[Tropical] Tropical Cyclone Discussion

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WTNT44 KNHC 251521 CCA
TCDAT4

Tropical Storm Ian Discussion Number  10...Corrected
NWS National Hurricane Center Miami FL       AL092022
1100 AM EDT Sun Sep 25 2022

Corrected timing of Ian becoming a hurricane in the intensity
discussion below to tonight or early Monday.

The satellite presentation of Ian is gradually improving this
morning. The overall circulation appears better defined in visible
satellite imagery, and fragmented bands of convection around the
center are showing increased signs of curvature. The low-level
center of Ian also appears better defined in the latest data
collected by the NOAA and Air Force Hurricane Hunters. Although the
vortex is still vertically tilted, tail Doppler radar data suggest
the low- and mid-level centers are beginning to converge. An earlier
center dropsonde indicated the minimum pressure dropped slightly to
1001 mb, but the aircraft winds thus far have not reflected any
strengthening. Therefore, initial intensity for this advisory is
held at 45 kt.

The latest fixes suggest Ian is beginning to make its turn around
the western side of the subtropical ridge, and the initial motion
is west-northwestward at 290/12 kt. A gradual turn to the northwest
is expected later today as the cyclone passes well southwest of
Jamaica, followed by a north-northwestward motion that brings the
center of Ian west of the Cayman Islands on Monday and near or over
western Cuba by early Tuesday. There is relatively high confidence
in this portion of the track forecast. However, once the cyclone
emerges over the southeastern Gulf of Mexico, the spread in the
track guidance increases at days 3-5. The HWRF and GFS still lie on
the western side of the guidance envelope and show Ian moving over
the central or western Florida panhandle, while the ECMWF and UKMET
models show a track farther east into west-central Florida. Overall,
the NHC track forecast remains near the center of the guidance
envelope and still lies very near the TVCA multi-model consensus.
However, there is still significant uncertainty in the long-range
track forecast of Ian, and future adjustments to this portion of the
forecast will likely be required.

The atmospheric and oceanic conditions over the northwestern
Caribbean Sea appear very conducive for significant strengthening.
So once Ian becomes more organized, the high oceanic heat content
and low vertical shear conditions appear likely to support rapid
intensification. The Deterministic to Probabilistic Statistical
Rapid Intensification Index (DTOPS) still shows a greater than 90
percent chance of rapid strengthening during the next 2-3 days. The
intensity guidance remains very aggressive with strengthening Ian,
and the NHC forecast reflects this potential. Ian is expected to
become a hurricane by tonight or early Monday, and is forecast to
reach major hurricane strength before it reaches western Cuba. This
forecast lies very near the latest SHIPS guidance and the IVCN aid.
By day 4, a significant increase in southwesterly shear is forecast
by the global models, and this is forecast to induce some weakening
as the vertical structure of the hurricane is disrupted. Despite
this, Ian is likely to have an expanding wind field and will be
slowing down by that time, which will have the potential to produce
significant wind and storm surge impacts across portions of the
Florida west coast and the Florida panhandle.

Key Messages:

1.  Ian is expected to produce heavy rainfall, flash flooding, and
possible mudslides in areas of higher terrain, particularly over
Jamaica and Cuba.  Flash and urban flooding is possible across the
Florida Keys and Florida peninsula through mid week. Additional
flooding on rivers across northern Florida and parts of the
southeast U.S. cannot be ruled out later this week.

2.  Life-threatening storm surge and hurricane-force winds are
expected in portions of western Cuba beginning late Monday, where
a hurricane warning is now in effect. Efforts to protect life and
property should be rushed to completion.

3.  Ian is expected to be a major hurricane in the eastern Gulf of
Mexico during the middle of the week, but uncertainty in the
long-term track and intensity forecasts is higher than usual.
Regardless of Ian’s exact track and intensity, there is a risk of
dangerous storm surge, hurricane-force winds, and heavy rainfall
along the west coast of Florida and the Florida Panhandle by the
middle of the week, and residents in Florida should ensure they
have their hurricane plan in place, follow any advice given by
local officials, and closely monitor updates to the forecast.

FORECAST POSITIONS AND MAX WINDS

INIT  25/1500Z 15.2N  79.8W   45 KT  50 MPH
 12H  26/0000Z 16.5N  81.1W   55 KT  65 MPH
 24H  26/1200Z 18.1N  82.5W   70 KT  80 MPH
 36H  27/0000Z 20.1N  83.7W   90 KT 105 MPH
 48H  27/1200Z 22.0N  84.4W  105 KT 120 MPH
 60H  28/0000Z 23.9N  84.8W  115 KT 130 MPH
 72H  28/1200Z 25.5N  84.8W  115 KT 130 MPH
 96H  29/1200Z 28.0N  84.4W   95 KT 110 MPH
120H  30/1200Z 30.3N  83.7W   65 KT  75 MPH...INLAND

$$
Forecaster Reinhart

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