[Tropical] Tropical Cyclone Discussion

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WTNT43 KNHC 091442
TCDAT3

Tropical Storm Julia Discussion Number  13
NWS National Hurricane Center Miami FL       AL132022
1000 AM CDT Sun Oct 09 2022

Julia continues to move westward across Nicaragua with a
well-defined circulation and deep convection persisting near the
center.  The terrain of southern and central Nicaragua is not as
rugged as areas farther north in Central America, and Julia is
probably only gradually weakening while it crosses land.  Based on
a typical decay rate, and interpolating from the previous forecast,
Julia is now estimated to be a 60-kt tropical storm.

Strong ridging over the Gulf of Mexico continues to propel the
storm quickly westward (270 degrees) at about 13 kt, and that
motion should continue today, with Julia's center expected to move
off the Pacific coast of Nicaragua by this evening.  By tonight and
Monday, Julia is forecast to turn toward the west-northwest and
move very close to and parallel to the Pacific coasts of Honduras,
El Salvador, and Guatemala.  The model trackers lose Julia in a day
or two and instead show a potential track farther offshore by
keying in on a broader circulation farther west that is associated
with an ongoing Gulf of Tehuantepec gap wind event.  However,
global model fields, in particular the GFS and ECWMF, show Julia's
smaller circulation more closely hugging the Pacific coast of
Central America, and the updated NHC track forecast more closely
follows that scenario.

Additional weakening is expected today while Julia continues moving
over land, but the cyclone should still be at tropical storm
strength when it moves offshore this evening.  In keeping with the
GFS and ECMWF solutions, Julia's contracting circulation is
forecast to weaken further over the Pacific waters, coincident with
an increase in easterly shear.  Based on the latest forecast, Julia
is expected to weaken to a tropical depression on Monday and then
dissipate by Monday night while moving close to the coast of
Guatemala.

Regardless of Julia's track and future status as a tropical cyclone,
the evolving weather pattern is likely to lead to heavy rains over
Central America and southern Mexico for several days, which could
cause life-threatening flash floods and mudslides, especially in
areas of mountainous terrain.

Since Julia's low-level circulation is expected to survive its
passage across Nicaragua, the cyclone will retain the same name
when it moves into the eastern Pacific basin.  The intermediate
advisory at 100 PM CDT (1800 UTC) will be issued under the same
Atlantic product headers as before.  However, now that all coastal
watches and warnings are located along the Pacific coast of Central
America, product headers will change to eastern Pacific headers
beginning with the next complete advisory at 400 PM CDT (2100 UTC),
with the ATCF identifier changing from AL132022 to EP182022.


Key Messages:

1. Julia is forecast to remain as a tropical storm while it moves
across Nicaragua today and reaches the adjacent Pacific waters
this evening.  Tropical storm warnings are in effect along the
Pacific coasts of Nicaragua, Honduras, and El Salvador to account
for the likelihood of tropical-storm-force winds in those areas
later today through Monday.  Tropical-force-winds are also possible
on Monday along the Pacific coast of Guatemala, where a tropical
storm watch is in effect.

2. Life-threatening flash flooding and mudslides are expected across
portions of Central America Sunday and Monday.  Flash flooding is
anticipated across the Isthmus of Tehuantepec in Mexico early this
week.


FORECAST POSITIONS AND MAX WINDS

INIT  09/1500Z 12.4N  85.4W   60 KT  70 MPH...INLAND
 12H  10/0000Z 12.5N  87.5W   45 KT  50 MPH...OVER WATER
 24H  10/1200Z 13.2N  89.6W   40 KT  45 MPH
 36H  11/0000Z 14.0N  91.9W   30 KT  35 MPH
 48H  11/1200Z...DISSIPATED

$$
Forecaster Berg
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