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Tropical Storm Kiko Forecast Discussion Number 23

2019-09-18 04:50:49| National Hurricane Center (East Pacific)

Issued at 800 PM PDT Tue Sep 17 2019 000 WTPZ43 KNHC 180250 TCDEP3 Tropical Storm Kiko Discussion Number 23 NWS National Hurricane Center Miami FL EP132019 800 PM PDT Tue Sep 17 2019 Kiko's convection has lacked some shape during the past few hours, with two main bursts observed near the center. Although subjective Dvorak Current Intensity numbers remain 3.5 (55 kt), ADT and SATCON estimates, as well as the afternoon ASCAT data, indicate that Kiko's winds are much weaker than that. The initial intensity is lowered to 45 kt as a compromise of all the available estimates, and even that could be generous. Kiko's future track looks like a roller coaster, with successive dips and rises in latitude resulting from cyclical strengthening and weakening of the mid-level ridge to the north. Although all of the models depict this general pattern, there is some model speed divergence after 36 hours. In the end, however, the updated NHC track forecast is very similar to the previous one, and it's close to the multi-model consensus aids and the HCCA model. Kiko has re-entered a zone of low shear, and it will soon be leaving an area of relatively low oceanic heat content. It may take a little time for the cyclone to feed off these better environmental conditions, but re-strengthening is anticipated to begin by 36 hours and continue for much of the forecast period. The new intensity forecast is just a little higher than the previous one, although it's not near the high end of the guidance envelope. Additional increases in the forecast peak intensity are possible in subsequent advisories if the higher-intensity models, including HCCA, don't come back down. FORECAST POSITIONS AND MAX WINDS INIT 18/0300Z 16.7N 125.5W 45 KT 50 MPH 12H 18/1200Z 16.4N 126.2W 45 KT 50 MPH 24H 19/0000Z 16.2N 127.3W 45 KT 50 MPH 36H 19/1200Z 16.2N 128.2W 50 KT 60 MPH 48H 20/0000Z 16.5N 128.9W 55 KT 65 MPH 72H 21/0000Z 17.0N 129.9W 65 KT 75 MPH 96H 22/0000Z 16.9N 131.4W 70 KT 80 MPH 120H 23/0000Z 15.9N 134.3W 70 KT 80 MPH $$ Forecaster Berg

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Tropical Depression Imelda Forecast Discussion Number 3

2019-09-18 04:48:45| National Hurricane Center (Atlantic)

Issued at 1000 PM CDT Tue Sep 17 2019 000 WTNT41 KNHC 180248 TCDAT1 Tropical Depression Imelda Discussion Number 3 NWS National Hurricane Center Miami FL AL112019 1000 PM CDT Tue Sep 17 2019 The center of the tropical cyclone continues to move farther inland over southeast Texas, with a motion estimate of 360/5 kt. Earlier surface observations along the coast indicated that the intensity had dropped below tropical storm strength, so the Tropical Storm Warning was discontinued. Although it has weakened, slow-moving Imelda will remain a rainfall/flood threat for at least the next couple of days. This is the last NHC advisory on Imelda. Future information on this system can be found in Public Advisories issued by the Weather Prediction Center beginning at 5 AM EDT, under AWIPS header TCPAT1, WMO header WTNT31 KWNH, and on the web at http://www.wpc.ncep.noaa.gov. Key Messages: 1. This system is likely to produce life-threatening flash flooding along portions of the Upper Texas Coast, including the Houston and Galveston areas. FORECAST POSITIONS AND MAX WINDS INIT 18/0300Z 29.8N 95.5W 30 KT 35 MPH...INLAND 12H 18/1200Z 30.5N 95.5W 25 KT 30 MPH...INLAND 24H 19/0000Z 31.2N 95.5W 25 KT 30 MPH...INLAND 36H 19/1200Z 31.8N 95.6W 25 KT 30 MPH...INLAND 48H 20/0000Z 32.7N 95.9W 20 KT 25 MPH...POST-TROP/REMNT LOW 72H 21/0000Z...DISSIPATED $$ Forecaster Pasch

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Tropical Storm Mario Forecast Discussion Number 3

2019-09-18 04:46:44| National Hurricane Center (East Pacific)

Issued at 900 PM MDT Tue Sep 17 2019 000 WTPZ44 KNHC 180246 TCDEP4 Tropical Storm Mario Discussion Number 3 NWS National Hurricane Center Miami FL EP142019 900 PM MDT Tue Sep 17 2019 Mario's center was partially exposed after the release of the previous advisory, but it is now covered by a new convective burst. The convection itself remains somewhat lopsided, favoring the southwestern quadrant due to strong upper-level easterly winds emanating away from the larger Tropical Storm Lorena to the east. Since subjective and objective satellite intensity estimates range from 30-40 kt, the initial intensity remains 35 kt on this advisory. The initial motion remains northwestward, or 325/8 kt. A mid-level ridge over Mexico should keep the cyclone on its northwestward trajectory for the next 2 days, but since the ridge retreats eastward a bit, Mario's forward motion is expected to decrease significantly during that time. By day 3, Mario and Lorena may get close enough to one another to cause Mario to almost stall. After day 3, Mario's track will mostly depend on Lorena's future, and there is significant model spread on days 4 and 5. The GFS has a stronger Lorena moving up near the Baja California peninsula, which pulls Mario farther toward the north and east. The ECMWF, on the other hand, dissipates Lorena near west-central Mexico, which allows Mario continue on a northwestward heading. For now, the official forecast splits the difference and closely follows the multi-model consensus aids and the HCCA model. Easterly to northeasterly shear is likely to continue over Mario during the next day or two, so only gradual strengthening is expected during that time. Vertical shear may decrease around the time that Mario stalls, and at that point the system is forecast to become a hurricane. Some weakening is anticipated by the end of the forecast period due to an increase in shear. The updated NHC intensity forecast is only slightly lower than the previous one based on the latest guidance. It should be noted that there is greater-than-normal uncertainty in this forecast since it is not known how much Mario and Lorena will interact in the coming days. FORECAST POSITIONS AND MAX WINDS INIT 18/0300Z 13.2N 109.3W 35 KT 40 MPH 12H 18/1200Z 14.2N 110.5W 40 KT 45 MPH 24H 19/0000Z 15.5N 112.0W 50 KT 60 MPH 36H 19/1200Z 16.3N 113.0W 55 KT 65 MPH 48H 20/0000Z 16.7N 113.5W 60 KT 70 MPH 72H 21/0000Z 16.9N 113.8W 65 KT 75 MPH 96H 22/0000Z 17.5N 114.3W 65 KT 75 MPH 120H 23/0000Z 19.4N 115.1W 55 KT 65 MPH $$ Forecaster Berg

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Hurricane Humberto Forecast Discussion Number 21

2019-09-17 22:46:41| National Hurricane Center (Atlantic)

Issued at 500 PM EDT Tue Sep 17 2019 754 WTNT44 KNHC 172046 TCDAT4 Hurricane Humberto Discussion Number 21 NWS National Hurricane Center Miami FL AL092019 500 PM EDT Tue Sep 17 2019 Humberto's satellite appearance has improved somewhat since the previous advisory, with the eye clearing out and becoming more distinct. This has resulted in satellite subjective intensity estimates increasing to T5.5/102 kt from TAFB and SAB, with objective ADT estimates from UW-CIMSS increasing to T5.9/112 kt. However, during the past 36 h or so, the satellite estimates have been running higher than the actual surface winds by about 10-15 percent. A 1425Z ASCAT-C overpass indicated surface winds of 72 kt in the southeastern eyewall, which is significant given that the scatterometer is well undersampling the actual peak winds due to the 25-km footprint of the instrument. The intensity has been increased to 90 kt based on the clearing and warming of the eye and allowing for some overestimation by the satellite agencies. The scatterometer wind data also showed that Humberto's wind field has expanded more since the earlier recon wind data, thus some additional adjustments were made to all of the wind radii in this advisory. Humberto continues to move east-northeastward or 075/10 kt. The large hurricane remains on track, and the latest NHC model guidance remains tightly packed around the previous advisory track. Thus, no significant changes were made to the previous forecast track through 48 hours. By 72 hours and beyond, however, the models are now in better agreement on Humberto accelerating and moving faster toward the northeast through 96 hours as an extratropical cyclone, followed by a turn toward the east-northeast on day 5. The official forecast track is based on a blend of the consensus models TVCN, HCCA, and FSSE, and shows the center of Humberto passing just to the northwest and north of Bermuda between 24-36 hours or late Wednesday night. The latest SHIPS intensity guidance shows near 30 kt of deep-layer vertical shear allegedly affecting Humberto, which obviously is a significant overestimate based on the presence of a well-defined eye and smooth CDO feature in visible satellite imagery. Given the likely overestimation of the shear values, Humberto is expected to strengthen to major hurricane status in the next 24 h. Thereafter, Humberto is forecast to steadily weaken due to cold upwelling as the hurricane moves over cooler waters, and into an environment consisting of very strong shear exceeding 40-50 kt and more stable, drier air. However, the usual rate of weakening due to the strong shear conditions is expected to be tempered by the increasing baroclinic forcing in the right-rear entrance region of a strong jetstream wind maximum. The NHC intensity closely follows a blend of the intensity consensus models IVCN, HCCA, and FSSE. Key Messages: 1. Hurricane conditions are expected in Bermuda Wednesday night and Thursday morning, with tropical-storm-force winds expected by Wednesday afternoon. Residents there should follow advice given by local officials. 2. Storm surge and dangerous breaking waves could cause coastal flooding Wednesday night and Thursday along the southern coast of Bermuda. 3. Swells will continue to affect the northwestern Bahamas and the southeastern coast of the United States from east-central Florida to North Carolina during the next couple of days, creating life- threatening surf and rip current conditions. FORECAST POSITIONS AND MAX WINDS INIT 17/2100Z 31.0N 72.3W 90 KT 105 MPH 12H 18/0600Z 31.5N 70.5W 95 KT 110 MPH 24H 18/1800Z 32.6N 67.6W 100 KT 115 MPH 36H 19/0600Z 34.6N 63.9W 95 KT 110 MPH 48H 19/1800Z 37.4N 61.0W 85 KT 100 MPH 72H 20/1800Z 41.5N 57.2W 65 KT 75 MPH 96H 21/1800Z 43.5N 48.5W 55 KT 65 MPH...POST-TROP/EXTRATROP 120H 22/1800Z 46.0N 34.0W 50 KT 60 MPH...POST-TROP/EXTRATROP $$ Forecaster Stewart

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Tropical Storm Lorena Forecast Discussion Number 2

2019-09-17 22:41:47| National Hurricane Center (East Pacific)

Issued at 400 PM CDT Tue Sep 17 2019 000 WTPZ45 KNHC 172041 TCDEP5 Tropical Storm Lorena Discussion Number 2 NWS National Hurricane Center Miami FL EP152019 400 PM CDT Tue Sep 17 2019 A pair of ASCAT passes sampled the circulation of Lorena earlier this afternoon and showed multiple 40-45 kt wind vectors. Based on that data, the initial wind speed has been increased to 45 kt for this advisory. Lorena's cloud structure has improved somewhat during the afternoon, though Dvorak-based wind estimates are still notably lower than the ASCAT winds. The track models have come into much better agreement, and there has been a large shift eastward in the track guidance. However, since the NHC track forecast was previously on the east side of the guidance envelope, only a slight eastward shift was made to the official forecast. Lorena is still expected to move generally northwestward for the next day or two, and should move over or very near the southwestern coast of Mexico by late Wednesday or early Thursday. If the circulation survives its interaction with land, it should continue to head northwestward, perhaps toward the Baja California peninsula. That said, this portion of the forecast is highly conditional, and Lorena may end up just dissipating over the high terrain of Mexico. The NHC track forecast is now very close to TVCN and HCCA, especially through 72 h, and confidence in the track forecast has increased. The tropical storm has strengthened, and conditions appear favorable for additional slow strengthening. Once the circulation approaches the coast of Mexico, its intensity will become closely tied to its track. If Lorena moves inland, it will likely weaken quickly and could dissipate entirely shortly thereafter. If it stays offshore, it could maintain its strength and even intensify further as it moves away from the coast of Mexico later this week, as shown by the HWRF, DSHP, and LGEM models. The NHC intensity forecast is consistent with the track forecast, and therefore shows Lorena weakening due to land interaction after 48 h, but is below the intensity consensus since a number of those models keep the cyclone farther from the coast. Key Messages: 1. Lorena is forecast to cause heavy rain over portions of the Mexican states of Guerrero, Michoacan, Colima, and Jalisco during the next few days. This rainfall may produce life-threatening flash flooding and mudslides. 2. Tropical storm conditions are expected along a portion of the southwestern coast of Mexico by late Wednesday. FORECAST POSITIONS AND MAX WINDS INIT 17/2100Z 14.6N 101.3W 45 KT 50 MPH 12H 18/0600Z 15.7N 102.3W 50 KT 60 MPH 24H 18/1800Z 17.3N 103.3W 55 KT 65 MPH 36H 19/0600Z 18.5N 104.1W 55 KT 65 MPH 48H 19/1800Z 19.2N 104.8W 55 KT 65 MPH...NEAR THE COAST 72H 20/1800Z 20.5N 106.5W 40 KT 45 MPH 96H 21/1800Z 22.0N 109.5W 35 KT 40 MPH 120H 22/1800Z 23.5N 112.0W 35 KT 40 MPH $$ Forecaster Zelinsky

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