Isaias, advisory 4

000
WTNT34 KNHC 071453
TCPAT4
 
BULLETIN
Tropical Storm Isaias Advisory Number   4
NWS National Hurricane Center Miami FL       AL092026
1000 AM CDT Wed Oct 07 2026
 
...HURRICANE AND STORM SURGE WATCHES ISSUED FOR PORTIONS OF THE 
NORTHERN GULF COAST FOR STRENGTHENING ISAIAS...
 
 
SUMMARY OF 1000 AM CDT...1500 UTC...INFORMATION
-----------------------------------------------
LOCATION...22.4N 93.6W
ABOUT 260 MI...420 KM WNW OF PROGRESO MEXICO
ABOUT 540 MI...870 KM SSW OF THE MOUTH OF THE MISSISSIPPI RIVER
MAXIMUM SUSTAINED WINDS...45 MPH...75 KM/H
PRESENT MOVEMENT...ENE OR 70 DEGREES AT 8 MPH...13 KM/H
MINIMUM CENTRAL PRESSURE...1000 MB...29.53 INCHES
 
 
WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY:
 
A Storm Surge Watch has been issued from the Mouth of the
Mississippi River eastward to Yankeetown, Florida.
 
A Hurricane Watch has been issued for the northern Gulf Coast from
Bay St. Louis, Mississippi to Indian Pass, Florida.
 
A Tropical Storm Watch has been issued for the northern Gulf Coast
from the Jefferson/Plaquemines Parish line, Louisiana to west 
of Bay St. Louis, and from east of Indian Pass to Aucilla River,
Florida.
 
SUMMARY OF WATCHES AND WARNINGS IN EFFECT:
 
A Storm Surge Watch is in effect for...
* Mouth of the Mississippi River to Yankeetown
 
A Hurricane Watch is in effect for...
* Bay St. Louis to Indian Pass
 
A Tropical Storm Watch is in effect for...
* Jefferson/Plaquemines Parish line to west of Bay St. Louis
* East of Indian Pass to Aucilla River
 
A Storm Surge Watch means there is a possibility of life-
threatening inundation, from rising water moving inland from the
coastline, in the indicated locations during the next 48 hours.
For a depiction of areas at risk, please see the National Weather
Service Storm Surge Watch/Warning Graphic, available at
hurricanes.gov.
 
A Hurricane Watch means that hurricane conditions are possible
within the watch area.  A watch is typically issued 48 hours
before the anticipated first occurrence of tropical-storm-force
winds, conditions that make outside preparations difficult or
dangerous.
 
A Tropical Storm Watch means that tropical storm conditions are
possible within the watch area, generally within 48 hours.
 
Interests in the Yucatan Peninsula of Mexico and elsewhere
around the U.S. northern Gulf Coast should closely monitor the
progress of this system.
 
Additional watches and warnings could be required for a portion of
the U.S. northern Gulf coast later today.
 
For storm information specific to your area, including possible
inland watches and warnings, please monitor products issued by your
local National Weather Service forecast office.
 
 
DISCUSSION AND OUTLOOK
----------------------
At 1000 AM CDT (1500 UTC), the center of Tropical Storm Isaias was
located by an Air Force Reserve Hurricane Hunter aircraft near 
latitude 22.4 North, longitude 93.6 West. Isaias is moving toward 
the east-northeast near 8 mph (13 km/h).  A continued
east-northeastward motion is expected today, followed by a turn
toward the northeast and north on Thursday and Friday. On the
forecast track, Isaias is expected to pass to the north of the
Yucatan Peninsula on Thursday and approach the U.S. northern Gulf
Coast on Friday.
 
Maximum sustained winds have increased to near 45 mph (75 km/h) 
with higher gusts. Rapid strengthening is forecast over the next day 
or two, and Isaias is expected to become a hurricane by Thursday.
 
Tropical-storm-force winds extend outward up to 45 miles (75 km)
from the center.
 
The estimated minimum central pressure is 1000 mb (29.53 inches) 
based on Air Force dropsonde data.
 
 
HAZARDS AFFECTING LAND
----------------------
Key messages for Isaias can be found in the Tropical Cyclone
Discussion under AWIPS header MIATCDAT4 and WMO header WTNT44 KNHC.

STORM SURGE:  The combination of a dangerous storm surge and the
tide will cause normally dry areas near the coast to be flooded by
rising waters moving inland from the shoreline.  The water could
reach the following heights above ground somewhere in the indicated
areas if the peak surge occurs at the time of high tide...

Ocean Springs, MS to Indian Pass, FL...5-7 ft
Mobile Bay...5-7 ft
Mouth of the Mississippi River, LA to Ocean Springs, MS...3-5 ft
Indian Pass, FL to Aucilla River, FL...3-5 ft
Aucilla River, FL to Yankeetown, FL...2-4 ft
Lake Pontchartrain...1-3 ft

The deepest water will occur along the immediate coast near and to
the east of the landfall location, where the surge will be
accompanied by large and dangerous waves.  Surge-related flooding 
depends on the relative timing of the surge and the tidal cycle, 
and can vary greatly over short distances.  For information
specific to your area, please see products issued by your local
National Weather Service forecast office.

For a complete depiction of areas at risk of storm surge 
inundation, please see the National Weather Service Peak 
Storm Surge Graphic, available at 
hurricanes.gov/graphics_at4.shtml?peakSurge.

WIND: Hurricane conditions could begin in the Hurricane Watch area 
late Friday, and tropical storm conditions could begin in the 
watches areas midday Friday.  

Gusty winds are possible in portions of the Yucatan Peninsula
on Thursday.
 
RAINFALL: Tropical Storm Isaias is expected to produce rainfall 
amounts of 2 to 4 inches through Thursday across coastal portions of 
the Bay of Campeche with isolated higher amounts possible in the 
states of Campeche and western Yucatan.

From Friday through the weekend, the system is expected to produce 
rainfall amounts of 3 to 6 inches, with localized totals up to 10 
inches, across the central U.S. Gulf Coast extending from far 
southeastern Louisiana to the Florida Panhandle. Rainfall amounts of 
1 to 3 inches, with localized amounts up to 5 inches, are possible 
across much of the Southeast as far north as the Tennessee Valley 
and the Carolinas. Flash and urban flooding, along with isolated 
river flooding, will be possible. 

For a complete depiction of forecast rainfall associated with 
Tropical Storm Isaias, please see the National Weather Service Storm 
Total Rainfall Graphic available at
hurricanes.gov/graphics_at4.shtml?rainqpf and the Flash Flood Risk 
graphic at hurricanes.gov/graphics_at4.shtml?ero
 
SURF: Swells are expected to affect the western and northern
portions of the Yucatan Peninsula beginning on Thursday and spread
northward toward the Gulf Coast late this week. These swells are
likely to cause life-threatening surf and rip current conditions.
Please consult products from your local weather office.
 
A depiction of rip current risk for the United States can be found
at: hurricanes.gov/graphics_at4.shtml?ripCurrents
 
 
NEXT ADVISORY
-------------
Next intermediate advisory at 100 PM CDT.
Next complete advisory at 400 PM CDT.
 
$$
Forecaster Blake
 

000
WTNT44 KNHC 071454
TCDAT4
 
Tropical Storm Isaias Discussion Number   4
NWS National Hurricane Center Miami FL       AL092026
1000 AM CDT Wed Oct 07 2026
 
Isaias has gotten better organized during the past several hours 
with a large area of deep convection near and northeast of the 
center.   Recent Air Force Hurricane Hunter data indicate that the 
center is re-forming a bit to the north of the previous advisory 
nearer to the mid-level center, with an estimated pressure of 
1000 mb derived from dropsonde data.  The initial wind speed is set 
to 40 kt in consideration of increase in satellite organization and 
the 4-mb dropsonde pressure fall, close to the UW-CIMSS SATCON 
values and many of the other objective estimates.
 
The storm is moving east-northeast at 7 kt.  The motion should
gradually bend northward and increase during the next few 
days as a trough along the northwestern Gulf coast amplifies and the
subtropical ridge east of Florida builds westward.  This pattern 
should cause a fast-moving Isaias to approach the northern Gulf 
coast by Friday afternoon.  Model guidance continues to be 
somewhat split, with the AI-based models generally on the right 
side of the model envelope, and the physics based models on the 
left side.   The new NHC forecast is nudged a bit eastward, but 
isn't as far east as the latest HFIP Corrected Consensus Approach 
(HCCA) or Google DeepMind ensemble mean (GDMI).  It is worth noting 
that many of the stronger solutions tend to be on the eastern half 
of the guidance and faster, which necessitates a variety of watches 
at this time.  

With the center re-formation, the low- and mid-level centers appear 
to be coming into better alignment.  This structural change could 
facilitate rapid intensification during the next day or two given 
light-to-moderate shear along the forecast track, near-record SSTs 
for this time of the year and a very moist environment.  Near 
landfall, increasing shear could cause some weakening, but it isn't 
certain how fast the winds will diminish.  Regardless, Isaias 
should be growing in size as it approaches the northern Gulf coast 
due to a trough interaction.  The latest guidance is very close to 
the last NHC intensity forecast, so little changes were made, and 
the NHC prediction is just below the corrected-consensus HCCA.
 
Key Messages:

1. Isaias is expected to strengthen into a strong hurricane before 
approaching 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 has been issued 
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 
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 over the next day or so.

 
FORECAST POSITIONS AND MAX WINDS
 
INIT  07/1500Z 22.4N  93.6W   40 KT  45 MPH
 12H  08/0000Z 22.7N  92.4W   50 KT  60 MPH
 24H  08/1200Z 23.4N  90.8W   65 KT  75 MPH
 36H  09/0000Z 24.6N  89.2W   80 KT  90 MPH
 48H  09/1200Z 26.6N  88.1W   95 KT 110 MPH
 60H  10/0000Z 29.2N  87.5W   90 KT 105 MPH
 72H  10/1200Z 32.2N  87.6W   45 KT  50 MPH...INLAND
 96H  11/1200Z 38.0N  87.5W   20 KT  25 MPH...POST-TROP/INLAND
120H  12/1200Z...DISSIPATED
 
$$
Forecaster Blake