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Post-Tropical Cyclone Leslie Forecast Discussion Number 70

2018-10-13 22:37:05| National Hurricane Center (Atlantic)

Issued at 500 PM AST Sat Oct 13 2018 000 WTNT43 KNHC 132036 TCDAT3 Post-Tropical Cyclone Leslie Discussion Number 70 NWS National Hurricane Center Miami FL AL132018 500 PM AST Sat Oct 13 2018 After a total of 70 advisories, long-lived Leslie has become post-tropical just west of the coast of Portugal, finally succumbing to the combination of cool waters, strong vertical wind shear, and interaction with an approaching cold front. The air mass ahead of the cyclone has moistened up in the low levels with Faro, Portugal, reporting a dewpoint of 70F/21C, but the dewpoints across central and northern Portugal ahead of Leslie are only in the low-60F range, which is not indicative of a tropical air mass. Thus, the cyclone is now a powerful post-tropical low pressure system that even has a partial eye noted in the most recent 2000Z Portuguese composite radar imagery. After landfall, rapid weakening is anticipated, and Leslie is forecast to degenerate into a broad low pressure area over or just north of Spain by late Sunday. Leslie is moving quickly toward the northeast or 050/30 kt. Post-tropical Cyclone Leslie should continue in a fast northeastward direction for the next 12-18 hours, making landfall near or just south of Porto, Portugal by 14/0000Z. This forecast motion is consistent with the previous advisory and the latest track model guidance. The meteorological services of Portugal and Spain are handling hazards information for their respective countries via local weather products. This is the last National Hurricane Center (NHC) advisory on this system. Key Messages: 1. Leslie is expected to bring near hurricane-force winds to portions of Portugal later tonight as a powerful post-tropical cyclone. Gale-force winds are also likely to affect portions of northwestern and northern Spain tonight and Sunday. 2. Leslie is expected to produce rainfall amounts of 25 to 75 mm (1 to 3 inches) with isolated amounts as high as 125 mm (5 inches) across portions of Portugal and Spain, which could cause flash flooding. 3. For more information on Leslie, interests in Portugal should refer to products from the Portuguese Institute for Sea and Atmosphere at www.ipma.pt. Interests in Spain should refer to products from the State Meteorological Agency at www.aemet.es. FORECAST POSITIONS AND MAX WINDS INIT 13/2100Z 40.5N 9.5W 60 KT 70 MPH...POST-TROPICAL 12H 14/0600Z 43.0N 4.9W 35 KT 40 MPH...POST-TROPICAL INLAND 24H 14/1800Z...DISSIPATED $$ Forecaster Stewart

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Hurricane Leslie Forecast Discussion Number 69

2018-10-13 16:33:59| National Hurricane Center (Atlantic)

Issued at 1100 AM AST Sat Oct 13 2018 000 WTNT43 KNHC 131433 TCDAT3 Hurricane Leslie Discussion Number 69 NWS National Hurricane Center Miami FL AL132018 1100 AM AST Sat Oct 13 2018 Despite Leslie moving over 20C ocean and being embedded within strong shear, satellite data indicate that Leslie has maintained its deep warm core and is running ahead of a cold front. Although convection has weakened considerably, Dvorak estimates indicate that the winds are still 65 kt. All indications are that Leslie will acquire extratropical characteristics in the next several hours, and by the time it reaches the Iberian peninsula later today, the system will be a powerful post-tropical cyclone. After landfall, rapid weakening is anticipated, and Leslie is forecast to degenerate into a broad low pressure area over Spain in a day or so. Leslie is racing toward the northeast or 055 degrees at about 29 kt while embedded within the fast mid-latitude westerlies. A continued northeastward motion with gradual decrease in forward speed is anticipated in the next 12 to 24 hours. This is consistent with most of the track guidance, which unanimously brings the core of the post-tropical cyclone over the Iberian peninsula tonight. The meteorological services of Portugal and Spain are handling hazards information for their respective countries via local weather products. Key Messages: 1. Leslie is expected to bring near hurricane-force winds to portions of Portugal late today as a powerful post-tropical cyclone. Gale-force winds are also likely to affect portions of western Spain tonight and Sunday. 2. Leslie is expected to produce rainfall amounts of 25 to 75 mm (1 to 3 inches) with isolated amounts as high as 125 mm (5 inches) across portions of Portugal and Spain, which could cause flash flooding. 3. For more information on Leslie, interests in Portugal should refer to products from the Portuguese Institute for Sea and Atmosphere at www.ipma.pt. Interests in Spain should refer to products from the State Meteorological Agency at www.aemet.es. FORECAST POSITIONS AND MAX WINDS INIT 13/1500Z 38.0N 12.6W 65 KT 75 MPH 12H 14/0000Z 40.0N 8.0W 50 KT 60 MPH...POST-TROP/INLAND 24H 14/1200Z 41.5N 4.0W 30 KT 35 MPH...POST-TROP/INLAND 36H 15/0000Z...DISSIPATED $$ Forecaster Avila

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Hurricane Leslie Forecast Discussion Number 68

2018-10-13 10:39:01| National Hurricane Center (Atlantic)

Issued at 500 AM AST Sat Oct 13 2018 000 WTNT43 KNHC 130838 TCDAT3 Hurricane Leslie Discussion Number 68 NWS National Hurricane Center Miami FL AL132018 500 AM AST Sat Oct 13 2018 Satellite imagery suggests that Leslie has started extratropical transition. The mid-level eye seen earlier in both conventional and microwave satellite imagery has become less distinct, and it is continuing to separate from the low-level center. In addition, colder air is entraining into the western and southern sides of the circulation. However, a sizable cluster of convection persists to the northeast of the center, indicating that the cyclone is still tropical at this time. The large-scale models forecast that Leslie will likely complete transition in 12 to perhaps 18 h, and that the associated winds should remain at or near hurricane force until the center moves over the Iberian Peninsula. After landfall, rapid weakening is forecast, and the cyclone should dissipate as it becomes part of a broad low pressure area over Spain between 36-48 h. The initial motion is 070/33 as Leslie is now well embedded in the mid-latitude westerlies. A continued east-northeastward motion with a gradual decrease in forward speed is expected for the next 36 h. This should bring the center of Leslie onshore on the Iberian Peninsula in about 18 h and into western Spain by about 24 h. There is little change in either the track guidance or the track forecast from the last advisory. The meteorological services of Portugal and Spain will handle hazard information for their respective countries via local weather products. Key Messages: 1. Leslie is expected to bring near hurricane-force winds to portions of Portugal late today as a powerful post-tropical cyclone. Gale-force winds are also likely to affect portions of western Spain tonight and Sunday. 2. Leslie is expected to produce rainfall amounts of 25 to 75 mm (1 to 3 inches) with isolated amounts as high as 125 mm (5 inches) across portions of Portugal and Spain, which could cause flash flooding. 3. For more information on Leslie, interests in Portugal should refer to products from the Portuguese Institute for Sea and Atmosphere at www.ipma.pt. Interests in Spain should refer to products from the State Meteorological Agency at www.aemet.es. FORECAST POSITIONS AND MAX WINDS INIT 13/0900Z 36.2N 16.7W 65 KT 75 MPH 12H 13/1800Z 37.7N 11.8W 65 KT 75 MPH...POST-TROP/EXTRATROP 24H 14/0600Z 39.6N 6.8W 35 KT 40 MPH...POST-TROP/INLAND 36H 14/1800Z 41.3N 2.7W 25 KT 30 MPH...POST-TROP/INLAND 48H 15/0600Z...DISSIPATED $$ Forecaster Beven

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Hurricane Leslie Forecast Discussion Number 67

2018-10-13 04:37:55| National Hurricane Center (Atlantic)

Issued at 1100 PM AST Fri Oct 12 2018 000 WTNT43 KNHC 130237 TCDAT3 Hurricane Leslie Discussion Number 67 NWS National Hurricane Center Miami FL AL132018 1100 PM AST Fri Oct 12 2018 Although Leslie continues to produce a compact area of deep convection, microwave data since the previous advisory indicate that the mid-level center is becoming more separated from the low-level center due to increasing shear. Dvorak final-T numbers have begun to decrease a bit, and the initial intensity is therefore set at 70 kt. A cold front is beginning to wrap around the western side of Leslie's circulation, and the global models indicate that the cyclone should lose its warm core and become fully embedded within the frontal zone by 24 hours, if not sooner. Despite sea surface temperatures of 17-23 degrees Celsius ahead of Leslie, baroclinic forcing is likely to maintain the system's intensity as it becomes extratropical. As a result, Leslie is forecast to reach the Iberian Peninsula as a hurricane-force extratropical low, with the NHC intensity forecast most closely following the GFS guidance. Rapid weakening is forecast once the low moves inland, and the system should dissipate over the higher terrain of Spain in about 48 hours. The forward motion is east-northeastward, or 075/31 kt. Located within the base of a progressive trough, Leslie should maintain this trajectory, slowing down only a little bit before it reaches Portugal and Spain in 24-36 hours. Except for the UKMET model, which shows Leslie turning more northeastward toward the northwestern Iberian Peninsula, the rest of the track guidance is tightly clustered and brings the center inland across central Portugal and western Spain. Because most of the models are in good agreement and are close to the previous official forecast, no significant changes were made to the NHC forecast on this cycle. Based on coordination from earlier today, the meteorological services of Portugal and Spain will handle hazard information for their respective countries via local weather products. Key Messages: 1. Leslie is expected to bring near hurricane-force winds to portions of Portugal late Saturday as a powerful post-tropical cyclone. Gale-force winds are also likely to affect portions of western Spain Saturday night and Sunday. 2. Leslie is expected to produce rainfall amounts of 25 to 75 mm (1 to 3 inches) with isolated amounts as high as 100 mm (4 inches) across portions of Portugal and Spain, which could cause flash flooding. 3. For more information on Leslie, interests in Portugal should refer to products from the Portuguese Institute for Sea and Atmosphere at www.ipma.pt. Interests in Spain should refer to products from the State Meteorological Agency at www.aemet.es. FORECAST POSITIONS AND MAX WINDS INIT 13/0300Z 34.7N 20.7W 70 KT 80 MPH 12H 13/1200Z 36.5N 15.4W 65 KT 75 MPH 24H 14/0000Z 38.9N 9.4W 65 KT 75 MPH...POST-TROP/EXTRATROP 36H 14/1200Z 41.0N 5.1W 40 KT 45 MPH...POST-TROP/EXTRATROP 48H 15/0000Z 42.3N 1.1W 25 KT 30 MPH...POST-TROP/EXTRATROP 72H 16/0000Z...DISSIPATED $$ Forecaster Berg

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Remnants of Nadine Forecast Discussion Number 16

2018-10-13 04:32:54| National Hurricane Center (Atlantic)

Issued at 1100 PM AST Fri Oct 12 2018 000 WTNT45 KNHC 130232 TCDAT5 Remnants Of Nadine Discussion Number 16 NWS National Hurricane Center Miami FL AL152018 1100 PM AST Fri Oct 12 2018 ASCAT data indicate that Nadine no longer has a closed circulation nor a well-defined center. This is also confirmed by low cloud motions from GOES-16. Thus Nadine has degenerated into an open wave, and this is the last advisory on this system. The initial wind speed is reduced to 30 kt to match the value from the scatterometer. Strong shear should cause the remnants to slowly weaken as the system moves quickly westward beneath the Atlantic subtropical ridge. Future information on the remnants of Nadine can be found in High Seas Forecasts issued by the National Weather Service, under AWIPS header NFDHSFAT1, WMO header FZNT01 KWBC, and available on the Web at https://ocean.weather.gov/shtml/NFDHSFAT1.shtml. FORECAST POSITIONS AND MAX WINDS INIT 13/0300Z 16.0N 39.5W 30 KT 35 MPH...REMNANTS OF NADINE 12H 13/1200Z...DISSIPATED $$ Forecaster Blake

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