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Tropical Storm HENRI Forecast Discussion Number 11

2015-09-11 16:56:14| National Hurricane Center (Atlantic)

Issued at 1100 AM AST FRI SEP 11 2015 000 WTNT43 KNHC 111456 TCDAT3 TROPICAL STORM HENRI DISCUSSION NUMBER 11 NWS NATIONAL HURRICANE CENTER MIAMI FL AL082015 1100 AM AST FRI SEP 11 2015 Visible satellite images indicate that the surface circulation of Henri has become rather distorted this morning. Multiple low-level swirls can be seen in the circulation that is elongated from southeast to northwest, with some suggestion that the cyclone may no longer be closed in the northwestern quadrant. The intensity is being held at 35 kt in agreement with the satellite estimate from TAFB. Although shear is somewhat lower over the cyclone, it appears that the low-level structure is too poor to take advantage of the more favorable environment. The intensity forecast has been lowered a little to reflect the less conducive conditions. The cyclone or its remnants are forecast to undergo extratropical transition in about 24 hours while moving over colder water with high shear, and the system is likely to be absorbed by a larger extratropical cyclone by 72 hours. An alternate scenario, one that is becoming more likely, is that Henri could degenerate into a trough later today. The initial motion estimate is 020/17. Henri is expected to accelerate north-northeastward and then northeastward during the next day or so as it encounters increasing flow ahead of a deep longwave trough digging into eastern North America and the western Atlantic. The post-tropical cyclone or its remnants should then turn east-northeastward over the north Atlantic. The new track forecast is very similar to the previous one and near or on the right side of the model consensus. FORECAST POSITIONS AND MAX WINDS INIT 11/1500Z 38.0N 59.4W 35 KT 40 MPH 12H 12/0000Z 41.0N 57.7W 35 KT 40 MPH 24H 12/1200Z 44.9N 54.0W 35 KT 40 MPH...POST-TROP/EXTRATROP 36H 13/0000Z 48.0N 48.5W 35 KT 40 MPH...POST-TROP/EXTRATROP 48H 13/1200Z 50.0N 42.0W 30 KT 35 MPH...POST-TROP/EXTRATROP 72H 14/1200Z...DISSIPATED $$ Forecaster Blake

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Tropical Storm HENRI Forecast Discussion Number 10

2015-09-11 10:40:50| National Hurricane Center (Atlantic)

Issued at 500 AM AST FRI SEP 11 2015 000 WTNT43 KNHC 110840 TCDAT3 TROPICAL STORM HENRI DISCUSSION NUMBER 10 NWS NATIONAL HURRICANE CENTER MIAMI FL AL082015 500 AM AST FRI SEP 11 2015 Overall, Henri's cloud pattern has become slightly better organized since the last advisory. While nearly all of the cyclone's deep convection is still located well to the northeast of the center, a relatively new convective burst over this area has grown in coverage and cloud tops have cooled. Subjective Dvorak classifications remain below tropical storm strength, but the initial intensity held at 35 kt due to the cyclone's increasing forward speed and somewhat improved satellite presentation. Southerly shear appears to be diminishing over the cyclone, as has been forecast by the large-scale models. The lower shear could allow for some additional intensification to take place during the next 12 hours or so while it remains over warm-enough waters. However, the continued presence of dry air in the near-storm environment and Henri's disorganized appearance suggest that any intensification should be negligible. After the cyclone crosses the northern wall of the Gulf Stream in less than 18 hours, substantially lower sea surface temperatures and increasingly stable air should induce weakening soon after that. A plausible alternate scenario, presented by some of the global models, is that Henri could degenerate into a trough later today. The cyclone or its remnants are forecast to undergo extratropical transition in about 36 hours, with the system likely to be absorbed by a larger extratropical cyclone by 72 hours. The new intensity forecast is very similar to the previous one. The initial motion estimate is 010/14. Henri is expected to accelerate north-northeastward and then northeastward during the next day or so as it encounters the fast-paced flow ahead of a deep longwave trough digging into eastern North America and the western Atlantic. The post-tropical cyclone or its remnants should then turn east-northeastward over the north Atlantic. The new track forecast is adjusted to the left of the previous forecast and lies on the right side of the guidance envelope. The latter part of this forecast, when the storm is expected to be post-tropical, is partially based on guidance provided by NOAA's Ocean Prediction Center. FORECAST POSITIONS AND MAX WINDS INIT 11/0900Z 36.2N 60.3W 35 KT 40 MPH 12H 11/1800Z 39.0N 59.3W 40 KT 45 MPH 24H 12/0600Z 43.0N 56.4W 40 KT 45 MPH 36H 12/1800Z 46.5N 52.0W 35 KT 40 MPH...POST-TROP/EXTRATROP 48H 13/0600Z 48.9N 45.9W 35 KT 40 MPH...POST-TROP/EXTRATROP 72H 14/0600Z...ABSORBED $$ Forecaster Kimberlain

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Tropical Storm HENRI Forecast Discussion Number 9

2015-09-11 04:32:41| National Hurricane Center (Atlantic)

Issued at 1100 PM AST THU SEP 10 2015 000 WTNT43 KNHC 110232 TCDAT3 TROPICAL STORM HENRI DISCUSSION NUMBER 9 NWS NATIONAL HURRICANE CENTER MIAMI FL AL082015 1100 PM AST THU SEP 10 2015 Henri has changed little in organization during the past several hours. The system continues to have some characteristics of a subtropical cyclone, with the convective banding and strongest winds well away from the center in the northeastern semicircle. The initial intensity remains 35 kt, as there has been no new scatterometer data from the area where the strongest winds are likely occurring. The initial motion is northward or 005/12. Henri should accelerate and turn to the northeast during the next 48 hours as it enters the mid-latitude westerlies. After that time, a quick eastward motion is expected until the cyclone dissipates. The new track forecast is an update of the previous forecast and is just to the right of the various consensus models. The vertical wind shear over Henri is diminishing, so there is a chance that the system could intensify a little before reaching cold water north of the Gulf Stream in about 18 hours. After that, the system should begin extratropical transition as it merges with a frontal system, and this process is expected to be complete in about 36 hours. The cyclone is likely to be absorbed by a larger extratropical system between 72-96 hours. An alternative scenario is that Henri could degenerate to a trough between 24-72 hours as indicated by several of the global models. 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 11/0300Z 34.8N 60.7W 35 KT 40 MPH 12H 11/1200Z 37.5N 60.1W 40 KT 45 MPH 24H 12/0000Z 41.2N 58.0W 40 KT 45 MPH 36H 12/1200Z 44.9N 54.5W 40 KT 45 MPH...POST-TROP/EXTRATROP 48H 13/0000Z 47.6N 48.5W 40 KT 45 MPH...POST-TROP/EXTRATROP 72H 14/0000Z 48.0N 33.0W 35 KT 40 MPH...POST-TROP/EXTRATROP 96H 15/0000Z...DISSIPATED $$ Forecaster Beven

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Tropical Storm HENRI Forecast Discussion Number 8

2015-09-10 22:33:38| National Hurricane Center (Atlantic)

Issued at 500 PM AST THU SEP 10 2015 000 WTNT43 KNHC 102033 TCDAT3 TROPICAL STORM HENRI DISCUSSION NUMBER 8 NWS NATIONAL HURRICANE CENTER MIAMI FL AL082015 500 PM AST THU SEP 10 2015 Henri continues to struggle with most of its deep convection well removed to the northeast of the center. In fact, it is taking on some characteristics of a subtropical cyclone with recent scatterometer data indicating that the radius of maximum winds has increased to a rather high value of 120 n mi. The initial wind speed will remain 35 kt on the basis of 30-35 kt winds observed in partial scatterometer pass that missed the area that likely has the strongest winds. Southerly shear is still forecast to relax overnight near Henri, which theoretically could result in intensification during the next day or so before the cyclone moves over cold water on Saturday. However, dry air aloft persists near the storm and the overall cloud pattern is quite disorganized. The unfavorable factors are starting to outweigh the favorable conditions, so the official intensity forecast is reduced from the previous one, a little below the model consensus. Extratropical transition is expected within 2 days due to strong shear and very cold water. A reasonable alternative solution provided by some of the global models is that the cyclone stays weak and opens up into a trough during the day on Friday. Henri is moving faster to the north, now about 13 kt. The storm should continue to accelerate northward tonight and northeastward tomorrow due to it encountering 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 flow. The guidance has trended to the left with the track of Henri, perhaps due to a weaker forecast representation of the storm. The NHC forecast is shifted in that direction, although remains on the right side of the guidance envelope. If it survives, the cyclone should become absorbed by a larger extratropical low by day 4 over the far North Atlantic. 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 10/2100Z 33.9N 60.7W 35 KT 40 MPH 12H 11/0600Z 36.1N 60.3W 40 KT 45 MPH 24H 11/1800Z 39.7N 59.1W 40 KT 45 MPH 36H 12/0600Z 43.5N 56.5W 40 KT 45 MPH 48H 12/1800Z 46.8N 51.8W 40 KT 45 MPH...POST-TROP/EXTRATROP 72H 13/1800Z 48.5N 36.5W 35 KT 40 MPH...POST-TROP/EXTRATROP 96H 14/1800Z...DISSIPATED $$ Forecaster Blake

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Post-Tropical Cyclone LINDA Forecast Discussion Number 20

2015-09-10 22:32:41| National Hurricane Center (East Pacific)

Issued at 200 PM PDT THU SEP 10 2015 000 WTPZ45 KNHC 102032 TCDEP5 POST-TROPICAL CYCLONE LINDA DISCUSSION NUMBER 20 NWS NATIONAL HURRICANE CENTER MIAMI FL EP152015 200 PM PDT THU SEP 10 2015 Linda is now a swirl of low clouds that has been devoid of deep convection for more than 12 hours. Based on the lack of convection, Linda is now a post-tropical cyclone and this will be the last NHC advisory. The initial intensity is set to 30 kt based on a blend of the latest Dvorak fixes from TAFB and SAB. The circulation of Linda should gradually spin down over the next 2 to 3 days until the cyclone dissipates. The initial motion estimate remains 320/06. The remnant low should gradually turn toward the west-northwest and then toward the west over the next 2 days as the low becomes steered by the low-level flow. A turn to the south of due west is shown at 72 hours. The new NHC track forecast is a little to the north of the previous one based on the latest trends in the track guidance. 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. For additional information on the remnant low please see High Seas Forecasts issued by the National Weather Service, under AWIPS header NFDHSFEPI, WMO header FZPN01 KWBC, and on the web at http://www.opc.ncep.noaa.gov/shtml/NFDHSFEP1.shtml. FORECAST POSITIONS AND MAX WINDS INIT 10/2100Z 26.4N 119.0W 30 KT 35 MPH...POST-TROP/REMNT LOW 12H 11/0600Z 26.9N 119.8W 30 KT 35 MPH...POST-TROP/REMNT LOW 24H 11/1800Z 27.4N 120.8W 25 KT 30 MPH...POST-TROP/REMNT LOW 36H 12/0600Z 27.7N 121.7W 20 KT 25 MPH...POST-TROP/REMNT LOW 48H 12/1800Z 27.8N 122.4W 20 KT 25 MPH...POST-TROP/REMNT LOW 72H 13/1800Z 27.2N 123.2W 15 KT 15 MPH...POST-TROP/REMNT LOW 96H 14/1800Z...DISSIPATED $$ Forecaster Brennan

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