[Tropical] Tropical Cyclone Discussion

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WTNT43 KNHC 081449
TCDAT3

Tropical Storm Julia Discussion Number   9
NWS National Hurricane Center Miami FL       AL132022
1100 AM EDT Sat Oct 08 2022

Air Force Reserve reconnaissance data indicate that Julia is not a
vertically stacked tropical cyclone.  The plane first made an
initial center fix to the north of the main area of deep convection
and found that the central pressure had fallen to 994 mb.  About an
hour later, a second center fix was made three tenths of a degree
farther south near the deep convection, although the lowest
pressure there was only about 998 mb.  The center has been placed
in between the two fixes, hedging toward the lower pressure to the
north.  Julia's initial intensity is set at 55 kt based on the
lowering of the central pressure and unanimous satellite
classifications of T3.5.  So far, the aircraft has measured peak
850-mb flight-level winds of 50 kt and reliable SFMR winds around
45 kt, so it's assumed the plane has not directly sampled the area
of highest winds.

Despite the uncertainty in Julia's initial position, it's clear
that the storm continues to move quickly westward with an estimated
motion of 270/18 kt.  With strong ridging to the north, a continued
fast westward trajectory is expected during the next couple of
days, which should bring Julia's center inland over Nicaragua by
early Sunday morning.  If Julia's center survives the passage over
Central America, it could move just offshore of or along the
Pacific coasts of Nicaragua, Honduras, and El Salvador Sunday night
and Monday.

It still appears that there is about 15 kt of northwesterly or
northerly shear affecting Julia, but model guidance indicates this
should abate and then turn out of the east-northeast later today and
tonight.  Therefore, further strengthening is anticipated, and Julia
is forecast to become a hurricane later today.  It's important to
keep in mind that Julia could have a higher intensity when it
reaches the coast of Nicaragua than what is explicitly shown, since
in this forecast landfall would occur between the 12- and 24-hour
forecast times.  In fact, SHIPS guidance suggests the intensity
could be in the 75-80 kt range at 18 hours, which mirrors what was
shown in the previous NHC forecast.

Due to Julia's more southern and faster track, there is increasing
global model support that the cyclone will be able to maintain a
well-defined center and circulation while it crosses Central
America, and it could also still be at tropical storm intensity
when it reaches the Pacific side of Central America.  However, even
if it survives the crossing, most of the guidance shows the
circulation becoming more diffuse or dissipating over the Pacific
waters in 2 to 3 days.  Based on the updated NHC forecast, and to
account for the possibility of tropical-storm-force winds along the
Pacific coast of Central America, tropical storm warnings and
watches have been issued for the Pacific coasts of Nicaragua,
Honduras, and El Salvador.  Regardless of Julia's track and
existence as a tropical cyclone, the evolving set up is likely to
lead to heavy rains over Central America for several days, which
could cause life-threatening flash floods and mudslides, especially
in areas of mountainous terrain.


Key Messages:

1. Julia is forecast to strengthen into a hurricane later today, and
a Hurricane Warning is in effect for portions of the Nicaragua coast
and the islands of Providencia and San Andres. Hurricane-force winds
and a dangerous storm surge are expected in areas where the core of
the system crosses the islands later today and moves onshore in
Nicaragua early Sunday morning.

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

3. There is an increasing chance that Julia could remain as a
tropical storm while it moves across Central America, and tropical
storm warnings and watches have been issued along the Pacific
coasts of Nicaragua, Honduras, and El Salvador to account for the
possibility of tropical-storm-force winds in those areas late
Sunday and Monday.


FORECAST POSITIONS AND MAX WINDS

INIT  08/1500Z 12.6N  79.9W   55 KT  65 MPH
 12H  09/0000Z 12.5N  81.9W   70 KT  80 MPH
 24H  09/1200Z 12.5N  84.3W   65 KT  75 MPH...INLAND
 36H  10/0000Z 12.7N  86.9W   40 KT  45 MPH...INLAND
 48H  10/1200Z 13.2N  89.5W   30 KT  35 MPH...OVER WATER
 60H  11/0000Z 13.7N  91.9W   25 KT  30 MPH...POST-TROP/REMNT LOW
 72H  11/1200Z...DISSIPATED

$$
Forecaster Berg
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