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Tropical Storm Karl Forecast Discussion


986 
WTNT44 KNHC 140231
TCDAT4

Tropical Storm Karl Discussion Number  11
NWS National Hurricane Center Miami FL       AL142022
1000 PM CDT Thu Oct 13 2022

Data from an Air Force Reserve Hurricane Hunter aircraft indicate
that Karl has a tilted vertical structure, typical for a cyclone
affected by shear. The low-level center remains on the northwestern
edge of an area of deep convection, with an elevated center found
by the plane slightly east of that location under the convective
canopy. The highest reliable surface winds sampled by the SFMR
instrument on board the aircraft were 34 kt in the southeastern
quadrant, and dropsonde data indicate that the central pressure has
fallen to 998 mb.  Earlier satellite wind data suggest that some
stronger winds were occurring to the south of where the aircraft
measured the recent peak winds. Based on these data and the lack of
much change in the appearance of Karl, its assumed that cyclone
still has maximum surface winds of around 40 kt.

Karl has been deviating to the east of the previous forecast track
this evening, likely due to the ongoing downshear development of the
deep convection, and the initial motion is 135/6 kt. The storm
should turn southward by Friday and then south-southwestward by
Friday night as the system reaches the periphery of a mid-level
ridge over west-central Mexico. This south-southwestward motion is
expected to continue until Karl dissipates over Mexico in a couple
of days. The model guidance has once again shifted slightly east,
likely due to the east-of-track initial position. The latest NHC
track forecast was nudged eastward as a result. Based on the
increasing possibility of impacts farther east along the southern
Mexico coast, a Tropical Storm Warning was issued from Ciudad del
Carmen to Sabancuy.

Moderate west-northwesterly shear impacting Karl is expected to
persist until landfall. Mid-level dry air intrusions are also
forecast to continue for the next day or so. Therefore,
strengthening is unlikely. The model guidance suggests that Karl
should maintain its current intensity overnight, and perhaps
weaken slightly before it reaches the coast of southern Mexico
Friday night or early Saturday. Once inland, the cyclone should
steadily weaken on Saturday and dissipate by Saturday night.


Key Messages:

1. Heavy rainfall associated with Karl could produce instances of
flash flooding, with mudslides in areas of higher terrain, across
portions of Veracruz, Tabasco, Chiapas and Oaxaca states in Mexico.

2. Tropical storm conditions are expected to begin within a portion
of the warning area in southern Mexico by late Friday.


FORECAST POSITIONS AND MAX WINDS

INIT  14/0300Z 20.6N  92.8W   40 KT  45 MPH
 12H  14/1200Z 19.9N  92.6W   40 KT  45 MPH
 24H  15/0000Z 19.0N  92.8W   35 KT  40 MPH
 36H  15/1200Z 18.0N  93.4W   30 KT  35 MPH...INLAND
 48H  16/0000Z...DISSIPATED

$$
Forecaster Latto/Berg




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