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Hurricane Michael Forecast Discussion Number 17

2018-10-10 22:55:08| National Hurricane Center (Atlantic)

Issued at 400 PM CDT Wed Oct 10 2018 000 WTNT44 KNHC 102054 TCDAT4 Hurricane Michael Discussion Number 17 NWS National Hurricane Center Miami FL AL142018 400 PM CDT Wed Oct 10 2018 Data from an Air Force Force Reserve Hurricane Hunter aircraft and NWS WSR-88D radar data showed that Michael continued to strengthen until it made landfall around 1730 UTC (12:30 PM CDT) along the coast of the Florida Panhandle between Mexico Beach and Tyndall Air Force Base. The aircraft found peak 700-mb flight-level winds of 152 kt during its final pass through southeast eyewall just before Michael made landfall. There were SFMR measurements of 132-138 kt, but the validity of those observations are questionable since they occurred in shallow water and were flagged. The landfall intensity was estimated at 135 kt (155 mph), which makes Michael the strongest hurricane to make landfall in the continental U.S. since Andrew (1992). The minimum pressure at landfall was estimated at 919 mb, which is the third lowest landfall pressure in the United States. A University of Florida/Weatherflow observing site measured a minimum pressure of 920.2 mb. Now that the entire eyewall has moved over land, the Doppler radar velocities have decreased and the initial intensity has been lowered to 110 kt. Although steady weakening is expected as Michael moves over the southeast U.S. through Thursday morning, hurricane-force winds will continue to penetrate inland over the Florida Panhandle, southeastern Alabama, and southwestern Georgia through this evening. The circulation is forecast to emerge over the western Atlantic Thursday night and Friday, where intensification as an extratropical cyclone is expected. The extratropical low is expected to remain quite strong while to moves over the north Atlantic through the weekend. The low is expected to be absorbed by another low pressure area over the eastern Atlantic by day 5. Michael is moving northeastward of 030/14 kt, and the hurricane should continue to accelerate northeastward as it becomes embedded within the mid-latitude westerlies. The post-tropical cyclone should turn east-northeastward and further accelerate as it moves over the north Atlantic. The track guidance remains tightly clustered, but has trended faster this cycle, and the NHC forecast has been adjusted accordingly. Gale- to storm-force winds are expected over portions of the Mid-Atlantic coast as Michael exits the U.S. east coast and becomes post-tropical. Non-tropical high wind watches, warnings, and advisories have been issued by local NWS offices for wind hazards in these areas north of Duck, North Carolina. Key Messages: 1. Life-threatening storm surge continues along portions of the Florida Panhandle, Big Bend, and Nature Coast. The worst storm surge is expected to continue between Tyndall Air Force Base and Aucilla River, where 5 to 10 feet of inundation is still ongoing. 2. Michael will continue to produce life-threatening hurricane-force winds well inland across portions of the Florida Panhandle, southeast Alabama, and southwestern Georgia this evening as the core of the hurricane continues to move inland. 3. Heavy rainfall from Michael could produce life-threatening flash flooding from the Florida Panhandle and Big Bend region into portions southeast Alabama, Georgia, the Carolinas, and southeast Virginia. 4. Tropical storm conditions will affect portions of the southeast U.S. coast from northeast Florida through North Carolina, and tropical storm warnings are in effect for these areas. FORECAST POSITIONS AND MAX WINDS INIT 10/2100Z 30.9N 85.1W 110 KT 125 MPH...INLAND 12H 11/0600Z 32.6N 83.2W 60 KT 70 MPH...INLAND 24H 11/1800Z 35.1N 79.6W 40 KT 45 MPH...INLAND 36H 12/0600Z 37.6N 74.4W 50 KT 60 MPH...OVER WATER 48H 12/1800Z 40.7N 66.2W 60 KT 70 MPH...POST-TROP/EXTRATROP 72H 13/1800Z 46.7N 43.5W 60 KT 70 MPH...POST-TROP/EXTRATROP 96H 14/1800Z 49.2N 19.0W 50 KT 60 MPH...POST-TROP/EXTRATROP 120H 15/1800Z...ABSORBED $$ Forecaster Brown

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Hurricane Leslie Forecast Discussion Number 58

2018-10-10 22:42:38| National Hurricane Center (Atlantic)

Issued at 500 PM AST Wed Oct 10 2018 000 WTNT43 KNHC 102042 TCDAT3 Hurricane Leslie Discussion Number 58 NWS National Hurricane Center Miami FL AL132018 500 PM AST Wed Oct 10 2018 Leslie has held nearly steady since this morning. Recent microwave data indicate that the cyclone still has a fairly well-defined inner-core that has persisted, though the deepest convection has fluctuated since last night. Satellite intensity estimates have fluctuated with the convection, but still support an initial value of 65 kt for this advisory. The last few IR and visible images before sunset suggest that Leslie may be developing a banding eye, and it's possible the intensity estimate is a little conservative. The track uncertainty is hopefully beginning to decrease a little. The most recent GFS and ECMWF ensembles are converging on a solution where Leslie accelerates east-northeastward on the south side of a mid-latitude trough, before separating from the trough over the weekend. The cyclone could then turn southward, and eventually back westward as a much weaker tropical cyclone or remnant low. This is generally consistent with previous NHC forecasts, so no large changes were required to the NHC forecast which is heavily based on the HFIP Corrected Consensus. Leslie is still expected to strengthen soon, and there has been no significant change to the intensity forecast. By 72 h, if not sooner, the hurricane will begin to encounter colder ocean waters and high shear, which should cause it to weaken. If Leslie follows the forecast track, it is possible that the system could become a post-tropical remnant low by early next week, and this is forecast by some of the global models. However, this is not explicitly shown in the NHC forecast and Leslie's strength and status early next week will likely heavily depend on its track at that time. The official forecast is close to the intensity consensus at all forecast hours, and the intensity model spread is not very large. FORECAST POSITIONS AND MAX WINDS INIT 10/2100Z 27.8N 41.9W 65 KT 75 MPH 12H 11/0600Z 28.0N 40.8W 70 KT 80 MPH 24H 11/1800Z 29.0N 38.0W 75 KT 85 MPH 36H 12/0600Z 30.4N 33.6W 75 KT 85 MPH 48H 12/1800Z 31.5N 28.4W 70 KT 80 MPH 72H 13/1800Z 32.0N 21.0W 50 KT 60 MPH 96H 14/1800Z 30.0N 21.0W 35 KT 40 MPH 120H 15/1800Z 27.0N 26.0W 30 KT 35 MPH $$ Forecaster Zelinsky

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Tropical Storm Sergio Forecast Discussion Number 46

2018-10-10 22:41:05| National Hurricane Center (East Pacific)

Issued at 200 PM PDT Wed Oct 10 2018 000 WTPZ41 KNHC 102040 TCDEP1 Tropical Storm Sergio Discussion Number 46 NWS National Hurricane Center Miami FL EP212018 200 PM PDT Wed Oct 10 2018 The organization of the cloud pattern has remained unchanged during the day, except that the deep convection has continued to weaken. Nevertheless, Dvorak numbers from TAFB and SAB still support an initial intensity of 55 kt. Some fluctuations in intensity are likely during the next 12 hours while the cyclone is over relatively warm waters and is embedded in a low shear environment. Since both of these factors will become unfavorable in about 12 to 24 hours, the NHC forecast calls for weakening. Sergio, however, is expected to still be a tropical storm by the time it approaches the Baja California peninsula. After that time, Sergio will move over mainland Mexico and weaken much faster. Sergio is moving toward the northeast or 050 degrees at 12 kt. The cyclone is embedded within the southwesterly winds associated with a large mid-latitude trough, and this flow pattern will continue to steer Sergio toward the northeast with an increase in forward speed. The forecast track brings the center of a weakened Sergio over the central portion of the Baja California peninsula in about a day and half, but winds will reach the coast a little bit earlier. Track models continue to be in very good agreement, and consequently the guidance envelope is quite tight. The NHC forecast remains unchanged and is in the middle of the guidance envelope. The primary threat associated with Sergio and its remnants continues to be life-threatening flash flooding and mudslides within mountainous terrain in the Mexico states of Baja California Sur, Sonora, the U.S. Southern Plains, and the Ozarks through the weekend. For more information about this potential hazard, see products from the Weather Prediction Center and your local weather forecast office. FORECAST POSITIONS AND MAX WINDS INIT 10/2100Z 19.2N 122.4W 55 KT 65 MPH 12H 11/0600Z 20.7N 120.6W 50 KT 60 MPH 24H 11/1800Z 23.3N 117.7W 50 KT 60 MPH 36H 12/0600Z 26.0N 114.5W 45 KT 50 MPH 48H 12/1800Z 29.0N 111.0W 40 KT 45 MPH...INLAND 72H 13/1800Z 33.0N 101.0W 25 KT 30 MPH...POST-TROP/INLAND 96H 14/1800Z...DISSIPATED $$ Forecaster Avila

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Tropical Storm Nadine Forecast Discussion Number 7

2018-10-10 22:39:07| National Hurricane Center (Atlantic)

Issued at 500 PM AST Wed Oct 10 2018 000 WTNT45 KNHC 102038 TCDAT5 Tropical Storm Nadine Discussion Number 7 NWS National Hurricane Center Miami FL AL152018 500 PM AST Wed Oct 10 2018 The exposed low-level center of Nadine is now peeking out from beneath its upper cloud canopy. The initial intensity has been held at 55 kt out of respect for earlier ASCAT data, but it is possible that some weakening has occurred since this morning. Strong westerly wind shear will likely prevent Nadine from becoming any better organized going forward, so the official intensity forecast now calls for steady weakening for the next 2 days. All of the dynamical models indicate that Nadine will degenerate into a trough of low pressure within the next 72 h, and the NHC forecast now shows dissipation occuring by that point. Nadine is moving steadily northwestward with an initial motion of 315/7 kt. As long as Nadine remains a tropical cyclone, it should stay on a similar heading, and the models are in generally good agreement on its track. The NHC track forecast has been adjusted a little to the southwest, and is generally close to the TVCX and HCCA consensus aids at all times. From 48 h onward, the cyclone or its remnant trough will likely be entirely separated from its convection and turn westward in low-level easterly flow. FORECAST POSITIONS AND MAX WINDS INIT 10/2100Z 13.1N 32.2W 55 KT 65 MPH 12H 11/0600Z 13.8N 32.9W 50 KT 60 MPH 24H 11/1800Z 14.8N 34.0W 45 KT 50 MPH 36H 12/0600Z 15.7N 35.1W 40 KT 45 MPH 48H 12/1800Z 16.2N 36.8W 35 KT 40 MPH 72H 13/1800Z...DISSIPATED $$ Forecaster Zelinsky

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Hurricane Michael Forecast Discussion Number 16

2018-10-10 16:51:05| National Hurricane Center (Atlantic)

Issued at 1000 AM CDT Wed Oct 10 2018 000 WTNT44 KNHC 101450 TCDAT4 Hurricane Michael Discussion Number 16 NWS National Hurricane Center Miami FL AL142018 1000 AM CDT Wed Oct 10 2018 Michael is an extremely impressive hurricane in visible and infrared satellite imagery this morning. The eye has continued to warm and become even more distinct, while remaining embedded within an area of very cold cloud tops. Data from NOAA and U.S. Air Force Hurricane Hunter aircraft indicate that the pressure has continued to fall this morning and is now around 928 mb. Flight-level, SFMR, and NWS WSR-88D Doppler wind data all support an intensity of 125 kt. The hurricane only has a few hours left over water during which additional intensification is possible. Recent radar imagery suggest that an outer eyewall may be trying to form, and this could slow or halt the intensification process. Although steady weakening is predicted once the hurricane moves inland, the core of Michael will bring hurricane-force winds well inland over the Florida Panhandle, southeastern Alabama, and southwest Georgia. As the circulation emerges over the western Atlantic, intensification due to baroclinic process is expected, and Michael should complete its transition to an extratropical low by 48 hours when it is off the U.S. Mid-Atlantic coast. The system is predicted to remain a powerful extratropical cyclone over the north Atlantic through at least day 4. Aircraft and radar fixes show that Michael has made its much anticipated north-northeastward turn, and the hurricane is expected to make landfall along the coast of the Florida Panhandle early this afternoon. Michael should turn northeastward and begin to accelerate as it becomes embedded within the mid-latitude flow while moving across the southeast U.S. through Thursday night. The cyclone is forecast to emerge over the western Atlantic on Friday, and move rapidly eastward-northeastward across the north Atlantic this weekend. The track guidance remains in excellent agreement, and the updated NHC track forecast is very close to the previous advisory. Tropical storm warnings have been extended northward along the U.S. East Coast to Duck, North Carolina. Non-tropical watches, warnings, and advisories will be issued by local NWS offices for wind hazards north of Duck, North Carolina, as Michael is expected to be post-tropical when it affects those areas. Key Messages: 1. Life-threatening storm surge is occurring along portions of the Florida Panhandle, Big Bend, and Nature Coast. The worst storm surge is expected later today and tonight between Tyndall Air Force Base and Keaton Beach, where 9 to 14 feet of inundation is possible. 2. Michael will produce potentially catastrophic wind damage where the core of the hurricane moves onshore later today in the Florida Panhandle, with the highest risk between Apalachicola and Panama City. 3. Life-threatening hurricane-force winds will occur well inland across portions of the Florida Panhandle, southeast Alabama, and southwestern Georgia as the core of the hurricane moves inland later today and this evening. 4. Heavy rainfall from Michael could produce life-threatening flash flooding from the Florida Panhandle and Big Bend region into portions of Georgia, the Carolinas, and southeast Virginia. 5. Tropical storm conditions will affect portions of the southeast U.S. coast from northeast Florida through North Carolina, and tropical storm warnings are in effect for these areas. FORECAST POSITIONS AND MAX WINDS INIT 10/1500Z 29.4N 86.0W 125 KT 145 MPH 12H 11/0000Z 31.3N 84.7W 85 KT 100 MPH...INLAND 24H 11/1200Z 33.6N 82.1W 40 KT 45 MPH...INLAND 36H 12/0000Z 35.8N 78.0W 45 KT 50 MPH...INLAND 48H 12/1200Z 38.7N 71.6W 55 KT 65 MPH...POST-TROP/EXTRATROP 72H 13/1200Z 45.5N 52.5W 60 KT 70 MPH...POST-TROP/EXTRATROP 96H 14/1200Z 49.0N 29.0W 60 KT 70 MPH...POST-TROP/EXTRATROP 120H 15/1200Z 50.0N 13.0W 35 KT 40 MPH...POST-TROP/EXTRATROP $$ Forecaster Brown

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