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Tropical Storm Gonzalo Forecast Discussion Number 12
2020-07-24 16:58:13| National Hurricane Center (Atlantic)
Issued at 1100 AM AST Fri Jul 24 2020 000 WTNT42 KNHC 241458 TCDAT2 Tropical Storm Gonzalo Discussion Number 12 NWS National Hurricane Center Miami FL AL072020 1100 AM AST Fri Jul 24 2020 Gonzalo continues to produce bursts of deep convection, especially in the southeast quadrant, but has not become any better organized overall since the last advisory. Microwave imagery overnight indicated the low-level structure of Gonzalo is still largely intact, but this has not translated into better convective organization. ASCAT data valid shortly after 12Z revealed that Gonzalo has accelerated west faster than anticipated and has not strengthened. In fact the strongest winds in the ASCAT data were only 30-35 kt. The resolution of ASCAT likely limits its ability to sample the actual max winds of small storms like Gonzalo, but it is another indication that the cyclone has not strengthened and could be weakening. The initial intensity for this advisory is set at 45 kt, based primarily on the latest TAFB Dvorak fix and the UW-CIMSS SATCON. An Air Force Reserve reconnaissance aircraft scheduled to investigate the storm this afternoon will provide a more information about Gonzalo's intensity and structure. Due primarily to the adjusted initial position, the NHC track forecast has been adjusted a fair amount west and south of the previous advisory. Overall Gonzalo is still forecast to move generally westward or west-northwestward through the period, steered by the subtropical ridge to the north. The new NHC forecast lies between the old forecast, adjusted for the new initial position, and the HFIP Corrected Consensus. The intensity guidance is generally lower than it has been for the last day or so, and none of the operational models forecast Gonzalo to reach hurricane strength. Unfortunately, small storms like Gonzalo are often subject to large swings in intensity, up or down, and that aspect of the forecast remains highly uncertain, even though the spread in the guidance is not particularly high. The NHC forecast has been adjusted only slightly lower for this cycle and is now above all of the guidance at the time the system is forecast to pass through the Windward Islands. A larger adjustment could be made later today if the most recent model trends continue, or if the recon mission finds that Gonzalo is even weaker than the current estimates. Key Messages 1. Gonzalo is forecast to bring tropical storm conditions across portions of the southern Windward Islands Saturday and Saturday night. Hurricane and Tropical Storm Warning and Watches are currently in effect for some of the islands. Interests in the southern Windward Islands should monitor the progress of Gonzalo and follow any advice given by local officials. 2. Gonzalo is expected to produce heavy rain over portions of the southern Windward Islands. This could lead to life-threatening flash flooding. FORECAST POSITIONS AND MAX WINDS INIT 24/1500Z 10.0N 54.2W 45 KT 50 MPH 12H 25/0000Z 10.5N 56.0W 50 KT 60 MPH 24H 25/1200Z 11.4N 59.1W 55 KT 65 MPH 36H 26/0000Z 12.4N 62.3W 60 KT 70 MPH 48H 26/1200Z 13.0N 65.7W 50 KT 60 MPH 60H 27/0000Z 13.7N 69.0W 40 KT 45 MPH 72H 27/1200Z 14.0N 72.0W 30 KT 35 MPH 96H 28/1200Z...DISSIPATED $$ Forecaster Zelinsky
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Hurricane Douglas Forecast Discussion Number 16
2020-07-24 10:48:35| National Hurricane Center (East Pacific)
Issued at 1100 PM HST Thu Jul 23 2020 000 WTPZ43 KNHC 240848 TCDEP3 Hurricane Douglas Discussion Number 16 NWS National Hurricane Center Miami FL EP082020 1100 PM HST Thu Jul 23 2020 Douglas continues to look impressive in satellite images, with a clear eye and symmetric convection in all quadrants. Broad outflow channels extend about 300 n mi in every direction from the cyclone, indicative of nearly zero wind shear. The latest Dvorak CI values from TAFB and SAB, as well as the recent UW/CIMSS ADT estimates are all T6.0, which supports keeping the initial advisory intensity at 115 kt. Douglas is crossing the 26 C isotherm, and will continue to move over relatively cooler waters of about 25 C over the next day or so. This should cause the cyclone to begin weakening very soon. In about 48 h, Douglas is forecast to move back across the 26 C isotherm, but at the same time the cyclone is forecast to begin encountering a drier, more stable airmass and increasing vertical wind shear. Despite the warmer waters, these other more hostile environmental factors are expected to cause Douglas to gradually weaken for the remainder of the 5-day forecast period. The latest NHC forecast is changed little from the previous advisory, and is very close to a blend of the corrected consensus HCCA and the IVCN/ICON consensus aids. Douglas is still moving quickly west-northwestward or 295/16 kt. A mid-level ridge to the north of the cyclone should keep moving the cyclone in the same general direction over the next couple of days. Over the weekend, as Douglas approaches the Hawaiian Islands, a more westward motion is forecast as another ridge builds to the north of the cyclone. There is some notable spread in the model guidance now compared to yesterday as Douglas approaches the Hawaiian Islands. The faster and southernmost guidance from the ECMWF takes the center of the cyclone over the big island, while the northernmost GFS and HWRF take the cyclone just north of the island chain. The other guidance, including the track consensus aids lie in between those solutions. The latest NHC forecast was nudged slightly northward between 48 h and 96 h, but still remains south of the consensus aids during those time periods. Otherwise, the NHC forecast was little changed from the previous one. This is the last advisory issued by the National Hurricane Center on Douglas. Future information on this system can be found in Forecast/Advisories issued by the Central Pacific Hurricane Center beginning at 1500 UTC under AWIPS header HFOTCMCP2 and WMO header WTPA22 PHFO. For information specific to the Hawaiian Islands, users should continue to consult products from the National Weather Service Forecast Office in Honolulu, Hawaii, at www.weather.gov/hfo. Key Messages: 1. Douglas is expected to move near or over portions of the Hawaiian Islands this weekend, and there is an increasing chance that strong winds, dangerous surf, and heavy rainfall could affect portions of the state beginning Saturday night or Sunday. Interests on the Hawaiian Islands should continue to monitor the progress of Douglas and the official forecasts as they evolve over the next few days. Watches could be issued on Friday. FORECAST POSITIONS AND MAX WINDS INIT 24/0900Z 15.7N 140.3W 115 KT 130 MPH 12H 24/1800Z 16.7N 142.6W 105 KT 120 MPH 24H 25/0600Z 17.9N 145.7W 95 KT 110 MPH 36H 25/1800Z 19.0N 148.7W 85 KT 100 MPH 48H 26/0600Z 19.9N 151.7W 75 KT 85 MPH 60H 26/1800Z 20.5N 154.5W 65 KT 75 MPH...NEAR HAWAII 72H 27/0600Z 21.0N 157.1W 60 KT 70 MPH...NEAR HAWAII 96H 28/0600Z 22.0N 163.2W 50 KT 60 MPH 120H 29/0600Z 22.4N 170.0W 45 KT 50 MPH $$ Forecaster Latto
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Tropical Storm Gonzalo Forecast Discussion Number 11
2020-07-24 10:42:38| National Hurricane Center (Atlantic)
Issued at 500 AM AST Fri Jul 24 2020 000 WTNT42 KNHC 240842 TCDAT2 Tropical Storm Gonzalo Discussion Number 11 NWS National Hurricane Center Miami FL AL072020 500 AM AST Fri Jul 24 2020 Conventional satellite imagery indicates that Gonzalo's cloud pattern has changed little during the past several hours. The cyclone continues to produce an area of deep convection, although quite shapeless, with very cold cloud tops. A compromise of the subjective T-numbers from TAFB and SAB along with an earlier SATCON estimate of 55 kt yields an initial intensity of 50 kt for this advisory. An Air Force Reserve reconnaissance aircraft scheduled to investigate the storm later this afternoon will provide a more precise intensity estimate. The statistical-dynamical intensity guidance as well as the deterministic models all show Gonzalo strengthening as it approaches the southern Windward Islands. The HWRF, Decay SHIPS and the LGEM are the only guidance indicating a hurricane around the 36 hour period. Afterward, Gonzalo is forecast to move into a more inhibiting thermodynamic environment over the weekend. Accordingly, the intensity forecast calls for weakening on Sunday as Gonzalo enters the eastern Caribbean sea and dissipation in 96 hours, or sooner as a couple of the large-scale models suggest. The intensity forecast is basically an update of the previous advisory through 36 hours, indicating a hurricane approaching and moving over the southern Windward Islands, and a faster weakening trend afterward, out of respect to the global model's prediction. The initial motion is estimated to be westward, or 275/12 kt and Gonzalo is being steered by a building subtropical ridge to the system's north. The cyclone is expected to increase in forward speed toward the west and west-northwest through the entire period. The NHC official forecast is an update of the previous advisory and is based on the various consensus aids. Key Messages 1. The risk of wind and rain impacts from Gonzalo in portions of the southern Windward Islands this weekend continues to increase, however there is significant uncertainty in how strong Gonzalo will be when it moves across the islands. 2. Despite the uncertainty in Gonzalo's future intensity, hurricane or tropical storm conditions are possible across portions of the southern Windward Islands Saturday and Saturday night. Hurricane and Tropical Storm Warning and Watches are currently in effect for some of the islands. Interests in the southern Windward Islands should monitor the progress of Gonzalo and follow any advice given by local officials. FORECAST POSITIONS AND MAX WINDS INIT 24/0900Z 10.0N 51.8W 50 KT 60 MPH 12H 24/1800Z 10.3N 53.9W 55 KT 65 MPH 24H 25/0600Z 11.0N 56.7W 60 KT 70 MPH 36H 25/1800Z 12.0N 59.9W 65 KT 75 MPH 48H 26/0600Z 13.0N 63.3W 55 KT 65 MPH 60H 26/1800Z 13.7N 66.6W 40 KT 45 MPH 72H 27/0600Z 14.0N 69.9W 35 KT 40 MPH 96H 28/0600Z...DISSIPATED $$ Forecaster Roberts
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Tropical Storm Hanna Forecast Discussion Number 6
2020-07-24 10:34:38| National Hurricane Center (Atlantic)
Issued at 400 AM CDT Fri Jul 24 2020 000 WTNT43 KNHC 240834 TCDAT3 Tropical Storm Hanna Discussion Number 6 NWS National Hurricane Center Miami FL AL082020 400 AM CDT Fri Jul 24 2020 Satellite imagery shows well-defined convective banding features over the eastern and southern portions of the circulation with some cooling of the cloud tops. This suggests that the associated thunderstorm activity is becoming more vigorous. However, surface observations over the Gulf and a scatterometer pass from a few hours ago indicate that the system has not strengthened further at this time. The current intensity estimate is held at 35 kt in agreement with a Dvorak classification from TAFB. A NOAA Hurricane Hunter aircraft is scheduled to investigate the storm later this morning and they should provide a good estimate of Hanna's intensity. The storm has an impressive upper-level anticyclonic outflow structure and should remain in a low shear environment until it reaches the coast. Therefore strengthening is likely prior to landfall and the NHC intensity forecast is near the model high end of the intensity model suite. The storm has moved a little faster toward the west-northwest over the past several hours, and the initial motion estimate is 290/8 kt. There is very little change to the official track forecast or reasoning from the previous cycle. A gradual turn toward the west is likely in 12 hours or so as a mid-level ridge to the north of Hanna builds a bit. The forecast track takes the center inland over Texas within the tropical storm warning area on Saturday. This is in good agreement with the dynamical model consensus and the latest ECMWF model solution. Key Messages 1. Hanna is forecast to strengthen and it is expected to bring tropical-storm-force winds to portions of the Texas coast, where a tropical storm warning is in effect. 2. Hanna is expected to produce heavy rains across portions of southern Texas. These rains could result in flash flooding and isolated minor to moderate river flooding. FORECAST POSITIONS AND MAX WINDS INIT 24/0900Z 26.7N 92.4W 35 KT 40 MPH 12H 24/1800Z 27.1N 93.7W 40 KT 45 MPH 24H 25/0600Z 27.3N 95.5W 50 KT 60 MPH 36H 25/1800Z 27.3N 97.1W 55 KT 65 MPH 48H 26/0600Z 27.2N 98.6W 40 KT 45 MPH...INLAND 60H 26/1800Z 26.5N 100.0W 30 KT 35 MPH...INLAND 72H 27/0600Z 26.0N 101.0W 20 KT 25 MPH...POST-TROP/REMNT LOW 96H 28/0600Z...DISSIPATED $$ Forecaster Pasch
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Tropical Storm Hanna Forecast Discussion Number 5
2020-07-24 04:58:03| National Hurricane Center (Atlantic)
Issued at 1000 PM CDT Thu Jul 23 2020 000 WTNT43 KNHC 240257 TCDAT3 Tropical Storm Hanna Discussion Number 5 NWS National Hurricane Center Miami FL AL082020 1000 PM CDT Thu Jul 23 2020 The system continues to organize with curved bands becoming better established around the center. The cyclone certainly has the appearance of a tropical storm, and just minutes ago the NOAA Hurricane Hunters found winds to support upgrading the system to a 35-kt tropical storm. Data from the aircraft also show that the minimum pressure has dropped to 1002 mb, indicating that the system is on a developing trend. Hanna is moving fairly slowly to the west-northwest, with the latest initial motion estimated to be 285/6 kt. This west-northwest motion should continue on Friday, but a turn to the west is expected by Friday night as a subtropical ridge strengthens to the north of the cyclone. This steering flow should take the center of the storm across the southern Texas coast in 36 to 48 hours. After landfall, the storm is forecast to turn south of west across extreme southern Texas and northern Mexico. The models have shifted southward again this cycle, and the NHC track forecast has been adjusted in that direction. Additional strengthening seems quite likely until the storm makes landfall since it is expected to remain over the very warm Gulf of Mexico waters and in generally low wind shear conditions. After landfall, steady weakening should commence, and the cyclone should dissipate over the rugged terrain of northern Mexico in about 4 days. The NHC intensity forecast is a little above the previous one and at the high end of the guidance given the system's well organized structure and favorable environment. Due to the southward shift in the track forecast, the tropical storm warning has been extended southward from Port Mansfield to the Mouth of the Rio Grande. Tropical Storm Hanna is the earliest 8th storm on record. The previous record was in 2005 when Harvey formed on August 3rd. Key Messages 1. Hanna is forecast to strengthen and it is expected to bring tropical-storm-force winds to portions of the Texas coast, where a tropical storm warning is in effect. 2. Hanna is expected to produce heavy rains across portions of Louisiana, southern Texas, and northern Mexico. These rains could result in flash flooding and isolated minor-to-moderate river flooding. FORECAST POSITIONS AND MAX WINDS INIT 24/0300Z 26.2N 91.4W 35 KT 40 MPH 12H 24/1200Z 26.6N 92.8W 40 KT 45 MPH 24H 25/0000Z 27.1N 94.5W 45 KT 50 MPH 36H 25/1200Z 27.2N 96.3W 55 KT 65 MPH 48H 26/0000Z 27.2N 97.8W 45 KT 50 MPH...INLAND 60H 26/1200Z 27.0N 99.3W 30 KT 35 MPH...INLAND 72H 27/0000Z 26.5N 100.5W 25 KT 30 MPH...INLAND 96H 28/0000Z...DISSIPATED $$ Forecaster Cangialosi
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