ZCZC MIATCDAT5 ALL
TTAA00 KNHC DDHHMM
Tropical Storm Idalia Discussion Number 7
NWS National Hurricane Center Miami FL AL102023
400 AM CDT Mon Aug 28 2023
Idalia has intensified overnight. Data from an Air Force Reserve
Hurricane Hunter aircraft showed believable surface winds of 50-55
kt and a central pressure falling to around 989 mb. The wind data
is also confirmed by NOAA buoy 42056, located just southeast of
the center, which has reported maximum 1-minute adjusted sustained
winds above 50 kt within the past hour or two. These data support
raising the initial wind speed to 55 kt.
It seems like Idalia is finally on the move, with aircraft fixes
indicating a northward motion of about 6 kt. This motion should
continue through Tuesday as Idalia moves between a mid-level trough
over the central Gulf of Mexico and a strengthening ridge over the
Greater Antilles. The storm is likely to move faster to the
north-northeast and northeast by early Wednesday due to a deeper
trough that is expected to swing across the mid-western United
States. The new NHC track forecast is quite close to the last one
with little significant changes to the track guidance. It should be
emphasized that only a small deviation in the track could cause a
big change in Idalia's landfall location in Florida due to the
paralleling track to the west coast of the state.
The center of Idalia is on the northern edge of the deep convective
mass, a refection of moderate northwesterly shear, and the last
aircraft pass showed a vortex tilted southward with height. This
shear and structure should persist for about the next 24 hours,
helping to keep the intensity of the storm from increasing too
quickly despite the extremely warm waters it will be traversing.
The NHC short-term forecast will continue to indicate Idalia as a
hurricane near western Cuba, similar to the guidance.
Over the Gulf of Mexico, the environment is forecast to become
conducive for significant strengthening of Idalia due to a new
trough dropping south over the western Gulf of Mexico as a
upper-level ridge builds near the cyclone. Additionally, Idalia
will be moving over waters near 31C, and some of the guidance is
even indicating favorable jet dynamics on Wednesday with Idalia in
the right-rear quadrant of the jet over the southeastern United
States. The bottom line is that rapid intensification is becoming
increasingly likely before landfall, and the NHC forecast now
explicitly indicates it between 24-48 h in the forecast. This is
consistent with almost all of the regional hurricane models and the
SHIPS rapid intensification indices, which are 5-10 times the
climatological mean. The new prediction shows a 100-kt hurricane
over the eastern Gulf of Mexico at 48 hours, but Idalia should keep
strengthening up to landfall along 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 for this increasingly dangerous situation.
KEY MESSAGES:
1. Idalia is now forecast to become a major hurricane before it
reaches the Gulf coast of Florida. The risk continues to increase
for life-threatening storm surge and dangerous hurricane-force
winds along portions of the west coast of Florida and the Florida
Panhandle beginning as early as late 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. Areas of flash and urban flooding, some of which may be locally
significant, are expected across portions of the west coast of
Florida, the Florida Panhandle, and southern Georgia Tuesday into
Wednesday, spreading into portions of the eastern Carolinas
Wednesday into Thursday.
3. Hurricane-force winds are expected across portions of far
western Cuba later today. Heavy rainfall is also expected across
portions of western Cuba and may produce areas of flash and urban
flooding as well as landslides across western Cuba.
FORECAST POSITIONS AND MAX WINDS
INIT 28/0900Z 20.1N 85.2W 55 KT 65 MPH
12H 28/1800Z 21.1N 85.1W 65 KT 75 MPH
24H 29/0600Z 22.6N 85.1W 70 KT 80 MPH
36H 29/1800Z 24.8N 84.8W 85 KT 100 MPH
48H 30/0600Z 27.7N 84.0W 100 KT 115 MPH
60H 30/1800Z 30.7N 82.1W 65 KT 75 MPH...INLAND
72H 31/0600Z 32.8N 79.0W 55 KT 65 MPH...OVER WATER
96H 01/0600Z 34.5N 72.0W 50 KT 60 MPH
120H 02/0600Z 34.5N 67.0W 50 KT 60 MPH
$$
Forecaster Blake
NNNN