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Tropical Depression Fourteen-E Forecast Discussion Number 1
2020-08-26 16:45:23| National Hurricane Center (East Pacific)
Issued at 800 AM PDT Wed Aug 26 2020 000 WTPZ44 KNHC 261445 TCDEP4 Tropical Depression Fourteen-E Discussion Number 1 NWS National Hurricane Center Miami FL EP142020 800 AM PDT Wed Aug 26 2020 Earlier scatterometer data and GOES-16 Proxy-VIS satellite imagery indicate that the area of low pressure located several hundred miles southwest of the southern tip of the Baja California peninsula has acquired sufficient convective organization and a well-defined surface circulation, and is now classified as a tropical cyclone. Dvorak satellite intensity estimates and the aforementioned scatterometer data support an initial wind speed of 30 kt for this advisory. Moderate to strong east-northeasterly shear, the same inhibiting upper wind pattern that is affecting depression Thirteen-E, is forecast to hamper significant development through the entire forecast period. Therefore, only modest strengthening in the next 24 hours is expected, which agrees with the statistical- dynamical guidance and the large-scale models. The depression is moving rather slowly toward the northeast, or 040/2 kt. The low to mid-level steering synoptic pattern consists of a cyclonic gyre stretching southwestward from Hurricane Laura over central Mexico and into the eastern Pacific. This feature should cause the depression to continue in a northeastward general direction at a relatively slow pace through Friday. Afterward, a gradual turn toward the north-northwest and west-northwest is expected as high pressure currently over the southwestern U.S. builds westward over the Baja California peninsula and adjacent eastern Pacific. The NHC official forecast is a reflection of a blend of the HCCA and TVCE consensus aids. FORECAST POSITIONS AND MAX WINDS INIT 26/1500Z 15.4N 117.2W 30 KT 35 MPH 12H 27/0000Z 15.8N 116.9W 30 KT 35 MPH 24H 27/1200Z 16.4N 116.4W 35 KT 40 MPH 36H 28/0000Z 17.0N 115.7W 35 KT 40 MPH 48H 28/1200Z 17.8N 114.9W 35 KT 40 MPH 60H 29/0000Z 18.6N 114.1W 30 KT 35 MPH 72H 29/1200Z 19.6N 113.5W 30 KT 35 MPH 96H 30/1200Z 21.4N 114.3W 30 KT 35 MPH...POST-TROP/REMNT LOW 120H 31/1200Z 22.4N 116.1W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ Forecaster Roberts
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Hurricane Laura Forecast Discussion Number 26
2020-08-26 10:58:21| National Hurricane Center (Atlantic)
Issued at 400 AM CDT Wed Aug 26 2020 000 WTNT43 KNHC 260858 TCDAT3 Hurricane Laura Discussion Number 26 NWS National Hurricane Center Miami FL AL132020 400 AM CDT Wed Aug 26 2020 Satellite images indicate that Laura has become a formidable hurricane since yesterday evening. Deep convection has intensified and become more symmetric, with an eye now trying to clear out. An earlier Air Force Hurricane Hunter mission found flight-level winds of 104 kt, along with peak SFMR values of 86 kt, which supported the 90-kt intensity on the intermediate advisory. Since that time, however, the cloud pattern has only continued to improve, so the initial wind speed is set to 95 kt for this advisory. Notably, the aircraft also recorded that the extent of the hurricane-force winds have increased substantially northeast of the center. A pair of Hurricane Hunter planes should be in the area within a couple of hours. The hurricane has intensified a remarkable 40 kt during the past 24 hours, and there are no signs it will stop soon, with shear remaining low-to-moderate over the deep warm waters of the central Gulf of Mexico. Guidance is noticeably higher than before, so the new peak intensity will be raised to 115 kt, and some models are even a little higher. Increasing shear is expected to slightly weaken the hurricane close to landfall, so the new forecast keeps the previous 105-kt intensity near the coast. Laura will weaken rapidly after landfall, but it will likely bring hurricane-force winds well inland over western Louisiana and eastern Texas. In the extended range, there is some chance that Laura re-intensifies as a tropical cyclone off the Mid-Atlantic coast, instead of becoming part of a frontal system, but for now the forecast will stay extratropical at 96 hours and beyond. Recent satellite shows that Laura has turned northwestward, now estimated at 13 kt. There are no substantial changes to the track forecast to report. The hurricane should gradually turn toward the northwest and north over the next day or two as it moves around the western periphery of a mid-level high. The models are in very good agreement on the center of Laura moving into extreme southwestern Louisiana or southeastern Texas in about 24 hours, so no changes were made to the previous NHC forecast. Later in the forecast period the weakened cyclone should turn toward the east-northeast and move with increasing forward speed while embedded within the mid-latitude westerlies. The official track forecast is shifted southward at longer range, not too far from the latest consensus track model predictions. It should be mentioned Laura is now a large hurricane, and wind, storm surge, and rainfall hazards will extend far from the center. Do not use the cone graphic for any representation of these hazards, it is just for the center uncertainty. Key Messages: 1. Life-threatening storm surge with large and dangerous waves is expected to produce potentially catastrophic damage from San Luis Pass, Texas, to the Mouth of the Mississippi River, including areas inside the Port Arthur Hurricane Flood Protection system. This surge could penetrate up to 30 miles inland from the immediate coastline in southwestern Louisiana and southeastern Texas. Actions to protect life and property should be rushed to completion as water levels will begin to rise later today. 2. Hurricane-force winds are expected tonight in the warning area from San Luis Pass, Texas, to west of Morgan City, Louisiana, and the strongest winds associated with Laura's eyewall will occur somewhere within this area. Hurricane-force winds and widespread damaging wind gusts are also expected to spread well inland into portions of eastern Texas and western Louisiana early Thursday. 3. Widespread flash flooding along small streams, urban areas, and roadways is expected to begin this afternoon into Thursday from far eastern Texas, across Louisiana and Arkansas. This will also lead to minor to isolated moderate freshwater river flooding. The heavy rainfall threat and localized flash and urban flooding potential will spread northeastward into the middle-Mississippi, lower Ohio and Tennessee Valleys Friday night and Saturday. FORECAST POSITIONS AND MAX WINDS INIT 26/0900Z 26.1N 90.7W 95 KT 110 MPH 12H 26/1800Z 27.4N 92.4W 115 KT 130 MPH 24H 27/0600Z 29.7N 93.5W 105 KT 120 MPH...NEAR COAST 36H 27/1800Z 32.4N 93.7W 50 KT 60 MPH...INLAND 48H 28/0600Z 34.8N 92.9W 30 KT 35 MPH...INLAND 60H 28/1800Z 36.4N 91.0W 25 KT 30 MPH...INLAND 72H 29/0600Z 37.3N 87.3W 30 KT 35 MPH...INLAND 96H 30/0600Z 38.0N 74.5W 35 KT 40 MPH...POST-TROP/EXTRATROP 120H 31/0600Z 44.0N 60.0W 45 KT 50 MPH...POST-TROP/EXTRATROP $$ Forecaster Blake
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Tropical Depression Thirteen-E Forecast Discussion Number 1
2020-08-26 10:49:50| National Hurricane Center (East Pacific)
Issued at 300 AM MDT Wed Aug 26 2020 000 WTPZ43 KNHC 260849 TCDEP3 Tropical Depression Thirteen-E Discussion Number 1 NWS National Hurricane Center Miami FL EP132020 300 AM MDT Wed Aug 26 2020 The broad area of low pressure that the NHC has been tracking the past few days has become better defined based on a 0356Z ASCAT-B scatterometer overpass. Although the system is slightly elongated northeast-to-southwest, the center is well defined and deep convection has persisted west of the center despite strong easterly vertical wind shear of 25-30 kt. Thus, the low has been upgraded to Tropical Depression 13-E. The initial intensity of 30 kt is based on scatterometer surface wind speeds of 30-32 kt, which are consistent with T2.0/30-kt satellite classifications from TAFB-SAB. The initial motion estimate is slowly north-northeastward or 025/04 kt. The depression is embedded within an east-to-west oriented cyclonic gyre with a high-amplitude mid-level ridge located over the southwestern U.S. and northern Mexico. These gyre will cause the cyclone to move slowly northward today and northwestward on Thursday, with the ridge acting as a poleward block and forcing to system to turn west-northwestward to westward on Friday and Saturday. On the forecast track, the cyclone is expected to remain just offshore the southwestern coast of Mexico today and Thursday, and pass near or just south of the southern tip of Baja California Sur on Friday and Saturday. The NHC official track forecast closely follows the simple consensus model TVCE, and lies a little to the left or west of the corrected-consensus model HCCA and the ECMWF model tracks. Strong easterly shear is forecast to persist through the next 24 hours, so little if any strengthening is expected during that time. In fact, convection is likely to erode a little during the day today, and then redevelop closer to the center tonight when the shear begins to abate somewhat. In the 36-60 hour period, the shear is forecast to weaken considerably from the northeast, allowing for some slight strengthening to occur. However, the intensity is not expected to increase to more than 35-40 kt, with the strongest winds and heaviest rains remaining offshore the southwestern coast of Mexico. For those reason, a tropical warning has not been issued for southwestern Mexico at this time. The official intensity forecast follows a blend of the HCCA, HWRF, and ECMWF models intensity forecasts. FORECAST POSITIONS AND MAX WINDS INIT 26/0900Z 17.5N 106.7W 30 KT 35 MPH 12H 26/1800Z 18.1N 106.3W 30 KT 35 MPH 24H 27/0600Z 19.0N 106.3W 35 KT 40 MPH 36H 27/1800Z 20.1N 107.0W 35 KT 40 MPH 48H 28/0600Z 21.3N 108.1W 35 KT 40 MPH 60H 28/1800Z 22.3N 109.4W 35 KT 40 MPH 72H 29/0600Z 23.3N 111.3W 30 KT 35 MPH 96H 30/0600Z 23.3N 114.1W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 31/0600Z 22.7N 115.5W 20 KT 25 MPH...POST-TROP/REMNT LOW $$ Forecaster Stewart
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Hurricane Laura Forecast Discussion Number 25
2020-08-26 04:50:46| National Hurricane Center (Atlantic)
Issued at 1000 PM CDT Tue Aug 25 2020 000 WTNT43 KNHC 260250 TCDAT3 Hurricane Laura Discussion Number 25 NWS National Hurricane Center Miami FL AL132020 1000 PM CDT Tue Aug 25 2020 Laura's cloud pattern is becoming better organized on satellite images, with a banding feature over the eastern portion of the circulation and an expanding central dense overcast with cloud tops of -80C or colder. The upper-level outflow is becoming better established over the northwestern quadrant. Flight-level and SFMR-observed surface winds from NOAA and Air Force Hurricane Hunter aircraft indicate that the maximum winds have increased to near 80 kt, and the central pressure is falling. The hurricane is expected to remain over SSTs near 30 deg C until it nears the coast, with only moderate vertical shear. The SHIPS Rapid Intensification Index shows a significant probability for a 25-30 kt increase in strength during the next 24 hours, and this is reflected in the official forecast. This is also between the simple and corrected intensity model consensus predictions. Laura will weaken rapidly after landfall, but it will likely bring hurricane-force winds well inland over extreme western Louisiana and eastern Texas. Aircraft and satellite fixes show a continued west-northwestward track with an initial motion estimate near 300/15 kt. The track forecast reasoning has not changed. The hurricane should gradually turn toward the northwest and north over the next day or two as it moves around the western periphery of a mid-level high and into a weakness into the subtropical ridge. Later in the forecast period the cyclone should turn toward the east-northeast and move with increasing forward speed while embedded within the westerlies. The official track forecast is very similar to the previous one and also very close to the simple and corrected consensus track model predictions. Users are again reminded not to focus on the exact details of the track or intensity forecasts as the average NHC track error at 36 h is around 60 miles and the average intensity error is close to 10 mph. In addition, wind, storm surge, and rainfall hazards will extend far from the center. Key Messages: 1. There is a danger of life-threatening storm surge with large and dangerous waves producing potentially catastrophic damage from San Luis Pass, Texas, to the Mouth of the Mississippi River, including areas inside the Port Arthur Hurricane Flood Protection system. This surge could penetrate up to 30 miles inland from the immediate coastline in southwestern Louisiana and far southeastern Texas. Actions to protect life and property should be rushed to completion, as water levels will begin to rise on Wednesday. 2. Hurricane-force winds are expected Wednesday night in the warning area from San Luis Pass, Texas, to west of Morgan City, Louisiana, and the strongest winds associated with Laura's eyewall will occur somewhere within this area. Hurricane-force winds and widespread damaging wind gusts are also expected to spread well inland into portions of eastern Texas and western Louisiana early Thursday. 3. Widespread flash flooding along small streams, urban areas, and roadways is expected to begin Wednesday night into Thursday across far eastern Texas, Louisiana, and Arkansas. This will also lead to minor to isolated moderate river flooding. The heavy rainfall threat and localized flash and urban flooding potential will spread northeastward into the middle-Mississippi, lower Ohio and Tennessee Valleys Friday night and Saturday. FORECAST POSITIONS AND MAX WINDS INIT 26/0300Z 25.2N 89.5W 80 KT 90 MPH 12H 26/1200Z 26.5N 91.4W 95 KT 110 MPH 24H 27/0000Z 28.7N 93.1W 105 KT 120 MPH 36H 27/1200Z 31.2N 93.8W 70 KT 80 MPH...INLAND 48H 28/0000Z 33.7N 93.6W 40 KT 45 MPH...INLAND 60H 28/1200Z 36.0N 92.3W 30 KT 35 MPH...INLAND 72H 29/0000Z 37.2N 89.5W 25 KT 30 MPH...INLAND 96H 30/0000Z 38.0N 78.0W 30 KT 35 MPH...POST-TROP/EXTRATROP 120H 31/0000Z 42.0N 65.0W 35 KT 40 MPH...POST-TROP/EXTRATROP $$ Forecaster Pasch
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Hurricane Laura Forecast Discussion Number 24
2020-08-25 22:40:45| National Hurricane Center (Atlantic)
Issued at 400 PM CDT Tue Aug 25 2020 000 WTNT43 KNHC 252040 TCDAT3 Hurricane Laura Discussion Number 24 NWS National Hurricane Center Miami FL AL132020 400 PM CDT Tue Aug 25 2020 Satellite imagery shows some changes in the convective pattern of Laura since the last advisory. The ragged central dense overcast seen earlier has been replaced by a curved convective band that wraps almost all the way around a cloud-filled banding-type eve. One possible reason for this change is that the imagery also suggests a tongue of dry air is trying to entrain into the cyclone just west of the central convection. Aircraft data received after the last advisory did not show any fall in the central pressure, but did have high enough flight-level and SFMR winds to justify nudging the initial intensity up to 70 kt. The initial motion is now west-northwestward or 300/15 kt. There is no change in the forecast philosophy since the last advisory. The hurricane is currently on the south side of a large-deep layer ridge over the southeastern United States, and it is moving toward a break in the ridge caused by mid- to -upper-level troughing over Texas and the southern Great Plains. The current and forecast synoptic pattern should steer Laura west-northwestward this evening, followed by a turn toward the northwest tonight and toward the north by Wednesday night and Thursday. This will result in the hurricane making landfall in the area of southwestern Louisiana or the upper Texas coast late Wednesday night or Thursday morning. The new forecast track has a slight eastward nudge during the first 12-24 h, but the landfall position is almost unchanged from that of the previous forecast. It should the be noted that the current forecast track lies to the east of the ECMWF and UKMET models, so it is still possible that the forecast track could nudge westward in later advisories. After landfall, Laura is expected to recurve into the westerlies and move eastward through the Tennessee Valley and the mid-Atlantic States before reaching the Atlantic in about 120 h. All indications are that the hurricane should steadily to rapidly intensify during the next 24 h, with the only negative factor being the possibility of more dry air entrainment. The intensity forecast will go with the scenario that the dry air will not significantly hinder strengthening. The global models are in good agreement that Laura will encounter increasing southwesterly shear in the last 6-12 h before landfall, so the intensity forecast shows slower strengthening during that time. With all that said, the landfall intensity of 100 kt is unchanged from the previous advisory. After landfall, Laura should weaken through the 96 h point, followed by re-intensification through baroclinic energy as the cyclone becomes extratropical. Users are again reminded not to focus on the exact details of the track or intensity forecasts as the average NHC track error at 36 h is around 60 miles and the average intensity error is close to 10 mph. In addition, wind, storm surge, and rainfall hazards will extend far from the center. Key Messages: 1. There is a danger of life-threatening storm surge with large and dangerous waves producing potentially catastrophic damage from San Luis Pass, Texas, to the Mouth of the Mississippi River, including areas inside the Port Arthur Hurricane Flood Protection system. This surge could penetrate up to 30 miles inland from the immediate coastline in southwestern Louisiana and far southeastern Texas. Actions to protect life and property should be rushed to completion this evening, as water levels will begin to rise on Wednesday. 2. Hurricane-force winds are expected Wednesday night in the warning area from San Luis Pass, Texas, to west of Morgan City, Louisiana, and the strongest winds associated with Laura's eyewall will occur somewhere within this area. Hurricane-force winds and widespread damaging wind gusts are also expected to spread well inland into portions of eastern Texas and western Louisiana early Thursday. 3. The threat of widespread flash and urban flooding along with small streams overflowing their banks will increase due to heavy rainfall Wednesday night into Thursday from far eastern Texas, across Louisiana, and Arkansas. This will also result in minor to isolated moderate river flooding. The heavy rainfall threat will spread northeastward into the middle-Mississippi, lower Ohio and Tennessee Valleys Friday night and Saturday. FORECAST POSITIONS AND MAX WINDS INIT 25/2100Z 24.7N 88.3W 70 KT 80 MPH 12H 26/0600Z 25.7N 90.3W 85 KT 100 MPH 24H 26/1800Z 27.5N 92.4W 95 KT 110 MPH 36H 27/0600Z 29.7N 93.8W 100 KT 115 MPH...ON COAST 48H 27/1800Z 32.2N 93.9W 65 KT 75 MPH...INLAND 60H 28/0600Z 34.7N 93.3W 40 KT 45 MPH...INLAND 72H 28/1800Z 36.5N 90.9W 30 KT 35 MPH...INLAND 96H 29/1800Z 38.5N 80.5W 25 KT 30 MPH...INLAND 120H 30/1800Z 42.0N 66.5W 40 KT 45 MPH...POST-TROP/EXTRATROP $$ Forecaster Beven
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