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Hurricane Eugene Forecast Discussion Number 6

2017-07-09 04:36:39| National Hurricane Center (East Pacific)

Issued at 900 PM MDT Sat Jul 08 2017 000 WTPZ45 KNHC 090236 TCDEP5 Hurricane Eugene Discussion Number 6 NWS National Hurricane Center Miami FL EP052017 900 PM MDT Sat Jul 08 2017 Eugene has strengthened rapidly over the past 24 h and has reached hurricane strength during the past few hours. Recent microwave imagery indicates that a 25 n mi wide eye has formed, and this feature has also appeared sporadically in visible and infrared imagery. The initial intensity is raised to 70 kt based on various satellite intensity estimates in the 65-75 kt range. The hurricane continues to have good to excellent cirrus outflow in all directions as it remains in an environment of light vertical wind shear. Smoothing through the wobbles of the formative eye, the initial motion is 320/7. The hurricane is moving toward a weakness in the subtropical ridge to the west of the Baja California Peninsula, and the track forecast guidance is in good agreement that a northwestward motion should continue through the forecast period, with some increase in forward speed during the first 24 h and some decrease in forward speed after 72 h. The guidance has changed little since the last advisory, and the new forecast track is similar to the previous forecast. Eugene should remain over warm water and in a light shear environment for about the next 24 h. Thus, additional strengthening is expected, with the main question being will the current rate of intensification continue. The forecast peak intensity is increased to 90 kt, which is above the intensity guidance but could be conservative if the intensification rate does not decrease. After 24 hours, the cyclone should move over colder water, with the sea surface temperature along the forecast track expected to be near 21C by 96 h. This should cause Eugene to steadily or rapidly weaken after 24 h, with the system expected to decay to a remnant low by 96 h. FORECAST POSITIONS AND MAX WINDS INIT 09/0300Z 14.4N 113.5W 70 KT 80 MPH 12H 09/1200Z 15.4N 114.3W 80 KT 90 MPH 24H 10/0000Z 16.9N 115.6W 90 KT 105 MPH 36H 10/1200Z 18.7N 117.1W 80 KT 90 MPH 48H 11/0000Z 20.2N 118.4W 65 KT 75 MPH 72H 12/0000Z 22.5N 120.5W 40 KT 45 MPH 96H 13/0000Z 24.5N 122.5W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 14/0000Z 26.0N 124.5W 20 KT 25 MPH...POST-TROP/REMNT LOW $$ Forecaster Beven

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Tropical Storm Eugene Forecast Discussion Number 5

2017-07-08 22:32:40| National Hurricane Center (East Pacific)

Issued at 300 PM MDT Sat Jul 08 2017 000 WTPZ45 KNHC 082032 TCDEP5 Tropical Storm Eugene Discussion Number 5 NWS National Hurricane Center Miami FL EP052017 300 PM MDT Sat Jul 08 2017 The cloud pattern in visible images looks much better than the infrared presentation. Eugene appears to be developing a banding type eye, and the outflow remains fair. Dvorak estimates are now T3.5 and T4.0, and on this basis, the initial intensity has been adjusted upward to 60 kt. Eugene has the opportunity to gather more strength and become a hurricane tonight. However, beyond 24 hours a portion of the circulation will begin to move over cooler waters resulting in gradual weakening. By the end of the forecast period, the cyclone will be over much cooler waters, and Eugene will probably lose most of its associated convection and become a remnant low. The intensity forecast brings the winds a little bit higher than the earlier forecast, but beyond 24 hours, the forecast is similar to the previous one. Eugene is moving toward the northwest or 320 degrees at 7 knots, steered by the flow around the periphery of a mid-level ridge centered over the western United States and northern Mexico. A weak mid-latitude trough will cause an erosion of the ridge, and this steering pattern will keep Eugene on a general northwest track during the next 4 to 5 days. The NHC forecast is basically in the middle of the tightly-packed track guidance, and very close to the multi-model consensus. No important changes to the previous NHC forecast track are necessary. FORECAST POSITIONS AND MAX WINDS INIT 08/2100Z 13.7N 113.4W 60 KT 70 MPH 12H 09/0600Z 14.7N 114.2W 70 KT 80 MPH 24H 09/1800Z 16.2N 115.5W 80 KT 90 MPH 36H 10/0600Z 17.8N 116.8W 70 KT 80 MPH 48H 10/1800Z 19.5N 118.2W 70 KT 80 MPH 72H 11/1800Z 22.0N 120.5W 50 KT 60 MPH 96H 12/1800Z 23.8N 122.2W 40 KT 45 MPH...POST-TROPICAL 120H 13/1800Z 25.5N 124.5W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ Forecaster Avila

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Tropical Storm Eugene Forecast Discussion Number 4

2017-07-08 16:32:33| National Hurricane Center (East Pacific)

Issued at 900 AM MDT Sat Jul 08 2017 000 WTPZ45 KNHC 081432 TCDEP5 Tropical Storm Eugene Discussion Number 4 NWS National Hurricane Center Miami FL EP052017 900 AM MDT Sat Jul 08 2017 Eugene's cloud pattern has improved significantly since yesterday, and it now consists of a cyclonically-curved convective band wrapping around the center. The upper-level outflow continues to be very well established in all quadrants. Based on the average of intensity estimates of T3.0 and T3.5 on the Dvorak scale from TAFB and SAB, respectively, and objective numbers from UW-CIMMS, the winds have been increased to 50 kt in this advisory. Eugene has the opportunity to gather some strength and become a hurricane during the next 24 hours or so. However, after that time, a portion of the circulation will begin to reach cooler waters and drier air resulting in gradual weakening. By the end of the forecast period, the cyclone will be over much cooler waters, and Eugene will probably lose most of its associated convection and become a remnant low. The intensity forecast is similar to the previous one. Eugene is moving toward the northwest or 315 degrees at 8 knots around the southwestern periphery of a mid-level ridge centered over the western United States and northern Mexico. A weak mid-latitude trough will cause an erosion of the ridge, and this steering pattern will keep Eugene on a general northwest track during the next 4 to 5 days. The NHC forecast is basically in the middle of the tightly-packed track guidance. No important changes to the previous NHC forecast are necessary. FORECAST POSITIONS AND MAX WINDS INIT 08/1500Z 13.6N 112.8W 50 KT 60 MPH 12H 09/0000Z 14.5N 113.6W 60 KT 70 MPH 24H 09/1200Z 15.8N 114.7W 70 KT 80 MPH 36H 10/0000Z 17.5N 115.9W 70 KT 80 MPH 48H 10/1200Z 18.9N 117.2W 70 KT 80 MPH 72H 11/1200Z 21.5N 119.5W 55 KT 65 MPH 96H 12/1200Z 23.8N 121.6W 40 KT 45 MPH...POST-TROPICAL 120H 13/1200Z 25.5N 124.0W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ Forecaster Avila

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Tropical Storm Eugene Forecast Discussion Number 3

2017-07-08 10:34:30| National Hurricane Center (East Pacific)

Issued at 300 AM MDT Sat Jul 08 2017 000 WTPZ45 KNHC 080834 TCDEP5 Tropical Storm Eugene Discussion Number 3 NWS National Hurricane Center Miami FL EP052017 300 AM MDT Sat Jul 08 2017 Eugene's convective pattern has continued to improve since the previous advisory, with a pronounced band of cold-topped convection now wrapping more than halfway around the center. An ASCAT-A pass at 0432Z indicated peak winds of 37 kt north of the center, but the northeastern quadrant was missed where stronger winds could be occurring. The initial intensity is being maintained at 40 kt for this advisory based on consensus T2.5/35 estimates from TAFB and SAB, and a UW-CIMSS ADT estimate of T2.7/39 kt. The initial motion remains 315/08 kt. There is no significant change to previous forecast track or reasoning. Eugene is expected to continue moving around the southwestern periphery of a deep-layer ridge that extends westward across central and northern Mexico for the next 36-48 hours, and afterwards move into a weakness that is is forecast to develop in the ridge well to the west of the Baja California peninsula. The latest NHC model guidance is tightly packed about the previous forecast track, so only minor along-track speed changes were required. The aforementioned ASCAT pass indicates that the inner-core wind field of Eugene has become better defined and that the radius of maximum winds has also contracted down to about 30 n mi. As mentioned in the previous discussion, this now smaller RMW, in conjunction with a nearly ideal environment, would typically support rapid intensification. However, AMSU microwave and new GOES-16 water vapor imagery indicate that a pronounced tongue of dry air has penetrated into the southwestern quadrant, temporarily disrupting the development of inner-core convection. But should the dry air mix out during the next 12 h or so, then rapid strengthening is still a distinct possibility before Eugene reaches colder water shortly after the 36-h period. Beyond that time, the cyclone will be moving over muh colder SSTs ranging from 21-24 deg C, which should induce rapid weakening despite the low vertical wind shear conditions that will exist throughout the forecast period. The new intensity forecast is similar to the previous advisory, and closely follows the HCCA consensus model. FORECAST POSITIONS AND MAX WINDS INIT 08/0900Z 12.9N 112.1W 40 KT 45 MPH 12H 08/1800Z 13.7N 113.0W 50 KT 60 MPH 24H 09/0600Z 14.9N 114.1W 60 KT 70 MPH 36H 09/1800Z 16.4N 115.2W 70 KT 80 MPH 48H 10/0600Z 17.9N 116.5W 70 KT 80 MPH 72H 11/0600Z 20.5N 119.0W 55 KT 65 MPH 96H 12/0600Z 22.9N 121.2W 40 KT 45 MPH...POST-TROPICAL 120H 13/0600Z 25.1N 123.3W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ Forecaster Stewart

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Tropical Storm Eugene Forecast Discussion Number 2

2017-07-08 04:35:02| National Hurricane Center (East Pacific)

Issued at 900 PM MDT Fri Jul 07 2017 000 WTPZ45 KNHC 080234 TCDEP5 Tropical Storm Eugene Discussion Number 2 NWS National Hurricane Center Miami FL EP052017 900 PM MDT Fri Jul 07 2017 Eugene is gradually becoming better organized this evening, with infrared and microwave satellite imagery showing a large band of convection developing over the southeastern semicircle. Various satellite intensity estimates range from 30 to 45 kt, and the initial intensity is increased to 40 kt in best agreement with the CIMSS satellite consensus technique. The initial motion is 315/8. There is little change to either the forecast philosophy or the forecast track since the previous advisory. A mid- to upper-level low moving westward from northwestern Mexico and an upper-level low seen in water vapor imagery near 19N 120W have created a weakness in the subtropical ridge west of the Baja California peninsula. This feature is likely to persist through 120 h allowing Eugene to move steadily northwestward into the weakness through the forecast period. The new forecast track is near the consensus models and the center of the guidance envelope. Eugene is currently in an environment of light shear and warm water with good to excellent outflow in all directions. The large-scale models forecast the shear to remain light until the storm moves over decreasing sea surface temperatures in about 48 h. Based on this, the intensity forecast calls for steady strengthening until 48 h, with the new forecast lying near the upper edge of the intensity guidance. It should be noted that the rapid intensification index of the SHIPS model responds to the nearly ideal environment by showing a better than a 50 percent chance of 25 kt of strengthening during the next 24 h. So, an alternative forecast scenario is for rapid intensification if Eugene develops a well-defined inner core. After 48 h, Eugene should weaken steadily to rapidly over the cooler water, with the system now forecast to degenerate to a remnant low over 21C sea surface temperatures by 120 h. FORECAST POSITIONS AND MAX WINDS INIT 08/0300Z 12.5N 111.6W 40 KT 45 MPH 12H 08/1200Z 13.2N 112.5W 45 KT 50 MPH 24H 09/0000Z 14.5N 113.7W 55 KT 65 MPH 36H 09/1200Z 15.8N 114.9W 65 KT 75 MPH 48H 10/0000Z 17.3N 116.1W 70 KT 80 MPH 72H 11/0000Z 20.0N 118.5W 65 KT 75 MPH 96H 12/0000Z 22.5N 121.0W 45 KT 50 MPH 120H 13/0000Z 25.0N 123.0W 30 KT 35 MPH...POST-TROP/REMNT LOW $$ Forecaster Beven

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