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Hurricane NICOLE Forecast Discussion Number 11

2016-10-06 22:42:05| National Hurricane Center (Atlantic)

Issued at 500 PM AST THU OCT 06 2016 000 WTNT45 KNHC 062041 TCDAT5 HURRICANE NICOLE DISCUSSION NUMBER 11 NWS NATIONAL HURRICANE CENTER MIAMI FL AL152016 500 PM AST THU OCT 06 2016 Nicole's cloud pattern has continued to increase in organization this afternoon. A small central dense overcast has become even more symmetric during the last few hours, with an eye intermittently visible. Dvorak classifications of T4.5 from TAFB and UW-CIMSS ADT values support increasing the intensity to 75 kt. Nicole is being affected by northerly shear associated with outflow of Hurricane Matthew, but it is suspected that this shear is confined to a narrow layer at upper levels since the cyclone has been unexpectedly strengthening. Given the current trends, additional intensification seems possible, at least during the short term. However, a mid- to upper-level trough digging over the central Atlantic should cause the shear over Nicole to greatly increase in 1 to 2 days and result in some weakening. There could also be some interaction of Nicole with a piece of the trough that breaks off in 2 to 3 days, as shown in the global models, but it is unclear how this could affect its intensity. The large-scale environment is forecast to potentially become more conducive for re- intensification by days 4 or 5, and some restrengthening is shown around that time. The new intensity forecast is above the multi-model consensus and higher than the previous one at the end of the forecast period. The initial motion estimate is 330/06. Steering currents are likely to collapse very soon as Nicole finds itself in a col area, making an erratic northward motion likely for the next 12 hours or so. A blocking ridge in the wake of the aforementioned trough should then impart a slow southerly motion for a couple of days. By 72 hours, a turn back toward the northwest or north-northwest is forecast as a mid-level high builds to the east of Nicole. Although there is considerable spread in the model guidance, this general scenario is shown except for the ECMWF, which is well to the right of the other model solutions through the next 3 days. The new track forecast is of low confidence, is faster than the previous one, and is between the previous forecast and an average of the ECMWF/GFS output. Swells associated with this slow-moving storm are affecting Bermuda, and these conditions are likely to continue for the next several days. FORECAST POSITIONS AND MAX WINDS INIT 06/2100Z 27.5N 65.1W 75 KT 85 MPH 12H 07/0600Z 27.9N 65.3W 85 KT 100 MPH 24H 07/1800Z 27.6N 65.2W 80 KT 90 MPH 36H 08/0600Z 27.0N 64.9W 75 KT 85 MPH 48H 08/1800Z 26.5N 64.6W 70 KT 80 MPH 72H 09/1800Z 26.4N 65.3W 60 KT 70 MPH 96H 10/1800Z 27.4N 66.7W 60 KT 70 MPH 120H 11/1800Z 29.4N 67.7W 65 KT 75 MPH $$ Forecaster Kimberlain

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Hurricane NICOLE Forecast Discussion Number 10

2016-10-06 19:44:52| National Hurricane Center (Atlantic)

Issued at 200 PM AST THU OCT 06 2016 000 WTNT45 KNHC 061744 TCDAT5 HURRICANE NICOLE SPECIAL DISCUSSION NUMBER 10 NWS NATIONAL HURRICANE CENTER MIAMI FL AL152016 200 PM AST THU OCT 06 2016 This is a special advisory issued to upgrade Nicole to a hurricane. The system's cloud pattern has become more symmetrical since this morning, with an eye evident on visible satellite images. The intensity is set to 70 kt, which is between the subjective and objective Dvorak intensity estimates. Nicole has been able to strengthen in an environment of shear on the order of 20 kt. Since the hurricane has been so resilient to the shear, some additional strengthening seems likely. By 48 hours, the shear is forecast to increase to over 40 kt, so some weakening is forecast around that time. The official intensity forecast is above the SHIPS and LGEM guidance for the early part of the period, and a blend of those 2 models thereafter. Little or no change was made to the track forecast from the previous regular advisory, and the track forecast reasoning is unchanged. Steering currents are expected to become weak within the next 12 to 24 hours, and Nicole should move slowly and erratically for the next several days. Swells associated with this slow-moving storm are affecting Bermuda, and these conditions are likely to continue for the next several days. FORECAST POSITIONS AND MAX WINDS INIT 06/1800Z 27.3N 65.0W 70 KT 80 MPH 12H 07/0000Z 27.7N 65.2W 75 KT 85 MPH 24H 07/1200Z 27.9N 65.0W 80 KT 90 MPH 36H 08/0000Z 27.3N 64.8W 80 KT 90 MPH 48H 08/1200Z 26.9N 64.8W 75 KT 85 MPH 72H 09/1200Z 26.5N 65.0W 65 KT 75 MPH 96H 10/1200Z 27.0N 66.0W 55 KT 65 MPH 120H 11/1200Z 28.5N 67.0W 45 KT 50 MPH $$ Forecaster Pasch

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Hurricane MATTHEW Forecast Discussion Number 34

2016-10-06 16:56:19| National Hurricane Center (Atlantic)

Issued at 1100 AM EDT THU OCT 06 2016 000 WTNT44 KNHC 061456 TCDAT4 HURRICANE MATTHEW DISCUSSION NUMBER 34 NWS NATIONAL HURRICANE CENTER MIAMI FL AL142016 1100 AM EDT THU OCT 06 2016 The satellite presentation of the hurricane has continued to improve, with a distinct eye surrounded by very deep convection, and T-numbers are oscillating around 6.0 on the Dvorak scale. Data from an Air Force reconnaissance plane traversing the eye of the hurricane also indicate that Matthew has strengthened. The initial intensity is estimated at 120 kt, based mainly on SFMR data and an eyewall dropsonde. Environmental conditions appear favorable for additional intensification today while Matthew approaches the east coast of Florida. After 24 hours, land interaction is likely to cause some weakening, and later in the period increasing shear should cause a more rapid decrease in winds. The NHC forecast is slightly above most of the guidance during the first 24 hours due to the recent intensification, and follows the weakening trend of the consensus thereafter. Aircraft fixes show that Matthew is moving toward the northwest or 325 degrees at 10 kt. The steering flow has not changed and Matthew is expected to move around the western periphery of the subtropical ridge located over the western Atlantic during the next 24 to 36 hours. After that time, the ridge will shift eastward allowing the hurricane to move northward and then sharply turn eastward while it becomes embedded within the mid-latitude westerlies. By the end of the forecast period the steering pattern is forecast to change again and a weakening cyclone is expected to turn southward. KEY MESSAGES: 1. Matthew is likely to produce devastating impacts from storm surge, extreme winds, and heavy rains in the northwestern Bahamas today, and along extensive portions of the east coast of Florida tonight. 2. Evacuations are not just a coastal event. Strong winds will occur well inland from the coast, and residents of mobile homes under evacuation orders are urged to heed those orders. 3. Hurricane winds increase very rapidly with height, and residents of high-rise buildings are at particular risk of strong winds. Winds at the top of a 30-story building will average one Saffir-Simpson category higher than the winds near the surface. 4. When a hurricane is forecast to take a track roughly parallel to a coastline, as Matthew is forecast to do from Florida through South Carolina, it becomes very difficult to specify impacts at any one location. Only a small deviation of the track to the left of the NHC forecast could bring the core of a major hurricane onshore within the hurricane warning area in Florida and Georgia. Modest deviations to the right could keep much of the hurricane-force winds offshore. Similarly large variations in impacts are possible in the hurricane watch and warning areas in northeast Georgia and South Carolina. 5. The National Hurricane Center is issuing Potential Storm Surge Flooding Maps, and Prototype Storm Surge Watch/Warning Graphics for Matthew. It is important to remember that the Potential Storm Surge Flooding Map does not represent a forecast of expected inundation, but rather depicts a reasonable worst-case scenario - the amount of inundation that has a 10 percent chance of being exceeded. In addition, because the Flooding Map is based on inputs that extend out only to about 72 hours, it best represents the flooding potential in those locations within the watch and warning areas in Florida and Georgia. FORECAST POSITIONS AND MAX WINDS INIT 06/1500Z 25.1N 77.8W 120 KT 140 MPH 12H 07/0000Z 26.4N 79.0W 125 KT 145 MPH 24H 07/1200Z 28.3N 80.4W 125 KT 145 MPH 36H 08/0000Z 30.2N 81.1W 115 KT 130 MPH 48H 08/1200Z 31.7N 80.0W 95 KT 110 MPH 72H 09/1200Z 32.5N 76.5W 75 KT 85 MPH 96H 10/1200Z 30.5N 75.0W 50 KT 60 MPH 120H 11/1200Z 28.5N 76.0W 40 KT 45 MPH $$ Forecaster Avila

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Tropical Storm NICOLE Forecast Discussion Number 9

2016-10-06 16:35:21| National Hurricane Center (Atlantic)

Issued at 1100 AM AST THU OCT 06 2016 000 WTNT45 KNHC 061435 TCDAT5 TROPICAL STORM NICOLE DISCUSSION NUMBER 9 NWS NATIONAL HURRICANE CENTER MIAMI FL AL152016 1100 AM AST THU OCT 06 2016 Nicole's cloud pattern hasn't changed much since the last advisory, and consists of a ragged CDO with some banding features over the southeastern portion of the circulation. Upper-level outflow is restricted over the northern semicircle of the storm. Dvorak classifications are unchanged from SAB and TAFB, yielding intensity estimates of 55 kt and 65 kt, respectively, so the advisory intensity is held at 60 kt. Although Nicole could reach hurricane strength today, increasing north-northwesterly shear should lead to a slow weakening trend, beginning tomorrow. The official intensity forecast is a blend of the latest LGEM and SHIPS guidance. The forward motion is slowing, and the motion is now estimated to be about 325/5 kt. A mid-level high pressure area to the northeast of Nicole should quickly collapse while a shortwave trough drops southward into the area. This will leave the tropical cyclone in weak steering currents within the next day or so. A high pressure area is forecast to build to the west and northwest of Nicole during the next couple of days, and this should force some southward component of motion. Overall, however, the official forecast, like the previous one, shows little overall motion throughout the period. This is in reasonable agreement with the dynamical model consensus. Swells associated with this slow-moving storm are affecting Bermuda, and these conditions are likely to continue for the next several days. FORECAST POSITIONS AND MAX WINDS INIT 06/1500Z 26.8N 64.8W 60 KT 70 MPH 12H 07/0000Z 27.5N 65.1W 60 KT 70 MPH 24H 07/1200Z 27.8N 65.0W 55 KT 65 MPH 36H 08/0000Z 27.3N 64.8W 55 KT 65 MPH 48H 08/1200Z 26.9N 64.8W 55 KT 65 MPH 72H 09/1200Z 26.5N 65.0W 50 KT 60 MPH 96H 10/1200Z 27.0N 66.0W 45 KT 50 MPH 120H 11/1200Z 28.5N 67.0W 45 KT 50 MPH $$ Forecaster Pasch

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Hurricane MATTHEW Forecast Discussion Number 33

2016-10-06 11:01:49| National Hurricane Center (Atlantic)

Issued at 500 AM EDT THU OCT 06 2016 000 WTNT44 KNHC 060901 TCDAT4 HURRICANE MATTHEW DISCUSSION NUMBER 33 NWS NATIONAL HURRICANE CENTER MIAMI FL AL142016 500 AM EDT THU OCT 06 2016 The satellite presentation of Matthew has improved markedly overnight with eye reappearing and warming within the past couple of hours. The eye is also embedded within a very symmetric central dense overcast with cloud tops colder than -70C. An Air Force Reconnaissance Hurricane Hunter that just flew through the center reported peak 700 mb flight-level winds of 132 kt, SFMR winds around 103 kt, and a pressure of 944 mb, which is down about 18 mb from last evening. Using a blend of the flight-level and SFMR winds, the initial intensity is set at 110 kt. Environmental conditions appear favorable for continued strengthening today and Matthew is expected to become an extremely dangerous category 4 hurricane while it moves over the northwestern Bahamas and approaches the east coast of Florida. After 24 hours, land interaction is likely to cause some weakening, and later in the period increasing shear should cause a more rapid decrease in winds. The NHC forecast is above the most of guidance during the first 24 hours due to the recent increase in organization, but is close to the consensus thereafter. Aircraft and satellite fixes show that Matthew is moving northwestward or 320/10 kt. Matthew is expected to move around the western periphery of a subtropical ridge that is forecast to gradually retreat eastward during the next day or two. This pattern should steer Matthew northwestward over the northwestern Bahamas today, then north-northwestward very near the east coast of Florida late today through Friday night. The models are tightly clustered through 48 hours, and the NHC track is near the consensus of the GFS and ECMWF models through that time. After 48 hours, the hurricane should turn northeastward as a broad trough approaches the Great Lakes region. The trough is expected to pass north of Matthew in about 72 hours, which is expected to cause the cyclone to turn eastward, then southeastward late in the forecast period. There is still significant spread in the long-range guidance so there is lower than normal confidence in the days 4 and 5 track prediction. KEY MESSAGES: 1. Matthew is likely to produce devastating impacts from storm surge, extreme winds, and heavy rains in the central and northwestern Bahamas today, and along portions of the east coast of Florida tonight. 2. When a hurricane is forecast to take a track roughly parallel to a coastline, as Matthew is forecast to do from Florida through South Carolina, it becomes very difficult to specify impacts at any one location. For example, only a small deviation of the track to the left of the NHC forecast could bring the core of a major hurricane onshore within the hurricane warning area in Florida and Georgia. However, a small deviation to the right could keep the hurricane-force winds offshore. Similarly large variations in impacts are possible in the hurricane watch area in northeast Georgia and South Carolina. 3. Tropical storm or hurricane conditions could affect eastern North Carolina later this week or this weekend, even if the center of Matthew remains offshore. 4. The National Hurricane Center is issuing Potential Storm Surge Flooding Maps, and Prototype Storm Surge Watch/Warning Graphics for Matthew. It is important to remember that the Potential Storm Surge Flooding Map does not represent a forecast of expected inundation, but rather depicts a reasonable worst-case scenario - the amount of inundation that has a 10 percent chance of being exceeded. In addition, because the Flooding Map is based on inputs that extend out only to about 72 hours, it best represents the flooding potential in those locations within the watch and warning areas in Florida and Georgia. FORECAST POSITIONS AND MAX WINDS INIT 06/0900Z 24.2N 77.1W 110 KT 125 MPH 12H 06/1800Z 25.5N 78.4W 120 KT 140 MPH 24H 07/0600Z 27.2N 79.9W 125 KT 145 MPH 36H 07/1800Z 29.0N 80.7W 115 KT 130 MPH 48H 08/0600Z 30.7N 80.7W 95 KT 110 MPH 72H 09/0600Z 32.4N 77.6W 80 KT 90 MPH 96H 10/0600Z 31.0N 75.0W 60 KT 70 MPH 120H 11/0600Z 29.5N 75.0W 50 KT 60 MPH $$ Forecaster Brown

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