Eastern Pacific Basin Tropical Cyclones

Tropical Storm Madeline Forecast Discussion


000
WTPZ44 KNHC 180908 CCA
TCDEP4

Tropical Storm Madeline Discussion Number   3...Corrected
NWS National Hurricane Center Miami FL       EP142022
300 AM MDT Sun Sep 18 2022

Corrected numbering of key messages

Early this morning, Madeline still appears to be feeling the effects 
of more than 20 kt of easterly shear, with the deepest convective 
cloud tops located some 75 to 100 n mi southwest of the center. The 
center structure itself is rather broad, and several mesovortices 
can be seen rotating around the mean center location. The latest 
round of subjective Dvorak intensity estimates were T2.5/35-kt from 
SAB and T3.0/45-kt from TAFB. Thus, the initial intensity is being 
held at 40 kt for this advisory.

The estimated motion of Madeline has actually been a little bit 
right of the previous track, currently estimated a bit east of due 
north at 005/7 kt. The track reasoning in the short-term is a bit 
complicated. Madeline is currently embedded in large-scale monsoonal 
southwesterly flow which appears to be partially responsible for its 
short-term rightward deviation from the prior forecast track. 
Tropical cyclones (TCs) in this region, including recent TCs Kay 
and Lester, have been known to move a bit east of model guidance. 
Thus, the initial track forecast has been nudged a bit further east 
for the first 12-24 h while the larger-scale low-level flow has a 
stronger foothold on Madeline's motion. After that period, a 
building mid-level ridge centered over Texas is expected to cause 
Madeline to take a rather sharp turn to the northwest, resulting in 
Madeline passing south of the Baja California Peninsula. The track 
guidance this cycle is notably further north and east early on, but 
then shifts back towards the previous track by the end of the 
forecast period. Thus, the NHC track forecast was nudged in that 
direction, but is not quite as far to the north and east as the 
latest HCCA consensus aid. As noted in the previous advisory, 
across-track spread at the end of the forecast is rather large, so 
this track forecast is of lower confidence.

Intensity-wise, Madeline has only a brief window where the vertical 
wind shear is expected to drop below 20 kts, mainly between 12-30 h. 
In addition, Madeline is currently a broad tropical cyclone, with a 
fairly large radius of maximum wind. Thus, only some modest 
additional strengthening is forecast, in line with the upper-end of 
the intensity guidance. After 36 h, easterly shear is expected to 
increase substantially, and both the GFS and ECMWF simulated IR 
brightness show Madeline's convection quickly shearing away as the 
storm also crosses the 26 C sea-surface temperature isotherm by 48 
h. With the further northward track over cooler waters, the latest 
intensity guidance has trended downward, and the NHC intensity 
forecast follows suit, weakening Madeline to a depression in 60 h 
and making it a remnant low by 72 h. Based on the latest guidance 
though, this could occur sooner than forecast.

Madeline is producing a large area of rough surf and high waves, 
especially on its south and eastern flank. Given the current large 
34-kt radii on the south side of Madeline and the eastward shift in 
the forecast track this cycle, the government of Mexico has issued a 
Tropical Storm Watch from Manzanillo northward to Cabo Corrientes. 
Any further deviation to the right of Madeline's track could require 
these watches to be upgraded to a warning later today.


KEY MESSAGES:

1. Heavy rains from Madeline are expected for portions of coastal
southwestern Mexico into Monday. This rainfall may produce flash and
urban flooding, along with possible mudslides in areas of higher
coastal terrain.

2. Tropical storm conditions are possible for the southwestern 
coast of Mexico from Manzanillo to Cabo Corrientes over the next 24 
to 36 hours.


FORECAST POSITIONS AND MAX WINDS

INIT  18/0900Z 17.7N 106.6W   40 KT  45 MPH
 12H  18/1800Z 18.8N 107.3W   40 KT  45 MPH
 24H  19/0600Z 19.9N 108.4W   45 KT  50 MPH
 36H  19/1800Z 20.6N 109.6W   45 KT  50 MPH
 48H  20/0600Z 20.9N 110.9W   35 KT  40 MPH
 60H  20/1800Z 21.1N 112.2W   30 KT  35 MPH
 72H  21/0600Z 21.2N 113.2W   30 KT  35 MPH...POST-TROP/REMNT LOW
 96H  22/0600Z 21.5N 116.0W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  23/0600Z 21.0N 118.5W   25 KT  30 MPH...POST-TROP/REMNT LOW

$$
Forecaster Papin



Source link