[Tropical] Tropical Cyclone Discussion

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WTNT41 KNHC 011504
TCDAT1

HURRICANE JOAQUIN DISCUSSION NUMBER  15
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL112015
1100 AM EDT THU OCT 01 2015

An Air Force Reserve Hurricane Hunter aircraft reported 700-mb
flight-level winds of 119 kt in the northwestern eyewall, with a
117 kt surface wind estimate from the Stepped Frequency Microwave
Radiometer in the southwestern eyewall.  The latest central
pressure was 942 mb.  Based on these data, the advisory intensity
is increased to 110 kt.  Satellite imagery indicates that an eye is
trying to form in the central dense overcast, and that the cirrus
outflow is good in all directions.

Joaquin is expected to intensify a little more in the next 12 to 24
hours as it remains over very warm waters and in an environment of
decreasing vertical shear.  After that time, there could be some
fluctuations in intensity due to eyewall replacement cycles.  There
is some uncertainty in the intensity forecast in the 48-96 hour
period.  The statistical models suggest that Joaquin should weaken
due to increasing shear.  However, several of the global models
forecast the hurricane to move into an area of strong upper-level
divergence and show a falling central pressure.  The new forecast
will continue to show weakening during this time, but it would not
be a surprise if it is stronger than currently forecast.

The initial motion is 220/5.  Water vapor imagery shows a mid- to
upper-level ridge north of the hurricane, with a developing
deep-layer trough over the eastern and southeastern United States.
The dynamical models forecast this trough to become a cut-off low as
it moves southeastward and weakens the ridge.  This pattern
evolution should cause Joaquin to turn northwestward in 24 hours or
so and then turn northward.  After 36 hours, the guidance remains
very divergent.  The Canadian, GFDL, HWRF, and NAVGEM models
forecast Joaquin to turn northwestward and make landfall over the
Carolinas and mid-Atlantic States.  The ECMWF continues to forecast
a slower northeastward motion taking Joaquin near Bermuda and out to
sea. The UKMET and GFS are in between these extremes showing a
generally northward motion.  Given the spread and the possibility
that the 1200 UTC guidance could show additional changes, the
forecast track after 36 hours is nudged only slightly to the east at
this time. The new track lies to the east of the landfalling models,
but to the west of the GFS, UKMET, ECMWF, and the various consensus
models. Further adjustments to the track may be needed later today
depending on how the models do (or do not) change.


KEY MESSAGES:

1.  Preparations to protect life and property in the central Bahamas
should be complete.  The slow motion of Joaquin over the next day or
so will bring a prolonged period of hurricane force winds, storm
surge, and very heavy rainfall to those islands.

2.  Confidence in the details of the forecast after 72 hours is
still low, since there have been some large changes in the model
guidance overnight and a large spread in the model solutions
remains, with potential impacts from the Carolinas through New
England.  It is also possible that Joaquin will remain far from the
U.S. east coast.  A hurricane watch for the U.S. coast would likely
not occur until at least Friday morning.

3.  Efforts to provide the forecast models with as much data as
possible continue, with twice daily NOAA G-IV jet missions in the
storm environment, and extra NWS balloon launches.

4.  It's too early to talk about specific wind, rain, or surge
impacts from Joaquin in the United States.  Regardless of Joaquin's
track, strong onshore winds will create minor to moderate coastal
flooding along the coasts of the mid-Atlantic and northeastern
states through the weekend.

5.  Many portions of the eastern U.S. are currently experiencing
heavy rains and gusty winds associated with a frontal system. These
heavy rains are likely to continue for the next few days, even if
the center of Joaquin stays offshore.  The resulting inland flood
potential could complicate preparations for Joaquin should it head
toward the coast, and even more substantial inland flooding is
possible if Joaquin later passes near or over these same areas.


FORECAST POSITIONS AND MAX WINDS

INIT  01/1500Z 23.0N  73.9W  110 KT 125 MPH
 12H  02/0000Z 22.9N  74.2W  115 KT 130 MPH
 24H  02/1200Z 23.7N  74.6W  120 KT 140 MPH
 36H  03/0000Z 25.2N  74.4W  120 KT 140 MPH
 48H  03/1200Z 27.5N  73.7W  110 KT 125 MPH
 72H  04/1200Z 32.0N  73.0W   95 KT 110 MPH
 96H  05/1200Z 36.0N  73.5W   75 KT  85 MPH
120H  06/1200Z 40.0N  72.5W   55 KT  65 MPH

$$
Forecaster Beven
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