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Tropical Storm Idalia Discussion Number   6
NWS National Hurricane Center Miami FL       AL102023
1000 PM CDT Sun Aug 27 2023
 
Idalia's center has become embedded beneath a large burst of deep
convection, with overshooting cloud-top temperatures as cold as -82
degrees Celsius.  NOAA buoy 42056, located just to the east of the
center, has reported maximum 1-minute sustained winds as high as 45
kt within the past hour or two.  The anemometer height of the buoy
is 4 meters, so converting the wind to a standard 10-meter height
indicates that Idalia's intensity is now up to at least 50 kt, which
is the initial intensity for this advisory.  An Air Force Reserve
reconnaissance aircraft is scheduled to investigate Idalia in a few
hours.
 
The center has been moving erratically since earlier today, and may
have even sagged southward, pulled toward the recently developed
deep convection.  A northward motion is expected to begin on Monday
and continue through Tuesday as Idalia moves between a mid-level
trough over the central Gulf of Mexico and strengthening ridging
over the Greater Antilles.  After 48 hours, a gradual turn toward
the northeast and then east is anticipated due to a deeper trough
that is expected to swing across the Great Lakes.  No significant
changes were required for the updated NHC track forecast compared
to the previous prediction.  The spread among the track models
remains relatively low, and the official track continues to lie
closest to the ECMWF and HCCA consensus aid.
 
Idalia is sitting over very warm waters of about 30 degrees
Celsius, and when it moves northward, it will be over the even
deeper warm waters of the Loop Current in 24-36 hours.  Although
the trough over the Gulf could impart some shear over the system,
this is likely to be offset by upper-level diffluence.  Idalia has
already strengthened more than anticipated, and the environment
looks ripe for additional intensification, possibly rapid.  The NHC
intensity forecast has been increased and lies at the upper bound of
the guidance.  The new prediction now shows a 95-kt hurricane over
the eastern Gulf of Mexico at 48 hours, but it should be stressed
that additional strengthening to major hurricane strength is
becoming increasingly likely before Idalia reaches the Gulf coast
of Florida.  Interests within the storm surge and hurricane watch
areas are urged to prepare for possible significant impacts and
monitor future updates to the forecast.
 
 
KEY MESSAGES:
 
1. Idalia is forecast to become a hurricane by the time it reaches
the southeastern Gulf of Mexico, and it could be near or at major
hurricane strength when it reaches the Gulf coast of Florida.  The
risk continues to increase for a life-threatening storm surge and
hurricane-force winds along portions of the west coast of Florida
and the Florida Panhandle beginning as early as Tuesday.  Storm
surge and hurricane watches are in effect for portions of the
west coast of Florida and the coast of the Florida Panhandle, and
residents in these areas should monitor updates to the forecast and
follow any advice given by local officials.
 
2. Scattered flash and urban flooding is expected across portions of
the west coast of Florida, the Florida Panhandle, and southern
Georgia late Tuesday night through Wednesday. Heavy rainfall may
lead to flash flooding across portions of the Carolinas Wednesday
into Thursday.
 
3. Hurricane-force winds are expected across portions of far
western Cuba late Monday.  Heavy rainfall is expected across
portions of the eastern Yucatan and western Cuba and may produce
areas of flash and urban flooding as well as landslides across
western Cuba.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  28/0300Z 19.8N  85.3W   50 KT  60 MPH
 12H  28/1200Z 20.7N  85.1W   60 KT  70 MPH
 24H  29/0000Z 22.2N  85.0W   70 KT  80 MPH
 36H  29/1200Z 24.2N  84.9W   80 KT  90 MPH
 48H  30/0000Z 26.8N  84.3W   95 KT 110 MPH
 60H  30/1200Z 29.6N  82.8W   85 KT 100 MPH...INLAND
 72H  31/0000Z 32.0N  80.1W   55 KT  65 MPH...OVER WATER
 96H  01/0000Z 34.3N  73.4W   50 KT  60 MPH
120H  02/0000Z 34.4N  67.8W   50 KT  60 MPH
 
$$
Forecaster Berg
 
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