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Tropical Storm Jerry Forecast Discussion Number 30

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

Issued at 500 PM AST Tue Sep 24 2019 000 WTNT45 KNHC 242049 TCDAT5 Tropical Storm Jerry Discussion Number 30 NWS National Hurricane Center Miami FL AL102019 500 PM AST Tue Sep 24 2019 Jerry no longer looks like either a tropical or a subtropical cyclone, since it lacks deep convection within a couple of hundred miles of the center. This is likely due to a combination of strong shear and drier air. The advisory intensity of 45 kt is based on SFMR-observed surface winds from earlier Hurricane Hunter observations. Another Hurricane Hunter plane is scheduled to investigate Jerry in a few hours, and given the lack of convection, will likely find a weaker cyclone. The numerical guidance indicates that strong shear and increasingly drier air will affect Jerry over the next few days. Therefore, additional weakening is likely, and the system will probably become a remnant low in 72 hours or less, and completely dissipate by the end of the period. This is also shown by the global models. Jerry has moved quite slowly today, and the estimated initial motion is just east of northward, or 010/5 kt. Jerry should pass through a weakness in the subtropical ridge tonight. A broad mid-latitude trough to the north of the cyclone should soon cause the system to turn toward the northeast with an increase in forward speed. Later in the period, the cyclone should turn south of east while moving around the northeastern periphery of a subtropical ridge. The official track forecast is close to the previous one, and leans toward the corrected consensus model guidance. Key Messages: 1. Tropical-storm-force winds are expected on Bermuda by early 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 24/2100Z 31.1N 69.0W 45 KT 50 MPH 12H 25/0600Z 31.9N 67.9W 40 KT 45 MPH 24H 25/1800Z 32.9N 65.6W 35 KT 40 MPH 36H 26/0600Z 33.7N 62.8W 35 KT 40 MPH 48H 26/1800Z 34.4N 60.1W 25 KT 30 MPH 72H 27/1800Z 34.5N 56.5W 20 KT 25 MPH...POST-TROP/REMNT LOW 96H 28/1800Z 33.0N 54.0W 20 KT 25 MPH...POST-TROP/REMNT LOW 120H 29/1800Z...DISSIPATED $$ Forecaster Pasch

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Tropical Storm Lorenzo Forecast Discussion Number 8

2019-09-24 22:48:40| National Hurricane Center (Atlantic)

Issued at 500 PM AST Tue Sep 24 2019 000 WTNT43 KNHC 242048 TCDAT3 Tropical Storm Lorenzo Discussion Number 8 NWS National Hurricane Center Miami FL AL132019 500 PM AST Tue Sep 24 2019 Based on recent microwave imagery and visible satellite loops, it appears that there's been just enough westerly shear over Lorenzo to disrupt the inner core and keep the storm from strengthening through the day. The CDO is slightly offset from the low-level center, and prominent convective banding is mostly within the southeastern semicircle. Subjective intensity estimates remain T3.5/55 kt from TAFB and SAB, and objective numbers have come up slightly to around 60 kt. However, since the morning scatterometer data was running about 10 kt lower than the satellite estimates, and the overall structure has not changed appreciably, the initial intensity will remain 55 kt. A mid-level high centered west of Madeira and the Canary Islands continues to drive Lorenzo quickly westward, or 285/15 kt. There has been no change to the track forecast thinking. A break in the ridge over the central Atlantic is expected to cause Lorenzo to begin recurving in about 48 hours, with the system ultimately moving northward by the end of the foreast period. The updated NHC forecast has only been nudged westward, but this is mainly due to the slightly faster initial forward motion. Otherwise, the spread in the guidance is still bounded by the GFS on the right and the ECMWF on the left, which is mirrored by those models' respective ensemble members. The official forecast hedges toward the western side of the guidance, roughly between the HCCA model and the other consensus aids. Global model guidance suggests that the westerly shear over Lorenzo should abate during the next 24 hours, allowing another intensification phase to begin. Whether or not rapid intensification occurs is difficult to know at this point until it becomes clearer if the cyclone can develop a well-defined inner core. The intensity guidance has decreased further on this cycle, but this is largely due to the hiatus in the strengthening trend during the day. There's still plenty of time for more strengthening to occur, so out of an abundance of caution, I did not lower the forecast peak intensities that have been shown in the previous few advisories. As such, the official forecast lies above nearly all the guidance during the first 2-3 days, and then is close to the HWRF and HCCA on days 4 and 5. FORECAST POSITIONS AND MAX WINDS INIT 24/2100Z 12.8N 31.0W 55 KT 65 MPH 12H 25/0600Z 13.2N 33.0W 65 KT 75 MPH 24H 25/1800Z 13.8N 35.6W 75 KT 85 MPH 36H 26/0600Z 14.5N 38.1W 85 KT 100 MPH 48H 26/1800Z 15.6N 40.0W 90 KT 105 MPH 72H 27/1800Z 18.8N 42.9W 100 KT 115 MPH 96H 28/1800Z 21.9N 45.1W 105 KT 120 MPH 120H 29/1800Z 24.9N 45.3W 100 KT 115 MPH $$ Forecaster Berg

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Tropical Storm Kiko Forecast Discussion Number 49

2019-09-24 16:55:04| National Hurricane Center (East Pacific)

Issued at 500 AM HST Tue Sep 24 2019 000 WTPZ43 KNHC 241454 TCDEP3 Tropical Storm Kiko Discussion Number 49 NWS National Hurricane Center Miami FL EP132019 500 AM HST Tue Sep 24 2019 Forty to forty-five knots of south-southwesterly shear has caused Kiko's convection to become displaced from the low-level center by about 70 n mi. A blend of final-T and CI numbers from TAFB and SAB, as well as the latest ADT, supports lowering the initial intensity to 40 kt. The UW-CIMSS shear analysis indicates that Kiko is heading for even stronger shear during the next 6-12 hours, which should lead to further degradation in the cyclone's structure and a quick decrease in its maximum winds. The GFS and ECMWF simulated infrared satellite fields suggest that all deep convection could dissipate by 24 hours, and as a result, the time of Kiko's degeneration into a remnant low has been moved up to 36 hours in the official forecast. Dissipation is expected by day 4. Kiko's initial motion is northwestward, or 310/9 kt. The cyclone is moving between a mid-/upper-level low to its west and mid-level ridging to its northeast. However, once it loses its deep convection and becomes a shallow vortex, Kiko is expected to turn westward (by 36 hours) and then west-southwestward (by 48 hours). Only minor adjustments to the NHC track forecast were required, and on the forecast track, Kiko should cross 140W into the central Pacific basin later this afternoon. FORECAST POSITIONS AND MAX WINDS INIT 24/1500Z 17.9N 138.9W 40 KT 45 MPH 12H 25/0000Z 18.7N 140.1W 30 KT 35 MPH 24H 25/1200Z 19.4N 141.4W 25 KT 30 MPH 36H 26/0000Z 19.4N 142.6W 20 KT 25 MPH...POST-TROP/REMNT LOW 48H 26/1200Z 19.0N 143.7W 20 KT 25 MPH...POST-TROP/REMNT LOW 72H 27/1200Z 18.3N 146.2W 15 KT 15 MPH...POST-TROP/REMNT LOW 96H 28/1200Z...DISSIPATED $$ Forecaster Berg

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Tropical Storm Karen Forecast Discussion Number 10

2019-09-24 16:52:32| National Hurricane Center (Atlantic)

Issued at 1100 AM AST Tue Sep 24 2019 000 WTNT42 KNHC 241452 TCDAT2 Tropical Storm Karen Discussion Number 10 NWS National Hurricane Center Miami FL AL122019 1100 AM AST Tue Sep 24 2019 Satellite imagery and reports from an Air Force Reserve Hurricane Hunter aircraft show that there has been little change in either the structure or the intensity of Karen since the last advisory. The broad and elongated low-level center is located to the north of the strong convection, and the aircraft has reported a central pressure of 1007 mb and maximum 1500 ft flight-level winds of 35 kt south of the center. The initial intensity is held at 35 kt for this advisory. The initial motion is now 360/7. Karen is 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 northward today, followed by a north-northeastward motion that should continue for a couple of days. This motion should bring the center of Karen near or over Puerto Rico and the Virgin Islands this afternoon, 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 new forecast track will continue the trend of the previous forecast and the ECMWF model in showing the ridge building enough to turn Karen west-southwestward by 120 h. However, other models suggest a looping motion or little motion during the 96-120 h, and this part of the forecast track is quite uncertain. The large-scale models forecast the shear that has been affecting Karen to diminish during the next couple of days, which should allow the cyclone to gradually strengthen. 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. The new intensity forecast is unchanged from the previous forecast, and it 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 24/1500Z 17.5N 65.8W 35 KT 40 MPH 12H 25/0000Z 19.1N 65.4W 35 KT 40 MPH 24H 25/1200Z 21.3N 64.9W 40 KT 45 MPH 36H 26/0000Z 23.6N 64.1W 45 KT 50 MPH 48H 26/1200Z 25.5N 63.4W 50 KT 60 MPH 72H 27/1200Z 27.8N 62.0W 55 KT 65 MPH 96H 28/1200Z 28.0N 62.5W 60 KT 70 MPH 120H 29/1200Z 27.5N 65.0W 60 KT 70 MPH $$ Forecaster Beven

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Tropical Storm Jerry Forecast Discussion Number 29

2019-09-24 16:46:06| National Hurricane Center (Atlantic)

Issued at 1100 AM AST Tue Sep 24 2019 000 WTNT45 KNHC 241445 TCDAT5 Tropical Storm Jerry Discussion Number 29 NWS National Hurricane Center Miami FL AL102019 1100 AM AST Tue Sep 24 2019 Jerry's interaction with an upper-level trough has resulted in a system that is less tropical in appearance, with a lack of central convection and most of the heavier showers displaced to the west and well southeast of the center. In fact, the cyclone looks somewhat subtropical at this time. For simplicity, however, we will continue to carry Jerry as a tropical storm. Flight-level winds from an Air Force Reserve Unit Hurricane Hunter plane still support an intensity of 50 kt. Jerry will be encountering an increasingly unfavorable environment during the next few days, with the ambient air mass becoming drier and vertical shear becoming stronger. The official intensity forecast calls for continued weakening and degeneration to a remnant low later in the forecast period. This is similar to the consensus of the model guidance. Based on fixes from the Hurricane Hunters, the center has moved a little to the left of previous estimates, and the initial motion estimate is 350/6 kt. There are no significant changes to the track forecast philosophy, however. Over the next couple of days Jerry should turn northeastward and then east-northeastward in the flow to the south of a broad mid-latitude trough. Later in the period, the weakening cyclone should move eastward to east-southeastward on the northeast side of a subtropical anticyclone. The official track forecast is close to the previous one and in general agreement with the corrected multi-model consensus guidance. Key Messages: 1. Tropical-storm-force winds are expected on Bermuda by tonight or early 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 24/1500Z 30.8N 69.3W 50 KT 60 MPH 12H 25/0000Z 31.7N 68.5W 45 KT 50 MPH 24H 25/1200Z 32.6N 66.7W 40 KT 45 MPH 36H 26/0000Z 33.5N 64.2W 35 KT 40 MPH 48H 26/1200Z 34.2N 61.5W 30 KT 35 MPH 72H 27/1200Z 35.0N 57.4W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 28/1200Z 34.5N 54.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 29/1200Z...DISSIPATED $$ Forecaster Pasch

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