suggested that the vortex is tilted a bit with height. Since Dvorak estimates from TAFB and SAB are a consensus T3.5, the initial intensity remains 55 kt. Irwin will be moving from 24-25C waters to 22-23C waters during the next 24 hours, so weakening should begin soon. In fact, it will be quite difficult for Irwin to continue producing organized deep convection in about 36 hours, and that is when the NHC forecast calls for it to degenerate into a remnant low. Based on global model fields, the remnant low is forecast to dissipate by day 4, if not sooner. No changes to the previous NHC forecast were required based on the latest intensity guidance. The forward motion continues to increase as Irwin trails behind Hilary, and the current estimate is 335/11 kt. A little more acceleration toward the north-northwest is expected during the next 12-24 hours, but Irwin should turn northwest and slow down on days 2 and 3 as it moves around the remnant circulation of Hilary. The updated NHC track forecast was nudged northeast of the previous forecast after 24 hours to be closer in line with the latest HCCA and TVCN guidance, but otherwise no significant changes were needed. FORECAST POSITIONS AND MAX WINDS INIT 31/0300Z 19.8N 126.2W 55 KT 65 MPH 12H 31/1200Z 21.5N 127.1W 50 KT 60 MPH 24H 01/0000Z 23.9N 128.2W 40 KT 45 MPH 36H 01/1200Z 26.0N 129.6W 30 KT 35 MPH...POST-TROP/REMNT LOW 48H 02/0000Z 27.6N 131.1W 25 KT 30 MPH...POST-TROP/REMNT LOW 72H 03/0000Z 28.9N 133.0W 20 KT 25 MPH...POST-TROP/REMNT LOW 96H 04/0000Z...DISSIPATED $$ Forecaster Berg

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Post-Tropical Cyclone HILARY Forecast Discussion Number 39

2017-07-31 04:34:08| National Hurricane Center (East Pacific)

Issued at 800 PM PDT Sun Jul 30 2017 000 WTPZ44 KNHC 310234 TCDEP4 Post-Tropical Cyclone Hilary Discussion Number 39 NWS National Hurricane Center Miami FL EP092017 800 PM PDT Sun Jul 30 2017 Hilary has been without deep convection for over 15 hours now, and there is little chance of any convection redeveloping since the cyclone is now over very cold waters. Thus, Hilary is no longer a tropical cyclone, and this is the last advisory. The initial wind speed is set to 30 kt, assuming some spin-down of the winds since the ASCAT pass nine hours ago. The remnant low should gradually weaken due to the cold waters and dry air mass. The remnants are forecast to turn westward and slow down in a day or so with most models dissipating the circulation in a couple of days. FORECAST POSITIONS AND MAX WINDS INIT 31/0300Z 25.6N 128.5W 30 KT 35 MPH...POST-TROP/REMNT LOW 12H 31/1200Z 26.4N 130.3W 25 KT 30 MPH...POST-TROP/REMNT LOW 24H 01/0000Z 27.3N 132.3W 20 KT 25 MPH...POST-TROP/REMNT LOW 36H 01/1200Z 27.5N 133.6W 15 KT 15 MPH...POST-TROP/REMNT LOW 48H 02/0000Z...DISSIPATED $$ Forecaster Blake

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