Tropical Storm Idalia Forecast Discussion Number 4

By | August 27, 2023

WTNT45 KNHC 271500

Tropical Depression Ten Discussion Number   4
NWS National Hurricane Center Miami FL       AL102023
1000 AM CDT Sun Aug 27 2023

So far this morning, the overall cloud pattern of the tropical
cyclone has not become significantly better organized.  The small
center is partially exposed on GOES-16 visible imagery, and
convective banding features are still not very well defined.  The 
current intensity is held at 30 kt for this advisory which is in 
line with the latest Dvorak Satellite estimates.  A NOAA Hurricane 
Hunter aircraft, flying at around 12000 ft, is near the center of 
the system taking Doppler radar wind velocity measurements.  These 
data should provide valuable information on the structure of the 
cyclone for initializing the numerical weather prediction models.

The center of the cyclone appears to have been moving in a small
clockwise loop overnight and into this morning, and it will
probably complete this loop today.  The initial motion estimate is
now around 090/2 kt.  Steering currents should remain weak through
today and tonight.  Beginning on Monday, a mid-level ridge starts to
build near southern Florida and eastward.  This evolution should
cause a generally northward motion during the next couple of days.
In 48 to 72 hours, a mid-level trough dropping into the eastern U.S.
will likely induce a turn toward the north-northeast and take the
system across the northeast Gulf of Mexico coast on Wednesday.  The
official forecast track has been nudged to the right of the
previous one, but is not quite as far east as the latest corrected
consensus, HCCA, prediction.  Users are reminded not to focus on
the exact forecast track, since strong winds, heavy rains and
dangerous storm surges extend well away from the center.

The cyclone will be moving over waters of high oceanic heat content 
over the eastern Gulf of Mexico and within a moist mid- to 
low-level air mass for the next few days.  An upper-tropospheric 
trough is predicted to develop over the western Gulf of Mexico in 48 
to 72 hours.  Although this feature could produce some moderate 
southwesterly vertical wind shear over the system,  positive 
vorticity advection and diffluent upper-level flow to the east of 
the trough will likely be conducive for strengthening.  The 
official forecast, like the previous one, calls for the cyclone to 
reach hurricane status over the eastern Gulf of Mexico in 48 to 72 
hours.  This is at the high end of the latest intensity model 


1. The depression is forecast to become a hurricane over the eastern 
Gulf of Mexico, and there is an increasing risk of life-threatening 
storm surge, flooding from heavy rainfall, and hurricane-force winds 
along portions of the west coast of Florida and the Florida 
Panhandle beginning as early as  Tuesday.  Although it is too soon 
to specify the exact location and magnitude of these impacts, 
residents in these areas should monitor updates to the forecast, 
have their hurricane plan in place, and follow any advice given by 
local officials.  Storm surge and hurricane watches may be required 
for portions of the Gulf coast of Florida later today.

2. Heavy rainfall is expected across the eastern Yucatan Peninsula 
and western Cuba and may produce areas of flash and urban flooding 
and landslides across western Cuba.  The depression is forecast to 
become a tropical storm later today, and tropical storm conditions 
are expected over portions of the Yucatan Peninsula and extreme 
western Cuba with tropical storm conditions possible on the Isle of 

3. Scattered flooding from heavy rainfall is likely over in 
portions of the southeast U.S. by mid to late week. 


INIT  27/1500Z 19.9N  85.8W   30 KT  35 MPH
 12H  28/0000Z 19.7N  85.9W   40 KT  45 MPH
 24H  28/1200Z 20.6N  85.7W   45 KT  50 MPH
 36H  29/0000Z 21.9N  85.5W   50 KT  60 MPH
 48H  29/1200Z 24.0N  85.2W   60 KT  70 MPH
 60H  30/0000Z 26.2N  85.0W   75 KT  85 MPH
 72H  30/1200Z 28.9N  84.0W   80 KT  90 MPH
 96H  31/1200Z 33.0N  79.5W   45 KT  50 MPH...INLAND
120H  01/1200Z 34.5N  74.0W   45 KT  50 MPH...OVER WATER

Forecaster Pasch

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