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Tropical Storm Karen Forecast Discussion Number 5

2019-09-23 10:56:21| National Hurricane Center (Atlantic)

Issued at 500 AM AST Mon Sep 23 2019 000 WTNT42 KNHC 230856 TCDAT2 Tropical Storm Karen Discussion Number 5 NWS National Hurricane Center Miami FL AL122019 500 AM AST Mon Sep 23 2019 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 watch 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 Jerry Forecast Discussion Number 24

2019-09-23 10:54:22| National Hurricane Center (Atlantic)

Issued at 500 AM AST Mon Sep 23 2019 000 WTNT45 KNHC 230854 TCDAT5 Tropical Storm Jerry Discussion Number 24 NWS National Hurricane Center Miami FL AL102019 500 AM AST Mon Sep 23 2019 Overnight the center of Jerry became partially exposed, a result of strong westerly shear. However, a new burst of very deep convection has recently formed and obscured the low-level center again. The initial wind speed is held at 55 kt, which is well supported by earlier ASCAT data, and another reconaissance mission is scheduled for this morning to take a closer look. The current shear is forecast to slightly weaken during the next few days as the storm moves over progressively cooler waters with drier air in the mid-levels. There will also be a mid-latitude trough that will be near Jerry in a day or so, but the evidence is piling up that the trough interaction will be a neutral or negative factor for the storm. The intensity forecast is held almost the same as the previous one, following the corrected- consensus guidance. The cyclone could be close to dissipating around day 5 due to continuation of the shear and cold water if the latest global models are correct, so the forecast is lowered at that time. Jerry is moving north-northwestward at 8 kt, and that general motion should continue for about another day as it remains steered by a mid-level ridge to its northeast. A sharp turn toward the northeast and then the east is forecast after that when the trough reaches the system causing it to become embedded in the mid-latitude westerlies. There are some substantial speed differences in the models, partially due to the aforementioned trough interaction, but most of the models are still in agreement with the above scenario. The new forecast is close to the previous one, adjusted somewhat to the south at longer range. Key Messages: 1. Tropical-storm-force winds are possible 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 23/0900Z 27.8N 67.7W 55 KT 65 MPH 12H 23/1800Z 28.6N 68.1W 55 KT 65 MPH 24H 24/0600Z 30.1N 68.5W 50 KT 60 MPH 36H 24/1800Z 31.3N 68.3W 50 KT 60 MPH 48H 25/0600Z 32.6N 66.5W 50 KT 60 MPH 72H 26/0600Z 35.5N 60.0W 45 KT 50 MPH 96H 27/0600Z 37.0N 54.5W 45 KT 50 MPH 120H 28/0600Z 37.0N 48.0W 35 KT 40 MPH $$ Forecaster Blake

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Tropical Depression Thirteen Forecast Discussion Number 2

2019-09-23 10:52:20| National Hurricane Center (Atlantic)

Issued at 500 AM AST Mon Sep 23 2019 000 WTNT43 KNHC 230852 TCDAT3 Tropical Depression Thirteen Discussion Number 2 NWS National Hurricane Center Miami FL AL132019 500 AM AST Mon Sep 23 2019 Infrared and passive microwave satellite imagery indicate that the depression is gradually getting better organized, with upper-level outflow improving in all quadrants. However, the low-level and mid-level circulations do not appear to be vertically aligned quite yet, with the mid-level center displaced a little to the west of the low-level center. As a result, the intensity has been maintained at 30 kt for this advisory. The initial motion is 270/13 kt. A strong deep-layer ridge to the north of the cyclone is expected to steer the system generally westward to west-northwestward for the next 72 hours or so, resulting in the center passing well to the south and southwest of the Cabo Verde Islands today and tonight. On days 4 and 5, a motion toward the northwest is expected as the cyclone begins to move into a weakness in the ridge. The new track guidance remains tightly clustered about the previous forecast track, so no significant changes were required. The cyclone is forecast to remain in light vertical shear conditions throughout the 5-day period. That favorable upper-level flow regime will combine with SSTs near 29 deg C and a moist mid-level environment to allow the cyclone to steadily strengthen into a hurricane by Tuesday and be near major hurricane strength by day 4. The new NHC intensity forecast is just an update of the previous advisory and closely follows the HCCA and IVCN consensus models. FORECAST POSITIONS AND MAX WINDS INIT 23/0900Z 10.8N 22.2W 30 KT 35 MPH 12H 23/1800Z 11.0N 24.2W 40 KT 45 MPH 24H 24/0600Z 11.5N 26.9W 45 KT 50 MPH 36H 24/1800Z 12.1N 29.6W 55 KT 65 MPH 48H 25/0600Z 12.8N 32.4W 65 KT 75 MPH 72H 26/0600Z 14.0N 37.9W 80 KT 90 MPH 96H 27/0600Z 16.3N 42.4W 95 KT 110 MPH 120H 28/0600Z 19.6N 45.7W 90 KT 105 MPH $$ Forecaster Stewart

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Tropical Depression Mario Forecast Discussion Number 24

2019-09-23 10:30:23| National Hurricane Center (East Pacific)

Issued at 300 AM MDT Mon Sep 23 2019 000 WTPZ44 KNHC 230830 TCDEP4 Tropical Depression Mario Discussion Number 24 NWS National Hurricane Center Miami FL EP142019 300 AM MDT Mon Sep 23 2019 Mario earned an extra life yesterday but has just about reached its time limit. Satellite images indicate that an earlier burst of deep convection has dissipated, with only a couple of small disorganized blobs left over. If there is no further convective re-development, Mario will likely be declared a remnant low later this morning. The initial wind speed is reduced to 25 kt in agreement with the latest satellite estimates. The depression is nearing cool waters and a drier, more stable environment. These conditions should be enough to cause Mario to continue to gradually weaken and open up into a trough within a day or so. The latest intensity and track forecasts are based on the consensus guidance, tilted toward the global models which generally do well at this stage of the tropical cyclone life cycle. No significant changes were made to the previous forecast. FORECAST POSITIONS AND MAX WINDS INIT 23/0900Z 24.3N 113.5W 25 KT 30 MPH 12H 23/1800Z 25.5N 114.1W 20 KT 25 MPH...POST-TROP/REMNT LOW 24H 24/0600Z 26.5N 114.5W 20 KT 25 MPH...POST-TROP/REMNT LOW 36H 24/1800Z...DISSIPATED $$ Forecaster Blake

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Tropical Storm Karen Forecast Discussion Number 4

2019-09-23 04:54:46| National Hurricane Center (Atlantic)

Issued at 1100 PM AST Sun Sep 22 2019 000 WTNT42 KNHC 230254 TCDAT2 Tropical Storm Karen Discussion Number 4 NWS National Hurricane Center Miami FL AL122019 1100 PM AST Sun Sep 22 2019 Karen remains poorly organized this evening, with the low-level center exposed to the north of the main convective mass due to the effects of 15-20 kt of northeasterly vertical shear. The initial intensity will be held at 35 kt based on earlier Air Force Reserve Hurricane Hunter data that included maximum 1500 ft flight-level winds of 42 kt and SFMR surface wind estimates near 35 kt. The initial motion is 295/10. The track guidance is in excellent agreement that Karen should turn northwestward during the next 6-12 h in response to a break in a ridge to the north of the storm, followed by a northward motion that would take the center near Puerto Rico and the Virgin Islands into the Atlantic between 36-48 h. Late in the forecast period, the steering currents are expected to weaken as a strong deep-layer ridge builds eastward from the United States into the western Atlantic. This should cause Karen to slow its forward motion. The new forecast track is little changed from the previous track and is near the center of the guidance envelope and the various consensus models. The upper-level winds are currently not favorable for significant development, and the current shear might get stronger during the next 12-24 h. Thus, little change in strength is forecast while Karen crosses the eastern Caribbean, and the system may have trouble maintaining tropical cyclone status. The environment becomes more favorable for development from 48 h on, and the intensity forecast calls for slow strengthening during this time. The new intensity forecast has only minor adjustments from the previous forecasts. 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 watch is in effect. Tropical-storm-force winds, heavy rainfall, and flash flooding are possible on these islands. FORECAST POSITIONS AND MAX WINDS INIT 23/0300Z 13.1N 63.5W 35 KT 40 MPH 12H 23/1200Z 13.9N 64.5W 35 KT 40 MPH 24H 24/0000Z 15.3N 65.2W 35 KT 40 MPH 36H 24/1200Z 16.9N 65.8W 35 KT 40 MPH 48H 25/0000Z 18.7N 66.0W 35 KT 40 MPH 72H 26/0000Z 22.4N 65.7W 40 KT 45 MPH 96H 27/0000Z 25.0N 66.0W 45 KT 50 MPH 120H 28/0000Z 26.0N 67.0W 55 KT 65 MPH $$ Forecaster Beven

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