Eastern Pacific Basin Tropical Cyclones

Hurricane Orlene Forecast Discussion


826 
WTPZ41 KNHC 030252
TCDEP1

Hurricane Orlene Discussion Number  18
NWS National Hurricane Center Miami FL       EP162022
900 PM MDT Sun Oct 02 2022

Orlene appears to be slowly weakening this evening. 1-minute GOES-17 
IR satellite imagery shows persistent bursting cloud tops below -80 
C in the northern semicircle of the hurricane, likely still 
associated with its eyewall. A 0116 UTC F-17 SSMIS microwave pass 
also showed an eyewall fragment remains in connection to these very 
cold cloud tops, though comparing microwave with geostationary 
satellite suggests the hurricane is starting to become more tilted. 
There are also subtle hints that upper-level westerly flow is 
beginning to undercut the cirrus on the western side of the 
convective plume. The subjective Dvorak intensity estimates were CI 
5.5/102-kt from TAFB and CI 5.0/90-kt from SAB. However, the Final 
T-numbers have been slowly decreasing and the initial intensity was 
set to 90 kt for this advisory.

The intensity forecast is somewhat tricky for Orlene over the next 
day or so. Deep-layer (200-850 mb) southwesterly vertical wind shear 
is steadily increasing over Orlene and is now over 20-kt in both the 
latest GFS- and ECMWF-based SHIPS guidance. This shear is expected 
to increase to 30-kt in the next 12-24 h, and will likely play a 
role in helping to import drier mid-level air into the core of the 
small hurricane. However, during this period, Orlene will also be 
traversing over very warm sea-surface temperatures, above 30 degrees 
Celsius, which could help the deep convection to remain quite 
vigorous, especially during the diurnal max period. Thus, while 
weakening appears likely, the rate of weakening has a higher than 
normal uncertainty. The intensity guidance this cycle has a faster 
rate of weakening, and the latest NHC intensity forecast was 
shifted in that direction, though not quite as dramatic. Orlene is 
still forecast to be a hurricane as it makes landfall in mainland 
Mexico sometime on Monday. After landfall, the small system should 
quickly weaken over the higher terrain of Mexico, with dissipation 
likely by 48 hours.

The hurricane appears to be moving a little more east of due north 
tonight, with the estimated motion at 010/7 kt. Orlene should 
continue this general heading for the next 12 to 24 hours, remaining 
steered by a mid-level ridge to its east, until the hurricane makes 
landfall at some point on Monday along the southwestern coast of 
Mexico. The track guidance this cycle has made a shift to the west, 
likely due to some of the guidance (GFS, HWRF) showing the tropical 
cyclone de-coupling from the deep convection in the immediate 
short-term. Since that process has not yet occurred, the track 
forecast this cycle was only shifted slightly west of the prior 
track, though is notably slower with the speed of Orlene shortly 
after the system makes landfall.

Key Messages:

1. Hurricane conditions are likely ongoing near Islas Marias
tonight. A Hurricane Warning is in effect for a portion of
west-central mainland Mexico, where hurricane conditions are
expected on Monday with tropical storm conditions beginning
overnight. Preparations to protect life and property should be
rushed to completion.

2. A dangerous storm surge is likely to cause coastal flooding in
the Islas Marias and along the coast of mainland Mexico in the
warning area in regions of onshore winds.

3. Heavy rainfall from Orlene is expected to lead to flash flooding,
as well as possible landslides in areas of rugged terrain of
southwest Mexico through Tuesday.


FORECAST POSITIONS AND MAX WINDS

INIT  03/0300Z 21.4N 106.5W   90 KT 105 MPH
 12H  03/1200Z 22.1N 106.4W   80 KT  90 MPH
 24H  04/0000Z 22.9N 106.2W   70 KT  80 MPH...ON THE COAST OF MEXICO
 36H  04/1200Z 23.6N 105.9W   35 KT  40 MPH...INLAND
 48H  05/0000Z...DISSIPATED

$$
Forecaster Papin/Blake




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