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Hurricane Hilda Forecast Discussion Number 10

2021-08-02 04:36:20| National Hurricane Center (East Pacific)

Issued at 800 PM PDT Sun Aug 01 2021 000 WTPZ43 KNHC 020236 TCDEP3 Hurricane Hilda Discussion Number 10 NWS National Hurricane Center Miami FL EP082021 800 PM PDT Sun Aug 01 2021 Hilda's satellite appearance is showing effects of easterly vertical wind shear this evening. Recent imagery shows a sharp edge to the upper-level outflow on the eastern side of the system. A 2130 UTC AMSR2 microwave pass reveals that the eyewall is no longer closed, as the inner core convection has been eroded on the eastern side of the circulation. Microwave data also indicate the vortex has become vertically tilted, with the mid-level center displaced about 10-15 n mi to the west-northwest of the low-level center. Thus, the initial intensity is lowered slightly to 70 kt for this advisory, in best agreement with the objective UW-CIMSS Dvorak estimates. Hilda is still moving west-northwestward at 285/8 kt, to the south of a ridge over the western U.S. and northern Mexico. A turn to the northwest is expected on Monday as the ridge weakens, likely in response to T.D. Ten-E located to the east-northeast of Hilda. A northwestward motion should continue through midweek before the ridge becomes reestablished and Hilda turns westward through the rest of the forecast period. There is greater track uncertainty later in the week due to possible interaction with another system that could redevelop from the remnants of T.D. Nine-E. The official NHC track forecast has been adjusted to the right of the previous one at 48 h and beyond based on the latest guidance, but it still lies slightly left of the multi-model consensus aids TVCE and HCCA. Environmental conditions are not expected to become any more favorable for strengthening during the next couple days, so Hilda's intensity has likely peaked. Moderate northeasterly shear is forecast to persist for the next 36-48 h, and the NHC forecast track brings Hilda north of the 26 deg C isotherm by the time these upper-level winds subside. Once over cooler waters, Hilda is forecast to quickly spin down and weaken to a tropical depression by 96 h. The NHC intensity forecast has again been lowered by 5-10 kt from the previous one at all forecast times, but it still lies slightly above the IVCN and HCCA consensus aids through 72 h. The system is forecast to degenerate to a remnant low by day 5. FORECAST POSITIONS AND MAX WINDS INIT 02/0300Z 15.1N 121.6W 70 KT 80 MPH 12H 02/1200Z 15.5N 122.5W 70 KT 80 MPH 24H 03/0000Z 16.2N 123.4W 65 KT 75 MPH 36H 03/1200Z 17.3N 124.3W 60 KT 70 MPH 48H 04/0000Z 18.4N 125.3W 50 KT 60 MPH 60H 04/1200Z 19.5N 126.6W 40 KT 45 MPH 72H 05/0000Z 20.3N 128.3W 35 KT 40 MPH 96H 06/0000Z 21.0N 132.3W 25 KT 30 MPH 120H 07/0000Z 21.5N 136.0W 20 KT 25 MPH...POST-TROP/REMNT LOW $$ Forecaster Reinhart/Pasch

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Tropical Depression Ten-E Forecast Discussion Number 2

2021-08-02 04:33:54| National Hurricane Center (East Pacific)

Issued at 900 PM MDT Sun Aug 01 2021 000 WTPZ45 KNHC 020233 TCDEP5 Tropical Depression Ten-E Discussion Number 2 NWS National Hurricane Center Miami FL EP102021 900 PM MDT Sun Aug 01 2021 The center of the tropical cyclone is located near the northeastern edge of the main area of deep convection, as the system is experiencing northeasterly shear due to the flow on the south side of a large upper-level anticyclone. Enhanced infrared imagery shows that the convection is very deep over the western part of the circulation, but there is little evidence of banding features. The current intensity is held at 30 kt in agreement with a Dvorak estimate from SAB. Hopefully we will soon obtain some additional scatterometer data to provide an intensity estimate. The depression continues its west-northwestward track with a motion near 295/11 kt. This heading should continue for the next day or two while the cyclone moves along the southwestern side of a mid-level high pressure area. In 2-3 days, the track could become complicated by the interaction with the circulation of Hilda to the southwest, but the system will probably be quite weak by that time. The official forecast is close to the previous one but somewhat slower in the latter part of the period. Assuming that the low-level center will become at least a little more embedded within the convection later tonight, the system is forecast to strengthen into a tropical storm overnight. The storm will probably be short-lived, however, with increased shear and cooler waters causing the system to degenerate into a remnant low in a couple of days. The official forecast is not far from the model consensus predictions, but a more rapid weakening is predicted by the global models. FORECAST POSITIONS AND MAX WINDS INIT 02/0300Z 17.6N 112.9W 30 KT 35 MPH 12H 02/1200Z 18.3N 114.4W 35 KT 40 MPH 24H 03/0000Z 19.2N 116.2W 35 KT 40 MPH 36H 03/1200Z 20.0N 117.5W 30 KT 35 MPH 48H 04/0000Z 20.4N 118.3W 25 KT 30 MPH...POST-TROP/REMNT LOW 60H 04/1200Z 20.7N 119.0W 20 KT 25 MPH...POST-TROP/REMNT LOW 72H 05/0000Z...DISSIPATED $$ Forecaster Pasch

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Hurricane Hilda Forecast Discussion Number 9

2021-08-01 22:33:42| National Hurricane Center (East Pacific)

Issued at 200 PM PDT Sun Aug 01 2021 000 WTPZ43 KNHC 012033 TCDEP3 Hurricane Hilda Discussion Number 9 NWS National Hurricane Center Miami FL EP082021 200 PM PDT Sun Aug 01 2021 Hilda has had a similar appearance all day with an elongated cloud pattern from southeast to northwest on satellite imagery. Recent microwave passes show that the center is located on the northern side of the central dense overcast. The current intensity estimates have a very wide range from 65 to 90 kt, and with the apparent steady-state of the hurricane, Hilda's wind speed will stay at 75 kt until clearer data emerges. Hilda continues moving west-northwestward at about 7 kt. The trends from the last advisory have continued with more interaction shown with new Tropical Depression 10-E to the east, leading to a weaker ridge and a faster northwestward turn of Hilda in a day or so. By midweek, Hilda should turn back to the west-northwest and westward later in the period under the influence of a stronger portion of the ridge. The new official forecast is shifted about a half a degree to the northeast, near the model consensus, although the corrected-consensus models are even farther to the right. With the forecast track shift, it is becoming unlikely that Hilda will get significantly stronger since it will move over cooler waters sooner. In addition, easterly shear should increase tomorrow, probably leading to the start of weakening. Guidance has trended downward since the last cycle, and considering the new track forecast moves over cooler waters faster, the latest NHC wind speed forecast has been lowered 5-10 kt at all time periods, and this still might be too high. In about 4 days, most of the models show little convection remaining with Hilda due to cold water and drier mid-level air, so the system should transition to a remnant low by day 5. FORECAST POSITIONS AND MAX WINDS INIT 01/2100Z 14.8N 120.8W 75 KT 85 MPH 12H 02/0600Z 15.2N 121.8W 75 KT 85 MPH 24H 02/1800Z 15.8N 122.9W 75 KT 85 MPH 36H 03/0600Z 16.6N 123.7W 70 KT 80 MPH 48H 03/1800Z 17.6N 124.6W 60 KT 70 MPH 60H 04/0600Z 18.7N 125.8W 50 KT 60 MPH 72H 04/1800Z 19.6N 127.5W 45 KT 50 MPH 96H 05/1800Z 20.7N 131.6W 35 KT 40 MPH 120H 06/1800Z 21.0N 135.5W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ Forecaster Blake

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Hurricane Hilda Forecast Discussion Number 8

2021-08-01 16:50:31| National Hurricane Center (East Pacific)

Issued at 800 AM PDT Sun Aug 01 2021 000 WTPZ43 KNHC 011450 TCDEP3 Hurricane Hilda Discussion Number 8 NWS National Hurricane Center Miami FL EP082021 800 AM PDT Sun Aug 01 2021 Hilda is a bit of a mess this morning with an elongated cloud pattern from southeast to northwest and no signs of an eye in conventional satellite imagery. However, microwave data near 1155 UTC from GPM still shows a well-defined low-level eye, although the mid-level structure remains degraded from easterly shear. The current wind speed is held at 75 kt, with this being an uncertain estimate due to a large spread in the various intensity techniques. Hilda is moving west-northwestward at about 7 kt, with microwave data helping to pinpoint the slower movement. The track forecast is no piece of cake this morning with some interaction anticipated with Invest 91E to the east in a day or two. While a mid-level ridge persists to the northwest of Hilda, the southern periphery of the ridge weakens due to 91E, causing Hilda to take a northwestward turn in a couple of days. Hilda then should turn back toward the west-northwest and west by midweek due to the ridge remaining in place and 91E weakening. This is a tricky forecast because the guidance is shifting to the right, which at some point will bring Hilda over cold waters and closer to 91E, changing which atmospheric layers will dominate steering the tropical cyclone. In addition, interactions between two systems this close together aren't easy to forecast in the best of circumstances, and the latest guidance isn't in great agreement on the future strength of 91E either. As a compromise, the NHC track forecast is more conservative in shifting the track to the northeast than the guidance (remaining on the westerly side of the track envelope), then gradually comes close to the previous NHC forecast by the end of the 5-day period. This forecast is obviously rather uncertain, and a lot of generally better performing aids are to the northeast of the latest NHC track. The hurricane still has some chance to intensify during the next day or so with moderate easterly shear and good inner-core structure. Still, it is becoming more likely that Hilda is close to its peak intensity with no signs of the easterly shear abating until the hurricane moves over cool waters in a few days. Model guidance generally is lower than the last cycle, and only a few show strengthening. I'm going to keep the chance for slight strengthening in the near term, then show a steady drop in intensity due to persistent (or stronger) easterly shear and marginal water temperatures. The new intensity forecast is 5 kt lower than the last one at 36 hours and beyond and that could still be too high, especially if the track shifts any farther to the north. FORECAST POSITIONS AND MAX WINDS INIT 01/1500Z 14.6N 120.2W 75 KT 85 MPH 12H 02/0000Z 14.9N 121.2W 80 KT 90 MPH 24H 02/1200Z 15.4N 122.4W 80 KT 90 MPH 36H 03/0000Z 16.1N 123.4W 75 KT 85 MPH 48H 03/1200Z 16.9N 124.2W 70 KT 80 MPH 60H 04/0000Z 18.0N 125.5W 60 KT 70 MPH 72H 04/1200Z 19.0N 127.0W 50 KT 60 MPH 96H 05/1200Z 20.2N 131.2W 40 KT 45 MPH 120H 06/1200Z 20.5N 135.5W 30 KT 35 MPH...POST-TROP/REMNT LOW $$ Forecaster Blake

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Post-Tropical Cyclone Nine-E Forecast Discussion Number 7

2021-08-01 10:39:01| National Hurricane Center (East Pacific)

Issued at 1100 PM HST Sat Jul 31 2021 000 WTPZ44 KNHC 010838 TCDEP4 Post-Tropical Cyclone Nine-E Discussion Number 7 NWS National Hurricane Center Miami FL EP092021 1100 PM HST Sat Jul 31 2021 The depression has remained poorly organized for more than 24 hours and has produced a very limited amount of convection during that time. As a result of the lack of organized deep convection over the past day, the system no longer meets the definition of a tropical cyclone, and it has degenerated into a remnant low. In addition, the original low-level swirl that was tracked over the past day or so appears to have been absorbed within the envelope of the broader low pressure area. The system's initial intensity is maintained at 25 kt, but this could be generous. The depression has been plagued by shear and dry air entrainment, and those conditions are expected to persist for at least the next couple of days. If the system is able to survive past 72 hours, there is some chance of redevelopment when the shear decreases later in the period. However, given the uncertainty surrounding the potential interaction with Hurricane Hilda located to the cyclone's northeast, the official forecast calls for the system to remain a remnant low, and this will be the final NHC advisory on this system unless regeneration occurs. The cyclone has been nearly stationary overnight, but it is forecast to begin a slow westward to west-northwestward motion later today, and that motion should continue for the next few days. After that time, possible interaction with Hilda increases the track forecast uncertainty, but since the majority of the dynamical models keep the low on a west-northwestward heading, so does the NHC forecast. Future information on the remnant low can be found in High Seas Forecasts issued by the National Weather Service, under AWIPS header NFDHSFEPI, WMO header FZPN02 KWBC, and on the web at ocean.weather.gov/shtml/NFDHSFEPI.php Information on potential regeneration will be available in the Tropical Weather Outlook as needed. FORECAST POSITIONS AND MAX WINDS INIT 01/0900Z 11.4N 127.5W 25 KT 30 MPH...POST-TROP/REMNT LOW 12H 01/1800Z 11.8N 128.3W 25 KT 30 MPH...POST-TROP/REMNT LOW 24H 02/0600Z 12.0N 129.9W 25 KT 30 MPH...POST-TROP/REMNT LOW 36H 02/1800Z 12.3N 131.5W 25 KT 30 MPH...POST-TROP/REMNT LOW 48H 03/0600Z 12.7N 132.9W 25 KT 30 MPH...POST-TROP/REMNT LOW 60H 03/1800Z 13.1N 134.2W 25 KT 30 MPH...POST-TROP/REMNT LOW 72H 04/0600Z 13.5N 135.5W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 05/0600Z 14.5N 137.8W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 06/0600Z 15.5N 140.5W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ Forecaster Brown

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