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Tropical Storm HENRI Forecast Discussion Number 7

2015-09-10 16:36:06| National Hurricane Center (Atlantic)

Issued at 1100 AM AST THU SEP 10 2015 000 WTNT43 KNHC 101435 TCDAT3 TROPICAL STORM HENRI DISCUSSION NUMBER 7 NWS NATIONAL HURRICANE CENTER MIAMI FL AL082015 1100 AM AST THU SEP 10 2015 The cloud pattern of Henri remains disorganized with most of the convection sheared off to the east and northeast of the center. Visible images also indicate that the system has little organization in the central core, with multiple smaller vortices rotating around a mean center. The initial wind speed remains 35 kt, although some Dvorak estimates suggest it could have weakened to a tropical depression. Southwesterly shear and dry air is currently limiting the amount of deep convection near the center of the cyclone. Global models, however, all weaken the shear later today, which could allow Henri to strengthen while it moves over warm waters before it crosses the north wall of the Gulf Stream in 36-48 hours. Henri is still forecast to lose tropical characteristics in a little over 2 days and then weaken while it moves over very cold water with high shear. The intensity guidance is in relatively good agreement on this scenario and the NHC forecast is very close to the previous one. Satellite fixes indicate that Henri is moving northward at about 8 kt. The storm should accelerate northward today and northeastward tomorrow as it encounters faster steering from the subtropical ridge. After that time, an even faster northeastward and then eastward motion is predicted when the cyclone becomes embedded in the mid-latitude westerlies. There have been no significant changes to the guidance, and the NHC track forecast is basically just an update of the previous prediction. The latter part of this forecast, when the storm is expected to be post-tropical, is based on guidance provided by NOAA's Ocean Prediction Center. FORECAST POSITIONS AND MAX WINDS INIT 10/1500Z 32.6N 60.8W 35 KT 40 MPH 12H 11/0000Z 34.5N 60.7W 40 KT 45 MPH 24H 11/1200Z 37.8N 60.0W 45 KT 50 MPH 36H 12/0000Z 41.4N 58.2W 45 KT 50 MPH 48H 12/1200Z 45.0N 53.5W 45 KT 50 MPH 72H 13/1200Z 49.0N 41.0W 40 KT 45 MPH...POST-TROP/EXTRATROP 96H 14/1200Z 45.5N 22.0W 35 KT 40 MPH...POST-TROP/EXTRATROP 120H 15/1200Z...DISSIPATED $$ Forecaster Blake

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Tropical Storm LINDA Forecast Discussion Number 19

2015-09-10 16:35:06| National Hurricane Center (East Pacific)

Issued at 800 AM PDT THU SEP 10 2015 000 WTPZ45 KNHC 101434 TCDEP5 TROPICAL STORM LINDA DISCUSSION NUMBER 19 NWS NATIONAL HURRICANE CENTER MIAMI FL EP152015 800 AM PDT THU SEP 10 2015 Linda remains void of any organized deep convection and the mid-level circulation is decoupling from the low-level vortex. The initial intensity has been lowered to 35 kt based on a blend of the latest Dvorak estimates and assuming some decay since last night's ASCAT passes. Gradual spin down of the circulation is forecast as it moves over cool waters during the next few days, and if deep convection does not return, Linda will likely become a remnant low later today. The initial motion estimate is 320/06. A gradual turn toward the west-northwest is forecast during the next day or so with a decrease in forward speed as the shallow vortex is steered by the low-level flow. Before the cyclone dissipates in 3 to 4 days, a motion south of due west is possible. The new NHC track forecast is an update of the previous one and is close to the middle of the guidance envelope. Large swells from Linda are affecting the Pacific coast of the Baja California peninsula and southern California. These swells could continue for another day or so. In addition, some of Linda's mid- and upper-level moisture is spreading northward into portions of the southwestern U.S., which could trigger locally heavy rainfall. For additional information, please consult products issued by the NOAA Weather Prediction Center and your local NWS forecast office. FORECAST POSITIONS AND MAX WINDS INIT 10/1500Z 26.0N 118.6W 35 KT 40 MPH 12H 11/0000Z 26.6N 119.3W 30 KT 35 MPH...POST-TROP/REMNT LOW 24H 11/1200Z 27.1N 120.2W 25 KT 30 MPH...POST-TROP/REMNT LOW 36H 12/0000Z 27.4N 121.1W 25 KT 30 MPH...POST-TROP/REMNT LOW 48H 12/1200Z 27.6N 122.0W 20 KT 25 MPH...POST-TROP/REMNT LOW 72H 13/1200Z 27.5N 122.5W 15 KT 15 MPH...POST-TROP/REMNT LOW 96H 14/1200Z...DISSIPATED $$ Forecaster Brennan

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Tropical Storm HENRI Forecast Discussion Number 6

2015-09-10 10:37:05| National Hurricane Center (Atlantic)

Issued at 500 AM AST THU SEP 10 2015 000 WTNT43 KNHC 100836 TCDAT3 TROPICAL STORM HENRI DISCUSSION NUMBER 6 NWS NATIONAL HURRICANE CENTER MIAMI FL AL082015 500 AM AST THU SEP 10 2015 There has been little change in the cloud pattern of Henri since the previous advisory. The tropical storm remains sheared with the low-level center displaced to the west of the main area of deep convection. The initial wind speed is held at 35 kt, which could be conservative based on the earlier scatterometer data. This intensity estimate is on the high side of the latest Dvorak analyses. Henri is currently being affected by 15-20 kt of west-southwesterly wind shear and dry air has wrapped around the west and south sides of the circulation. The shear is expected to lessen later today, and that could allow Henri to gain some strength. However, significant intensification is not expected as the cyclone should cross the north wall of the Gulf Stream in 36-48 hours, where a sharp gradient in sea surface temperatures exist. Henri is forecast to lose tropical characteristics in a little over 2 days, when it is expected to be over cold water. Most of the guidance shows the extratropical low dissipating by day 5, and the NHC forecast follows suit. The tropical storm has been moving erratically during the last several hours, but the general motion has been slowly northward. A faster northward motion is expected to begin later today and continue for the next 24 to 36 hours as a subtropical ridge strengthens to the east of Henri. After that time, an even faster northeastward and then eastward motion is predicted when the cyclone becomes embedded in the mid-latitude westerlies. The models are in good agreement on this overall scenario, and little change was made to the previous track forecast. The latter part of this forecast, when the storm is expected to be post-tropical, is based on guidance provided by NOAA's Ocean Prediction Center. FORECAST POSITIONS AND MAX WINDS INIT 10/0900Z 31.4N 61.0W 35 KT 40 MPH 12H 10/1800Z 33.0N 61.3W 40 KT 45 MPH 24H 11/0600Z 35.9N 60.9W 45 KT 50 MPH 36H 11/1800Z 39.3N 59.7W 50 KT 60 MPH 48H 12/0600Z 43.0N 56.5W 45 KT 50 MPH 72H 13/0600Z 48.0N 45.0W 40 KT 45 MPH...POST-TROP/EXTRATROP 96H 14/0600Z 46.5N 29.0W 40 KT 45 MPH...POST-TROP/EXTRATROP 120H 15/0600Z...DISSIPATED $$ Forecaster Cangialosi

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Tropical Storm LINDA Forecast Discussion Number 18

2015-09-10 10:34:33| National Hurricane Center (East Pacific)

Issued at 200 AM PDT THU SEP 10 2015 000 WTPZ45 KNHC 100834 TCDEP5 TROPICAL STORM LINDA DISCUSSION NUMBER 18 NWS NATIONAL HURRICANE CENTER MIAMI FL EP152015 200 AM PDT THU SEP 10 2015 Linda continues to decay. Much of the deep convection has now dissipated, and the cyclone is weakening over cool water and within a stable air mass. A pair of ASCAT passes recently sampled the circulation of Linda and revealed that the winds and are near 40 kt. This is in agreement with an average of the Dvorak Final T- and CI-numbers from TAFB and SAB. The scatterometer data also indicated that the size of the tropical storm force wind field has decreased considerably and is confined to an area within 60 n mi north of the center. Additional weakening is forecast since sea surface temperatures are expected to decrease even more along the projected path. Linda will likely become a tropical depression later today and a remnant low by tonight. Dissipation is forecast to occur in about 4 days, following the global model guidance. The weakening storm is moving northwestward at 8 kt. A gradual turn to the west-northwest and then west with a decrease in forward speed is predicted over the next few days as the cyclone is steered by the low-level flow. The NHC track forecast is adjusted a little to the right of the previous one and is very near a consensus of the GFS and ECMWF models. Large swells from Linda are affecting the Pacific coast of the Baja California peninsula and southern California. These swells could continue for another day or so. In addition, some of Linda's mid- and upper-level moisture is spreading northward into portions of the southwestern U.S., which could trigger locally heavy rainfall. For additional information, please consult products issued by the NOAA Weather Prediction Center and your local NWS forecast office. FORECAST POSITIONS AND MAX WINDS INIT 10/0900Z 25.6N 118.2W 40 KT 45 MPH 12H 10/1800Z 26.3N 118.9W 30 KT 35 MPH 24H 11/0600Z 26.9N 119.7W 25 KT 30 MPH...POST-TROP/REMNT LOW 36H 11/1800Z 27.3N 120.6W 25 KT 30 MPH...POST-TROP/REMNT LOW 48H 12/0600Z 27.5N 121.5W 20 KT 25 MPH...POST-TROP/REMNT LOW 72H 13/0600Z 27.6N 122.3W 15 KT 15 MPH...POST-TROP/REMNT LOW 96H 14/0600Z...DISSIPATED $$ Forecaster Cangialosi

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Tropical Storm HENRI Forecast Discussion Number 5

2015-09-10 04:45:19| National Hurricane Center (Atlantic)

Issued at 1100 PM AST WED SEP 09 2015 000 WTNT43 KNHC 100244 TCDAT3 TROPICAL STORM HENRI DISCUSSION NUMBER 5 NWS NATIONAL HURRICANE CENTER MIAMI FL AL082015 1100 PM AST WED SEP 09 2015 Recently received ASCAT-B scatterometer data showed an area of 35-40 kt wind vectors in the convection about 75-100 n mi east of the center. Based on this, the initial intensity is increased to a possibly conservative 35 kt and the cyclone is upgraded to a tropical storm. Despite the upgrade, Henri remains a disorganized system, with the low-level center remaining exposed to the west of the convection due to 15-20 kt of shear. In addition, microwave satellite data and experimental European multispectral satellite imagery suggest a tongue of dry air is entraining into the cyclone around the west, south, and southeast sides of the circulation. Henri has started its expected northward track with the initial motion of 355/4. For the next 36-48 hours, the cyclone should move generally northward with an increase in forward speed between the subtropical ridge to the east and a deep-layer trough moving eastward through the eastern United States. After that time, Henri should turn northeastward and eastward as it enters the westerlies. The new forecast track is similar to the previous track, but it lies a little south of the center of the guidance envelope after 36 hours due to a northward shift in the guidance. The dynamical models suggest that the shear should subside during the next 36-48 hours, and that the dry air entrainment should also decrease. This combination should allow Henri to strengthen until it reaches colder sea surface temperatures north of the Gulf Stream in a little under 48 hours. After that, the cyclone is expected to become extratropical as it merges with a frontal system. The new intensity forecast calls for a peak intensity near 50 kt in 36-48 hours, followed by gradual weakening. The first 48 hours are in best agreement with the SHIPS model, and the intensities after extratropical transition are based on input from the NOAA Ocean Prediction Center. FORECAST POSITIONS AND MAX WINDS INIT 10/0300Z 31.3N 60.7W 35 KT 40 MPH 12H 10/1200Z 32.8N 60.9W 40 KT 45 MPH 24H 11/0000Z 35.3N 60.9W 45 KT 50 MPH 36H 11/1200Z 38.6N 60.2W 50 KT 60 MPH 48H 12/0000Z 42.4N 58.0W 50 KT 60 MPH 72H 13/0000Z 47.5N 48.5W 45 KT 50 MPH...POST-TROP/EXTRATROP 96H 14/0000Z 47.5N 32.5W 40 KT 45 MPH...POST-TROP/EXTRATROP 120H 15/0000Z 47.0N 17.0W 35 KT 40 MPH...POST-TROP/EXTRATROP $$ Forecaster Beven

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