Hurricane Jerry Forecast Discussion

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106 
WTNT45 KNHC 210259
TCDAT5

Hurricane Jerry Discussion Number  15
NWS National Hurricane Center Miami FL       AL102019
1100 PM AST Fri Sep 20 2019

Jerry has been displaying a classic bursting convective pattern with
a nearly circular CDO that expanded over the circulation since the
last advisory.  An Air Force Hurricane Hunter mission that just
arrived in Jerry indicated that the center is farther northeast than
previously estimated, which appears coincident with the location of
the most recent bursts of convection. Since subjective and
objective Dvorak intensity estimates range from 61 kt to 77 kt, the
initial intensity remains 70 kt. This intensity could be adjusted
based on what the plane finds while investigating the circulation.
The central pressure is estimated to be 993 mb based on the center
drop from the plane.

The hurricane is still moving quickly west-northwestward with an
initial motion of 295/15 kt.  The track forecast is fairly
straightforward.  Jerry is approaching a break in the subtropical
ridge, created by a deep-layer trough currently moving across the
northwestern Atlantic. This pattern is expected to cause Jerry to
gradually recurve around the ridge during the next 5 days, with its
forward motion reaching a minimum between 48-72 hours when it moves
near the ridge axis.  There is very good agreement among the track
guidance on this scenario, and the only notable spread is related
to the system's forward speed when it accelerates on day 5.  The
consensus aids are holding tough on a relatively consistent
trajectory, so little change was made from the previous official
forecast.

Dropsonde data from a NOAA G-IV synoptic surveillance mission
indicate that anticyclonic flow continues over the hurricane at the
200-mb outflow level (except it's restricted a bit to the west), but
15-25 kt of northeasterly flow is cutting through the circulation
just below 250 mb.  Despite this flow, Jerry's structure does not
appear to have degraded too much.  Since the hurricane appears that
it will move beneath an upper-level anticyclone in about 24 hours,
its intensity may not decrease too much over the next several days.
And despite an increase in westerly shear after 48 hours, enhanced
upper-level divergence to the east of an upper-level trough could
offset the potential for weakening.  Accounting for uncertainties,
the NHC intensity forecast maintains a fairly steady strength for
the entire forecast period, keeping Jerry as a hurricane for the
next 5 days.  This forecast is close to the HCCA model and the
simple consensus aids, but it's notable that it's up to 20 kt lower
than the statistical-dynamical models by the end of the forecast
period.

Key Messages:

1. Although the core of Jerry is passing north of the northern
Leeward Islands, heavy rainfall and flash floods are possible there
overnight.


FORECAST POSITIONS AND MAX WINDS

INIT  21/0300Z 20.5N  62.8W   70 KT  80 MPH
 12H  21/1200Z 21.4N  64.4W   65 KT  75 MPH
 24H  22/0000Z 22.6N  66.6W   65 KT  75 MPH
 36H  22/1200Z 24.0N  68.1W   65 KT  75 MPH
 48H  23/0000Z 25.3N  68.7W   70 KT  80 MPH
 72H  24/0000Z 27.9N  68.2W   70 KT  80 MPH
 96H  25/0000Z 30.8N  66.3W   65 KT  75 MPH
120H  26/0000Z 34.5N  62.1W   65 KT  75 MPH

$$
Forecaster Berg




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