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Hurricane Norman Forecast Discussion Number 11

2018-08-30 22:37:54| National Hurricane Center (East Pacific)

Issued at 200 PM PDT Thu Aug 30 2018 167 WTPZ41 KNHC 302037 TCDEP1 Hurricane Norman Discussion Number 11 NWS National Hurricane Center Miami FL EP162018 200 PM PDT Thu Aug 30 2018 Norman is a very impressive hurricane in visible and infrared satellite imagery. The hurricane's CDO is very symmetric and has a well-defined 20-nmi-wide eye. The surrounding ring of cold cloud tops have warmed slightly, but the various satellite intensity estimates are still catching up to the improved satellite presentation and range from 127 kt to 135 kt. Based on a blend of these data, the initial intensity is set at 130 kt, and it appears that Norman's rapid strengthening phase is easing. There is still a potential for some additional increase in intensity within the next 12 hour or so, however, eyewall replacement probabilities from UW/CIMSS indicate a very high likelihood of an eyewall replacement beginning within the next 12-24 hours which will probably lead to some fluctuations in intensity. Slightly lower sea surface temperatures and a subtle increase in northeasterly shear are expected to cause a gradual decrease in wind speed over the weekend. The NHC intensity forecast shows gradual weakening but it does not weaken Norman as quickly as the statistical guidance, and it is in best agreement with the HFIP corrected consensus model. Recent satellite fixes indicated that Norman is moving slightly south of due west. A strong mid- to upper-level ridge that extends west-southwestward from the Baja California peninsula should steer Norman west-southwestward during the next 36 hours. After that time, the ridge changes orientation which is expected to cause Norman to turn back toward the west or west-northwest by early next week. The track guidance is once again tightly clustered but the overall model enveloped has shifted slightly southward. As a result, the NHC forecast has been nudged in that direction to be closer to the various consensus aids. FORECAST POSITIONS AND MAX WINDS INIT 30/2100Z 17.5N 118.8W 130 KT 150 MPH 12H 31/0600Z 17.2N 120.0W 135 KT 155 MPH 24H 31/1800Z 16.8N 121.5W 130 KT 150 MPH 36H 01/0600Z 16.3N 123.2W 120 KT 140 MPH 48H 01/1800Z 16.2N 125.1W 115 KT 130 MPH 72H 02/1800Z 17.1N 129.4W 105 KT 120 MPH 96H 03/1800Z 18.9N 135.2W 85 KT 100 MPH 120H 04/1800Z 20.2N 140.5W 65 KT 75 MPH $$ Forecaster Brown

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Potential Tropical Cyclone Six Forecast Discussion Number 2

2018-08-30 22:32:25| National Hurricane Center (Atlantic)

Issued at 500 PM AST Thu Aug 30 2018 270 WTNT41 KNHC 302032 TCDAT1 Potential Tropical Cyclone Six Discussion Number 2 NWS National Hurricane Center Miami FL AL062018 500 PM AST Thu Aug 30 2018 The area of low pressure has continued to become better defined, and is still accompanied by a large area of disturbed weather with gusty winds. However, the system lacks a well-defined center, and Dvorak classifications do not support to classify the disturbance as a tropical depression at this time. An environment of high moisture and low shear favors genesis, and the disturbance is expected to become a tropical cyclone within the next 12 to 24 hours. These favorable conditions are expected to prevail, so the NHC forecast gradually brings the winds up at a similar rate as the intensity consensus. Since the system lacks a well defined center, the initial motion is uncertain. The best estimate is toward the west or 280 degrees at 8 kt. The disturbance is moving rather slow because it is still embedded within the strong southwesterly monsoonal flow. Once it moves away from that region near Africa, it will be steered by the trade winds around the subtropical ridge, and the system will increase its westward or west-northwestward forward speed. By the end of the forecast period, a turn toward the northwest should begin as the cyclone reaches a weakness in the subtropical high. The NHC forecast is similar to the earlier one, and is in between the corrected consensus HCCA and the multi-model aids. FORECAST POSITIONS AND MAX WINDS INIT 30/2100Z 12.9N 19.4W 25 KT 30 MPH...POTENTIAL TROP CYCLONE 12H 31/0600Z 13.1N 20.5W 30 KT 35 MPH...TROPICAL DEPRESSION 24H 31/1800Z 14.0N 23.0W 40 KT 45 MPH 36H 01/0600Z 14.7N 26.0W 45 KT 50 MPH 48H 01/1800Z 15.5N 29.0W 50 KT 60 MPH 72H 02/1800Z 17.0N 34.5W 60 KT 70 MPH 96H 03/1800Z 18.7N 39.0W 65 KT 75 MPH 120H 04/1800Z 21.0N 43.0W 65 KT 75 MPH $$ Forecaster Avila

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Hurricane Norman Forecast Discussion Number 10

2018-08-30 16:47:55| National Hurricane Center (East Pacific)

Issued at 800 AM PDT Thu Aug 30 2018 951 WTPZ41 KNHC 301447 TCDEP1 Hurricane Norman Discussion Number 10 NWS National Hurricane Center Miami FL EP162018 800 AM PDT Thu Aug 30 2018 Norman has rapidly strengthened during the past 12 to 24 hours, with the development of a well-defined 20-nmi-wide eye and a thick ring of cold cloud tops of -70 to -85C. Dvorak constraints have limited the amount of increase in the subjective and objective final T-numbers, but the most recent raw data T-numbers are between T6.5 and T7.2, which yields an initial intensity estimate of 130 kt. Norman's intensity has increased an estimated 70 kt from 1200 UTC yesterday morning to 1200 UTC this morning- the fastest in the basin since Patricia in 2015. Norman has become the 5th category 4 hurricane in the eastern Pacific in 2018 and is also the strongest hurricane in the basin so far this season. The hurricane remains in a low-shear environment and will continue to move over very warm waters of 29-30 degrees Celsius for another 24 hours. These conditions are expected to allow for additional strengthening and Norman is forecast to become a category 5 hurricane later today. Eyewall replacement cycles are likely after that time, which are difficult to predict, and should cause some fluctuations in intensity during the next couple of days. Later in the period, gradually decreasing sea surface temperatures and a slight increase in shear are forecast to cause gradual weakening. However, Norman is predicted to remain a hurricane throughout the 5-day forecast period. Norman is moving westward or 270/7 kt. A strong subtropical ridge that extends from the Baja California peninsula west-southwestward into the eastern Pacific is expected to turn Norman west-southwestward later today or tonight, with this motion continuing over the next couple of days. The global models shift the orientation of the ridge in a few days which should cause Norman to turn west-northwestward by early next week. The dynamical model guidance is tightly clustered, and the NHC track forecast is close to the multi-model consensus. FORECAST POSITIONS AND MAX WINDS INIT 30/1500Z 17.8N 118.0W 130 KT 150 MPH 12H 31/0000Z 17.7N 119.1W 140 KT 160 MPH 24H 31/1200Z 17.2N 120.7W 135 KT 155 MPH 36H 01/0000Z 16.6N 122.3W 125 KT 145 MPH 48H 01/1200Z 16.1N 124.1W 120 KT 140 MPH 72H 02/1200Z 16.7N 128.0W 110 KT 125 MPH 96H 03/1200Z 18.5N 133.2W 95 KT 110 MPH 120H 04/1200Z 20.2N 138.5W 70 KT 80 MPH $$ Forecaster Brown

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Potential Tropical Cyclone Six Forecast Discussion Number 1

2018-08-30 16:44:53| National Hurricane Center (Atlantic)

Issued at 1100 AM AST Thu Aug 30 2018 882 WTNT41 KNHC 301444 TCDAT1 Potential Tropical Cyclone Six Discussion Number 1 NWS National Hurricane Center Miami FL AL062018 1100 AM AST Thu Aug 30 2018 The area of low pressure that moved off the coast of Africa has continued to become better organized, and is producing a large area of disturbed weather with gusty winds, but currently lacks a well-defined center. Environmental conditions are favorable for additional development, and a tropical depression or a tropical storm could form an any time today or Friday. Given the high chances that this system could bring tropical storm conditions to a portion of the southern Cabo Verde Islands, advisories have been initiated on Potential Tropical Cyclone Six. Most of the intensity guidance calls for strengthening and so does the NHC forecast. The system is embedded within the easterly trades and this flow pattern will steer the disturbance toward the west or west- northwest during the next few days. By the end of the forecast period, a turn toward the northwest should begin as the system reaches a weakness in the subtropical high. This is consistent with the output of the global models. FORECAST POSITIONS AND MAX WINDS INIT 30/1500Z 12.9N 18.4W 25 KT 30 MPH...POTENTIAL TROP CYCLONE 12H 31/0000Z 13.2N 20.1W 30 KT 35 MPH...TROPICAL DEPRESSION 24H 31/1200Z 13.5N 22.0W 35 KT 40 MPH 36H 01/0000Z 14.0N 24.0W 45 KT 50 MPH 48H 01/1200Z 15.0N 27.0W 55 KT 65 MPH 72H 02/1200Z 16.5N 33.0W 65 KT 75 MPH 96H 03/1200Z 18.5N 38.0W 65 KT 75 MPH 120H 04/1200Z 20.0N 42.0W 65 KT 75 MPH $$ Forecaster Avila

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Hurricane Norman Forecast Discussion Number 9

2018-08-30 14:32:56| National Hurricane Center (East Pacific)

Issued at 530 AM PDT Thu Aug 30 2018 326 WTPZ41 KNHC 301232 TCDEP1 Hurricane Norman Special Discussion Number 9 NWS National Hurricane Center Miami FL EP162018 530 AM PDT Thu Aug 30 2018 Satellite data show that Norman continues to rapidly strengthen. Objective Dvorak data T-numbers from UW/CIMSS have increased to T6.5 or higher and the latest TAFB subjective data T-number is T6.5. These estimates support an initial intensity of 125 kt, making Norman a category 4 hurricane on the Saffir-Simpson Hurricane Wind Scale. As a result of the increased initial intensity, the NHC intensity forecast has been adjusted upward through 36 h, but it is otherwise unchanged. There has been no change to the NHC track forecast. FORECAST POSITIONS AND MAX WINDS INIT 30/1230Z 17.8N 117.7W 125 KT 145 MPH 12H 30/1800Z 17.9N 118.5W 135 KT 155 MPH 24H 31/0600Z 17.6N 120.1W 135 KT 155 MPH 36H 31/1800Z 17.0N 121.6W 125 KT 145 MPH 48H 01/0600Z 16.3N 123.3W 115 KT 130 MPH 72H 02/0600Z 16.2N 127.1W 105 KT 120 MPH 96H 03/0600Z 18.0N 132.0W 95 KT 110 MPH 120H 04/0600Z 20.0N 137.5W 75 KT 85 MPH $$ Forecaster Brown

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