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Hurricane Delta Forecast Discussion Number 6

2020-10-06 04:55:10| National Hurricane Center (Atlantic)

Issued at 1100 PM EDT Mon Oct 05 2020 000 WTNT41 KNHC 060255 TCDAT1 Hurricane Delta Discussion Number 6 NWS National Hurricane Center Miami FL AL262020 1100 PM EDT Mon Oct 05 2020 A few hours ago, data from the NOAA Hurricane Hunters supported upgrading Delta to a hurricane. Very recent reports from the Air Force Hurricane Hunters, who are currently in Delta, support increasing the intensity a little more to 70 kt. The minimum pressure has also decreased a few mb from the NOAA mission, and is now estimated to be 977 mb. Delta has strengthened at a rapid rate of 40 kt since genesis occurred just 24 hours ago. The hurricane is quite compact with a developing tight inner core, and even the tropical-storm-force winds extend only up to 60 n mi or so from the center. After moving westward for much of the day, aircraft fixes from NOAA and the Air Force indicate that the hurricane has resumed a west-northwest motion, with the latest initial motion estimated to be 295/6 kt. Delta is expected to move to the northwest at a fairly quick pace on Tuesday and Wednesday as it moves in the flow between a subtropical high over the western Atlantic and Post-Tropical Cyclone Gamma over or near the Yucatan Peninsula. This motion should take Delta over or very near the northeastern portion of the Yucatan Peninsula by Tuesday night and over the southern Gulf of Mexico on Wednesday. After that time, the western part of the ridge is expected to slowly erode as a trough moves eastward across the south-central U.S. This change in the steering pattern should cause Delta to slow down and then turn northward toward the northern Gulf coast, and it will likely make landfall there in a little more than 4 days. The models are in fair agreement, and the NHC track forecast is only a touch to the west of the previous one. The hurricane has taken advantage of the near ideal conditions of low vertical wind shear, high amounts of moisture, and very warm 29-30 C SSTs. These favorable environmental conditions for the hurricane will persist for the next 2 or 3 days or so, and therefore, it seems reasonable to believe that rapid intensification will continue in the short term. Delta is expected to become a major hurricane in about 24 hours when it is near the Yuctan Peninsula. If Delta makes landfall on that landmass, it would likely temper the cyclone's strength for a period of time. Beyond a few days, when Delta is forecast to approach the northern Gulf coast, there will likely be an increase in southwesterly wind shear. These less conducive upper-level winds and cooler shelf waters should end the strengthening trend prior to the U.S. landfall. The NHC intensity forecast is largely an update of the previous one and lies close to the HCCA and IVCN consensus models. Users are reminded to not focus on the details of the track or intensity forecasts, as the average 4-day track error is around 150 miles and the average 4-day intensity error is close to 15 mph. Key Messages: 1. Dangerous storm surge and hurricane conditions are expected within portions of the northern Yucatan Peninsula of Mexico beginning Tuesday night, and a Hurricane Warning is in effect. 2. Heavy rainfall will affect portions of Jamaica, the Cayman Islands, western Cuba and the northern Yucatan Peninsula during the next few days. This rainfall could lead to significant flash flooding and mudslides. 3. Tropical storm conditions are expected in portions of the Cayman Islands beginning early Tuesday, and a Tropical Storm Warning is in effect. 4. Delta is forecast to approach the northern Gulf Coast late this week as a hurricane. While there is large uncertainty in the track and intensity forecasts, there is an increasing risk of dangerous storm surge, wind, and rainfall hazards along the coast from Louisiana to the western Florida Panhandle beginning Thursday night or Friday. Residents in these areas should ensure they have their hurricane plan in place and monitor updates to the forecast of Delta. FORECAST POSITIONS AND MAX WINDS INIT 06/0300Z 16.8N 80.3W 70 KT 80 MPH 12H 06/1200Z 18.1N 82.0W 85 KT 100 MPH 24H 07/0000Z 19.8N 84.6W 100 KT 115 MPH 36H 07/1200Z 21.5N 87.1W 105 KT 120 MPH...INLAND 48H 08/0000Z 23.0N 89.5W 105 KT 120 MPH 60H 08/1200Z 24.0N 90.8W 105 KT 120 MPH 72H 09/0000Z 25.2N 91.7W 100 KT 115 MPH 96H 10/0000Z 28.6N 91.2W 85 KT 100 MPH 120H 11/0000Z 33.6N 88.4W 35 KT 40 MPH...INLAND $$ Forecaster Cangialosi

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Tropical Depression Nineteen-E Forecast Discussion Number 2

2020-10-06 04:51:09| National Hurricane Center (East Pacific)

Issued at 1000 PM CDT Mon Oct 05 2020 000 WTPZ44 KNHC 060251 TCDEP4 Tropical Depression Nineteen-E Discussion Number 2 NWS National Hurricane Center Miami FL EP192020 1000 PM CDT Mon Oct 05 2020 Tropical Depression Nineteen-E is beginning to show better signs of organization tonight. Recent satellite imagery depicts a burst of deep convection near the estimated center of the depression with cloud top temperatures colder than -70 degrees Celsius. This trend, along with recent UW-CIMSS ADT estimates, suggests the system may be nearing tropical storm strength. The initial intensity is perhaps conservatively held at 30 kt for this advisory based on earlier T2.0 classifications from TAFB and SAB. The estimated initial motion of the depression remains 340/6 kt. This general motion should continue through the overnight hours as the system is steered by a mid-level ridge over southern Mexico. As the ridge weakens through the middle of the week, the steering currents will break down and the system will likely meander well offshore of the southwestern coast of Mexico for several days. By days 4-5, global models indicate the ridge should rebuild over southern Mexico, which would eventually support a northwestward motion late in the forecast period. The NHC forecast track shows little change with this advisory, and remains close to the HFIP corrected consensus HCCA. The intensity forecast remains challenging with above average spread in the guidance. The environmental conditions generally appear favorable, with low to moderate deep-layer wind shear and warm sea surface temperatures. The statistical-dynamical SHIPS guidance indicates gradual strengthening will occur over the next several days. However, global models including the GFS and ECMWF, along with the HWRF and HMON, forecast little intensity change or even weakening as the system meanders well offshore. This could be a product of the system struggling to separate from the Intertropical Convergence Zone (ITCZ), or possible upwelling as it drifts over the same general area for several days. Given these mixed signals in the guidance, the NHC intensity forecast remains close to the previous advisory and only shows modest strengthening during the forecast period. This forecast still lies slightly above the IVCN and HCCA consensus aids. FORECAST POSITIONS AND MAX WINDS INIT 06/0300Z 13.3N 105.6W 30 KT 35 MPH 12H 06/1200Z 13.8N 106.1W 35 KT 40 MPH 24H 07/0000Z 14.0N 106.6W 35 KT 40 MPH 36H 07/1200Z 13.8N 106.6W 35 KT 40 MPH 48H 08/0000Z 13.7N 106.5W 35 KT 40 MPH 60H 08/1200Z 13.9N 106.5W 35 KT 40 MPH 72H 09/0000Z 14.1N 106.6W 40 KT 45 MPH 96H 10/0000Z 14.5N 107.5W 40 KT 45 MPH 120H 11/0000Z 15.0N 108.5W 40 KT 45 MPH $$ Forecaster Reinhart/Zelinsky

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Tropical Storm Marie Forecast Discussion Number 28

2020-10-06 04:33:38| National Hurricane Center (East Pacific)

Issued at 500 PM HST Mon Oct 05 2020 000 WTPZ43 KNHC 060233 TCDEP3 Tropical Storm Marie Discussion Number 28 NWS National Hurricane Center Miami FL EP182020 500 PM HST Mon Oct 05 2020 Marie is making one last grasp at holding on to tropical cyclone status. Convection has both deepened and moved closer to the center of the cyclone since the last advisory. Although this convection is still displaced well to the north of Marie's center, it appears to be sufficient to maintain advisories for the moment. The initial intensity of 40 kt is based on earlier ASCAT data, assuming gradual weakening since then. This assessment may be generous, but we will likely get more scatterometer data before the next advisory. Despite its recent marginal convective resurgence, Marie is still moving over cold SSTs and through a hostile environment. It is therefore forecast to become a remnant low within 12 h. The aforementioned ASCAT data showed Marie was still producing a wide area of 35 kt or greater winds, and it will take a little while for the large circulation to spin down. Most of the models indicate that Marie will degenerate into a trough of low pressure in about 4 days, and this is reflected in the NHC forecast. FORECAST POSITIONS AND MAX WINDS INIT 06/0300Z 21.4N 133.5W 40 KT 45 MPH 12H 06/1200Z 21.9N 134.7W 35 KT 40 MPH...POST-TROP/REMNT LOW 24H 07/0000Z 22.5N 136.2W 30 KT 35 MPH...POST-TROP/REMNT LOW 36H 07/1200Z 22.9N 137.3W 30 KT 35 MPH...POST-TROP/REMNT LOW 48H 08/0000Z 23.1N 138.2W 30 KT 35 MPH...POST-TROP/REMNT LOW 60H 08/1200Z 23.0N 139.2W 25 KT 30 MPH...POST-TROP/REMNT LOW 72H 09/0000Z 22.9N 140.3W 20 KT 25 MPH...POST-TROP/REMNT LOW 96H 10/0000Z...DISSIPATED $$ Forecaster Zelinsky

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Post-Tropical Cyclone Gamma Forecast Discussion Number 15

2020-10-06 04:31:40| National Hurricane Center (Atlantic)

Issued at 1000 PM CDT Mon Oct 05 2020 000 WTNT45 KNHC 060231 TCDAT5 Post-Tropical Cyclone Gamma Discussion Number 15 NWS National Hurricane Center Miami FL AL252020 1000 PM CDT Mon Oct 05 2020 Gamma was entirely devoid of convection for most of the day. Shortly before sunset, a few disorganized thunderstorms developed to the southeast of the cyclone's center, however these appear to be forced at least in part by a sea breeze boundary and are not exclusively associated with Gamma. A few other small cells of convection have developed to the west of Gamma's center during the past hour or so, but not nearly enough to be considered sufficiently organized to meet the requirement for a tropical cyclone. Gamma is therefore now considered to be post-tropical and this will be the last NHC advisory. The cyclone could still produce some additional disorganized convection and periods of heavy rain overnight as it moves inland over the Yucatan peninsula, but this is not expected to result in significant regeneration. Some of this rain could impact areas that are preparing for the much more significant approach of Hurricane Delta in a day or so. The cyclone is moving southwestward near 5 kt, and this should continue for another day or so until it dissipates. The winds associated with Gamma's remnants should gradually weaken through that time, though the system could still produce a few areas of heavy rain over southeastern Mexico. It is worth noting that several model trackers, and consequently the consensus aids, depict that Gamma will move northward over the Gulf of Mexico and strengthen significantly in a couple of days. This is because the trackers lose track of Gamma when it dissipates and start following nearby Hurricane Delta instead. In reality, no models forecast that Gamma will remain a well-defined cyclone for more than another day or two. FORECAST POSITIONS AND MAX WINDS INIT 06/0300Z 21.6N 88.4W 30 KT 35 MPH...POST-TROPICAL 12H 06/1200Z 21.1N 88.9W 30 KT 35 MPH...POST-TROP/INLAND 24H 07/0000Z 20.2N 89.6W 25 KT 30 MPH...POST-TROP/INLAND 36H 07/1200Z...DISSIPATED $$ Forecaster Zelinsky

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Tropical Depression Nineteen-E Forecast Discussion Number 1

2020-10-05 22:58:39| National Hurricane Center (East Pacific)

Issued at 400 PM CDT Mon Oct 05 2020 000 WTPZ44 KNHC 052058 TCDEP4 Tropical Depression Nineteen-E Discussion Number 1 NWS National Hurricane Center Miami FL EP192020 400 PM CDT Mon Oct 05 2020 Satellite imagery and ASCAT-C data indicate that the area of low pressure located several hundred miles south of the southwestern coast of Mexico has become better-defined today. The associated deep convection has also become more organized and convection has persisted over the low-level center since early this morning. In addition, a banding feature has also developed over the western portion of the circulation. Based on these trends, advisories have been initiated for Tropical Depression Nineteen-E. The ASCAT data showed winds as high as 32 kt. However, these vectors were at the very edge of the data swath, and may be unreliable. The initial intensity of 30 kt is therefore based off the latest Dvorak intensity estimate from TAFB. The forecast for the depression is not straightforward and there is a larger than normal amount of uncertainty for both the future track and intensity of the cyclone. The global models generally do not favor much strengthening beyond 24 h and some of the guidance, including the GFS and HWRF indicate weakening. On the other hand, the SHIPS guidance suggests gradual strengthening and indicate the cyclone could be near hurricane intensity by the end of the 5-day forecast period. The overall environment appears conducive for the depression to intensify over the next several days, with very warm SSTs, low vertical wind shear, and plenty of atmospheric moisture to work with. One negative influence that the global models could be picking up on is an ongoing interaction with the larger scale Intertropical Convergence Zone (ITCZ). The NHC forecast, out of respect for the skilled global and dynamical models, does not show as a robust rate of strengthening as suggested by the SHIPS guidance. However, some intensification is indicated throughout the forecast period due to the aforementioned favorable environmental factors. The initial motion of the depression is 340/6 kt. This motion is expected to continue through tonight as the depression is steered by a mid-level ridge centered over southern Mexico. The ridge is forecast to weaken tomorrow and steering currents over the depression are expected to collapse through the middle of the week. The track guidance is highly divergent after 48 h, as the models appear to steer the cyclone in varying directions based off the interaction with the ITCZ in the midst of weak synoptic steering. By the end of the forecast period, the models are generally in better agreement on a slow northwesterly motion as the ridge rebuilds to the northeast of the cyclone. The NHC track forecast lies near the HFIP corrected consensus HCCA. FORECAST POSITIONS AND MAX WINDS INIT 05/2100Z 12.8N 105.4W 30 KT 35 MPH 12H 06/0600Z 13.5N 105.9W 35 KT 40 MPH 24H 06/1800Z 13.9N 106.5W 35 KT 40 MPH 36H 07/0600Z 13.7N 106.8W 35 KT 40 MPH 48H 07/1800Z 13.5N 106.8W 40 KT 45 MPH 60H 08/0600Z 13.5N 106.6W 40 KT 45 MPH 72H 08/1800Z 13.6N 106.5W 40 KT 45 MPH 96H 09/1800Z 13.7N 106.9W 45 KT 50 MPH 120H 10/1800Z 14.7N 108.2W 45 KT 50 MPH $$ Forecaster Latto

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