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Hurricane GUILLERMO Forecast Discussion Number 11
2015-08-01 16:32:53| National Hurricane Center (East Pacific)
Issued at 800 AM PDT SAT AUG 01 2015 000 WTPZ44 KNHC 011432 TCDEP4 HURRICANE GUILLERMO DISCUSSION NUMBER 11 NWS NATIONAL HURRICANE CENTER MIAMI FL EP092015 800 AM PDT SAT AUG 01 2015 The cloud pattern is not as impressive as it was yesterday when there was a hint of an eye on satellite imagery. However, Dvorak T-numbers from all agencies still support an initial intensity of 90 kt. It appears that Guillermo has already peaked in intensity, and the hurricane is heading toward an environment no longer favorable for strengthening. On this basis, the NHC forecast calls for a steady state during the next 12 hours or so, and a gradual weakening thereafter. By the time Guillermo approaches the Hawaiian Islands, the upper-level winds are forecast to be even more unfavorable, and by then, Guillermo is expected to have weakened to a tropical storm. The NHC forecast is very close to the intensity consensus model ICON. The steering currents have begun to weaken, and Guillermo is slowing down. The best estimate of the initial motion is toward the west or 280 degrees at 12 kt. The hurricane is already located on the southwestern edge of the subtropical ridge, and there is a large weakness of the ridge to its northwest. This pattern should force the cyclone to slow down even further and turn more to the west-northwest. The GFS insists on a more northwesterly component bringing the center of Guillermo north of the Hawaiian Islands. The ECMWF, on the other hand, brings the cyclone south or near the Islands. The NHC forecast is very similar to the previous one, and is basically on top of the consensus of the ECMWF and the GFS models. Due to uncertainties in longer-range track predictions, it is important for users not to focus on the exact track forecasts at 96 and 120 hours. Given the large spread of the models beyond 72 hours in this case, the forecast uncertainty is particularly high at those time periods. FORECAST POSITIONS AND MAX WINDS INIT 01/1500Z 13.5N 139.0W 90 KT 105 MPH 12H 02/0000Z 13.9N 141.0W 90 KT 105 MPH 24H 02/1200Z 14.5N 143.0W 85 KT 100 MPH 36H 03/0000Z 15.3N 144.7W 80 KT 90 MPH 48H 03/1200Z 16.2N 146.0W 70 KT 80 MPH 72H 04/1200Z 17.5N 148.5W 60 KT 70 MPH 96H 05/1200Z 19.0N 151.5W 50 KT 60 MPH 120H 06/1200Z 20.7N 155.0W 40 KT 45 MPH $$ Forecaster Avila
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Hurricane GUILLERMO Forecast Discussion Number 10
2015-08-01 10:33:50| National Hurricane Center (East Pacific)
Issued at 200 AM PDT SAT AUG 01 2015 000 WTPZ44 KNHC 010833 TCDEP4 HURRICANE GUILLERMO DISCUSSION NUMBER 10 NWS NATIONAL HURRICANE CENTER MIAMI FL EP092015 200 AM PDT SAT AUG 01 2015 Guillermo's cloud pattern has changed little in organization over the past several hours. Convective banding features are not as well defined as they were 24 hours ago, and the CDO lacks a circular shape. Dvorak T-numbers remain unchanged from the previous advisory package, so the intensity estimate is held at 90 kt. Upper-level outflow has become restricted to the northwest of the cyclone. The oceanic and atmospheric environment is not likely to become more conducive for strengthening over the next couple of days, and the numerical intensity guidance generally shows a gradual weakening trend. Near the end of the forecast period, global models indicate a significant increase in vertical shear associated with strong upper-tropospheric westerlies near the Hawaiian Islands. The official forecast is near or slightly above the intensity model consensus and shows, as in the previous advisory, weakening to tropical storm status in 96 hours. Based on geostationary and microwave center fixes, in particular an earlier SSMI/S pass from 0424Z, the motion has slowed somewhat and is now estimated to be about 285/14 kt. Guillermo is approaching a weakness in the zonally-oriented mid-level ridge to its north, and this should result in further deceleration over the next couple of days. In 3-5 days, the steering currents become less well defined in the global models and there is a fair amount of spread in the dynamical track predictions. The ECMWF model has been doing a bit of a flip-flop in its last few runs, and it has shifted back the south after shifting northward in the previous run. The official forecast is held very close to the previous NHC track and is close to the latest track model consensus, TVCN, which combines not only the GFS and ECMWF solutions but also the HWRF, GFDL, and U.K. Met. Office model forecasts. Due to uncertainties in longer-range track predictions, it is important for users not to focus on the exact track forecasts at 96 and 120 hours. FORECAST POSITIONS AND MAX WINDS INIT 01/0900Z 13.4N 137.4W 90 KT 105 MPH 12H 01/1800Z 13.9N 139.6W 90 KT 105 MPH 24H 02/0600Z 14.5N 142.0W 90 KT 105 MPH 36H 02/1800Z 15.1N 144.0W 85 KT 100 MPH 48H 03/0600Z 15.8N 145.4W 75 KT 85 MPH 72H 04/0600Z 17.3N 148.0W 65 KT 75 MPH 96H 05/0600Z 19.0N 151.0W 60 KT 70 MPH 120H 06/0600Z 20.5N 154.0W 50 KT 60 MPH $$ Forecaster Pasch
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Hurricane GUILLERMO Forecast Discussion Number 9
2015-08-01 04:58:20| National Hurricane Center (East Pacific)
Issued at 800 PM PDT FRI JUL 31 2015 000 WTPZ44 KNHC 010258 TCDEP4 HURRICANE GUILLERMO DISCUSSION NUMBER 9 NWS NATIONAL HURRICANE CENTER MIAMI FL EP092015 800 PM PDT FRI JUL 31 2015 Both microwave and conventional satellite imagery indicate that Guillermo has not become any better organized during the past several hours. In fact, the satellite presentation appears to have deteriorated since earlier today with microwave data showing the northwestern portion of the eyewall eroding. Satellite intensity estimates from TAFB and SAB and the latest objective intensity estimate from UW-CIMSS ADT suggest that initial intensity remains 90 kt. Guillermo continues to move rapidly to the west-northwest, with an initial motion estimate of 285/18 kt. Little change to this motion is expected for the next 24 hours, with the cyclone remaining to the south of a mid-level subtropical ridge. Beyond 24 hours to around 72 hours, a deepening mid- to upper-level trough over the central Pacific is forecast to create a break in the subtropical ridge, which should cause the tropical cyclone to slow down and turn more toward the northwest. The spread in the guidance suite increases beyond 72 hours, but most of the models maintain a general west-northwestward motion. The new forecast track is basically an update of the previous track through 72 hours, and is then nudged slightly to the right or north of the previous track toward the multi-model consensus thereafter. The intensity forecast has become somewhat problematic. The reason for the recent arrested development is unclear, although it might be related to dry air entrainment into the northwestern quadrant of the cyclone. However, there is still the opportunity for Guillermo to strengthen a bit more during the next 12 to 24 hours, while the system remains within a low-shear environment and over warm sea surface temperatures. The new intensity forecast is adjusted slightly downward to 95 kt at the 12- and 24-hour forecast times. Thereafter, the cyclone is forecast to move into an upper-level deformation zone between subtropical ridges to the east and west, which is a less favorable environment. Also, sea surface temperatures gradually cool along the forecast track. We have followed the previous forecast trend of gradual weakening, which is in good agreement with the latest SHIPS/LGEM and IVCN consensus guidance. When Guillermo approaches the Hawaiian Islands, it is expected to encounter increasing westerly shear, and the new intensity forecast follows the previous forecast in weakening Guillermo to tropical storm strength. FORECAST POSITIONS AND MAX WINDS INIT 01/0300Z 13.2N 136.1W 90 KT 105 MPH 12H 01/1200Z 13.7N 138.5W 95 KT 110 MPH 24H 02/0000Z 14.3N 141.1W 95 KT 110 MPH 36H 02/1200Z 15.0N 143.2W 90 KT 105 MPH 48H 03/0000Z 15.8N 145.0W 80 KT 90 MPH 72H 04/0000Z 17.0N 147.5W 65 KT 75 MPH 96H 05/0000Z 19.0N 150.5W 60 KT 70 MPH 120H 06/0000Z 20.5N 153.5W 50 KT 60 MPH $$ Forecaster Beven/Jacobson
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Hurricane GUILLERMO Forecast Discussion Number 8
2015-07-31 22:33:47| National Hurricane Center (East Pacific)
Issued at 200 PM PDT FRI JUL 31 2015 000 WTPZ44 KNHC 312033 TCDEP4 HURRICANE GUILLERMO DISCUSSION NUMBER 8 NWS NATIONAL HURRICANE CENTER MIAMI FL EP092015 200 PM PDT FRI JUL 31 2015 The satellite presentation has improved a little more during past few hours. Although the eye is much better defined on microwave, it is not completely clear on visible or infrared imagery. The average of intensity estimates from TAFB, SAB and objective numbers from UW-CIMSS suggests an initial intensity of 90 kt. The current environment of low shear and a warm ocean is quite favorable for Guillermo to intensify further in the short term, and the NHC forecast brings the winds up to 100 kt within 12 hours. Beyond two days, the hurricane will begin to move into a less favorable shear environment as Guillermo approaches prevailing upper-level westerlies. By the end of the forecast period, when Guillermo is expected to be nearing the Hawaiian Islands, most of the guidance indicate that Guillermo should have weakened to a tropical storm, and so does the NHC forecast. The hurricane continues to move west-northwestward or 285 degrees at 16 kt. Guillermo will likely continue at this fast pace for another 24 to 36 hours while embedded within a layer of deep easterlies to the south of the subtropical ridge. After that time, the hurricane is expected to slow down as it approaches the southwestern edge of the subtropical ridge and encounters weaker steering currents. The latest multi-model consensus GFEX has shifted considerably northward primarily due to the fact that the ECMWF changed its tune, and is now closer to the northernmost GFS. On this basis, the NHC forecast is adjusted northward a little bit, but not as much as the consensus, in case the ECMWF changes its tune again tonight. The NHC forecast is on southern edge of the guidance envelope, and perhaps will have to be adjusted farther northward when new model runs become available. FORECAST POSITIONS AND MAX WINDS INIT 31/2100Z 12.7N 134.8W 90 KT 105 MPH 12H 01/0600Z 13.3N 137.2W 100 KT 115 MPH 24H 01/1800Z 14.0N 140.1W 100 KT 115 MPH 36H 02/0600Z 14.8N 142.3W 90 KT 105 MPH 48H 02/1800Z 15.5N 144.3W 80 KT 90 MPH 72H 03/1800Z 17.0N 147.0W 65 KT 75 MPH 96H 04/1800Z 18.5N 150.0W 60 KT 70 MPH 120H 05/1800Z 19.5N 153.0W 50 KT 60 MPH $$ Forecaster Avila
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Hurricane GUILLERMO Forecast Discussion Number 7
2015-07-31 16:44:44| National Hurricane Center (East Pacific)
Issued at 800 AM PDT FRI JUL 31 2015 000 WTPZ44 KNHC 311444 TCDEP4 HURRICANE GUILLERMO DISCUSSION NUMBER 7 NWS NATIONAL HURRICANE CENTER MIAMI FL EP092015 800 AM PDT FRI JUL 31 2015 The satellite presentation has improved during the past several hours. The eye, however, is not completely closed on microwave imagery at this time. There are several cyclonically curved convective bands around the center, and the outflow is symmetric. Both objective and subjective Dvorak numbers have continued to increase, and the average of these numbers leads to an initial intensity of 80 kt. The current environment of low shear and warm ocean is quite favorable for Guillermo to intensity further, and the NHC forecast brings the winds up to 100 kt in about 24 hours. This forecast is a little bit higher than the SHIPS guidance, but follows the upward trend of the consensus. Beyond two days, the hurricane will encounter a less favorable shear environment as Guillermo approaches the prevailing upper-level westerlies. By the end of the forecast period, when Guillermo is expected to be nearing the Hawaiian Islands, the cyclone should have weakened to a tropical storm. The hurricane is racing west-northwestward or 285 degrees at about 15 kt. The cyclone will likely continue on this track and speed for the next day or two while embedded within a layer of deep easterlies to the south of the subtropical ridge. After 48 hours, the hurricane is expected to slow down as it approaches the southwestern edge of the subtropical ridge. By then, the presence of weaker steering currents makes the track forecast uncertain, and even more uncertain as the cyclone approaches the Hawaiian islands in about five days. The NHC forecast is consistent with the solution provided by global models. The forecast is also near the consensus, but heavily weighted on the GFS and ECMWF models. FORECAST POSITIONS AND MAX WINDS INIT 31/1500Z 12.4N 132.7W 80 KT 90 MPH 12H 01/0000Z 13.0N 134.9W 90 KT 105 MPH 24H 01/1200Z 13.6N 137.8W 100 KT 115 MPH 36H 02/0000Z 14.3N 140.4W 100 KT 115 MPH 48H 02/1200Z 15.0N 142.4W 90 KT 105 MPH 72H 03/1200Z 16.3N 145.4W 70 KT 80 MPH 96H 04/1200Z 17.5N 148.3W 60 KT 70 MPH 120H 05/1200Z 18.5N 152.0W 50 KT 60 MPH $$ Forecaster Avila
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