592
WTNT44 KNHC 072049
TCDAT4

Tropical Storm Isaias Discussion Number 5
NWS National Hurricane Center Miami FL AL092026
400 PM CDT Wed Oct 07 2026

Satellite and aircraft data show that Isaias continues to
strengthen. GOES-19 imagery indicates that a central dense overcast
has formed, and the system has become more symmetric than this
morning. The peak NOAA Hurricane Hunter aircraft 700-mb winds
were 61 kt, with the pressure dropping to 994 mb. The initial
intensity is set to 55 kt as a reflection of this data.

Isaias is basically on track, moving east-northeast at 7 kt. There
is no change to the synoptic reasoning as a deepening trough along
the northwestern Gulf Coast and a strengthening Atlantic subtropical
ridge should cause the system to move faster to the northeast
tomorrow and northward on Friday. As long as the cyclone remains
intact, it makes physical sense that the system will move on the
faster and eastward side of the guidance due to the stronger shear
Isaias should encounter near landfall. Thus, the new forecast is
adjusted slightly to the east, closer to the AI-based and
corrected-consensus models.

NOAA radar data (P3-TDR) show that the system is experiencing some southwesterly shear, with tilt analyses displaying the mid-level
circulation displaced 5-10 n mi to the northeast of the low-level
center. This structure seems sufficient for further intensification
given a continuation of similar low or moderate shear and very warm
SSTs in a very humid environment. Models are fairly consistent
about the shear increasing on Friday, but almost all guidance still
shows a category 1 or 2 hurricane at landfall. While the regional
hurricane models have generally come down on the peak intensity this
cycle, it is unknown whether this is the start of a real trend, and
we would prefer to see more than one guidance cycle before making
any adjustments. The new forecast is close to the previous one,
near the high side of the model suite.

Key Messages:

1. Isaias is expected to strengthen and be a strong hurricane when
it approaches the northern Gulf Coast on Friday. There is an
increasing risk of life-threatening storm surge along portions of
the northern Gulf Coast, and a Storm Surge Watch is in effect from
The Mouth of the Mississippi River to Yankeetown, Florida. Residents
in the watch area should follow advice given by local officials and
evacuate if told to do so.

2. The risk of damaging hurricane-force winds is increasing over
portions of the Florida Panhandle, southern Alabama, and southern
Mississippi. A Hurricane Watch has been issued from Bay St. Louis, Mississippi, to Indian Pass, Florida. Residents in these areas
should prepare for the possibility of long-duration power outages.

3. Isaias will bring areas of heavy rainfall to the central U.S.
Gulf Coast and much of the Southeast Friday into the weekend. Flash
and urban flooding, along with isolated river flooding, will be
possible.

4. Isaias could bring gusty winds and areas of heavy rain to the
western portion of the Yucatan Peninsula through Thursday.


FORECAST POSITIONS AND MAX WINDS

INIT 07/2100Z 22.7N 92.9W 55 KT 65 MPH
12H 08/0600Z 23.1N 91.8W 70 KT 80 MPH
24H 08/1800Z 24.1N 90.1W 80 KT 90 MPH
36H 09/0600Z 25.8N 88.7W 90 KT 105 MPH
48H 09/1800Z 28.1N 87.6W 95 KT 110 MPH
60H 10/0600Z 31.0N 87.3W 60 KT 70 MPH...INLAND
72H 10/1800Z 34.0N 87.5W 30 KT 35 MPH...POST-TROP/INLAND
96H 11/1800Z 37.5N 84.5W 15 KT 15 MPH...POST-TROP/INLAND
120H 12/1800Z...DISSIPATED

$$
Forecaster Blake


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