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Tropical Storm Jerry Forecast Discussion Number 31

2019-09-25 04:40:49| National Hurricane Center (Atlantic)

Issued at 1100 PM AST Tue Sep 24 2019 000 WTNT45 KNHC 250240 TCDAT5 Tropical Storm Jerry Discussion Number 31 NWS National Hurricane Center Miami FL AL102019 1100 PM AST Tue Sep 24 2019 Dry air and shear have continued to take a toll on Jerry, and the cyclone has been devoid of deep convection for about 12 hours. An Air Force reconnaissance aircraft that has been in the storm this evening measured peak flight-level winds of 43 kt, and SFMR winds of 34 to 36 kt. The aircraft has not sampled the entire circulation yet, so the initial intensity has been lowered, perhaps conservatively, to 40 kt. Increasing shear and dry air that is being entrained into the circulation from the west are likely to continue to contribute to Jerry's gradual spin down over the next couple of days. If deep convection does not return overnight, Jerry could become a post-tropical cyclone as early as tomorrow morning. Regardless of the status of the system, it still has the potential to bring tropical-storm-force winds to Bermuda and advisories would continue as long as the Tropical Storm Warning is needed for that island. The global models completely dissipate Jerry in a little more than 3 days, and so does the new NHC forecast. Jerry has turned northeastward but continues to move very slowly, or 025/4 kt. The cyclone should pick up its pace tonight and Wednesday as a broad trough passes to the north and the system gets caught within the southern edge of the mid-latitude westerlies. As Jerry get increasingly weaker it is forecast to again slow down and turn southeastward before dissipation occurs. The official track forecast is not very different than the previous advisory, and is closest to the TCVN multi-model consensus. Key Messages: 1. Tropical-storm-force winds are expected on Bermuda beginning on Wednesday. Large swells are also expected to affect the coast of Bermuda during the next few days. These swells could cause life-threatening rip currents. See products issued by the Bermuda Weather Service for more information. FORECAST POSITIONS AND MAX WINDS INIT 25/0300Z 31.4N 68.7W 40 KT 45 MPH 12H 25/1200Z 32.2N 67.3W 35 KT 40 MPH 24H 26/0000Z 33.0N 64.9W 35 KT 40 MPH 36H 26/1200Z 33.8N 62.3W 30 KT 35 MPH...POST-TROP/REMNT LOW 48H 27/0000Z 34.4N 59.9W 25 KT 30 MPH...POST-TROP/REMNT LOW 72H 28/0000Z 34.0N 56.5W 20 KT 25 MPH...POST-TROP/REMNT LOW 96H 29/0000Z...DISSIPATED $$ Forecaster Brown

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Tropical Storm Karen Forecast Discussion Number 12

2019-09-25 04:37:49| National Hurricane Center (Atlantic)

Issued at 1100 PM AST Tue Sep 24 2019 000 WTNT42 KNHC 250237 TCDAT2 Tropical Storm Karen Discussion Number 12 NWS National Hurricane Center Miami FL AL122019 1100 PM AST Tue Sep 24 2019 During the afternoon and early evening hours, satellite images indicated that the cloud pattern associated with Karen was becoming a little better organized. Then, surface observations from the area just east of Puerto Rico indicated that the pressures were falling, and a center was apparently becoming better defined. The presence of this center was confirmed by a reconnaissance plane which was able to fix a tight small circulation of about 1002 or 1003 mb. This, by no means, indicates that the overall circulation of the cyclone is well organized. Winds are still swirly on the western portion of the circulation and are responding to an elongated trough of low pressure north of Puerto Rico. In fact, I would not be surprised if another center reforms father to west within the trough or the large cyclonic envelope, and the center we are tracking dissipates. In any case, preliminary analysis indicates that the center of Karen that we were tracking moved very near or over Vieques around 2100 UTC and then over Culebra a little bit later. This small center could also have been a meso-vortex within the larger circulation. Data from the reconnaissance plane and satellite intensity estimates yield an initial intensity of 40 kt. These winds are occurring primarily to the southeast of the center. Karen is heading toward a shear environment that is not ideal at all for significant intensification. As previously indicated, the NHC forecast calls for a very modest increase in intensity during the next 3 to 5 days as indicated by the HCCA model. However, some of the statistical guidance brings Karen to hurricane status by the end of the forecast period. Satellite and reconnaissance fixes indicate that Karen is moving toward the north-northeast or 015 degrees at 12 kt. This motion however, is highly uncertain because it includes the reformation of the center. The circulation of Karen is trapped between a subtropical high over the Atlantic and a mid-level trough over the Bahamas. This flow pattern will continue to steer Karen in this same generaldirection for the next 3 days. After that time, the steering flow is forecast to collapse, and Karen, if it is still a cyclone, will begin to meander. This would allow another ridge to develop north of the cyclone and force it to move westward. This is the solution provided by most of the global models. Key Messages: 1. Karen will continue to bring heavy rainfall, flash floods and mudslides to Puerto Rico, Vieques and the U.S. and British Virgin Islands into Wednesday even as the center moves away from the region. FORECAST POSITIONS AND MAX WINDS INIT 25/0300Z 19.1N 65.0W 40 KT 45 MPH 12H 25/1200Z 20.8N 64.6W 45 KT 50 MPH 24H 26/0000Z 23.2N 64.0W 45 KT 50 MPH 36H 26/1200Z 25.5N 63.4W 50 KT 60 MPH 48H 27/0000Z 27.0N 62.5W 55 KT 65 MPH 72H 28/0000Z 26.8N 61.5W 55 KT 65 MPH 96H 29/0000Z 26.5N 61.5W 55 KT 65 MPH 120H 30/0000Z 26.0N 65.5W 55 KT 65 MPH $$ Forecaster Avila

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Tropical Storm Lorenzo Forecast Discussion Number 9

2019-09-25 04:36:48| National Hurricane Center (Atlantic)

Issued at 1100 PM AST Tue Sep 24 2019 000 WTNT43 KNHC 250236 TCDAT3 Tropical Storm Lorenzo Discussion Number 9 NWS National Hurricane Center Miami FL AL132019 1100 PM AST Tue Sep 24 2019 Over the past several hours, deep convection has increased in coverage and intensity near Lorenzo's center, with cloud tops now as cold as -85 degrees Celsius. Some modest northwesterly shear impacted the cyclone starting early today and lasted through this evening, but now Lorenzo seems to be overcoming the shear. The initial intensity has been increased to 60 kt and this is a blend of the latest subjective Dvorak estimates from TAFB and SAB. Recent scatterometer passes show that the wind radii have continued to expand, with tropical storm force winds now reaching up to 180 n mi from the center. Lorenzo is moving west-northwestward at 14 kt to the south of a mid-level ridge. A break in the ridge is forecast to develop between 40-50W in a few days, which should cause the cyclone to turn to the northwest. By late in the forecast period, Lorenzo will turn to the north as it rounds the western periphery of the ridge. This forecast track scenario is in very good agreement with the numerical models, and little change was made from the previous official forecast. The shear that has been occurring over Lorenzo is expected to decrease through Wednesday, and based on the current convective trend, strengthening appears likely over the next couple of days. Dynamical and statistical models are in good agreement on bringing Lorenzo to hurricane intensity by Wednesday morning, and then continuing some gradual strengthening through 72 hours. After that time, the dynamical model intensity forecasts diverge from the statistical model forecasts. SHIPS and LGEM suggest that Lorenzo will reach its peak intensity in about 3 or 4 days, and weakening is possible by day 5. The dynamical models disagree with this scenario, and the consensus of those models makes Lorenzo a major hurricane in about 72 hours, with additional strengthening possible through the end of the forecast period. The official forecast is more in line with the dynamical guidance, although it is not as high as some of those solutions late in the period. Due to the divergence in model intensity forecasts beyond 72 hours, the confidence in the official forecast at that time is not high. FORECAST POSITIONS AND MAX WINDS INIT 25/0300Z 13.2N 32.4W 60 KT 70 MPH 12H 25/1200Z 13.6N 34.4W 70 KT 80 MPH 24H 26/0000Z 14.2N 37.0W 80 KT 90 MPH 36H 26/1200Z 15.1N 39.1W 90 KT 105 MPH 48H 27/0000Z 16.4N 40.9W 95 KT 110 MPH 72H 28/0000Z 19.9N 43.6W 100 KT 115 MPH 96H 29/0000Z 23.0N 45.5W 105 KT 120 MPH 120H 30/0000Z 26.0N 45.0W 105 KT 120 MPH $$ Forecaster Latto

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Tropical Storm Kiko Forecast Discussion Number 50

2019-09-24 22:51:12| National Hurricane Center (East Pacific)

Issued at 1100 AM HST Tue Sep 24 2019 000 WTPZ43 KNHC 242051 TCDEP3 Tropical Storm Kiko Discussion Number 50 NWS National Hurricane Center Miami FL EP132019 Issued by NWS Central Pacific Hurricane Center Honolulu HI 1100 AM HST Tue Sep 24 2019 Kiko is now a swirl of low clouds devoid of deep convection in the face of 40 kt of southwest shear as analyzed by UW-CIMSS. The initial intensity was lowered to 35 kt, though ADT and ASCAT passes just coming in suggest this may be a bit generous. Strong southwest shear is expected to continue to prevent the development of persistent deep convection through the forecast period. This will allow the low-level center to turn westward, and then southwestward following the trade wind flow and weaken. The current forecast lies very close to the previous one. Without deep convection, Kiko's wind field should continue to steadily spin down. Kiko will be moving into the central Pacific basin this afternoon and subsequent advisories will be issued by the Central Pacific Hurricane Center. Products will continue to be available on the web at hurricanes.gov. FORECAST POSITIONS AND MAX WINDS INIT 24/2100Z 18.0N 139.6W 35 KT 40 MPH 12H 25/0600Z 18.5N 140.7W 30 KT 35 MPH 24H 25/1800Z 18.9N 142.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 36H 26/0600Z 18.8N 143.2W 20 KT 25 MPH...POST-TROP/REMNT LOW 48H 26/1800Z 18.5N 144.3W 20 KT 25 MPH...POST-TROP/REMNT LOW 72H 27/1800Z...DISSIPATED $$ Forecaster R Ballard

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Tropical Storm Karen Forecast Discussion Number 11

2019-09-24 22:49:14| National Hurricane Center (Atlantic)

Issued at 500 PM AST Tue Sep 24 2019 000 WTNT42 KNHC 242049 TCDAT2 Tropical Storm Karen Discussion Number 11 NWS National Hurricane Center Miami FL AL122019 500 PM AST Tue Sep 24 2019 The satellite appearance of Karen has improved over the past several hours, with a large convective band wrapped about halfway around the center in the western semicircle and an outer band in the southeastern semicircle. However, surface observations, Doppler radar data, and reports from an Air Force Reserve Hurricane Hunter aircraft indicate that the low-level circulation is elongated from south to north and that multiple vorticity centers are present. The lowest pressures and the strongest winds are at the southern end of the elongation near the eastern end of the convective band, and this is the center used for this advisory. The Hurricane Hunter aircraft reported 53 kt flight-level winds at 850 mb and data suggesting a central pressure near 1005 mb, so the initial intensity is increased to 40 kt. The initial motion is again 360/7, with some uncertainty due to the multiple vorticity centers and an apparent re-formation of the center closer to the convection between 15Z-18Z. Karen remains in a complex steering environment that includes a low- to mid-level ridge to the east and northeast, Tropical Storm Jerry to the north- northwest, and a large mid- to upper-level trough extending from near Jerry to eastern Cuba. These weather systems should steer Karen generally north-northeastward for the next couple of days. This motion should bring the center of Karen near or over Puerto Rico and the Virgin Islands during the next few hours and then into the open Atlantic tonight. During the 72-120 h period, the large-scale models forecast a low- to mid-level ridge to build near Karen, which will significantly slow its forward motion. The track guidance is in somewhat better agreement that this ridge will cause Karen to turn westward near the end of the forecast period, although there remains a lot of uncertainty about when and how fast. The new forecast track keeps Karen a little farther south before this turn occurs, and thus the 120-h position is a little to the south of the previous forecast. Karen is moving into an area of weaker shear, and should remain in that environment for the next 2-3 days. Thus, strengthening is expected, with the main limiting factor being the current poor organization of the circulation. From 72-120 h, the storm is expected to start entraining dry air, which could limit intensification despite the otherwise favorable shear and sea surface temperature environment. In addition, several of the global models suggest that another round of shear could affect Karen near the 120 h point. If this occurs, the cyclone could end up weaker than forecast in this advisory. The new intensity forecast has minor changes from the previous forecast, and it again lies between the weaker dynamical models and the stronger statistical-dynamical models. Key Messages: 1. Karen is expected to bring heavy rainfall, flash floods and mudslides to Puerto Rico and the U.S. and British Virgin Islands today, where a tropical storm warning is in effect. The rainfall and potential flooding will likely continue on Wednesday even as the center of Karen moves away from Puerto Rico and the Virgin Islands. FORECAST POSITIONS AND MAX WINDS INIT 24/2100Z 18.0N 65.8W 40 KT 45 MPH 12H 25/0600Z 19.6N 65.5W 40 KT 45 MPH 24H 25/1800Z 21.9N 64.9W 45 KT 50 MPH 36H 26/0600Z 24.2N 64.2W 50 KT 60 MPH 48H 26/1800Z 25.9N 63.5W 50 KT 60 MPH 72H 27/1800Z 27.2N 61.9W 55 KT 65 MPH 96H 28/1800Z 27.0N 62.5W 60 KT 70 MPH 120H 29/1800Z 26.5N 65.5W 60 KT 70 MPH $$ Forecaster Beven

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