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| #804060 (Received by flhurricane at: 4:55 AM 30.Sep.2015) TCDAT1 TROPICAL STORM JOAQUIN DISCUSSION NUMBER 10 NWS NATIONAL HURRICANE CENTER MIAMI FL AL112015 500 AM EDT WED SEP 30 2015 The coldest convective cloud tops are located to the east of the estimated center position, but there have been hints of an eye in infrared imagery overnight. Based on a blend of the latest Dvorak estimates from TAFB and SAB, the initial intensity remains 60 kt. An Air Force Reserve Hurricane Hunter aircraft is on its way to investigate Joaquin this morning. Conditions are expected to be conducive for intensification during the next few days, with Joaquin moving over very warm waters with shear steadily decreasing. The hurricane intensity guidance and the latest runs of the GFS, UKMET, and ECMWF all show Joaquin intensifying, and in fact, the global models show the central pressure in the 950s or lower. The NHC forecast is near the latest intensity model consensus, and has Joaquin peaking in 72 hours. After that time, the cyclone will be moving into a higher shear environment and over cooler waters, which should result in slow weakening. Joaquin continues to move west-southwestward under the influence of a short-wave ridge to its north, and the initial motion estimate is 245/05. This motion should continue for the next 24 hours, and Joaquin is expected to then turn slowly westward as the ridge weakens on Thursday. The UKMET and ECMWF continue to show Joaquin moving farther southwestward into the central Bahamas than the rest of the guidance. The new NHC track in the short range is a little south of the previous one, but north of the UKMET/ECMWF solution. Given this new forecast, the government of the Bahamas has issued a Hurricane Warning for the central Bahamas and a Hurricane Watch for part of the northwestern Bahamas. After 36 hours, Joaquin is forecast to turn northwestward and then northward as it interacts with a deep-layer trough that cuts off over the southeastern United States in about 3 days. Much of the deterministic guidance shows Joaquin turning northwestward toward the mid-Atlantic coast by days 4 and 5. However, the ECMWF continues to show an offshore solution with a track west of Bermuda, but has shifted to the left this cycle by about 150 miles at day 5. While the overall synoptic pattern is similar between the models, the eventual track of Joaquin appears sensitive to just how far southwest it moves in the first 36 to 48 hours and how this affect the eventual interaction with the upper-level low. The GFS, HWRF, and GFDL show a sharp turn back to toward the coast in 4 days, while the ECMWF is slower to bring Joaquin northward and ejects the cyclone toward the northeast. The UKMET is between those two scenarios with a broader turn back toward the coast by day 5. There is still ensemble support for a wide range of solutions, so confidence in any deterministic model solution remains quite low. The NHC track has been nudged a little to the left this cycle to reflect the westward shift in the guidance, but lies on the eastern side of the guidance envelope given the ECMWF solution. Confidence in the details of the track forecast late in the period remains very low, since the environmental steering currents are complex and not being handled in a consistent manner by the models. Given that a wide range of outcomes is possible, it is too soon to say what impacts, if any, Joaquin will have on the United States. FORECAST POSITIONS AND MAX WINDS INIT 30/0900Z 25.4N 72.5W 60 KT 70 MPH 12H 30/1800Z 25.1N 73.0W 70 KT 80 MPH 24H 01/0600Z 24.7N 73.8W 75 KT 85 MPH 36H 01/1800Z 24.7N 74.5W 80 KT 90 MPH 48H 02/0600Z 25.2N 74.7W 90 KT 105 MPH 72H 03/0600Z 28.3N 73.5W 95 KT 110 MPH 96H 04/0600Z 33.0N 73.0W 85 KT 100 MPH 120H 05/0600Z 37.0N 73.5W 80 KT 90 MPH $$ Forecaster Brennan |
