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Hurricane Flossie Discussion Number  12
NWS National Hurricane Center Miami FL       EP072019
1100 PM HST Tue Jul 30 2019

High-resolution WindSat imagery from 0227 UTC gave quite a
surprise when it arrived a few hours ago:  Flossie is not as
organized as it seemed.  The low-level center was displaced
about 40 n mi to the west of overshooting convective tops and
mid-level rotation seen in infrared satellite images, the result of
moderate to strong westerly shear.  A 0513 UTC ASCAT-C pass also
revealed an asymmetric wind field, with no tropical-storm-force
winds in the southwestern quadrant.  The initial intensity is held
at 70 kt, mainly for the sake of continuity, but the ASCAT data and
recent SATCON estimates suggest that it could be lower.

Flossie continues to move west-northwestward (285 degrees), now at a
speed of 13 kt.  A narrow mid-level ridge centered along 24N is
forecast to build westward toward the Hawaiian Islands over the
next 3 days, with the flow on the southern side expected to keep
Flossie moving west-northwestward or westward at a steady clip for
the entire forecast period.  The track guidance remains tightly
clustered, and the new NHC forecast has only been nudged northward
from the previous one to account for the more-apparent initial
position.

It's difficult at the moment to see how Flossie will be able to
strengthen much in the coming days.  The cyclone's structure is
already suffering from the effects of shear, and diagnostics from
the SHIPS model suggest that the shear could increase further, or
at least hold steady, during the next 48 hours.  There's an
opportunity for the shear to decrease a bit in 2-3 days, but by
that time, Flossie will have reached marginally warm waters with
little to no ocean heat content.  Given these less-than-ideal
environmental factors, the NHC intensity forecast has again been
reduced from the previous one, and it generally lies between the
HCCA and the Florida State Superensemble.  This solution is still
near the high end of the guidance envelope and above the
conventional intensity consensus aids.


FORECAST POSITIONS AND MAX WINDS

INIT  31/0900Z 13.5N 124.4W   70 KT  80 MPH
 12H  31/1800Z 14.1N 126.3W   70 KT  80 MPH
 24H  01/0600Z 14.8N 128.9W   75 KT  85 MPH
 36H  01/1800Z 15.5N 131.6W   80 KT  90 MPH
 48H  02/0600Z 16.1N 134.3W   80 KT  90 MPH
 72H  03/0600Z 17.2N 139.9W   80 KT  90 MPH
 96H  04/0600Z 18.0N 145.0W   75 KT  85 MPH
120H  05/0600Z 18.5N 150.0W   60 KT  70 MPH

$$
Forecaster Berg

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