Home › discussion
 

Keywords :   


Tag: discussion

Tropical Depression Nine Forecast Discussion Number 4

2018-09-08 16:57:36| National Hurricane Center (Atlantic)

Issued at 1100 AM AST Sat Sep 08 2018 571 WTNT44 KNHC 081457 TCDAT4 Tropical Depression Nine Discussion Number 4 NWS National Hurricane Center Miami FL AL092018 1100 AM AST Sat Sep 08 2018 The structure of Tropical Depression Nine is improving as the ongoing shear diminishes, with the convection getting closer to the low-level center. However, recent scatterometer data indicates that the system has not yet become a tropical storm, and the initial intensity remains 30 kt. The cyclone is still moving fairly slowly, with the initial motion now 300/5. The subtropical ridge to the north of the cyclone is forecast to steer the system westward with an increasing forward speed for at least the next 2-3 days. After that time, there is some uncertainty in the track forecast due to the formation of a mid- to upper-level trough over the central Atlantic. The Canadian and UKMET models forecast the cyclone to slow down and turn northwestward near the end of the forecast period due to the trough, while the ECMWF and GFS show a continued westward motion. The track forecast follows the ECMWF/GFS scenario and shows a faster westward motion than the previous forecast. The new forecast also lies near the various consensus models. With the shear diminishing, conditions are becoming more favorable for the cyclone to strengthen during the next 72 h. However, there are still concerns about dry air entraining into the system. The new intensity forecast is similar to the previous forecast with the cyclone becoming a tropical storm in about 12 h and a hurricane in about 72 h. After 72 h, the system is expected to encounter another round of shear, which is expected to cause some weakening. FORECAST POSITIONS AND MAX WINDS INIT 08/1500Z 14.6N 36.0W 30 KT 35 MPH 12H 09/0000Z 14.7N 36.9W 35 KT 40 MPH 24H 09/1200Z 14.8N 38.5W 40 KT 45 MPH 36H 10/0000Z 14.8N 40.8W 50 KT 60 MPH 48H 10/1200Z 14.8N 43.5W 60 KT 70 MPH 72H 11/1200Z 14.5N 49.0W 75 KT 85 MPH 96H 12/1200Z 14.5N 55.0W 80 KT 90 MPH 120H 13/1200Z 14.5N 60.0W 75 KT 85 MPH $$ Forecaster Beven

Tags: number discussion tropical depression

 

Tropical Storm Florence Forecast Discussion Number 37

2018-09-08 16:53:38| National Hurricane Center (Atlantic)

Issued at 1100 AM AST Sat Sep 08 2018 863 WTNT41 KNHC 081453 TCDAT1 Tropical Storm Florence Discussion Number 37 NWS National Hurricane Center Miami FL AL062018 1100 AM AST Sat Sep 08 2018 Florence has undergone a dramatic structural evolution just within the past 6 hours or so. Vertical shear has decreased just enough for the storm to take on a more symmetric shape, with convection developing in a ring around the low-level center, and an elongated band wrapping around to the northeastern part of the circulation. The convection has waned a little bit in intensity, however, due to the presence of dry air, and Dvorak estimates support maintaining an initial intensity of 55 kt for now. A NOAA P-3 aircraft is approaching Florence now on a research mission and should provide some useful data to better assess the storm's intensity. Recent WindSat microwave data revealed that Florence has a well-defined low-level ring in the 37-GHz channel, which tends to be a harbinger of strengthening when environmental conditions are favorable. Since vertical shear is decreasing and should be 10 kt or less by later today, and Florence is heading toward a deeper pool of warm water over the southwestern Atlantic, a significant phase of intensification is likely to begin by tonight, continuing through Tuesday or Wednesday. In fact, the official intensity forecast explicitly shows rapid intensification occurring between 24 and 48 hours from now, and Florence is expected to become a major hurricane by Monday. The HFIP Corrected Consensus (HCCA) and the Florida State Superensemble (FSSE), both of which tend to do well in these scenarios, are both near the upper end of the guidance suite, especially through day 3. Even by days 4 and 5, the HWRF, HMON, and ICON intensity consensus are near the top end of the guidance, close to HCCA and FSSE. Given the signals in the environment, and the solutions provided by these models, the NHC intensity forecast shows Florence reaching category 4 intensity by day 3 and maintains that through the end of the forecast period. Florence's longer-term motion is 265/6 kt. The cyclone appears to be slowing down as was expected, and this type of motion is likely to continue for the next 24-36 hours. In fact, the track guidance has slowed down during this period, and the updated NHC track forecast is a little slower than the previous one. After 36 hours, the most notable change in the models was a northeastward shift in the 06Z GFS. However, that run appears to be an outlier from the rest of the dynamical models, and its trend opposes the slight westward shift noted in the HCCA and FSSE aids. The updated NHC track forecast is therefore very close to or slightly west of the previous forecast on days 4 and 5. The exact path of Florence as it approaches the southeastern U.S. coastline will depend heavily on the position and strength of the blocking high pressure that is expected to develop north of Bermuda and extend westward over the eastern U.S., and so far there has not been much more clarity on those important details. Key Messages: 1. Florence is forecast to be a dangerous major hurricane near the southeast U.S. coast by late next week, and the risk of direct impacts continues to increase. However, given the uncertainty in track and intensity forecasts at those time ranges, it's too soon to determine the exact timing, location, and magnitude of those impacts. 2. Interests along the U.S. East Coast, particularly from north Florida through North Carolina, should closely monitor the progress of Florence, ensure they have their hurricane plan in place, and follow any advice given by local officials. 3. Large swells are affecting Bermuda and will begin to affect portions of the U.S. East Coast this weekend, resulting in life-threatening surf and rip currents. FORECAST POSITIONS AND MAX WINDS INIT 08/1500Z 24.5N 54.3W 55 KT 65 MPH 12H 09/0000Z 24.6N 55.0W 60 KT 70 MPH 24H 09/1200Z 24.6N 56.1W 70 KT 80 MPH 36H 10/0000Z 24.8N 57.5W 85 KT 100 MPH 48H 10/1200Z 25.1N 59.3W 100 KT 115 MPH 72H 11/1200Z 26.3N 64.9W 115 KT 130 MPH 96H 12/1200Z 28.5N 71.5W 125 KT 145 MPH 120H 13/1200Z 31.5N 77.0W 120 KT 140 MPH $$ Forecaster Berg

Tags: number discussion storm tropical

 
 

Tropical Storm Helene Forecast Discussion Number 5

2018-09-08 16:44:34| National Hurricane Center (Atlantic)

Issued at 1100 AM AST Sat Sep 08 2018 532 WTNT43 KNHC 081444 TCDAT3 Tropical Storm Helene Discussion Number 5 NWS National Hurricane Center Miami FL AL082018 1100 AM AST Sat Sep 08 2018 The structure of Helene continues to improve, with convective banding wrapping around almost completely around the center of the cyclone in visible satellite imagery. Infrared imagery suggests this convection is not very strong at the moment, though, and this may be why recent scatterometer data indicates that the storm has not strengthened since the last advisory. The initial intensity remains 40 kt based on the scatterometer winds. All indications are that Helene should strengthen through at least 72 h in a light vertical shear environment over sea surface temperatures near 27C. This part of the intensity forecast is similar to the previous forecast and lies near the intensity consensus. However, there are a couple of alternate forecast scenarios. The first is that Helene could rapidly intensify and become stronger than currently forecast. The second is that a large plume of African dust and associated dry air that has spread over the northern Cabo Verde Islands starts entraining into the cyclone and inhibits intensification. The former alternative seems more likely than the latter at this time, and if RI begins later intensity forecasts will need to be increased. After 72 h, Helene is expected to encounter increasing southwesterly shear associated with a mid- to upper-level trough over the central Atlantic, which should cause the system to weaken. Helene's center appears to have again re-formed, this time a little to the south. The somewhat uncertain initial motion is 265/11. Other than a slight nudge to the south due to the initial position, there is little change in the forecast track for Helene. The cyclone should moved westward to west-northwestward for the next 3-4 days on the south side of the subtropical ridge, then turn northwestward in response to the aforementioned trough. FORECAST POSITIONS AND MAX WINDS INIT 08/1500Z 13.4N 20.6W 40 KT 45 MPH 12H 09/0000Z 13.6N 22.4W 50 KT 60 MPH 24H 09/1200Z 13.9N 24.9W 60 KT 70 MPH 36H 10/0000Z 14.6N 27.8W 70 KT 80 MPH 48H 10/1200Z 15.3N 30.8W 80 KT 90 MPH 72H 11/1200Z 17.0N 36.0W 80 KT 90 MPH 96H 12/1200Z 19.0N 40.0W 70 KT 80 MPH 120H 13/1200Z 22.5N 42.5W 60 KT 70 MPH $$ Forecaster Beven

Tags: number discussion storm tropical

 

Tropical Depression Eighteen-E Forecast Discussion Number 1

2018-09-08 16:36:35| National Hurricane Center (East Pacific)

Issued at 800 AM PDT Sat Sep 08 2018 506 WTPZ43 KNHC 081436 TCDEP3 Tropical Depression Eighteen-E Discussion Number 1 NWS National Hurricane Center Miami FL EP182018 800 AM PDT Sat Sep 08 2018 The area of low pressure that NHC has been tracking for several days has enough organized deep convection this morning to be classified as a tropical depression. Some northeasterly shear is affecting the cyclone, with the apparent center on the northeastern side of a growing area of deep convection. The initial wind speed is set to 30 kt, in accordance with the Dvorak classification from TAFB. Gradual strengthening is forecast while the cyclone remains over warm waters within a light-to-moderate shear environment. After 72 hours, the water temperatures drop off quite a bit and weakening should begin. The NHC forecast is close to, but a little above, the model consensus near peak intensity to account for the low bias the model guidance has had for many eastern Pacific storms this year. An uncertain initial motion estimate is 290/10. All of the model guidance turn the cyclone northwestward by tomorrow as the cyclone rounds the southwestern side of a mid-level ridge located over Mexico. A turn back toward the west-northwest is anticipated in a few days due to the system coming under the influence of the primary eastern Pacific subtropical ridge. For a first advisory, the model guidance isn't in terrible disagreement, so the NHC prediction will lie near close to the various consensus and corrected-consensus aids. FORECAST POSITIONS AND MAX WINDS INIT 08/1500Z 16.1N 115.9W 30 KT 35 MPH 12H 09/0000Z 16.6N 116.8W 35 KT 40 MPH 24H 09/1200Z 17.7N 117.8W 40 KT 45 MPH 36H 10/0000Z 18.9N 118.7W 45 KT 50 MPH 48H 10/1200Z 20.1N 119.8W 50 KT 60 MPH 72H 11/1200Z 21.5N 123.0W 65 KT 75 MPH 96H 12/1200Z 23.0N 126.5W 60 KT 70 MPH 120H 13/1200Z 24.5N 129.0W 40 KT 45 MPH $$ Forecaster Blake

Tags: number discussion tropical depression

 

Tropical Depression Nine Forecast Discussion Number 3

2018-09-08 10:55:34| National Hurricane Center (Atlantic)

Issued at 500 AM AST Sat Sep 08 2018 357 WTNT44 KNHC 080855 TCDAT4 Tropical Depression Nine Discussion Number 3 NWS National Hurricane Center Miami FL AL092018 500 AM AST Sat Sep 08 2018 The depression continues to be affected by moderate to strong east to southeasterly vertical wind shear, which has resulted in the bulk of the deep convection being displaced to the west of the low-level center. The initial intensity has been held at 30 kt based on Dvorak satellite intensity estimate of T2.0/30 kt from both TAFB and SAB. The depression has been meandering in the same general area for the past 12-18 h due to being caught in a weakness in the subtropical ridge. However, recent microwave satellite data suggest that the cyclone is now moving slowly northwestward. A turn toward the west is expected to occur later today as a shortwave trough to the north that has weakened the ridge lifts out, allowing the ridge to fill back in and build westward to the north of the Lesser Antilles. The latest NHC model guidance suite remains tightly packed, and the official forecast track lies down the middle of the envelope near a blend of the consensus aids TCVA, HCCA, FSSE. Although the wind shear is forecast to gradually weaken and become less than 5 kt by 36-48 h, which would favor rapid strengthening, the airmass that the cyclone is embedded is fairly dry. Since mid-level humidity values are forecast to decrease from the current 60-percent range down to around 50 percent by 48 hours and beyond, only modest strengthening is expected during the next 4 days. By day 5, vertical wind shear from the southwest is forecast to increase to 20-25 kt, serving to cap the intensification process. The NHC intensity forecast is based on a blend of the IVCN and the HCCA consensus models, and continues to remain below the stronger HWRF model at days 4 and 5, which makes the cyclone a major hurricane in 78 h. FORECAST POSITIONS AND MAX WINDS INIT 08/0900Z 14.3N 35.4W 30 KT 35 MPH 12H 08/1800Z 14.4N 36.1W 35 KT 40 MPH 24H 09/0600Z 14.5N 37.5W 40 KT 45 MPH 36H 09/1800Z 14.7N 39.5W 45 KT 50 MPH 48H 10/0600Z 14.6N 42.0W 55 KT 65 MPH 72H 11/0600Z 14.5N 47.3W 75 KT 85 MPH 96H 12/0600Z 14.6N 52.7W 80 KT 90 MPH 120H 13/0600Z 14.9N 57.2W 80 KT 90 MPH $$ Forecaster Stewart

Tags: number discussion tropical depression

 

Sites : [521] [522] [523] [524] [525] [526] [527] [528] [529] [530] [531] [532] [533] [534] [535] [536] [537] [538] [539] [540] next »