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  1. NHC have declared TD9. Forecast to develop rapidly and could hit the Gulf Coast as early as Sunday after a trip over Cuba tomorrow. UKMO, GFS, Euro operationals range from about 950mb to 980mb however HWRF (specialist intensity model for the tropics and highly accurate according to the NHC) has been punting in the 930mb range. Tropical Depression Nine Discussion Number 1 NWS National Hurricane Center Miami FL AL092021 1100 AM EDT Thu Aug 26 2021 Early morning visible satellite imagery shows that the circulation associated with the area of low pressure over west-central Caribbean Sea has become better defined. There has also been an increase in the organization of the associated convective activity, and based on consensus Dvorak T-numbers of 2.0 from TAFB and SAB, advisories are being initiated on a tropical depression. The initial intensity is set at 30 kt, in agreement with the subjective satellite estimates. The official reporting station in Kingston, Jamaica, has reported sustained winds of 25 kt with gusts to 35 kt during the past couple of hours. An Air Force Reserve reconnaissance aircraft is scheduled to be in the system later this afternoon to provide more information on the system's structure and intensity. The depression is moving northwestward or 325/11 kt, however the initial motion is a bit more uncertain than normal since the low- level center has only recently formed. The cyclone is forecast to move steadily northwestward around the southwestern portion of a deep-layer ridge centered over the western Atlantic. This track should bring the center near or over western Cuba late Friday, over the southeastern and central Gulf of Mexico Friday night and Saturday, and have the center approach the northern Gulf coast on Sunday. The track guidance is in relatively good agreement, however the average NHC track forecast error at day 4 is around 175 miles, so users should not focus on the details of the long range track forecast. Some shifts in the track are likely until the system consolidates and becomes better defined. The NHC track is near the various consensus model aids and is in best agreement with the GFS ensemble mean. The depression will be moving over the high ocean heat content waters of the northwestern Caribbean Sea during the next 24-36 hours. This, in combination with low vertical wind shear and a moist environment, should allow for steady strengthening. The depression is forecast to become a tropical storm later today or tonight, and could approach hurricane strength as it passes near or over western Cuba. Once the system moves into the Gulf of Mexico, conditions are expected to be conducive for additional strengthening, and rapid intensification is explicitly shown in the NHC forecast between 48 and 72 hours. The NHC intensity forecast brings the system near major hurricane strength when it approaches the northern Gulf coast on Sunday. This forecast is supported by the HWRF and CTCI models, and the GFS, ECMWF, and UKMET global model guidance, which all significantly deepen the cyclone over the Gulf of Mexico. As a result, there is higher-than-normal confidence that a strengthening tropical cyclone will be moving over the Gulf this weekend. Key Messages: 1. Tropical storm conditions are likely in portions of the Cayman Islands tonight and western Cuba Friday and Friday night, with dangerous storm surge possible in portions of western Cuba, including the Isle of Youth, in areas of onshore flow. 2. The system is expected to produce life-threatening heavy rains, flash flooding and mudslides across Jamaica, the Cayman Islands, western Cuba, including the Isle of Youth and northeastern portions of the Yucatan Peninsula. 3. This system is forecast to approach the northern Gulf Coast at or near major hurricane intensity on Sunday, although the forecast uncertainty is larger than usual since the system is just forming. There is a risk of life-threatening storm surge, damaging hurricane-force winds, and heavy rainfall Sunday and Monday along the northern Gulf Coast from the Florida Panhandle to the upper Texas coast, with the greatest risk along the coast of Louisiana. Interests in these areas should closely monitor the progress of this system and ensure they have their hurricane plan in place. FORECAST POSITIONS AND MAX WINDS INIT 26/1500Z 16.9N 79.2W 30 KT 35 MPH 12H 27/0000Z 18.2N 80.4W 35 KT 40 MPH 24H 27/1200Z 20.3N 82.0W 45 KT 50 MPH 36H 28/0000Z 22.5N 83.9W 55 KT 65 MPH...INLAND 48H 28/1200Z 24.4N 86.0W 65 KT 75 MPH...OVER WATER 60H 29/0000Z 26.1N 88.1W 80 KT 90 MPH 72H 29/1200Z 27.7N 90.0W 95 KT 110 MPH 96H 30/1200Z 30.5N 92.0W 70 KT 80 MPH...INLAND ...... For a first advisory i don't most of you will be aware of just how agressive that is. The NHC are normally very conservative in their initial forecasts.
  2. Hurricane conditions for Barbados now "ELSA STRENGTHENS INTO A HURRICANE... ...HURRICANE CONDITIONS SPREADING THROUGH THE WINDWARD ISLANDS." NHC A Hurricane Warning is in effect for... * Barbados * St. Lucia * St. Vincent and the Grenadines A Tropical Storm Warning is in effect for... * Martinique * The southern coast of Dominican Republic from Cabo Engano to the border with Haiti * Entire coast of Haiti A Hurricane Watch is in effect for... * Southern portion of Haiti from Port Au Prince to the southern border with the Dominican Republic
  3. 98L in the Central Atlantic has now been declared Tropical Depression 13. Tropical Depression Thirteen Discussion Number 2 NWS National Hurricane Center Miami FL There has been little change in the organization of Tropical Depression Thirteen during the past several hours. An area of ragged but persistent convection continues near the estimated center position, and there is some outer banding in the southern semicircle. Dvorak-based satellite intensity estimates have changed little since the last advisory, so the initial intensity remains 30 kt. The initial motion is a somewhat uncertain 295/18. The subtropical ridge to the north of the cyclone is expected to build westward to the north of the Greater Antilles during the next several days, and this should steer the cyclone generally west-northwestward through the forecast period. The track guidance remains in fairly good agreement with this scenario, but there remains a spread between the GFS/UKMET on the south side of the guidance and the Canadian/HMON on the north side. Overall, the envelope has shifted a little to the south since the previous advisory and the new forecast track, which lies just to the north of the consensus models, is also nudged southward. The new track calls for the cyclone to pass near the Leeward Islands in 36-48 h, near or north of Puerto Rico and the Virgin Islands in 48-60 h, and then near or over Hispaniola and the southeastern Bahamas by 72 h. Overall, the environment looks generally favorable for strengthening, with the cyclone expected to encounter light- to moderate shear during forecast period. However, the guidance responds to this environment with a wide range of solutions. The HWRF/HMON forecast the cyclone to intensify into a major hurricane by 120 h. On the other hand, the GFS and ECMWF show the system degenerating into an open wave by 120 h. The UKMET and Canadian models are between these extremes. The weak GFS solution appears to be due to forecast dry air entrainment, which is a possibility as satellite imagery suggests Saharan dust not far from the cyclone. Between these factors and the possibility of land interaction, the low-confidence intensity forecast is changed little from the previous advisory. Key Messages: 1. Tropical storm conditions are possible across portions of the northern Leeward Islands by Friday night, and Tropical Storm Watches have been issued for some of these islands. Heavy rainfall is likely across this area beginning late Friday. 2. There is a risk of tropical storm conditions in the Virgin Islands and Puerto Rico Friday night and Saturday and Tropical Storm Watches could be required for these islands later today. Interests there should closely monitor the progress of this system. 3. The details of the long-range track and intensity forecasts are more uncertain than usual since the system could move over portions of the Greater Antilles this weekend. However, this system could bring some rainfall and wind impacts to portions of Hispaniola, Cuba, the Bahamas, and Florida this weekend and early next week. Interests there should monitor this system's progress and updates to the forecast over the next few days. FORECAST POSITIONS AND MAX WINDS INIT 20/0900Z 15.2N 49.8W 30 KT 35 MPH 12H 20/1800Z 16.4N 52.7W 30 KT 35 MPH 24H 21/0600Z 17.5N 56.4W 35 KT 40 MPH 36H 21/1800Z 18.4N 60.2W 40 KT 45 MPH 48H 22/0600Z 19.1N 63.9W 45 KT 50 MPH 60H 22/1800Z 19.8N 67.1W 50 KT 60 MPH 72H 23/0600Z 20.8N 71.0W 55 KT 65 MPH 96H 24/0600Z 23.0N 78.0W 60 KT 70 MPH 120H 25/0600Z 26.0N 83.0W 60 KT 70 MPH $$ Forecaster Beven Track carries a risk from interaction with the Greater Antilles however Florida and the Gulf Coast are at risk. As alluded to in the NHC discussion shear is light although convergent (westerly) until day 6. Moisture and speed profiles are also good.
  4. Currently at W for the central Pacific naming, they do not return to A at the beginning of each season but just continue through the whole list. The red dot Johnston Atoll, or Kalama identified on the NHC text with a hurricane warning is uninhabited, now a Fish and wildlife haven after years as a US military base. @USFWSPacific https://www.fws.gov/refuge/johnston_atoll/ http://www.prh.noaa.gov/cphc/ In 1981, the US Army began planning for the Johnston Atoll Chemical Agent Disposal System (JACADS). Construction began in 1986. It is the world's first full-scale facility built to destroy chemical weapons. The design is based on technologies used for years by the Army and industry. The facility actually did not begin full-scale operations until August 1993. Approaching hurricanes in both 1993 and 1994 necessitated facility shutdown and the evacuation of more than 1,100 soldiers, Department of the Army civilians, and Army contractors from Johnston Island to Hawaii. During each of these instances, JACADS production was disrupted for a period of time. As a result of the hurricane striking Johnston Island in August 1994, JACADS production was disrupted for approximately 70 days
  5. TD17 is now a tropical storm in open waters of mid-Atlantic. Not heading to US
  6. Mediterranean tropical cyclones, known as "medicanes", are a rare meteorological phenomenon in which tropical cyclones form in the Mediterranean Sea. The reason why they are so rare is because the Mediterranean region is fairly dry and so tropical cyclongenesis cannot occur, however if moisture is able to reach the region, usually in the form of a extratropical cyclone from the North Atlantic, then it may pass over the warmer waters of the sea and undergo tropical transition into a tropical cyclone. They are more common in the autumn and winter months when the jetstream moves farther south and allows low-pressure areas to reach the Mediterranean region. There have been rare instances of them though. Between 1948 and 2011, only 99 low-pressure systems with tropical or subtropical characteristics formed in the Mediterranean Basin. One example is the storm pictured below that formed in January 1995, that formed a distinctive eye.
  7. After a lull of about a month in TC activity, a new subtropical storm has developed in the Central Atlantic, and it has been named Melissa. The system is quite large, and seems to have a quite large range of tropical storm winds, but in the last few hours, convection has also built at the center of Melissa, which is a characteristic of a (sub-)tropical cyclone. Current OSCAT data shows the large radius of tropical storm winds associated with the system (winds of at least three and a half flag suggest tropical storm force winds) Current water vapor imagery shows a tongue of dry air curving toward the center of Melissa, likely impeding in development. Shear analysis by CIMSS (not shown here) shows the system is currently in a sharp shear gradient, with values ranging from 20 kt to the east, to 50 kt to the west of the system, providing, along with the dry air, only marginal conditions for development. The NHC is currently forecasting Melissa to get close to hurricane strength, as shear values are expected to drop to values below 10 kt, and SSTS are about 27 degrees Celsius. Thereafter, extratropical transition is about to begin. The storm is forecast to move northward during most of its lifetime, with a recurve toward the northeast afterward. Behind that time, it is yet uncertain if the system will turn back toward Greenland, or continue its recurve toward Spain. The NHC is currently forecasting a backward curve toward Greenland, on which an increasing amount of models seem to agree upon. The track of Melissa as forecast by the NHC. Although the model spread has been reduced in the past 24 hours, there remains a considerable amount of uncertanity about the angle of the recurve. An image of the different forecasts of different models, showing the current spread at the medium to long range. It will be interesting to see how the models handle this system now it has been qualified as a subtropical storm, and especially the effects on the forecasted blockade west of Ireland. It is likely that there will be quite some model-hopping in the medium to long term time frame. It is also very nice to see how tropical cyclones could have a significant impact on the weather in Europe, directly or indirectly. To illustrate the model-hopping of the various models on the handling on the storm, some output of the GFS and ECMWF models at T96hr below: GFS: EC: While the GFS suggests a very pronounced southern part of the complex low pressure area (extreme left, remnants of Melissa), the ECMWF shows a much more pronounced northern part of the system (in this case, the remnants of Melissa would be absorbed). The different handle could easily result in very different outcomes at bigger timeframes. And finally (to get back to the storm itself), a visible image of the subtropical cyclone.
  8. Hi Still no hurricanes to mention this year [2013] in the North Atlantic. A couple more tropical storms in August – Erin & Fernand – bringing the tally up to six so far since the start of the season. NOAA still going for above active season, but if it doesn’t kick of this month, that may not come to pass. The graphic is a home made one showing an activity index of the season by simply adding up the days for each tropical cyclone or higher – pretty crude but the NHC don’t produce figures in real time. It still show things not far from normal. Bruce. More info on my blog as usual.
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