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Hurricane Lee Forecast Discussion Number 24

2017-09-24 08:33:13| National Hurricane Center (Atlantic)

Issued at 200 AM AST Sun Sep 24 2017 000 WTNT44 KNHC 240625 TCDAT4 Hurricane Lee Special Discussion Number 24 NWS National Hurricane Center Miami FL AL142017 200 AM AST Sun Sep 24 2017 Infrared satellite imagery indicates that an eye is developing in Lee's central dense overcast. This special advisory is thus being issued to make Lee a hurricane with 65 kt winds. The intensity forecast has been significantly increased based on the current intensity and trends, and the initial wind radii have been somewhat modified. However, the track forecast is unchanged from the previous advisory. FORECAST POSITIONS AND MAX WINDS INIT 24/0630Z 31.9N 50.1W 65 KT 75 MPH 12H 24/1200Z 31.8N 50.0W 75 KT 85 MPH 24H 25/0000Z 31.5N 49.4W 85 KT 100 MPH 36H 25/1200Z 30.9N 48.9W 90 KT 105 MPH 48H 26/0000Z 30.2N 48.9W 90 KT 105 MPH 72H 27/0000Z 30.0N 50.5W 90 KT 105 MPH 96H 28/0000Z 31.5N 52.0W 85 KT 100 MPH 120H 29/0000Z 34.5N 52.5W 80 KT 90 MPH $$ Forecaster Beven

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Tropical Storm Pilar Forecast Discussion Number 2

2017-09-24 04:56:51| National Hurricane Center (East Pacific)

Issued at 1000 PM CDT Sat Sep 23 2017 000 WTPZ43 KNHC 240256 TCDEP3 Tropical Storm Pilar Discussion Number 2 NWS National Hurricane Center Miami FL EP182017 1000 PM CDT Sat Sep 23 2017 The structure of the cyclone near Mexico has improved over the past 6 hours. Dvorak intensity estimates from TAFB and SAB now support an estimated intensity of 35 kt, so the system is now classified as Tropical Storm Pilar. The initial motion based on recent satellite fixes is 350/4 kt. Pilar is still expected to move generally toward the north-northwest or north to the east of a mid-level ridge centered over Mexico for the next couple of days, and the primary source of uncertainty in the forecast is possible interaction with land. Due in part to initial position uncertainty, the global models vary on whether Pilar will clip the coast of Jalisco or remain just offshore, but the model consensus now shows a landfall in about 24 hours. The NHC forecast has been adjusted slightly to the east toward the model consensus, but it is certainly possible that the tropical storm could remain offshore and enter the Gulf of California. Regardless of whether the center makes landfall or not, heavy rain is still likely along the coast of Mexico through early next week. The possibility of land interaction makes the intensity forecast particularly difficult. Very warm SSTs and only moderate shear should allow for some strengthening for at least the next 36 hours. However, if Pilar makes landfall sooner than that, it will likely quickly weaken. Since my track forecast shows Pilar making landfall in about 24 hours, my intensity forecast peaks at that time, and shows steady weakening thereafter. Beginning around 48 h, the GFS and ECMWF show that the shear will increase substantially, which should cause Pilar to quickly become a remnant low, even if it remains over water. FORECAST POSITIONS AND MAX WINDS INIT 24/0300Z 18.7N 105.3W 35 KT 40 MPH 12H 24/1200Z 19.3N 105.5W 45 KT 50 MPH 24H 25/0000Z 20.3N 105.6W 50 KT 60 MPH 36H 25/1200Z 21.1N 105.7W 45 KT 50 MPH 48H 26/0000Z 21.9N 105.9W 40 KT 45 MPH 72H 27/0000Z 23.3N 106.4W 30 KT 35 MPH...POST-TROP/REMNT LOW 96H 28/0000Z 24.7N 107.3W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 29/0000Z...DISSIPATED $$ Forecaster Zelinsky

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Hurricane Maria Forecast Discussion Number 32

2017-09-24 04:56:20| National Hurricane Center (Atlantic)

Issued at 1100 PM EDT Sat Sep 23 2017 000 WTNT45 KNHC 240256 TCDAT5 Hurricane Maria Discussion Number 32 NWS National Hurricane Center Miami FL AL152017 1100 PM EDT Sat Sep 23 2017 Once again tonight, the cloud pattern has become more impressive with a distinct eye of 30 n mi in diameter surrounded by a ring of very deep convection. Wind data sampled by the reconnaissance plane this evening perhaps do not justify winds as high as 100 kt. However, since the central pressure has dropped to 942 mb, and both objective and subjective Dvorak numbers have increased slightly due to the improvement of the cloud pattern, the initial intensity is kept at 100 kt in this advisory. During the next 24 hours while Maria is moving through a low shear environment and over warm waters, slight strengthening could occur. However, this will not be a significant change, and I have opted to show Maria with the same intensity for about a day or so. From 36 hours and beyond, the hurricane will find cooler waters and gradual weakening should then begin. Satellite and recon fixes indicate that the hurricane is moving toward the north or 350 degrees at 8 kt, steered by the flow between the Atlantic subtropical ridge and a cut-off low/trough digging southward over the eastern Gulf of Mexico. The subtropical high is forecast to amplify, and this pattern should keep Maria moving slowly northward for the next 3 days. As the subtropical ridge slides eastward, Maria will encounter the mid-latitude westerlies and should recurve away from the United States coast. The track guidance unanimously brings the hurricane northward to near latitude 34N where recurvature should occur. The uncertainty is how close to the North Carolina coast Maria's turn will occur. At this time and with the current guidance, the core of Maria should turn northeast well east of the Outer Banks. However, Maria is a large cyclone and the tropical storm force winds extend outward a great distance. These winds could eventually reach a portion of the North Carolina coast. The NHC forecast is very similar to the previous one and follows very closely the multi-model consensus and the corrected consensus HCCA. KEY MESSAGES: 1. Maria's forecast track continues to be northward, paralleling the U.S. east coast, and it is likely that some direct impacts will occur along portions of the coast next week. Interests along the coast of the Carolinas and the Mid-Atlantic should monitor the progress of Maria, as tropical storm or hurricane watches may be needed for part of this area on Sunday. 2. Swells from Maria are increasing along the coast of the southeastern United States and are expected to reach the Mid-Atlantic coast on Sunday. These swells will likely cause dangerous surf and rip currents at the beach through much of next week. For more information, please monitor information from your local National Weather Service office at www.weather.gov. FORECAST POSITIONS AND MAX WINDS INIT 24/0300Z 27.0N 72.5W 100 KT 115 MPH 12H 24/1200Z 28.2N 72.7W 100 KT 115 MPH 24H 25/0000Z 29.5N 73.0W 100 KT 115 MPH 36H 25/1200Z 30.5N 73.1W 95 KT 110 MPH 48H 26/0000Z 31.5N 73.2W 90 KT 105 MPH 72H 27/0000Z 33.2N 73.3W 80 KT 90 MPH 96H 28/0000Z 34.5N 72.7W 70 KT 80 MPH 120H 29/0000Z 35.5N 69.0W 65 KT 75 MPH $$ Forecaster Avila

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Tropical Storm Lee Forecast Discussion Number 23

2017-09-24 04:55:52| National Hurricane Center (Atlantic)

Issued at 1100 PM AST Sat Sep 23 2017 000 WTNT44 KNHC 240255 TCDAT4 Tropical Storm Lee Discussion Number 23 NWS National Hurricane Center Miami FL AL142017 1100 PM AST Sat Sep 23 2017 An ASCAT overpass around 0014 UTC caught the western half of Lee, and showed a maximum wind of about 40 kt. On that basis, the initial intensity has been increased to 45 kt, on the assumption that the ASCAT instrument is undersampling the tiny circulation of the tropical storm. A WindSat overpass from 2102 UTC indicated that Lee has developed a coherent inner-core. In fact, the 37 GHz RGB composite from the WindSat overpass indicated that a ring of shallow to moderate convection surrounds the center of Lee, often a signature of a rapidly intensifying cyclone. The NHC intensity forecast has therefore been significantly increased for the first 48 hours of the forecast, but falls short of explicitly forecasting rapid intensification. Beyond that time, most of the intensity guidance is higher than before, and shows Lee maintaining hurricane throughout the forecast period. The NHC forecast is just a little above the previous forecast at days 3-5, and close to the intensity consensus. It is still worth noting that small tropical cyclones can go up or down quickly in intensity with little warning, and confidence in the forecast is low, even with reasonable agreement among the intensity models. After turning almost due west earlier this evening, Lee appears to have come to a near halt and is beginning to turn slowly toward the southeast. Lee continues to follow the trend of the ECMWF, so the NHC forecast has been moved farther west, closer to that model. Although the GFS continues to insist on a east to northeast track, I am treating it as an outlier at this time. The remaining global models (and the HWRF) show that Lee will gradually rotate clockwise around a building mid-level ridge to the northwest for the next few days before turning more toward the north at day 4. The NHC forecast lies between HCCA and the ECMWF, but confidence in the track forecast is still low given the high model spread at this time. FORECAST POSITIONS AND MAX WINDS INIT 24/0300Z 31.9N 50.1W 45 KT 50 MPH 12H 24/1200Z 31.8N 50.0W 55 KT 65 MPH 24H 25/0000Z 31.5N 49.4W 65 KT 75 MPH 36H 25/1200Z 30.9N 48.9W 75 KT 85 MPH 48H 26/0000Z 30.2N 48.9W 75 KT 85 MPH 72H 27/0000Z 30.0N 50.5W 75 KT 85 MPH 96H 28/0000Z 31.5N 52.0W 75 KT 85 MPH 120H 29/0000Z 34.5N 52.5W 70 KT 80 MPH $$ Forecaster Zelinsky

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Hurricane Maria Forecast Discussion Number 31

2017-09-23 22:48:40| National Hurricane Center (Atlantic)

Issued at 500 PM EDT Sat Sep 23 2017 000 WTNT45 KNHC 232048 TCDAT5 Hurricane Maria Discussion Number 31 NWS National Hurricane Center Miami FL AL152017 500 PM EDT Sat Sep 23 2017 Maria's eye became cloud filled again today, although convective cloud tops have been cooling within the eyewall during the past couple of hours. A NOAA Hurricane Hunter plane conducting a research mission has not yet sampled the entire circulation, but they did report that the central pressure had fallen by a couple of millibars. In addition, a Coyote unmanned aerial vehicle launched by the plane has been measuring winds of 120-125 kt at altitudes of 1200-1300 ft, which supports maximum surface winds of 100 kt. The initial motion remains north-northwestward, or 345/8 kt, but Maria is expected to turn northward by this evening or overnight while moving between a mid-level high near Bermuda and a cut-off low over the northeastern Gulf coast. A blocking ridge sliding eastward over the northeastern U.S. should cause Maria to slow down to a forward motion of 5 kt or less beginning in about 36 hours, lasting through the end of the forecast period. The track models appear to have stabilized for the moment, with this being the first cycle in about a day where they have not shown a significant westward shift. Therefore, the updated NHC track forecast is relatively unchanged from the previous forecast during the first 3 days. The day 4 point was shifted a little closer to the North Carolina coast to be closer to the consensus aids and the Florida State Superensemble, and all the models indicate that a northeastward motion away from the coast should begin by day 5. Vertical shear will remain relatively low over Maria for the next several days, and the hurricane will be moving over warm waters at least for the next 3 days. However, the depth of the thermocline does become more shallow, with oceanic heat content values steadily decreasing over the next 36 hours. With Maria expected to slow down, upwelling of colder water becomes a greater factor, and that could modulate the hurricane's intensity during the next several days. Maria also could still move over Jose's cold wake in 4-5 days, which would likely cause additional weakening. The NHC intensity forecast remains just above the intensity consensus, however it should be noted that the normally skillful HCCA model is toward the lower end of the guidance suite. It therefore wouldn't be surprising if Maria weakened more than shown in the official forecast. KEY MESSAGES: 1. Maria's forecast track has shifted closer to the U.S. east coast, and it is becoming increasingly likely that some direct impacts will occur along portions of the coast next week. Interests along the coast of the Carolinas and the Mid-Atlantic should monitor the progress of Maria, as tropical storm or hurricane watches may be needed for part of this area on Sunday. 2. Swells from Maria are increasing along the coast of the southeastern United States and are expected to reach the Mid-Atlantic coast tonight and on Sunday. These swells will likely cause dangerous surf and rip currents at the beach through much of next week. For more information, please monitor information from your local National Weather Service office at www.weather.gov. FORECAST POSITIONS AND MAX WINDS INIT 23/2100Z 26.3N 72.5W 100 KT 115 MPH 12H 24/0600Z 27.6N 72.8W 100 KT 115 MPH 24H 24/1800Z 29.1N 73.1W 100 KT 115 MPH 36H 25/0600Z 30.1N 73.3W 95 KT 110 MPH 48H 25/1800Z 31.1N 73.3W 90 KT 105 MPH 72H 26/1800Z 32.9N 73.3W 80 KT 90 MPH 96H 27/1800Z 34.5N 73.5W 70 KT 80 MPH 120H 28/1800Z 35.0N 72.0W 65 KT 75 MPH $$ Forecaster Berg

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