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Tropical Depression Karen Forecast Discussion Number 8

2019-09-24 04:51:32| National Hurricane Center (Atlantic)

Issued at 1100 PM AST Mon Sep 23 2019 000 WTNT42 KNHC 240251 TCDAT2 Tropical Depression Karen Discussion Number 8 NWS National Hurricane Center Miami FL AL122019 1100 PM AST Mon Sep 23 2019 Deep convection associated with Karen has increased during the past few hours, but the thunderstorm activity remains confined to the south of the center due to north-northeasterly shear. The Air Force Hurricane Hunters have been investigating the depression this evening, and a combination of the flight-level and SFMR data indicate that winds are just below tropical-storm-force. The aircraft measured a minimum pressure of about 1008 mb. Karen is currently situated near the western periphery of a subtropical ridge, and it is forecast to turn northward on Tuesday as it passes Puerto Rico and the Virgin Islands. After that time, a northward to north-northeastward motion seems likely as the cyclone moves into a weakness left behind by Tropical Storm Jerry. However, the models indicate that the trough will not capture Karen, and instead the cyclone could come to a stop or drift westward by the weekend as a ridge builds to the north of the system. Although the models agree on the overall scenario, the details are quite uncertain and there remains a large spread in the guidance at days 4 and 5. The new NHC track forecast is adjusted a little to the right of the previous one to be in better agreement with the latest consensus models. The environment is still quite hostile around Karen with north-northeasterly shear of about 20 kt currently impacting the cyclone. However, the upper-level wind pattern is expected to become more favorable during the next few days, and that could give it an opportunity to strengthen. The NHC intensity forecast shows a slow increase in winds through the forecast period. This forecast is similar to the previous one, and lies roughly between the aggressive SHIPS/LGEM models and the HWRF/HMON models which show little change in intensity during the next several days. Key Messages: 1. Regardless of Karen's status and intensity, the system is expected to bring 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. 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 24/0300Z 16.1N 65.8W 30 KT 35 MPH 12H 24/1200Z 17.5N 66.2W 35 KT 40 MPH 24H 25/0000Z 19.6N 66.2W 35 KT 40 MPH 36H 25/1200Z 22.0N 65.8W 35 KT 40 MPH 48H 26/0000Z 23.9N 65.2W 40 KT 45 MPH 72H 27/0000Z 26.8N 64.1W 45 KT 50 MPH 96H 28/0000Z 28.0N 64.0W 50 KT 60 MPH 120H 29/0000Z 28.0N 66.5W 55 KT 65 MPH $$ Forecaster Cangialosi

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Tropical Storm Kiko Forecast Discussion Number 47

2019-09-24 04:39:34| National Hurricane Center (East Pacific)

Issued at 500 PM HST Mon Sep 23 2019 000 WTPZ43 KNHC 240239 TCDEP3 Tropical Storm Kiko Discussion Number 47 NWS National Hurricane Center Miami FL EP132019 500 PM HST Mon Sep 23 2019 Earlier this afternoon, infrared satellite imagery showed the initial presence of an eye developing. Since that time, the gradient of the convection has become sharp over the southwestern semicircle, with that cirrus clouds now covering the eye-like feature. This suggests that the anticipated southerly shear over the cyclone could be beginning. The initial intensity remains at 50 kt, and this is based off a combination of the available subjective and objective intensity estimates. Kiko is moving northwestward at 10 kt. There is no change to the forecast track philosophy. Kiko is expected to turn to the northwest tonight, and that motion should continue through Tuesday in the flow between a mid-level ridge to the northeast and a mid- to upper-level low to its west. By Wednesday, Kiko is expected to turn back to the west as the shallower system is steered by the the low-level trade winds. Based on the current forecast track, Kiko is expected to enter the central Pacific basin by tomorrow night. Since it now appears that the shear is beginning to occur over the storm, the forecast no longer calls for any additional strengthening. The southerly shear is expected to increase much more tomorrow, and the system should begin to entrain dry and stable marine air to its west. This is expected to cause a weakening trend to begin, and by Wednesday, Kiko is expected to become a tropical depression, and it will likely become a remnant low shortly thereafter. Other than removing the near term intensification, the official forecast is essentially an update of the previous one. FORECAST POSITIONS AND MAX WINDS INIT 24/0300Z 17.0N 137.5W 50 KT 60 MPH 12H 24/1200Z 18.0N 138.6W 50 KT 60 MPH 24H 25/0000Z 19.1N 140.0W 40 KT 45 MPH 36H 25/1200Z 19.7N 141.3W 35 KT 40 MPH 48H 26/0000Z 19.8N 142.4W 30 KT 35 MPH 72H 27/0000Z 19.5N 145.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 28/0000Z 19.5N 146.3W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 29/0000Z...DISSIPATED $$ Forecaster Latto

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Tropical Storm Jerry Forecast Discussion Number 27

2019-09-24 04:38:31| National Hurricane Center (Atlantic)

Issued at 1100 PM AST Mon Sep 23 2019 000 WTNT45 KNHC 240238 TCDAT5 Tropical Storm Jerry Discussion Number 27 NWS National Hurricane Center Miami FL AL102019 1100 PM AST Mon Sep 23 2019 Surface and flight-level data from Air Force Reserve Hurricane Hunter aircraft investigating Jerry this evening indicate that Jerry's maximum sustained winds are holding steady at 55 kt. The measured minimum central pressure of 991 mb is also unchanged. Therefore, the initial intensity for this advisory remains at 55 kt. Jerry is currently moving within a rather harsh environment produced by a high amplitude mid- to upper-level trough situated between the cyclone and the eastern seaboard of the United States. The statistical-dynamical Decay SHIPS from both the GFS and ECMWF show the moderate westerly shear and the inhibiting thermodynamic environment persisting through the entire forecast. Therefore, gradual weakening is forecast. The NHC forecast is basically an update of the previous advisory and is based on the NOAA HFIP HCCA intensity consensus. The initial motion is estimated to be northward, or 350/6 kt. Jerry will continue moving within a large break in the subtropical ridge during the next 12 hours or so, and then turn northeastward within the mid-tropospheric southwesterly flow produced by the aforementioned trough. Around mid-period, Jerry should move east-northeastward within the deep-layer mid-latitude zonal flow, then a little to the south of east in the peripheral flow of the subtropical high anchored to the southwest of the cyclone. The official forecast is a little to the south of the previous one beyond day 3, and lies between the TVCN simple consensus and the GFS and ECMWF global models. 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 24/0300Z 29.2N 68.3W 55 KT 65 MPH 12H 24/1200Z 30.1N 68.5W 50 KT 60 MPH 24H 25/0000Z 31.2N 67.7W 45 KT 50 MPH 36H 25/1200Z 32.4N 65.7W 45 KT 50 MPH 48H 26/0000Z 33.3N 62.7W 45 KT 50 MPH 72H 27/0000Z 34.9N 56.8W 45 KT 50 MPH 96H 28/0000Z 35.0N 52.7W 40 KT 45 MPH 120H 29/0000Z 33.9N 49.6W 35 KT 40 MPH $$ Forecaster Roberts

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Tropical Storm Lorenzo Forecast Discussion Number 5

2019-09-24 04:37:33| National Hurricane Center (Atlantic)

Issued at 1100 PM AST Mon Sep 23 2019 000 WTNT43 KNHC 240237 TCDAT3 Tropical Storm Lorenzo Discussion Number 5 NWS National Hurricane Center Miami FL AL132019 1100 PM AST Mon Sep 23 2019 Infrared satellite imagery and microwave data indicate that convection and banding has been on the increase this evening very near the the center of Lorenzo, while the existing bands that extend well away from the center have been growing in size. This improving organization supports raising the initial intensity to 45 kt, and this is in agreement with the latest subjective Dvorak estimates from both TAFB and SAB. A recent ASCAT-C overpass sampled tropical-storm-force winds that now extend up to 80 n mi in the northern semicircle and suggested that the initial wind speed could be a little conservative. Lorenzo will be in an environment favorable for intensification for the next several days. And, given the recent increase in convection near the storm's center, there is now greater confidence that Lorenzo could become a hurricane by late tomorrow. If the near-term forecast trend verifies, then it will raise confidence that Lorenzo may become a major hurricane in the medium range. Only at the very end of the forecast period does it appear that the system will begin to encounter increasing shear and some drier air, which should limit any further strengthening. The official NHC wind speed prediction shows intensification a little faster than the last forecast through the first couple of days, but is near the previous advisory thereafter. This forecast is very close to the HFIP corrected-consensus HCCA. Lorenzo is moving westward at 13 kt. A strong mid-level ridge to the north of the cyclone will steer it generally westward to west-northwestward over the next few days. Late in the forecast period, a break in the ridge is forecast to develop between 40-45W, which should cause Lorenzo to turn to the northwest. The official NHC forecast is very close to the previous one, and near the tightly clustered consensus aids. FORECAST POSITIONS AND MAX WINDS INIT 24/0300Z 11.6N 26.7W 45 KT 50 MPH 12H 24/1200Z 12.1N 28.9W 55 KT 65 MPH 24H 25/0000Z 12.8N 31.5W 65 KT 75 MPH 36H 25/1200Z 13.4N 34.3W 75 KT 85 MPH 48H 26/0000Z 14.0N 37.0W 80 KT 90 MPH 72H 27/0000Z 16.1N 41.3W 90 KT 105 MPH 96H 28/0000Z 19.0N 44.2W 100 KT 115 MPH 120H 29/0000Z 22.0N 46.0W 100 KT 115 MPH $$ Forecaster Latto

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Tropical Depression Karen Forecast Discussion Number 7

2019-09-23 22:40:31| National Hurricane Center (Atlantic)

Issued at 500 PM AST Mon Sep 23 2019 000 WTNT42 KNHC 232040 TCDAT2 Tropical Depression Karen Discussion Number 7 NWS National Hurricane Center Miami FL AL122019 500 PM AST Mon Sep 23 2019 Karen has become increasingly disorganized today. Visible satellite imagery and surface observations suggest that there is a broad low-level circulation, but the aircraft struggled to find a well-defined center. Based on the current lack of organization, the initial wind speed has been lowered to 30 kt. The environment ahead of Karen is forecast to remain quite hostile, with dry mid-level air and strong northeasterly shear continuing overnight. After Karen moves north of Puerto Rico over the western Atlantic, it may find itself in a more favorable upper-level environment, but given the current structure of the cyclone it should take some time for any potential re-strengthening to occur. As a result, the long-range intensity forecast is a little lower than the previous advisory and remains of very low confidence. Karen is moving northwestward or 335/11 kt. Karen should turn northward later tonight or early Tuesday toward a weakness in the subtropical ridge over the western Atlantic caused by Jerry. A northward to north-northeast motion should then take the storm over the western Atlantic well to the east of the Bahamas around mid- week. After that time, a deep-layer ridge is forecast to build over the southeastern United States and far western Atlantic, which should cause Karen to slow down and become nearly stationary at days 4 and 5. The track guidance has trended toward Karen gaining more latitude before slowing, and the new NHC track forecast as been adjusted accordingly. The latter portion of the track forecast is still quite uncertain as the dynamical model guidance and their ensembles still exhibit large spread. Although Karen in shown to remain a tropical depression as it passed Puerto Rico and the Virgin Islands, the tropical storm warning is begin maintained since only a small increase in the wind speed would make Karen a tropical storm again. In addition, windward facing areas at high elevation on the islands could experience winds higher than those shown in the official forecast. Key Messages: 1. Regardless of Karen's status and intensity, the system is expected to bring 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. 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 23/2100Z 15.9N 65.6W 30 KT 35 MPH 12H 24/0600Z 17.2N 66.2W 30 KT 35 MPH 24H 24/1800Z 18.9N 66.6W 30 KT 35 MPH 36H 25/0600Z 21.3N 66.3W 30 KT 35 MPH 48H 25/1800Z 23.3N 65.9W 35 KT 40 MPH 72H 26/1800Z 26.5N 65.0W 45 KT 50 MPH 96H 27/1800Z 27.5N 65.5W 50 KT 60 MPH 120H 28/1800Z 27.5N 67.0W 55 KT 65 MPH $$ Forecaster Brown

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