204 
 WTNT41 KNHC 300849
 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