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Potential Tropical Cyclone Fourteen-E Forecast Discussion Number 4
2017-08-30 16:37:53| National Hurricane Center (East Pacific)
Issued at 900 AM MDT Wed Aug 30 2017 000 WTPZ44 KNHC 301437 TCDEP4 Potential Tropical Cyclone Fourteen-E Discussion Number 4 NWS National Hurricane Center Miami FL EP142017 900 AM MDT Wed Aug 30 2017 The potential tropical cyclone has not become any better organized overnight, though available data indicate that the pressures continue to fall and that the winds have increased to 30 kt. It appears that there are two centers in the broad circulation, and the NHC position uses a mean center. Only slow strengthening is forecast today due to the disorganized surface circulation, but a more significant intensification could start tomorrow. If the circulation consolidates, the upper-level winds and water temperatures are very conducive to strengthening. The NHC forecast is similar to the previous one, just a bit above the model consensus. Because the system is forecast to be approaching hurricane strength as it nears Baja California Sur, the hurricane watch is maintained. Later in the forecast period, the cyclone should weaken while it traverses either land or the cooler waters west of the Baja peninsula. As before, with the lack of a definite center the initial motion is quite uncertain, with the current estimate at 335/8 kt. For the next couple of days, the system/tropical cyclone is expected to move slowly north-northwestward on the eastern end of a broad mid-level cyclonic gyre. In 3-5 days the motion should bend toward the northwest and west-northwest due to a mid-level ridge to the north. Model guidance has shifted a bit to the east today, and the official forecast is adjusted in that direction. A tropical storm watch has been issued for the west coast of Mexico due to the changes in the forecast. Since the disturbance still lacks a well-defined center and there is considerable spread in the model guidance, this official track forecast has greater-than-usual uncertainty. It is also important to note that very heavy rain causing life-threatening flash floods and mudslides is possible over portions of western Mexico and Baja California Sur. Regardless of exactly how strong the cyclone becomes, this is expected to be a significant hazard. FORECAST POSITIONS AND MAX WINDS INIT 30/1500Z 19.3N 108.6W 30 KT 35 MPH...POTENTIAL TROP CYCLONE 12H 31/0000Z 20.4N 109.2W 35 KT 40 MPH...TROPICAL STORM 24H 31/1200Z 21.4N 109.6W 40 KT 45 MPH 36H 01/0000Z 22.3N 109.9W 50 KT 60 MPH 48H 01/1200Z 23.4N 110.4W 55 KT 65 MPH 72H 02/1200Z 25.4N 112.3W 45 KT 50 MPH 96H 03/1200Z 27.5N 115.0W 35 KT 40 MPH 120H 04/1200Z 28.5N 118.5W 25 KT 30 MPH $$ Forecaster Blake
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Tropical Storm Harvey Forecast Discussion Number 40
2017-08-30 10:52:19| National Hurricane Center (Atlantic)
Issued at 400 AM CDT Wed Aug 30 2017 000 WTNT44 KNHC 300852 TCDAT4 Tropical Storm Harvey Discussion Number 40 NWS National Hurricane Center Miami FL AL092017 400 AM CDT Wed Aug 30 2017 Radar, satellite, and surface observations indicate that Harvey's center has crossed the coast just west of Cameron, Louisiana, with most of the associated deep convection located over extreme southeastern Texas and western Louisiana. Although the rain has ended in the Houston/Galveston area, the Beaumont/Port Arthur area was particularly hard hit overnight, with about 12.5 inches reported at the Jack Brooks Regional Airport since 7 pm CDT. ASCAT data from late last night indicated that Harvey's maximum winds were near 40 kt, and the tropical-storm-force wind radii on the eastern side were a little smaller than previously estimated. Harvey has turned north-northeastward and is moving a little faster with an initial motion of 030/6 kt. The cyclone is located on the northwestern side of a mid-tropospheric high, which should steer it north-northeastward and the northeastward across the Lower Mississippi and Tennessee Valleys during the next few days. The global models indicate that the surface low should dissipate over the Ohio Valley by day 4, which is now indicated in the NHC forecast. Now that Harvey's center is moving inland, the maximum winds should gradually decrease during the next few days. Harvey is likely to weaken to a tropical depression by tonight, and then it could become a remnant low by day 3. This weakening will not eliminate the risk of continued heavy rainfall and flooding along Harvey's path, although the system's faster motion will prevent rainfall totals from being anywhere near what occurred over southeastern Texas. Key Messages: 1. Ongoing catastrophic and life-threatening flooding will continue across southeastern Texas. While the threat of heavy rains has ended in the Houston/Galveston area, catastrophic and life- threatening flooding will continue in and around Houston eastward into southwest Louisiana for the rest of the week. Isolated storm totals have reached 50 inches over the upper Texas coast, including the Houston/Galveston metropolitan area. Please heed the advice of local officials. Do not attempt to travel if you are in a safe place, and do not drive into flooded roadways. Refer to products from your local National Weather Service office and the NOAA Weather Prediction Center for more information on the flooding hazard. A summary of rainfall totals compiled by the Weather Prediction Center can be found at: www.wpc.ncep.noaa.gov/discussions/nfdscc1.html 2. The flood threat has spread farther east, and additional rainfall accumulations of 3 to 6 inches with isolated amounts up to 10 inches are expected from southwestern Louisiana and the adjacent border of eastern Texas northeastward into western Kentucky through Friday. Please heed the advice of local officials and refer to products from your local National Weather Service office and the NOAA Weather Prediction Center for more information on the flooding hazard in these areas. FORECAST POSITIONS AND MAX WINDS INIT 30/0900Z 29.8N 93.4W 40 KT 45 MPH...INLAND 12H 30/1800Z 30.4N 92.9W 35 KT 40 MPH...INLAND 24H 31/0600Z 31.7N 92.0W 30 KT 35 MPH...INLAND 36H 31/1800Z 33.3N 90.6W 25 KT 30 MPH...INLAND 48H 01/0600Z 35.0N 88.7W 25 KT 30 MPH...INLAND 72H 02/0600Z 37.5N 84.9W 20 KT 25 MPH...POST-TROP/REMNT LOW 96H 03/0600Z...DISSIPATED $$ Forecaster Berg
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Tropical Storm Harvey Forecast Discussion Number 39
2017-08-30 04:54:48| National Hurricane Center (Atlantic)
Issued at 1000 PM CDT Tue Aug 29 2017 000 WTNT44 KNHC 300254 TCDAT4 Tropical Storm Harvey Discussion Number 39 NWS National Hurricane Center Miami FL AL092017 1000 PM CDT Tue Aug 29 2017 Latest radar imagery shows that heavy rainfall continues over far eastern Texas and southwestern Louisiana. Outer bands are also producing heavy rain farther east along portions of the northern Gulf coast. However, rains have begun to diminish over the Greater Houston area, where some locations have received more than 50 inches during this historic event. Harvey took an eastward jog this evening, but recent satellite images suggest that a northeastward motion has resumed. The storm is expected to move north-northeastward to northeastward between a ridge over the eastern Gulf of Mexico and a trough over the east-central United States. This motion should bring the center onshore over southwestern Louisiana early Wednesday, and into the Tennessee Valley region later this week. The global models show the system becoming an open trough near the Ohio Valley or Appalachians in 4 to 5 days. The latest NHC track forecast has been shifted eastward partially due to the more eastward initial position. There has been little overall change to Harvey's convective structure since the previous advisory, and the initial intensity remains 45 kt, which was supported by the earlier aircraft data. Little change in strength is anticipate before Harvey reaches the Louisiana coast. After that time, gradual weakening should occur while Harvey moves farther inland. The latest forecast required an extension of the tropical storm warning eastward to Grand Isle, Louisiana. Key Messages: 1. Ongoing catastrophic and life-threatening flooding will continue across southeastern Texas. Additional rainfall accumulations of 6 to 12 inches are expected to the north and east of Houston from far east Texas into southwestern Louisiana. Isolated storm totals have reached 50 inches over the upper Texas coast, including the Houston/Galveston metropolitan area. Please heed the advice of local officials. Do not attempt to travel if you are in a safe place, and do not drive into flooded roadways. Refer to products from your local National Weather Service office and the NOAA Weather Prediction Center for more information on the flooding hazard. A summary of rainfall totals compiled by the Weather Prediction Center can be found at: www.wpc.ncep.noaa.gov/discussions/nfdscc1.html 2. The flood threat has spread farther east, and additional rainfall amounts of 5 to 10 inches are expected in southern Louisiana into coastal Mississippi and Alabama. These rains will spread north by mid to late week, with rainfall amounts of 4 to 8 inches in portions of Arkansas and the Tennessee Valley. Please heed the advice of local officials and refer to products from your local National Weather Service office and the NOAA Weather Prediction Center for more information on the flooding hazard in these areas. FORECAST POSITIONS AND MAX WINDS INIT 30/0300Z 29.0N 93.6W 45 KT 50 MPH 12H 30/1200Z 29.8N 93.0W 40 KT 45 MPH...INLAND 24H 31/0000Z 31.1N 92.3W 30 KT 35 MPH...INLAND 36H 31/1200Z 32.5N 91.2W 30 KT 35 MPH...INLAND 48H 01/0000Z 34.3N 89.5W 25 KT 30 MPH...INLAND 72H 02/0000Z 36.8N 85.9W 25 KT 30 MPH...POST-TROP/INLAND 96H 03/0000Z 39.0N 81.5W 20 KT 25 MPH...POST-TROP/INLAND 120H 04/0000Z...DISSIPATED $$ Forecaster Brown
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Potential Tropical Cyclone Fourteen-E Forecast Discussion Number 1
2017-08-29 22:46:43| National Hurricane Center (East Pacific)
Issued at 300 PM MDT Tue Aug 29 2017 000 WTPZ44 KNHC 292046 TCDEP4 Potential Tropical Cyclone Fourteen-E Discussion Number 1 NWS National Hurricane Center Miami FL EP142017 300 PM MDT Tue Aug 29 2017 Satellite images indicate that the large disturbance southwest of Mexico is gradually becoming better organized. While the system still lacks a well-defined center, all indications are that it will become a tropical storm tomorrow. Since the system is forecast to bring tropical-storm-force winds to Baja California Sur within 36 hours, advisories are being initiated on a potential tropical cyclone. The system has 2-3 days over very warm water with decreasing shear. Although the system is quite broad for the moment, the favorable environmental conditions noted above should allow for at least steady strengthening. Thus, the official forecast is higher than the model consensus, but lower than the bullish SHIPS model. The initial motion is a highly uncertain 315/8. A weak ridge over central Mexico should steer the cyclone to the northwest or north- northwest for the next few days. Thereafter, the system should turn toward the west-northwest as it moves around a stronger ridge over the southwestern United States. While there is some spread in the guidance, the models are in reasonable agreement for a first forecast, taking the system near or just west of Baja California Sur. The official NHC track prediction is between the model consensus and the NOAA corrected-consensus model HCCA. It is important to note that outside the watch/warning area, very heavy rain is possible, which could cause life-threatening flooding and mudslides over southwestern Mexico. In addition, wind gusts to tropical-storm force are possible along the coast of Michoacan, Colima and Jalisco states tonight into early Wednesday due to the large circulation. The National Hurricane Center now has the option to issue advisories, watches, and warnings for disturbances that are not yet a tropical cyclone, but which pose the threat of bringing tropical storm or hurricane conditions to land areas within 48 hours. Under previous policy this was not possible. These systems are known as Potential Tropical Cyclones in advisory products and are numbered from the same list as depressions. Because of the threat to Baja California Sur, advisories have been initiated on Potential Tropical Cyclone Fourteen-E and the appropriate watches and warnings have been issued by the government of Mexico. Advisory packages will continue until the threat of tropical-storm-force winds for land areas sufficiently diminishes, although if the system becomes a tropical cyclone, the normal rules for discontinuing advisories would apply. Users should be aware that forecast uncertainty for disturbances is generally larger than for tropical cyclones, especially beyond 48-72 hours. FORECAST POSITIONS AND MAX WINDS INIT 29/2100Z 17.2N 107.2W 25 KT 30 MPH...POTENTIAL TROP CYCLONE 12H 30/0600Z 18.1N 108.0W 30 KT 35 MPH 24H 30/1800Z 19.3N 108.9W 35 KT 40 MPH...TROPICAL STORM 36H 31/0600Z 20.4N 109.8W 45 KT 50 MPH 48H 31/1800Z 21.4N 110.4W 55 KT 65 MPH 72H 01/1800Z 23.5N 112.0W 60 KT 70 MPH 96H 02/1800Z 25.0N 114.0W 50 KT 60 MPH 120H 03/1800Z 26.5N 117.5W 35 KT 40 MPH $$ Forecaster Blake
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Tropical Storm Harvey Forecast Discussion Number 38
2017-08-29 22:40:49| National Hurricane Center (Atlantic)
Issued at 400 PM CDT Tue Aug 29 2017 000 WTNT44 KNHC 292040 TCDAT4 Tropical Storm Harvey Discussion Number 38 NWS National Hurricane Center Miami FL AL092017 400 PM CDT Tue Aug 29 2017 Heavy rains continue to spread over southeastern Texas and southern Louisiana, exacerbating what is already a catastrophic flood event. Rainfall totals are around 50 inches at some isolated locations in the Greater Houston area and southeastern Texas. Convection blossomed a couple of hours ago, and the center jumped a little northward into the thunderstorm activity. Since that time, the center is back on track and is moving slower again toward the north-northeast at about 5 kt. Recent data from an Air Force Hurricane Hunter plane indicate that winds are about 45 kt, with a minimum pressure of around 994 mb. The SFMR on the plane reported some higher wind values but the plane was flying in shallow waters and these numbers appear inflated. Flight-level winds in the same area were much lower. Strong shear prevails over the cyclone, so no significant change in intensity is anticipated before the broad center of circulation makes landfall. A gradual weakening is forecast once the system moves inland. Harvey has been steered north-northeastward by a light southwesterly flow between a high in the Gulf of Mexico and a trough over the central United States. This flow pattern should keep Harvey on the same general track and speed with a gradual turn to the northeast in about 3 days. By then the cyclone is forecast to degenerate into a remnant low and then become absorbed by an extratropical low. Most of the guidance is consistent with this solution, and the NHC forecast is in the middle of the guidance envelope and very close to the multi-model consensus. Key Messages: 1. Ongoing catastrophic and life-threatening flooding will continue across southeastern Texas. Additional rainfall accumulations of 6 to 12 inches are expected across the upper Texas coast into southwestern Louisiana, with isolated storm totals as high as 50 inches. Please heed the advice of local officials. Do not attempt to travel if you are in a safe place, and do not drive into flooded roadways. Refer to products from your local National Weather Service office and the NOAA Weather Prediction Center for more information on the flooding hazard. A summary of rainfall totals compiled by the Weather Prediction Center can be found at: www.wpc.ncep.noaa.gov/discussions/nfdscc1.html 2. The flood threat has spread farther east, and additional rainfall amounts of 5 to 10 inches are expected in southern Louisiana into coastal Mississippi and Alabama. Please heed the advice of local officials and refer to products from your local National Weather Service office and the NOAA Weather Prediction Center for more information on the flooding hazard in these areas. FORECAST POSITIONS AND MAX WINDS INIT 29/2100Z 29.2N 94.3W 45 KT 50 MPH 12H 30/0600Z 30.1N 93.7W 40 KT 45 MPH...INLAND 24H 30/1800Z 31.5N 93.0W 30 KT 35 MPH...INLAND 36H 31/0600Z 32.5N 92.5W 30 KT 35 MPH...INLAND 48H 31/1800Z 34.0N 91.0W 30 KT 35 MPH...INLAND 72H 01/1800Z 36.5N 88.0W 25 KT 30 MPH...POST-TROP/INLAND 96H 02/1800Z 37.5N 85.5W 25 KT 30 MPH...POST-TROP/INLAND 120H 03/1800Z...ABSORBED BY AN EXTRATROPICAL LOW $$ Forecaster Avila
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