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Tropical Depression NINETEEN-E Forecast Discussion Number 7

2015-10-16 16:44:38| National Hurricane Center (East Pacific)

Issued at 800 AM PDT FRI OCT 16 2015 000 WTPZ44 KNHC 161444 TCDEP4 TROPICAL DEPRESSION NINETEEN-E DISCUSSION NUMBER 7 NWS NATIONAL HURRICANE CENTER MIAMI FL EP192015 800 AM PDT FRI OCT 16 2015 The depression's cloud pattern consists of a recently formed cluster of deep convection and fragmented convective banding features around the outer circulation. An 0910 UTC AMSR-2 overpass suggested that the center was underneath this newly formed convective burst, which would place it a little south of previous position estimates and open the possibility that the center recently reformed. An expansive upper-level outflow is also noted in association with the cyclone. Dvorak intensity estimates are unchanged from 6 hours ago, so the initial intensity estimate remains 25 kt. It is unclear why the cyclone has not yet responded by intensifying in a large-scale environment of light shear, a relatively moist mid-troposphere, and very warm waters. Perhaps the structure of the circulation has been a limiting factor. Regardless, global models continue to develop a hurricane in the far western portion of the eastern Pacific basin within a few days. The statistical and dynamical intensity guidance is quite similar this cycle, though the statistical output is slightly lower than before as a result of the cyclone's not intensifying yet. The official intensity forecast continues to indicate strengthening at a rate very similar to the multi-model consensus. The initial motion estimate is a little faster and just south of due west or 265/14. The cyclone is forecast to maintain a generally westward motion underneath a subtropical ridge to the north during the next few days and decelerate as the tail of a mid- to upper- level trough extending from the U.S. west coast causes the ridge to weaken. A further weakening of the ridge after 48 hours should cause the cyclone to begin to gain more latitude, and an encounter with a more significant weakness west of 140W should result in an even more poleward track by 96 hours. The track guidance has shifted significantly to the left this cycle and is a bit faster, and the official track forecast follows that trend but is on the right-side of the guidance envelope. FORECAST POSITIONS AND MAX WINDS INIT 16/1500Z 9.7N 125.2W 25 KT 30 MPH 12H 17/0000Z 9.6N 127.0W 30 KT 35 MPH 24H 17/1200Z 9.6N 129.0W 40 KT 45 MPH 36H 18/0000Z 9.6N 130.6W 45 KT 50 MPH 48H 18/1200Z 9.9N 132.0W 55 KT 65 MPH 72H 19/1200Z 10.9N 135.0W 75 KT 85 MPH 96H 20/1200Z 12.8N 137.9W 85 KT 100 MPH 120H 21/1200Z 14.9N 140.5W 85 KT 100 MPH $$ Forecaster Kimberlain

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Tropical Depression NINETEEN-E Forecast Discussion Number 6

2015-10-16 10:36:05| National Hurricane Center (East Pacific)

Issued at 200 AM PDT FRI OCT 16 2015 000 WTPZ44 KNHC 160835 TCDEP4 TROPICAL DEPRESSION NINETEEN-E DISCUSSION NUMBER 6 NWS NATIONAL HURRICANE CENTER MIAMI FL EP192015 200 AM PDT FRI OCT 16 2015 The cloud pattern remains poorly organized and consists of a small area of deep convection with little or no banding features. Microwave data suggest that the low-level center is still on the eastern edge of the convective region. Given that the Dvorak CI-numbers have not changed significantly, the initial intensity is kept at 25 kt. It is surprising that the depression has not responded to the quite favorable environment of low shear and warm waters yet. In fact, most the guidance indicated that the depression should have been already a strong tropical storm or even a hurricane. Since the opportunity for strengthening is still there, the NHC forecast insists on intensification and calls for the depression to become a hurricane in about 3 days. The depression is trapped south of strong subtropical ridge moving toward the west at 12 kt. Global models indicate that the ridge will gradually move eastward. This steering pattern should allow the cyclone to turn more to the west-northwest in about 3 days, and eventually to move northward by the end of the forecast period. The NHC forecast is basically on top of the multi-model consensus and the GFS/ECMWF solutions. The spread in the guidance has decreased a little bit, and in general, most of the models now turn the cyclone northward around 140 W. This increases slightly the confidence in the long range track forecast. FORECAST POSITIONS AND MAX WINDS INIT 16/0900Z 10.1N 123.5W 25 KT 30 MPH 12H 16/1800Z 10.0N 125.4W 35 KT 40 MPH 24H 17/0600Z 10.0N 127.5W 40 KT 45 MPH 36H 17/1800Z 10.0N 129.0W 45 KT 50 MPH 48H 18/0600Z 10.3N 130.5W 55 KT 65 MPH 72H 19/0600Z 11.5N 133.5W 75 KT 85 MPH 96H 20/0600Z 13.0N 136.5W 85 KT 100 MPH 120H 21/0600Z 15.0N 139.0W 85 KT 100 MPH $$ Forecaster Avila

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Tropical Depression NINETEEN-E Forecast Discussion Number 5

2015-10-16 04:32:08| National Hurricane Center (East Pacific)

Issued at 800 PM PDT THU OCT 15 2015 000 WTPZ44 KNHC 160231 TCDEP4 TROPICAL DEPRESSION NINETEEN-E DISCUSSION NUMBER 5 NWS NATIONAL HURRICANE CENTER MIAMI FL EP192015 800 PM PDT THU OCT 15 2015 The cloud pattern of the depression has appeared ragged in satellite images most of the day, and the latest Dvorak CI-numbers from TAFB and SAB have decreased to 1.5/25 kt. The associated deep convection does not have much curvature and it is largely confined to areas to the north and west of the estimated center. Based on the degraded appearance, the initial wind speed is lowered slightly to 25 kt. It is not clear why the depression has not strengthened today as the large-scale environmental conditions have been quite conducive for intensification. The depression is expected to remain in a low wind shear and high moisture environment and over warm water for at least the next few days. Therefore, it is assumed that the system will have the opportunity to gain strength. The GFS, as well as the GFS-based SHIPS and LGEM guidance, are the most aggressive models and show the cyclone becoming a hurricane in a couple of days with continued strengthening thereafter. Conversely, the GFDL and HWRF models show much less strengthening. Given the poor initial structure of the cyclone, the official intensity forecast has been lowered in the short term but remains relatively unchanged from the previous prediction at the later forecast times. The depression is moving westward at about 11 kt steered by a subtropical ridge to its north. A continued westward motion but at a slower pace is forecast during the next couple of days while the ridge weakens in place. After that time, a turn to the northwest is expected as a weakness develops in the ridge east of the Hawaiian Islands. Although there is considerable spread in the guidance on when the northwestward turn should occur, the models agree on the overall theme. The new official track forecast is essentially an update of the previous one for the first couple of days, but then is shifted westward to come into better agreement with the latest model consensus aids. FORECAST POSITIONS AND MAX WINDS INIT 16/0300Z 10.2N 122.1W 25 KT 30 MPH 12H 16/1200Z 10.1N 124.0W 30 KT 35 MPH 24H 17/0000Z 10.0N 126.2W 35 KT 40 MPH 36H 17/1200Z 9.9N 128.0W 45 KT 50 MPH 48H 18/0000Z 10.2N 129.6W 55 KT 65 MPH 72H 19/0000Z 11.1N 132.3W 75 KT 85 MPH 96H 20/0000Z 12.7N 135.1W 85 KT 100 MPH 120H 21/0000Z 15.1N 137.8W 85 KT 100 MPH $$ Forecaster Cangialosi

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Tropical Depression NINETEEN-E Forecast Discussion Number 4

2015-10-15 22:36:32| National Hurricane Center (East Pacific)

Issued at 200 PM PDT THU OCT 15 2015 000 WTPZ44 KNHC 152036 TCDEP4 TROPICAL DEPRESSION NINETEEN-E DISCUSSION NUMBER 4 NWS NATIONAL HURRICANE CENTER MIAMI FL EP192015 200 PM PDT THU OCT 15 2015 Visible satellite images suggest that the depression is not very well organized. The circulation is still somewhat elongated, and the low-level center is located near the eastern edge of a cluster of deep convection. The convection itself also appears to have lost some organization since earlier today. The maximum winds remain 30 kt based on Dvorak CI numbers of 2.0 from TAFB and SAB. Even though environmental conditions appear conducive for strengthening, the depression is not in any hurry to intensify. The hurricane intensity models and the global models all insist that the depression will strengthen soon. However, the one prominent difference in this afternoon's model suite is that the ECMWF model does not deepen the cyclone for another 48 hours or so. Since most of the guidance intensifies the system through 5 days, the NHC intensity forecast remains consistent with the previous forecasts, making the cyclone a hurricane in about 2-3 days. This is also consistent with the latest intensity consensus. However, given the latest ECMWF run and the current structure of the depression, it's possible that intensification could be delayed. The initial motion is 265/11 kt. A mid-level ridge is steering the depression westward, and this motion is likely to continue for at least another 48 hours. After that time, the ridge is forecast to weaken and give way to a broad trough west of the Baja California peninsula. This should allow the cyclone to turn west-northwestward and then northwestward by day 5. Although the track models generally agree on this scenario, the system's weaker representation in the ECMWF during the first few days causes it to continue westward beyond 48 hours and make a more gradual turn compared to the other models. This now places the ECMWF closer to the UKMET model, which was the only outlier on the previous forecast cycle. Based on the new guidance, the NHC track forecast has been shifted westward and is a little bit slower than the previous forecast, especially at days 4 and 5. FORECAST POSITIONS AND MAX WINDS INIT 15/2100Z 10.1N 120.9W 30 KT 35 MPH 12H 16/0600Z 9.9N 122.8W 35 KT 40 MPH 24H 16/1800Z 9.9N 125.1W 45 KT 50 MPH 36H 17/0600Z 9.8N 127.0W 55 KT 65 MPH 48H 17/1800Z 9.9N 128.6W 65 KT 75 MPH 72H 18/1800Z 10.7N 131.3W 80 KT 90 MPH 96H 19/1800Z 12.5N 134.0W 85 KT 100 MPH 120H 20/1800Z 15.0N 137.0W 90 KT 105 MPH $$ Forecaster Berg

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Tropical Depression NINETEEN-E Forecast Discussion Number 3

2015-10-15 16:48:59| National Hurricane Center (East Pacific)

Issued at 800 AM PDT THU OCT 15 2015 000 WTPZ44 KNHC 151448 TCDEP4 TROPICAL DEPRESSION NINETEEN-E DISCUSSION NUMBER 3 NWS NATIONAL HURRICANE CENTER MIAMI FL EP192015 800 AM PDT THU OCT 15 2015 Tropical Depression Nineteen-E's cloud pattern has changed little during the past 6-12 hours and consists of a persistent cluster of deep convection near the low-level center and a lengthening band extending to the north and northeast. The maximum winds remain 30 kt based on Dvorak estimates of T2.0 from TAFB and SAB. Although the depression has not strengthened yet, low vertical shear, very warm waters, and a moist atmosphere favor intensification throughout the five-day forecast period. As such, the NHC intensity forecast is very similar to the previous one and shows the depression reaching hurricane intensity in a couple of days. The intensity models all show intensification to varying degrees, and the official forecast closely follows the intensity consensus through 48 hours but then is a little higher (close to the SHIPS and LGEM models) on days 3 through 5. The low-level center has been difficult to locate, but the depression appears to be moving westward, or 270/11 kt. An elongated mid-level ridge is expected to remain north of the depression for the next 3 days or so, but the ridge is expected to weaken through the weekend as broad troughing develops west of the Baja California peninsula. This pattern change should cause the cyclone to gradually slow down and turn west-northwestward by day 3 and northwestward by day 5. With the exception of the UKMET model, which does not show a northwestward turn by day 5, the remainder of the track models are tightly clustered. The updated NHC track forecast is close to the multi-model consensus and essentially unchanged from the previous forecast. FORECAST POSITIONS AND MAX WINDS INIT 15/1500Z 10.2N 119.5W 30 KT 35 MPH 12H 16/0000Z 10.1N 121.3W 35 KT 40 MPH 24H 16/1200Z 10.0N 124.0W 45 KT 50 MPH 36H 17/0000Z 10.0N 126.4W 55 KT 65 MPH 48H 17/1200Z 10.0N 128.1W 65 KT 75 MPH 72H 18/1200Z 10.8N 131.0W 85 KT 100 MPH 96H 19/1200Z 12.0N 133.5W 90 KT 105 MPH 120H 20/1200Z 14.5N 136.0W 95 KT 110 MPH $$ Forecaster Berg

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