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Tropical Storm ESTELLE Forecast Discussion Number 12

2016-07-18 10:49:14| National Hurricane Center (East Pacific)

Issued at 300 AM MDT MON JUL 18 2016 000 WTPZ41 KNHC 180849 TCDEP1 TROPICAL STORM ESTELLE DISCUSSION NUMBER 12 NWS NATIONAL HURRICANE CENTER MIAMI FL EP062016 300 AM MDT MON JUL 18 2016 Estelle has changed little overall since the previous advisory due to the combined effects of moderate northwesterly wind shear and intrusions of dry mid-level air. The result has been the inability of the cyclone to develop a persistent eye feature in microwave satellite imagery. The initial intensity has been maintained at 60 kt for this advisory, based on a blend of the T- and CI-numbers from TAFB/SAB, which is supported by a 0432Z ASCAT-B scatterometer pass that contained a couple of wind speeds of 50-55 kt. The initial motion estimates remains a steady 290/08kt. There is no significant change to the previous forecast track or reasoning. Estelle is expected to move west-northwestward for the next 72-96 hours, followed by a turn toward the northwest by day 5 when the cyclone moves into a developing break in the subtropical ridge. The latest NHC model guidance remains in excellent agreement on this track scenario. The new forecast track is essentially just an update of the previous advisory track through 72 hours, and then is shifted slightly northward in line with the trend in the guidance. Estelle still has about another 36 hours or so to strengthen, during which time the shear is forecast to decrease to less than 5 kt and SSTs remain above 26 deg C. Thereafter, steady weakening is expected due to SSTs decreasing below 25 deg C around 48 h and to 23 deg C by 96 h. The new intensity forecast to the similar to the previous NHC intensity forecast, and closely follows the consensus model IVCN. FORECAST POSITIONS AND MAX WINDS INIT 18/0900Z 17.2N 114.0W 60 KT 70 MPH 12H 18/1800Z 17.7N 115.3W 65 KT 75 MPH 24H 19/0600Z 18.3N 117.1W 70 KT 80 MPH 36H 19/1800Z 18.8N 119.0W 75 KT 85 MPH 48H 20/0600Z 19.2N 121.2W 70 KT 80 MPH 72H 21/0600Z 20.2N 125.8W 60 KT 70 MPH 96H 22/0600Z 22.0N 130.8W 45 KT 50 MPH 120H 23/0600Z 25.5N 135.2W 30 KT 35 MPH...POST-TROP/REMNT LOW $$ Forecaster Stewart

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Hurricane DARBY Forecast Discussion Number 26

2016-07-18 04:36:47| National Hurricane Center (East Pacific)

Issued at 800 PM PDT SUN JUL 17 2016 000 WTPZ45 KNHC 180236 TCDEP5 HURRICANE DARBY DISCUSSION NUMBER 26 NWS NATIONAL HURRICANE CENTER MIAMI FL EP052016 800 PM PDT SUN JUL 17 2016 Darby has not weakened since the last advisory; in fact the hurricane looks a little more impressive than it did earlier today. Although central convection has not strengthened appreciably, the CDO has become more symmetric and the eye a little more distinct. The current intensity estimate is held at 80 kt which is close to a consensus of Dvorak estimates from SAB and TAFB, along with ADT estimates from UW-CIMSS. Darby is over SSTs near 24 deg C and will be moving over slightly cooler waters overnight. After that, the cyclone should traverse SSTs near 25 deg C through 48 hours. Gradual weakening is predicted due to these somewhat cool waters, and Darby should lose hurricane status in about 24 hours with additional weakening thereafter. In 72 hours or so, the ocean under Darby will warm slightly to 25-26 deg C but by that time the vertical shear, which had been low, is forecast to increase and this should prevent restrenghtening in the latter part of the forecast period. The official intensity forecast is close to the latest model consensus. Darby continues on a westward track and the initial motion estimate remains 275/8 kt. There is no reason to change the track forecast from the previous advisory package. A narrow east-west oriented mid-level ridge is expected to be maintained to the north of Darby for the next several days. Late in the period, a mid-level high builds to the northwest of the tropical cyclone which should cause a slightly south of west motion. The official forecast lies a little south of the dynamical model consensus and is a blend of the latest GFS and ECMWF predictions. FORECAST POSITIONS AND MAX WINDS INIT 18/0300Z 18.4N 129.0W 80 KT 90 MPH 12H 18/1200Z 18.6N 130.7W 70 KT 80 MPH 24H 19/0000Z 19.0N 133.0W 60 KT 70 MPH 36H 19/1200Z 19.4N 135.4W 55 KT 65 MPH 48H 20/0000Z 19.7N 137.7W 50 KT 60 MPH 72H 21/0000Z 19.5N 142.3W 45 KT 50 MPH 96H 22/0000Z 18.7N 147.0W 35 KT 40 MPH 120H 23/0000Z 18.0N 151.0W 35 KT 40 MPH $$ Forecaster Pasch

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Tropical Storm ESTELLE Forecast Discussion Number 11

2016-07-18 04:34:45| National Hurricane Center (East Pacific)

Issued at 900 PM MDT SUN JUL 17 2016 000 WTPZ41 KNHC 180234 TCDEP1 TROPICAL STORM ESTELLE DISCUSSION NUMBER 11 NWS NATIONAL HURRICANE CENTER MIAMI FL EP062016 900 PM MDT SUN JUL 17 2016 Estelle looks a little less organized than this afternoon, since the eye feature seen on previous microwave imagery has disappeared and the tropical cyclone is displaying a more asymmetric pattern. The initial wind speed is held at 60 kt for this advisory, a blend of the T- and CI-numbers from TAFB/SAB. It seems like some northwesterly shear is preventing much intensification at this time. The shear, however, should abate during the next 24 hours, which would allow for gradual strengthening until the storm reaches cooler water in a couple of days. Thereafter, a more steady weakening is likely, and Estelle should become post-tropical in about 5 days while it moves over 23 deg C waters. The models have backed off somewhat on the peak intensity, and the official forecast follows suit, although the new prediction is higher than the consensus for the first few days. Best estimate of initial motion is to the west-northwest at about 8 kt. Estelle should continue to move on that general course for the next couple of days, with perhaps a bend toward the west in 3 days due to the subtropical ridge to the north temporarily strengthening. Overall, the global models are showing less ridging between 130-140W at long range, which would cause Estelle to turn west-northwestward or even northwestward by the end of the forecast period. Accordingly, most of the models have again shifted northward this cycle, and the official forecast is moved in that direction. FORECAST POSITIONS AND MAX WINDS INIT 18/0300Z 17.0N 113.2W 60 KT 70 MPH 12H 18/1200Z 17.4N 114.5W 65 KT 75 MPH 24H 19/0000Z 18.0N 116.2W 70 KT 80 MPH 36H 19/1200Z 18.6N 117.9W 75 KT 85 MPH 48H 20/0000Z 19.0N 120.0W 75 KT 85 MPH 72H 21/0000Z 19.6N 124.4W 65 KT 75 MPH 96H 22/0000Z 21.0N 129.5W 50 KT 60 MPH 120H 23/0000Z 23.5N 134.5W 35 KT 40 MPH...POST-TROPICAL $$ Forecaster Blake

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Tropical Storm ESTELLE Forecast Discussion Number 10

2016-07-17 22:49:16| National Hurricane Center (East Pacific)

Issued at 300 PM MDT SUN JUL 17 2016 000 WTPZ41 KNHC 172049 TCDEP1 TROPICAL STORM ESTELLE DISCUSSION NUMBER 10 NWS NATIONAL HURRICANE CENTER MIAMI FL EP062016 300 PM MDT SUN JUL 17 2016 Recent satellite data have given mixed signals on the overall structure of Estelle. In visible satellite pictures, a band of convection has wrapped around the center, and what looks like a ragged eye has appeared. However, recent microwave imagery suggest that the structure is not as well organized with the low-level center displaced to west of the mid-level center, likely the result of continued northwesterly shear. Subjective T-numbers of 4.0 from TAFB and SAB support an intensity of 65 kt, but, given the lack of inner-core organization, the initial wind speed is set to 60 kt. Recent ASCAT data revealed a large radius of maximum winds, and larger area of tropical-storm-force winds, which required an outward adjustment of the wind radii. Estelle continues to move westward to west-northwestward at about 7 kt. The track forecast reasoning remains the same as the previous advisory. The tropical storm is forecast to move west-northwestward to the south of a strong subtropical ridge during the next several days. Estelle will be nearing the western portion of the ridge by day 5 and a turn toward the northwest is predicted near the end of the period. Although the guidance is still in fairly good agreement, most of the models have shifted northward this cycle. The NHC track has been adjusted accordingly, but it lies just south of the multi-model consensus and the latest GFS and ECMWF tracks. The moderate northwesterly shear over the tropical storm is expected to weaken during the next 24 hours, which should allow for gradual intensification. Estelle is predicted to reach peak intensity in 36-48 hours, and the NHC intensity forecast is near the high end of the guidance. After that time, cooler water and a more stable airmass should induce weakening, and Estelle is predicted to become a post-tropical cyclone in about 5 days. FORECAST POSITIONS AND MAX WINDS INIT 17/2100Z 16.5N 112.5W 60 KT 70 MPH 12H 18/0600Z 17.0N 113.7W 70 KT 80 MPH 24H 18/1800Z 17.6N 115.4W 75 KT 85 MPH 36H 19/0600Z 18.0N 117.2W 80 KT 90 MPH 48H 19/1800Z 18.4N 119.1W 80 KT 90 MPH 72H 20/1800Z 19.0N 123.3W 65 KT 75 MPH 96H 21/1800Z 20.0N 128.2W 55 KT 65 MPH 120H 22/1800Z 22.0N 133.5W 35 KT 40 MPH...POST-TROPICAL $$ Forecaster Brown

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Tropical Storm ESTELLE Forecast Discussion Number 9

2016-07-17 16:37:14| National Hurricane Center (East Pacific)

Issued at 900 AM MDT SUN JUL 17 2016 000 WTPZ41 KNHC 171437 TCDEP1 TROPICAL STORM ESTELLE DISCUSSION NUMBER 9 NWS NATIONAL HURRICANE CENTER MIAMI FL EP062016 900 AM MDT SUN JUL 17 2016 A large burst of deep convection developed over the center of Estelle overnight and continues this morning. A timely SSMIS microwave overpass was very helpful in examining the structure and center location of the tropical cyclone. The microwave data revealed a well-defined low-level ring located near the northwestern edge of the primary convective band, but there was no evidence of a mid-level eye. The latest Dvorak T-numbers from SAB and TAFB are 3.5 and 4.0, respectively, and UW/CIMSS ADT estimates have risen to T3.5/55 kt. These data support an initial wind speed of 55 kt for this advisory. The initial motion estimate is 285/7 kt. A strong subtropical ridge to the north of Estelle should keep the tropical cyclone moving on a westward to west-northwestward heading during the next several days. Near the end of the forecast period, Estelle will be approaching the western portion of the ridge, which should allow the tropical cyclone to gain more latitude. The guidance is more tightly clustered today than it was 24 hours ago, so there is increased confidence in the track forecast. The new NHC track is near the Florida State Superensemble and an average of the GFS/ECMWF models. There appears to be some north or northwesterly shear still affecting Estelle, but the shear is not expected to be strong enough to prevent intensification during the next day or so. After that time, the shear is forecast to relax, and Estelle is forecast to strengthen at a faster rate on Monday. The track of the tropical cyclone brings it over cooler waters in 2 to 3 days, which should start the weakening process, and it should continue throughout the remainder of the forecast period. The updated intensity forecast is similar to the previous advisory, and is closest to the Florida State Superensemble and the intensity consensus IVCN. FORECAST POSITIONS AND MAX WINDS INIT 17/1500Z 16.3N 111.8W 55 KT 65 MPH 12H 18/0000Z 16.6N 112.9W 65 KT 75 MPH 24H 18/1200Z 17.2N 114.6W 70 KT 80 MPH 36H 19/0000Z 17.6N 116.3W 80 KT 90 MPH 48H 19/1200Z 17.9N 118.1W 85 KT 100 MPH 72H 20/1200Z 18.2N 122.2W 80 KT 90 MPH 96H 21/1200Z 19.0N 127.0W 65 KT 75 MPH 120H 22/1200Z 20.8N 132.5W 45 KT 50 MPH $$ Forecaster Brown

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