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Tropical Storm HERNAN Forecast Discussion Number 6

2014-07-27 16:35:38| National Hurricane Center (East Pacific)

Issued at 800 AM PDT SUN JUL 27 2014 000 WTPZ43 KNHC 271435 TCDEP3 TROPICAL STORM HERNAN DISCUSSION NUMBER 6 NWS NATIONAL HURRICANE CENTER MIAMI FL EP082014 800 AM PDT SUN JUL 27 2014 Enhanced BD-curve infrared imagery and an earlier GCOM-W1 (AMSR2) microwave overpass indicate that Hernan has continued to strengthen this morning. The imagery shows an impressive well-developed banding feature over the northwest quadrant of the cyclone with -80 to -90 deg C cloud tops, while the microwave pass reveals a more distinct inner core with a partial eyewall feature. Based on a blend of the Dvorak classifications from TAFB and SAB, and the latest UW-CIMSS SATCON estimate, the NHC initial intensity is raised to 60 kt. Current favorable environmental conditions should allow for further intensification during the next 8-12 hours, and Hernan still has a chance to become a hurricane today or tonight. Afterward, increasing westerly shear and decreasing sea surface temperatures are expected to weaken Hernan through the remainder of the forecast period. The available statistical/dynamical guidance agree with weakening Hernan into a remnant low in 96 hours. The initial motion is estimated to be northwestward, or 305/13 kt. Hernan continues to be steered by the mid-level southeasterly flow produced by a ridge over the southwestern United States. The cyclone should move in this general direction through the 36 hour period, and then turn westward within the low-level trade wind flow as a degenerated, vertically shallow system. The official NHC forecast is based on the multi-model consensus and is slightly to the right of the previous forecast beyond 48 hours. FORECAST POSITIONS AND MAX WINDS INIT 27/1500Z 17.8N 111.1W 60 KT 70 MPH 12H 28/0000Z 19.0N 112.8W 65 KT 75 MPH 24H 28/1200Z 20.5N 115.2W 60 KT 70 MPH 36H 29/0000Z 21.9N 117.6W 50 KT 60 MPH 48H 29/1200Z 22.9N 119.8W 45 KT 50 MPH 72H 30/1200Z 23.9N 123.0W 30 KT 35 MPH 96H 31/1200Z 24.0N 126.5W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 01/1200Z 24.0N 129.5W 20 KT 25 MPH...POST-TROP/REMNT LOW $$ Forecaster Roberts

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Tropical Storm HERNAN Forecast Discussion Number 5

2014-07-27 10:43:59| National Hurricane Center (East Pacific)

Issued at 200 AM PDT SUN JUL 27 2014 000 WTPZ43 KNHC 270843 TCDEP3 TROPICAL STORM HERNAN DISCUSSION NUMBER 5 NWS NATIONAL HURRICANE CENTER MIAMI FL EP082014 200 AM PDT SUN JUL 27 2014 Conventional satellite imagery and scatterometer wind data indicate that Hernan has continued to strengthen. A small central dense overcast has persisted over the center during the past 6 hours, and 0418 UTC and 0510 UTC ASCAT-A and ASCAT-B overpasses indicated surface winds of 48 kt and 51 kt, respectively, were present just east of center. Assuming that the coarse resolution ASCAT data has under-sampled the rather small and tight inner core wind field, the initial intensity has been increased to 55 kt. This intensity is supported by satellite intensity estimates of 55 kt from TAFB and 56 kt from UW-CIMSS ADT. The initial motion estimate is northwestward or 310/12 kt. Hernan is being steered along the southwestern periphery of a strong subtropical ridge located across the southwestern and southern United States. This persistent steering pattern is expected to keep Hernan moving in a general northwestward direction for the next 2-3 days, followed by a turn toward the west when the cyclone weakens and is steered primarily the by low-level easterly trade wind flow. Although the models have again shifted slightly northward, the new NHC track forecast is just an update of the previous advisory track and lies along the southern edge of the guidance envelope due to the expected quicker weakening than what the more northerly track GFS and GFDL models are forecasting. Hernan has strengthened 20 kt in the past 12 hours, which is a faster-than-normal rate of intensification. The cyclone has about another 12 hours or so of favorable conditions that could allow Hernan to achieve hurricane strength. After that, however, increasing westerly vertical wind shear should induce at least some weakening until around 48 hours, at which time more rapid weakening is expected as the the system moves over sub-25C SSTs. By Days 4 and 5, decreasing sea surface temperatures and even stronger shear should cause Hernan to degenerate into a remnant low pressure system. FORECAST POSITIONS AND MAX WINDS INIT 27/0900Z 16.9N 110.0W 55 KT 65 MPH 12H 27/1800Z 18.1N 111.7W 65 KT 75 MPH 24H 28/0600Z 19.6N 114.1W 60 KT 70 MPH 36H 28/1800Z 21.0N 116.5W 55 KT 65 MPH 48H 29/0600Z 22.1N 118.6W 45 KT 50 MPH 72H 30/0600Z 23.3N 122.3W 30 KT 35 MPH 96H 31/0600Z 23.6N 125.8W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 01/0600Z 23.6N 128.7W 20 KT 25 MPH...POST-TROP/REMNT LOW $$ Forecaster Stewart

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Tropical Depression GENEVIEVE Forecast Discussion Number 9

2014-07-27 10:42:01| National Hurricane Center (East Pacific)

Issued at 200 AM PDT SUN JUL 27 2014 000 WTPZ42 KNHC 270841 TCDEP2 TROPICAL DEPRESSION GENEVIEVE DISCUSSION NUMBER 9 NWS NATIONAL HURRICANE CENTER MIAMI FL EP072014 200 AM PDT SUN JUL 27 2014 Genevieve continues to battle westerly shear. The low-level center remains exposed to the west of the deep convection, which has been pulsating during the past several hours. The initial intensity is held at 30 kt, in agreement with a Dvorak classification from TAFB. The official forecast calls for little change in strength during the next several days. Although the strength of the system is not expected to change much, the depression is anticipated to become a remnant low in the next 24 h due to the continued influence of shear and dry air. Regeneration into a tropical cyclone is possible, however, in a couple of days when the system moves into a more favorable atmospheric environment. The depression is moving westward at about 8 kt on the south side of a low- to mid-level ridge. A turn to the west-northwest is expected during the next 24 to 48 hours, and that motion should persist through the remainder of the forecast period. The official track forecast is slightly slower than the previous one and near the middle of the guidance envelope. Genevieve has crossed 140W longitude and, therefore, the next advisory on this system will be issued by the Central Pacific Hurricane Center. Forecast discussions can be found under AWIPS header HFOTCDCP2 and WMO header WTPA42 PHFO. FORECAST POSITIONS AND MAX WINDS INIT 27/0900Z 12.4N 140.1W 30 KT 35 MPH 12H 27/1800Z 12.4N 141.5W 30 KT 35 MPH 24H 28/0600Z 12.7N 143.0W 30 KT 35 MPH...POST-TROP/REMNT LOW 36H 28/1800Z 13.1N 144.6W 30 KT 35 MPH...POST-TROP/REMNT LOW 48H 29/0600Z 13.4N 146.0W 30 KT 35 MPH...POST-TROP/REMNT LOW 72H 30/0600Z 13.9N 148.2W 30 KT 35 MPH...POST-TROP/REMNT LOW 96H 31/0600Z 14.3N 149.9W 30 KT 35 MPH...POST-TROP/REMNT LOW 120H 01/0600Z 14.9N 151.8W 30 KT 35 MPH...POST-TROP/REMNT LOW $$ Forecaster Cangialosi

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Tropical Storm HERNAN Forecast Discussion Number 3

2014-07-26 22:32:56| National Hurricane Center (East Pacific)

Issued at 200 PM PDT SAT JUL 26 2014 000 WTPZ43 KNHC 262032 TCDEP3 TROPICAL STORM HERNAN DISCUSSION NUMBER 3 NWS NATIONAL HURRICANE CENTER MIAMI FL EP082014 200 PM PDT SAT JUL 26 2014 Satellite data indicate that the depression has strengthened. The cloud pattern has become better organized during the past several hours with banding features now more distinct and symmetric around the center. A recent ASCAT pass showed maximum winds near 35 kt, and Dvorak classifications from TAFB and UW-CIMSS also support a similar wind speed. Based on these data, the initial intensity is increased to 35 kt, making the cyclone Tropical Storm Hernan. Some additional strengthening appears likely during the next day or so while the environmental conditions remain favorable. Beyond that time, however, Hernan will be moving over cooler water and into an atmosphere of stronger shear and dry air. These expected hostile conditions should cause the storm to lose strength. The intensity guidance has not changed significantly, and this forecast is an update of the previous one. Hernan is moving northwestward at about 13 kt on the southwest side of a strong mid-level ridge centered over the southern United States. This steering pattern is expected to persist, and that should keep the system moving west-northwestward to northwestward at about the same speed for the next couple of days. After that time, a gradual turn toward the west with a decrease in forward speed is expected when the weakening cyclone is steered by the lighter low-level flow. The models have shifted northward this cycle, and the official track forecast is adjusted in that direction. FORECAST POSITIONS AND MAX WINDS INIT 26/2100Z 15.4N 108.3W 35 KT 40 MPH 12H 27/0600Z 16.7N 110.0W 45 KT 50 MPH 24H 27/1800Z 18.3N 112.5W 50 KT 60 MPH 36H 28/0600Z 19.7N 114.7W 50 KT 60 MPH 48H 28/1800Z 20.9N 117.0W 45 KT 50 MPH 72H 29/1800Z 22.6N 121.2W 30 KT 35 MPH 96H 30/1800Z 23.0N 124.5W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 31/1800Z 23.0N 127.5W 20 KT 25 MPH...POST-TROP/REMNT LOW $$ Forecaster Cangialosi

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Tropical Depression EIGHT-E Forecast Discussion Number 2

2014-07-26 16:32:56| National Hurricane Center (East Pacific)

Issued at 800 AM PDT SAT JUL 26 2014 000 WTPZ43 KNHC 261432 TCDEP3 TROPICAL DEPRESSION EIGHT-E DISCUSSION NUMBER 2 NWS NATIONAL HURRICANE CENTER MIAMI FL EP082014 800 AM PDT SAT JUL 26 2014 The tropical depression has not changed much during the past several hours. Although the system is producing a considerable amount of deep convection, it is mainly confined to the north side of the cyclone and is not wrapping around the center. The initial intensity remains 30 kt based on a blend of the Dvorak intensity estimates. The environment is currently favorable for the depression to strengthen, but it is not expected to remain that way for very long. In about 2 days, the cyclone will be moving over cooler waters and into an atmosphere of stronger shear and dry air. The models show less strengthening this cycle, and the official intensity forecast is a little lower than the previous one based on this guidance. The system is moving northwestward at about 13 kt. A slightly faster west-northwest to northwest motion is expected during the next couple of days while the cyclone remains embedded in the fast flow on the southwest side of a strong mid-level ridge over the southern United States. A gradual turn toward the west with a decrease in forward speed is expected beyond a few days when the weakening cyclone becomes steered by the lighter low-level flow. The models are tightly clustered, and the official track forecast is essentially an update of the previous one. FORECAST POSITIONS AND MAX WINDS INIT 26/1500Z 14.4N 107.3W 30 KT 35 MPH 12H 27/0000Z 15.7N 109.3W 35 KT 40 MPH 24H 27/1200Z 17.3N 111.9W 45 KT 50 MPH 36H 28/0000Z 18.7N 114.4W 50 KT 60 MPH 48H 28/1200Z 20.0N 116.8W 50 KT 60 MPH 72H 29/1200Z 21.6N 120.9W 35 KT 40 MPH 96H 30/1200Z 22.0N 124.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 31/1200Z 22.0N 126.5W 20 KT 25 MPH...POST-TROP/REMNT LOW $$ Forecaster Cangialosi

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