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Tropical Storm Kiko Forecast Discussion Number 45

2019-09-23 16:43:54| National Hurricane Center (East Pacific)

Issued at 500 AM HST Mon Sep 23 2019 000 WTPZ43 KNHC 231443 TCDEP3 Tropical Storm Kiko Discussion Number 45 NWS National Hurricane Center Miami FL EP132019 500 AM HST Mon Sep 23 2019 Kiko's convection has dramatically increased this morning, and satellite intensity estimates have increased in turn. The initial intensity is back up to 45 kt based on a blend of objective and subjective fixes that range from 40 to 55 kt. Kiko's small size is likely making it particularly susceptible to short-term intensity fluctuations, so it is unclear at this time how long this upward trend will continue. It appears that the tropical storm has a chance to intensify some more today while it is located in a relatively low shear environment and over warm SSTs. However, the global models indicate that strong southwesterly shear will once again affect the cyclone in about 24 h, and weakening is still anticipated from that time onward. The dynamical models all show Kiko becoming a post-tropical remnant low in about 72 h, and it could dissipate a couple of days after that. The NHC intensity forecast is above most of the guidance at 12 h, but closely follows the intensity consensus through the rest of the forecast period. Kiko appears to have turned west-northwestward and the initial motion is a rather uncertain 285/7 kt. The models are in good agreement that Kiko will move generally west-northwestward to northwestward for the next couple of days as the subtropical ridge weakens yet again. Around 72 h, Kiko is forecast to turn westward or west-southwestward as it is steered by the low-level tradewind flow. The NHC forecast is a little faster than the previous one, and closely follows the TVCE and HCCA consensus aids. FORECAST POSITIONS AND MAX WINDS INIT 23/1500Z 15.7N 135.8W 45 KT 50 MPH 12H 24/0000Z 16.4N 136.9W 50 KT 60 MPH 24H 24/1200Z 17.6N 138.3W 45 KT 50 MPH 36H 25/0000Z 19.0N 139.9W 40 KT 45 MPH 48H 25/1200Z 19.6N 140.8W 30 KT 35 MPH 72H 26/1200Z 19.7N 143.6W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 27/1200Z 19.3N 145.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 28/1200Z...DISSIPATED $$ Forecaster Zelinsky

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Tropical Storm Jerry Forecast Discussion Number 25

2019-09-23 16:41:54| National Hurricane Center (Atlantic)

Issued at 1100 AM AST Mon Sep 23 2019 000 WTNT45 KNHC 231441 TCDAT5 Tropical Storm Jerry Discussion Number 25 NWS National Hurricane Center Miami FL AL102019 1100 AM AST Mon Sep 23 2019 Strong shear associated with an upper-level trough off the southeast U.S. coast continues to affect Jerry, and the low-level center is exposed to the west-southwest of the main convective mass. Observations from an Air Force Reserve Unit Hurricane Hunter aircraft indicated that the intensity remains near 55 kt. However, if the current sheared state persists, then a weakening trend is likely to commence soon. For now, the official forecast will only show a very slow weakening over the next few days. This prediction is somewhat higher than the intensity model consensus. It should be noted that experience has shown that tropical cyclones at subtropical latitudes tend to be more resilient to shear than those in the deep tropics. Jerry has slowed its forward speed and is now moving north- northwestward at around 6 kt. The storm will continue passing through a break in the subtropical ridge through tonight. On Tuesday, a trough moving off the northeast U.S. coast will cause Jerry to turn northward. Within a couple of days, the trough should steer the tropical cyclone northeastward at a faster forward speed. In days 3-5, Jerry should move east-northeastward to eastward while embedded in the southern portion of the mid-latitude westerlies. The official track forecast is similar to the previous one and close to the model consensus. Key Messages: 1. Tropical-storm-force winds are expected on Bermuda by late Tuesday. 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 23/1500Z 28.1N 68.0W 55 KT 65 MPH 12H 24/0000Z 29.2N 68.3W 55 KT 65 MPH 24H 24/1200Z 30.4N 68.4W 50 KT 60 MPH 36H 25/0000Z 31.8N 67.3W 50 KT 60 MPH 48H 25/1200Z 33.3N 65.0W 50 KT 60 MPH 72H 26/1200Z 35.8N 58.5W 45 KT 50 MPH 96H 27/1200Z 37.0N 53.5W 45 KT 50 MPH 120H 28/1200Z 37.0N 48.0W 35 KT 40 MPH $$ Forecaster Pasch

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Tropical Storm Karen Forecast Discussion Number 6

2019-09-23 16:41:54| National Hurricane Center (Atlantic)

Issued at 1100 AM AST Mon Sep 23 2019 000 WTNT42 KNHC 231441 TCDAT2 Tropical Storm Karen Discussion Number 6 NWS National Hurricane Center Miami FL AL122019 1100 AM AST Mon Sep 23 2019 Although deep convection has recently developed near the low-level swirl seen in early morning visible satellite imagery, the Air Force Reserve reconnaissance aircraft that has been investigating Karen has had difficultly finding a closed surface circulation. It is possible that a center reformation will occur near the new convection, so the system is still being classified as a tropical cyclone for now. The aircraft has found believable SFMR winds of 30-35 kt over the eastern portion of the system, which still supports an initial intensity of 35 kt. Given the current structure of Karen and moderate to strong northeasterly shear that should remain over the storm for the next 24 hours, no change in strength is anticipated during that time. It is also possible that Karen could degenerate into an open wave, if it has not done so already. Regardless of whether or not Karen is a tropical cyclone when it passes near Puerto Rico and the Virgin Islands, the system is likely to produce tropical-storm-force winds in squalls and heavy rainfall over those areas. After that time, upper-level winds are forecast to become more conducive for intensification, and the NHC forecast calls for gradual strengthening like most of the typically reliable intensity guidance, however, the confidence in this portion of the intensity forecast is low. The initial motion estimate is 335/10 kt. Despite the overall lack of organization of the system, the track guidance is still in good agreement on Karen turning northward tonight or early Tuesday into a weakness in the ridge over the western Atlantic caused by Tropical Storm Jerry to its north. After 72 hours, a deep-layer ridge is forecast to build over the southeastern United States and western Atlantic which should slow Karen's northward progress and could cause the system to essentially stall over the western Atlantic by the end of the period. The new NHC track forecast is again close to the previous advisory, and is near the consensus aids through 96 h. At 120 h, the NHC forecast is south of the consensus models in deference to the more equatorward position shown by the ECMWF, but the spread of the guidance by that time is quite large, and confidence in the track forecast at days 4 and 5 is quite low. Key Messages: 1. Regardless of Karen's status as a tropical cyclone, this system is expected to bring tropical-storm-force winds, heavy rainfall, flash floods and mudslides to Puerto Rico and the U.S. and British Virgin Islands on Tuesday, where a tropical storm warning is in effect. FORECAST POSITIONS AND MAX WINDS INIT 23/1500Z 14.9N 64.8W 35 KT 40 MPH 12H 24/0000Z 16.0N 65.3W 35 KT 40 MPH 24H 24/1200Z 17.7N 65.8W 35 KT 40 MPH 36H 25/0000Z 19.6N 65.9W 35 KT 40 MPH 48H 25/1200Z 21.9N 65.7W 40 KT 45 MPH 72H 26/1200Z 25.6N 65.3W 45 KT 50 MPH 96H 27/1200Z 27.0N 65.8W 50 KT 60 MPH 120H 28/1200Z 27.0N 67.0W 60 KT 70 MPH $$ Forecaster Brown

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Tropical Storm Karen Forecast Discussion Number 5

2019-09-23 11:12:20| National Hurricane Center (Atlantic)

Issued at 500 AM AST Mon Sep 23 2019 000 WTNT42 KNHC 230911 CCA TCDAT2 Tropical Storm Karen Discussion Number 5...Corrected NWS National Hurricane Center Miami FL AL122019 500 AM AST Mon Sep 23 2019 Corrected Key Messages Karen's convective pattern has become quite disheveled looking this morning due to 20-25 kt of northeasterly vertical wind shear. a narrow band of deep convection has recently reformed in the southeastern quadrant, but proximity to dry air has been hindering development and organization of that convection. The initial intensity has been held at 35 kt until the next reconnaissance flight later this morning provides new information on the strength of the cyclone. However, I would not be surprised if Karen has weakened to a tropical depression based on the lack of significant convection. The initial motion is now 320/07 kt. The track guidance remains in excellent agreement that Karen should continue a northwestward motion today toward a break in the subtropical ridge, followed by a northward motion on Tuesday that would take the center of the cyclone near or over Puerto Rico and the U.S. Virgin Islands in about 36 hours. Karen is forecast to emerge over the southwestern Atlantic near 48 hours and then slow down significantly and possibly even stall or loop several hundred nmi north of Puerto Rico on days 4 and 5 as a large ridge builds to the north of the cyclone. The new NHC track forecast is similar to the previous advisory, and lies close to the average of the consensus track models TVCN, NOAA-HCCA, and FSSE. The upper-level winds are expected to remain unfavorable for the next 24 hours or so, and I would not be surprised if Karen weakens to a tropical depression during that time. By 36 hours and beyond, however, upper-level winds are expected to become much less hostile, allowing some modest strengthening to occur. By days 4 and 5, Karen is forecast to move underneath an upper-level anticyclone, which should allow for more significant intensification to occur. The new official intensity forecast is similar to the previous one, and follows the trend of the various intensity consensus models. Key Messages: 1. Heavy rainfall will continue to affect portions of the southern Windward Islands through tonight. 2. Karen is forecast to approach Puerto Rico, and the U.S. and British Virgin Islands on Tuesday, and a tropical storm warning is in effect. Tropical-storm-force winds, heavy rainfall, and flash flooding are possible on these islands. FORECAST POSITIONS AND MAX WINDS INIT 23/0900Z 13.6N 63.9W 35 KT 40 MPH 12H 23/1800Z 14.5N 64.6W 35 KT 40 MPH 24H 24/0600Z 16.1N 65.2W 35 KT 40 MPH 36H 24/1800Z 18.0N 65.6W 35 KT 40 MPH 48H 25/0600Z 20.1N 65.5W 40 KT 45 MPH 72H 26/0600Z 24.6N 64.9W 45 KT 50 MPH 96H 27/0600Z 26.5N 65.5W 50 KT 60 MPH 120H 28/0600Z 27.0N 67.0W 60 KT 70 MPH $$ Forecaster Stewart

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Tropical Storm Kiko Forecast Discussion Number 44

2019-09-23 10:59:26| National Hurricane Center (East Pacific)

Issued at 1100 PM HST Sun Sep 22 2019 000 WTPZ43 KNHC 230859 TCDEP3 Tropical Storm Kiko Discussion Number 44 NWS National Hurricane Center Miami FL EP132019 1100 PM HST Sun Sep 22 2019 GOES-17 enhance infrared imagery and an earlier METOP-A AMSU pass show that resilient Kiko is producing intermittent bursts of deep convection with associated -77C cold cloud tops near the surface center. These convective bursts, based on the TAFB and SAB intensity estimates, are substantial enough to maintain its tropical storm status of 35 kt for this advisory. Both the ECMWF and FV3GFS Decay SHIPS statistical-dynamical intensity models show Kiko briefly re-strengthening as it continues moving over warm SSTs and in a favorable upper-level wind environment. By Tuesday afternoon, increasing southwesterly shear and cooler waters should induce a weakening trend, and Kiko is forecast to become a remnant low in less than 3 days with dissipation occuring by the end of the forecast period. The initial motion is estimated to be west-southwestward, or 255/8 kt, just south of due west. Kiko is expected to turn westward to west-northwestward on Monday, and then northwestward on Tuesday as a high amplitude mid-tropospheric trough cuts off, from the upper-level westerlies, to the northwest of the cyclone. At the 72 hour period, as the cyclone degenerates into a vertically shallow remnant low, Kiko should, once again, turn back toward the southwest within the low-level tradewind flow. The NHC track forecast is close to the previous advisory and based on a blend of the various multi-model consensus aids. FORECAST POSITIONS AND MAX WINDS INIT 23/0900Z 15.5N 135.3W 35 KT 40 MPH 12H 23/1800Z 15.8N 136.4W 40 KT 45 MPH 24H 24/0600Z 16.9N 137.6W 40 KT 45 MPH 36H 24/1800Z 18.1N 138.9W 35 KT 40 MPH 48H 25/0600Z 19.2N 140.3W 30 KT 35 MPH 72H 26/0600Z 19.3N 142.2W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 27/0600Z 18.2N 143.6W 20 KT 25 MPH...POST-TROP/REMNT LOW 120H 28/0600Z...DISSIPATED $$ Forecaster Roberts

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