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Tropical Depression Twenty-Five Forecast Discussion Number 2

2020-10-02 22:34:45| National Hurricane Center (Atlantic)

Issued at 400 PM CDT Fri Oct 02 2020 000 WTNT45 KNHC 022034 TCDAT5 Tropical Depression Twenty-Five Discussion Number 2 NWS National Hurricane Center Miami FL AL252020 400 PM CDT Fri Oct 02 2020 Convective banding features have become a little better defined over the southern portion of the circulation, but otherwise the system has not changed much in organization since earlier today. The current intensity estimate remains at 30 kt in agreement with a Dvorak estimate from TAFB, and scatterometer observations from a few hours ago. The SHIPS model output now shows some south-southwesterly shear affecting the system during the next few days. Otherwise, the environment should favor at least gradual strengthening, and the cyclone is likely to become a tropical storm prior to moving near the Yucatan Peninsula. The official intensity forecast is within the range of most of the model guidance. The initial motion estimate is the same as in the morning advisory, 315/8 kt. The depression should move along the southwestern periphery of a mid-tropospheric high pressure area for the next couple of days, causing the cyclone to move on a northwestward to north-northwestward heading. Later in the forecast period, the global models build a weak ridge across the northern half of the Gulf of Mexico. This should induce the cyclone to turn westward or even a little south of west in 3-5 days. The latest NHC forecast lies between the simple and corrected dynamical model consensus predictions, TVCA and HCCA, and is quite similar to the previous official forecast. At this time, the biggest threat from this slow-moving system is rain and flooding, particularly near and over mountainous terrain. KEY MESSAGES: 1. The system is expected to produce heavy rainfall that could result in life-threatening flash flooding over portions of the Yucatan Peninsula, far western Cuba and well away from the center in the Mexican states of Campeche, Tabasco, and northern Chiapas. 2. The depression is forecast to become a tropical storm and bring tropical storm conditions to portions of the Yucatan Peninsula on Saturday, where a Tropical Storm Warning is in effect. FORECAST POSITIONS AND MAX WINDS INIT 02/2100Z 18.8N 85.3W 30 KT 35 MPH 12H 03/0600Z 19.5N 86.1W 35 KT 40 MPH 24H 03/1800Z 20.5N 87.0W 40 KT 45 MPH 36H 04/0600Z 21.6N 87.5W 40 KT 45 MPH 48H 04/1800Z 22.3N 87.7W 40 KT 45 MPH 60H 05/0600Z 22.5N 88.0W 45 KT 50 MPH 72H 05/1800Z 22.5N 88.8W 50 KT 60 MPH 96H 06/1800Z 22.5N 91.0W 50 KT 60 MPH 120H 07/1800Z 22.0N 92.5W 50 KT 60 MPH $$ Forecaster Pasch

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Tropical Depression Twenty-Five Forecast Discussion Number 1

2020-10-02 16:56:14| National Hurricane Center (Atlantic)

Issued at 1100 AM EDT Fri Oct 02 2020 000 WTNT45 KNHC 021456 TCDAT5 Tropical Depression Twenty-Five Discussion Number 1 NWS National Hurricane Center Miami FL AL252020 1100 AM EDT Fri Oct 02 2020 Visible satellite images show that cloudiness and showers associated with the low pressure area over the northwestern Caribbean Sea have become significantly better organized since yesterday, with convective banding features becoming prominent. Moreover, low cloud motions suggest that a closed circulation has become better defined. Therefore, advisories are being initiated on Tropical Depression Twenty-Five at this time. The initial intensity estimate is 30 kt based on Dvorak T-numbers, but an Air Force Reserve Hurricane Hunter aircraft is scheduled to investigate the system later today to provide a better intensity estimate. Sea surface temperatures are very warm, near 30 deg C, and vertical shear should remain low for at least the next couple of days, so the cyclone is likely to become a tropical storm by the time it nears the Yucatan Peninsula tomorrow. The main impediment to strengthening over the next few days should be the interaction with land. Given the uncertainties about how far offshore the center will be over the next several days, the official intensity forecast is conservative. Since there is still a lot of scatter in the center fixes, the initial motion estimate, 315/8 kt, is rather uncertain. For the next couple of days, the system is expected to move northwestward to north-northwestward on the southwestern edge of a mid-level high pressure area. This would take the center near or over the northeastern Yucatan Peninsula. After about 48 hours, the steering currents are not well-defined and there is considerable spread in the track models. At this time, it appears the cyclone should move slowly westward over the latter part of the forecast period in response to weak ridging over the north-central Gulf of Mexico. The official forecast is near or a little north of the corrected and simple model consensus predictions. Tropical Storm Warnings and Watches have been issued for a portion of the Yucatan Peninsula. KEY MESSAGES: 1. The system is expected to produce heavy rainfall that could result in life-threatening flash flooding over portions of the Yucatan Peninsula, far western Cuba and well away from the center in the Mexican states of Campeche, Tabasco, and northern Chiapas. 2. The depression is forecast to become a tropical storm and bring tropical storm conditions to portions of the Yucatan Peninsula on Saturday, where a Tropical Storm Warning is in effect. FORECAST POSITIONS AND MAX WINDS INIT 02/1500Z 18.1N 84.7W 30 KT 35 MPH 12H 03/0000Z 18.9N 85.6W 30 KT 35 MPH 24H 03/1200Z 19.8N 86.6W 35 KT 40 MPH 36H 04/0000Z 20.6N 87.2W 40 KT 45 MPH...INLAND 48H 04/1200Z 21.4N 87.5W 40 KT 45 MPH...INLAND 60H 05/0000Z 22.0N 87.6W 40 KT 45 MPH 72H 05/1200Z 22.0N 88.2W 45 KT 50 MPH 96H 06/1200Z 21.5N 90.5W 45 KT 50 MPH 120H 07/1200Z 21.5N 92.5W 45 KT 50 MPH $$ Forecaster Pasch

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Hurricane Marie Forecast Discussion Number 14

2020-10-02 16:47:39| National Hurricane Center (East Pacific)

Issued at 800 AM PDT Fri Oct 02 2020 000 WTPZ43 KNHC 021447 TCDEP3 Hurricane Marie Discussion Number 14 NWS National Hurricane Center Miami FL EP182020 800 AM PDT Fri Oct 02 2020 Marie's structure has not changed significantly since the previous advisory. A recent AMSR microwave image showed that the hurricane continues to have a closed eyewall that is a little thin on the southeast side, but there are no clear indications that an eyewall replacement is occuring. Dvorak final-T numbers from TAFB and SAB diverged from 6 hours ago, with TAFB's going up to T6.5 and SAB's falling to T5.5. In addition, final-T numbers from the objective ADT scheme have decreased since six hours ago. Because of the estimate discrepancies, the initial intensity is being held at 115 kt. Marie is moving west-northwestward (290 degrees) at 12 kt, just a little to the left of and slower than the previous motion estimate. A large mid-tropospheric high centered over the southwestern United States continues to be the main driver of Marie's motion, but the hurricane should begin to reach a break in the ridge and turn toward the northwest in the next 24 hours. After that time, a general motion toward the northwest or west-northwest should continue through the end of the forecast period. The spread in the guidance does increase a bit by days 4 and 5, which appears to be related to the depth of the cyclone and how it interacts with the steering flow. Overall, though, the guidance envelope has not shifted, and the NHC forecast was only slowed down a bit to be more in line with the latest TVCE multi-model consensus and HCCA aid. Marie should remain in a low-shear environment and over waters warmer than 26 degrees Celsius for the next 24 hours, during which time some additional strengthening is possible. Any intensification could be thwarted by an eyewall replacement, but as stated above, that does not appear to be occuring at this time. Increasing deep-layer southwesterly shear and cooler waters should induce a definitive weakening trend after 24 hours, with Marie falling below hurricane strength by day 3, and then becoming a tropical depression by day 5. The NHC intensity forecast has been adjusted downward a bit during the weakening phase and lies near or just above the IVCN intensity consensus and the HCCA aid. FORECAST POSITIONS AND MAX WINDS INIT 02/1500Z 16.5N 124.3W 115 KT 130 MPH 12H 03/0000Z 17.2N 125.7W 120 KT 140 MPH 24H 03/1200Z 18.3N 127.1W 115 KT 130 MPH 36H 04/0000Z 19.3N 128.3W 100 KT 115 MPH 48H 04/1200Z 20.0N 129.4W 80 KT 90 MPH 60H 05/0000Z 20.6N 130.7W 65 KT 75 MPH 72H 05/1200Z 21.0N 132.1W 55 KT 65 MPH 96H 06/1200Z 22.0N 135.0W 40 KT 45 MPH 120H 07/1200Z 23.5N 137.0W 30 KT 35 MPH $$ Forecaster Berg/Reinhart

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Hurricane Marie Forecast Discussion Number 13

2020-10-02 10:44:15| National Hurricane Center (East Pacific)

Issued at 200 AM PDT Fri Oct 02 2020 000 WTPZ43 KNHC 020844 TCDEP3 Hurricane Marie Discussion Number 13 NWS National Hurricane Center Miami FL EP182020 200 AM PDT Fri Oct 02 2020 Marie has strengthened further since the last advisory, with satellite intensity estimates from TAFB and SAB now at 115 kt and the CIMSS ADT estimate now near 130 kt. However, during the past couple of hours, satellite imagery shows that the eye has become less well defined. It is unclear at this time whether this is because the hurricane is starting an eyewall replacement or whether it has peaked in intensity. The initial intensity for this advisory is increased to a possibly conservative 115 kt. Marie currently has good to excellent cirrus outflow in all directions. The initial motion is west-northwestward or 295/13 kt as the hurricane is being steered by a mid-level ridge to the north. The system is expected to move toward the west-northwest or northwest at a slower forward speed during the next several days as it approaches the western periphery of the ridge and a broad mid-latitude trough well off the California coast. The track guidance remains in good agreement on this scenario through 72 h, but there remains increasing spread after that time, which is likely due to model differences in the vertical depth of Marie and how much the trough influences its steering. The guidance shifted a little to the north of the previous guidance through 72 h, so the new forecast track is also nudged northward during that time. The new track is in best agreement with the HCCA corrected consensus model. If Marie is not undergoing an eyewall replacement cycle, conditions appear favorable for additional strengthening during the next 12-18 h. After that, the system will be moving over decreasing sea surface temperatures and entraining dryer air, which should cause weakening. An faster weakening is expected after 36 h due to increasing westerly shear. The new intensity forecast has minor adjustments from the previous forecast, and through 72 h it lies near the upper edge of the intensity guidance. FORECAST POSITIONS AND MAX WINDS INIT 02/0900Z 16.2N 123.2W 115 KT 130 MPH 12H 02/1800Z 16.9N 124.8W 125 KT 145 MPH 24H 03/0600Z 17.9N 126.5W 120 KT 140 MPH 36H 03/1800Z 19.0N 127.8W 110 KT 125 MPH 48H 04/0600Z 19.9N 129.0W 95 KT 110 MPH 60H 04/1800Z 20.6N 130.2W 80 KT 90 MPH 72H 05/0600Z 21.1N 131.7W 60 KT 70 MPH 96H 06/0600Z 22.0N 134.5W 45 KT 50 MPH 120H 07/0600Z 23.5N 136.5W 30 KT 35 MPH $$ Forecaster Beven

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Hurricane Marie Forecast Discussion Number 12

2020-10-02 04:35:03| National Hurricane Center (East Pacific)

Issued at 800 PM PDT Thu Oct 01 2020 000 WTPZ43 KNHC 020234 TCDEP3 Hurricane Marie Discussion Number 12 NWS National Hurricane Center Miami FL EP182020 800 PM PDT Thu Oct 01 2020 Marie is still strengthening this evening. Satellite images indicate that the hurricane has a well-defined compact eye with a ring of cold cloud tops surrounding that feature. The Dvorak classifications at 0000Z were T5.5/102 kt from both TAFB and SAB, but since the cyclone has continued to strengthen, the initial intensity is increased to 110 kt. This value is below the latest Dvorak ADT numbers that are currently around 6.2/120 kt. Marie has strengthened at an impressive rate of 45 kt over the past 24 hours. Satellite fixes indicate that the hurricane is moving fairly quickly to the west-northwest on the south side of a mid-level ridge, with the latest initial motion estimated to be 285/13 kt. The system is expected to move slower to the west-northwest or northwest during the next several days as it nears the western periphery of the ridge and moves toward a broad trough well off the California coast. The models are in fair agreement in the short term, but there is a notable amount of spread in the guidance in 4 to 5 days, likely due to differences in the vertical depth of Marie and how much the trough influences its steering. The NHC track forecast remains near the consensus aids, and is largely an update of the previous one. The major hurricane will likely continue to strengthen during the next 12 to 24 hours while it remains in quite favorable conditions of low vertical wind shear, a moist air mass, and over warm 28-29 C SSTs. It should be noted that eyewall replacement cycles could occur during that time, which might cause fluctuations in the cyclone's strength. By Saturday, Marie is expected to level off in intensity and then rapidly weaken when the hurricane crosses the 26-deg-C SST isotherm and moves into an environment of increasing west-southwesterly shear and drier air. The NHC intensity forecast remains above the guidance in the short term, but falls in line with the bulk of the models beyond 36 hours. FORECAST POSITIONS AND MAX WINDS INIT 02/0300Z 15.6N 122.1W 110 KT 125 MPH 12H 02/1200Z 16.3N 123.9W 125 KT 145 MPH 24H 03/0000Z 17.3N 125.9W 125 KT 145 MPH 36H 03/1200Z 18.4N 127.4W 115 KT 130 MPH 48H 04/0000Z 19.4N 128.7W 95 KT 110 MPH 60H 04/1200Z 20.2N 130.0W 80 KT 90 MPH 72H 05/0000Z 20.8N 131.5W 65 KT 75 MPH 96H 06/0000Z 22.0N 134.4W 50 KT 60 MPH 120H 07/0000Z 23.4N 136.4W 35 KT 40 MPH $$ Forecaster Cangialosi

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