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Tropical Storm Sergio Forecast Discussion Number 48

2018-10-11 10:37:12| National Hurricane Center (East Pacific)

Issued at 200 AM PDT Thu Oct 11 2018 000 WTPZ41 KNHC 110837 TCDEP1 Tropical Storm Sergio Discussion Number 48 NWS National Hurricane Center Miami FL EP212018 200 AM PDT Thu Oct 11 2018 Sergio's cloud pattern has changed little during the past several hours, and the Dvorak satellite intensity estimates from TAFB and SAB haven't changed either. A partial ASCAT-B scatterometer pass revealed numerous 45-kt winds and a 50-kt northerly wind in the coldest cloud tops of the curved band wrapping around the north portion of the circulation. Based on these data, the initial intensity is held at 55 kt for this advisory. The intensity forecast philosophy remains unchanged. A combination of increasing southwesterly shear, a drier and more stable surrounding environment, and slightly cooler oceanic temperatures should influence some weakening as it approaches the Baja California peninsula. The cyclone is expected to move inland over Baja California Sur on Friday and into the northwestern Mexico state of Sonora early Saturday. Afterward, rapid weakening, and ultimately dissipation, is expected after Sergio makes its second landfall along the coast of the mainland Mexico. A 72 hour post-tropical/remnant low point is maintained to simply represent the inland motion of Sergio. The intensity forecast is once again based on the NOAA-HCCA, and the GFS/ECMWF global models, which show Sergio making landfall Friday as a tropical storm. The initial motion is estimated to be northeastward, or 050/15 kt, within the deep-layer southwesterly flow produced by a mid-latitude trough stretching southwestward over the eastern Pacific from the southwestern United States. Sergio should continue moving in this general motion through the entire 72 hour period with a continued increase in forward speed. Sergio will be approaching the central Baja California peninsula Friday, although the tropical-storm-force winds are likely to arrive Thursday night. The NHC forecast lies in the middle of the tightly clustered guidance and is close to the multi-model consensus aids. 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 11/0900Z 21.0N 120.2W 55 KT 65 MPH 12H 11/1800Z 23.0N 117.9W 55 KT 65 MPH 24H 12/0600Z 25.7N 114.8W 50 KT 60 MPH 36H 12/1800Z 28.4N 111.4W 35 KT 40 MPH...INLAND 48H 13/0600Z 31.0N 107.2W 30 KT 35 MPH...INLAND 72H 14/0600Z 35.3N 96.0W 20 KT 25 MPH...POST-TROP/INLAND 96H 15/0600Z...DISSIPATED $$ Forecaster Roberts

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Tropical Storm Michael Forecast Discussion Number 18

2018-10-11 05:00:15| National Hurricane Center (Atlantic)

Issued at 1100 PM EDT Wed Oct 10 2018 000 WTNT44 KNHC 110300 TCDAT4 Hurricane Michael Discussion Number 18 NWS National Hurricane Center Miami FL AL142018 1100 PM EDT Wed Oct 10 2018 Data from NOAA WSR-88D Doppler weather radars indicate that Michael has been steadily weakening a a typical rate of decay since it moved inland. However, peak Doppler velocity values are still 80-85 kt between 5000-7000 ft above ground level in large areas in the eastern semicircle. With a recent burst of convection near the low-level center, some of those hurricane-force winds are likely making it down to the surface. Additional weakening is expected due to frictional effects, and the official intensity follows the trend of the Decay-SHIPS model for the next 24 hours while the cyclone remains over land. Sustained winds have dropped below tropical-storm-force across the northern Gulf coast, so the Hurricane Warning has been discontinued for that area. Michael is forecast to emerge over the western Atlantic Thursday night and Friday, where intensification as a robust extratropical cyclone is expected. The low is forecast to be absorbed by another low pressure area over the eastern Atlantic by day 5. The initial motion is now 045/17 kt. Michael will continue to accelerate northeastward as it becomes embedded within deeper mid-latitude southwesterly flow ahead of an eastward moving frontal system. By 36 hours, the expected post-tropical cyclone should turn east-northeastward and accelerate further while it moves over the north Atlantic. The latest track guidance is tightly clustered about the previous forecast track, so no significant changes were made. 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 and the Florida Big Bend. The worst storm surge is expected to continue between Panama City and Keaton Beach, where 3 to 5 feet of inundation is still ongoing. 2. Heavy rainfall from Michael could produce life-threatening flash flooding over portions of Georgia, the Carolinas, and southeastern Virginia. 3. 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 11/0300Z 32.1N 83.8W 65 KT 75 MPH 12H 11/1200Z 34.0N 81.5W 35 KT 40 MPH...INLAND 24H 12/0000Z 36.4N 77.1W 40 KT 45 MPH...INLAND 36H 12/1200Z 39.3N 70.3W 50 KT 60 MPH...POST-TROP/EXTRATROP 48H 13/0000Z 42.4N 60.8W 55 KT 65 MPH...POST-TROP/EXTRATROP 72H 14/0000Z 47.9N 35.9W 55 KT 65 MPH...POST-TROP/EXTRATROP 96H 15/0000Z 49.7N 13.1W 45 KT 50 MPH...POST-TROP/EXTRATROP 120H 16/0000Z...ABSORBED $$ Forecaster Stewart

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Hurricane Leslie Forecast Discussion Number 59

2018-10-11 04:49:10| National Hurricane Center (Atlantic)

Issued at 1100 PM AST Wed Oct 10 2018 000 WTNT43 KNHC 110249 TCDAT3 Hurricane Leslie Discussion Number 59 NWS National Hurricane Center Miami FL AL132018 1100 PM AST Wed Oct 10 2018 The overall cloud pattern of Leslie has become somewhat better organized over the past several hours with increasing convection in the central dense overcast and tighter banding features. A blend of the subjective Dvorak and microwave estimates suggest an initial wind speed of 70 kt for this advisory. Satellite fixes indicate that Leslie has turned toward the east- northeast and is moving faster at about 10 kt. The track forecast really hinges on whether Leslie gets accelerated in southwesterly flow ahead of an eastern Atlantic trough or gets dropped by that trough and turns southwestward around a new subtropical ridge. Sadly, the forecast agreement from the previous advisory has disintegrated, with all of the GFS-based guidance now indicating a track more toward Europe, while the ECMWF/UKMET send Leslie in the exact opposite direction toward the east-central Atlantic. I clearly drew the small straw in having to make Leslie's forecast tonight because this situation is resulting in one of the largest guidance spreads I have seen, about 1000 miles on day 3 and over 2000 miles at day 5. Furthermore, the corrected-consensus guidance is closer to the GFS guidance, which is way to the northeast of the previous forecast. The new forecast will somewhat reflect the latest guidance, showing an adjustment to the east, but is still hundreds of miles to the southwest of the latest model consensus. Obviously this is a zero-confidence forecast tonight. Marginally warm waters and moderate shear could support additional strengthening of Leslie during the next day or two, although the guidance is generally lower than yesterday. By Saturday, colder ocean waters, higher shear and a drier mid-level atmosphere should cause Leslie to weaken. No significant changes were made to the previous intensity forecast. By Monday, Leslie, whether it follows the forecast track or not, will likely be struggling to produce convection or have already transitioned into an extratropical low. Thus the 5 day point shows post-tropical status, perhaps optimistically, but this seems like the most likely option for now. FORECAST POSITIONS AND MAX WINDS INIT 11/0300Z 27.9N 41.1W 70 KT 80 MPH 12H 11/1200Z 28.4N 39.4W 75 KT 85 MPH 24H 12/0000Z 29.9N 35.7W 75 KT 85 MPH 36H 12/1200Z 31.3N 30.5W 75 KT 85 MPH 48H 13/0000Z 32.3N 25.0W 70 KT 80 MPH 72H 14/0000Z 32.0N 20.0W 50 KT 60 MPH 96H 15/0000Z 29.5N 20.5W 35 KT 40 MPH 120H 16/0000Z 27.5N 25.0W 30 KT 35 MPH...POST-TROPICAL $$ Forecaster Blake

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Tropical Storm Sergio Forecast Discussion Number 47

2018-10-11 04:41:07| National Hurricane Center (East Pacific)

Issued at 800 PM PDT Wed Oct 10 2018 000 WTPZ41 KNHC 110241 TCDEP1 Tropical Storm Sergio Discussion Number 47 NWS National Hurricane Center Miami FL EP212018 800 PM PDT Wed Oct 10 2018 This evening's satellite presentation depicts a rather ragged and elongated banding eye-like feature with fragmented curved bands encircling the periphery of cyclone. The subjective intensity estimates from TAFB and SAB, however, still yield an initial intensity of 55 kt. The UW-CIMSS shear analysis shows that the westerly shear has increased to 15-20 kt, and the Decay-SHIPS as well as the global models indicate that the shear magnitude will increase further to near 50 kt prior to landfall. This inhibiting upper wind pattern along with slightly cooler oceanic temperatures should influence some further weakening as it approaches the Baja California peninsula. Sergio is forecast to move inland over Baja California Sur on Friday and into the northwestern Mexico state of Sonora early Saturday as a depression. At the end of the forecast period, Sergio is expected to further degenerate into a post-tropical weak low over the southwestern United States. The intensity forecast is based on the NOAA-HCCA, and the GFS/ECMWF global models which show Sergio making landfall Friday as a tropical storm. The initial motion is estimated to be northeastward, or 050/14 kt, and this general motion is forecast through the entire 72 hour period with a continued increase in forward speed. Sergio will be approaching the central Baja California peninsula Friday, although the tropical-storm-force winds are likely to arrive Thursday night. There is continued high confidence in the forecast track as the available large-scale and hurricane models are clustered tightly together through 72 hours. The NHC forecast lies in the middle of the guidance cluster and is close to the TVCN/HCCA consensus models. 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 11/0300Z 20.0N 121.5W 55 KT 65 MPH 12H 11/1200Z 21.8N 119.3W 55 KT 65 MPH 24H 12/0000Z 24.4N 116.4W 50 KT 60 MPH 36H 12/1200Z 27.2N 113.1W 45 KT 50 MPH...INLAND 48H 13/0000Z 30.0N 109.1W 30 KT 35 MPH...INLAND 72H 14/0000Z 34.4N 98.8W 20 KT 25 MPH...POST-TROP/INLAND 96H 15/0000Z...DISSIPATED $$ Forecaster Roberts

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Tropical Storm Nadine Forecast Discussion Number 8

2018-10-11 04:40:42| National Hurricane Center (Atlantic)

Issued at 1100 PM AST Wed Oct 10 2018 000 WTNT45 KNHC 110240 TCDAT5 Tropical Storm Nadine Discussion Number 8 NWS National Hurricane Center Miami FL AL152018 1100 PM AST Wed Oct 10 2018 Another burst of deep convection has formed near the center of Nadine, which is typical in sheared tropical cyclones. A recent ASCAT pass indicated several believable 50-55 kt winds, so the initial intensity is held at 55 kt for this advisory. The shear is only forecast to increase over the next couple of days, which should lead to weakening, especially by Friday. All of the dynamical models indicate that Nadine will degenerate into a trough of low pressure over the weekend, and no significant changes were made to the previous forecast. Nadine continues to move northwestward due to a ridge near the Cabo Verde Islands. This general course is forecast for the next day or so until Nadine become a more shallow system, which should cause the cyclone to turn toward the west-northwest. The previous interpolated forecast came in basically on top of the new consensus and corrected-consensus guidance, so the new track forecast is very close to the previous NHC prediction. FORECAST POSITIONS AND MAX WINDS INIT 11/0300Z 13.6N 32.7W 55 KT 65 MPH 12H 11/1200Z 14.3N 33.4W 50 KT 60 MPH 24H 12/0000Z 15.3N 34.5W 40 KT 45 MPH 36H 12/1200Z 16.0N 36.0W 35 KT 40 MPH 48H 13/0000Z 16.5N 37.5W 30 KT 35 MPH 72H 14/0000Z...DISSIPATED $$ Forecaster Blake

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