Tropical Storm Isaias

[40/70 Benchmark]

1 minute ago, BlizzardNole said:

Yeah.  CoCoRaHS has numerous 8-14" rain amounts over and east of Pensacola for the last seven days.

Ah...didn't know about antecedent conditions...

[jm1220]

1 hour ago, 40/70 Benchmark said:

Strikes me as one of those N GOM collapse-deals, like Opal or Ivan....

Probably very half-a-cane looking if dry air and shear get shoved in at the end. If it really ramps up for a while to high end Cat 3 or something, surge will still be a big deal but mitigated somewhat if it remains a smaller storm. The main story might be where it inevitably rains 10”+ east of the eye or what’s left of it in the training bands. 

[PhiEaglesfan712]

1 hour ago, jconsor said:

Side comment - I think we will see 1-3 named storms after this one with about a 50% chance of of another hurricane (likely in the subtropics).  But yeah, it's pretty comical that this one seems to be defying many of our expectations.

If it was September, maybe. But we're now in October, so I think at most, only one more named storm. There's no way we get 3 more named storms after this point, especially in an el nino.

Recent history says this will probably be the last storm of the storm. In the last 15 years, several seasons ended with the last active storm being the biggest (Sandy in 2012, Iota in 2020, and Melissa last year come to mind). 

[ROOSTA]

A prolific tornado set-up which probably will be a high impact event. 

[yoda]

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

[yoda]

 

[Vicious Fluid]

I was thinking the same thing as the track moved East this morning. I'm in NGA and after how cool its been, and knowing tropical moisture is heading this way....sounds like the perfect setup for a southeastern tornado event. We're watching closely, especially after the last few "weaker" systems that came through here over the last few years permanently altered the landscape. 

[yoda]

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

[olafminesaw]

13 minutes ago, yoda said:

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

Who would have thought as of a year or two ago the NHC would already be explicitly using AI models as part of their forecast in 2026 (courtesy of Google, of all entities)

[SnowGoose69]

13 minutes ago, olafminesaw said:

Who would have thought as of a year or two ago the NHC would already be explicitly using AI models as part of their forecast in 2026 (courtesy of Google, of all entities)

I still am reluctant to trust AI models too heavily.  We saw them botch the NE blizzard last winter and also with tropicals it seems til the system reaches peak intensity or near it their tracks undergo more drastic shifts than non AI models.

[jm1220]

29 minutes ago, Vicious Fluid said:

I was thinking the same thing as the track moved East this morning. I'm in NGA and after how cool its been, and knowing tropical moisture is heading this way....sounds like the perfect setup for a southeastern tornado event. We're watching closely, especially after the last few "weaker" systems that came through here over the last few years permanently altered the landscape. 

Yep-what happens with the banding on the east side is probably what ends up getting remembered the most. Flooding under training bands and the tornadoes. GA could be in for a rough time. 

[SnowGoose69]

31 minutes ago, Vicious Fluid said:

I was thinking the same thing as the track moved East this morning. I'm in NGA and after how cool its been, and knowing tropical moisture is heading this way....sounds like the perfect setup for a southeastern tornado event. We're watching closely, especially after the last few "weaker" systems that came through here over the last few years permanently altered the landscape. 

Tornado risk could be significant, especially if it landfalls PNS east but overall the impacts on winds should be more in line with Michael in your area vs Irma/Zeta.  I don't see 40-50-60 mph winds at the moment based on the size of the system and the likely track, you'd need it to come in markedly more east than even the east edge of the cone.  The direction of the winds though being S-SE is risky however as those are infrequent directions with high speeds over GA.  WNW-ENE are more common.  One of the few areas JB makes good points is tree roots being used to winds from various directions.  When they are, not severe damage can happen even at speeds of 45-50 equivalent to what you might see at 60-70 mph, especially if the ground is saturated.

[SnowenOutThere]

Forgot this whole subform existed till now! Though the recon this morning showed a weaker storm than expected based on IR presentation, it also appears to be on it's way to vertical alignment of its low levels with the convection flares now surrounding the center. Will be very interesting to see if the next recon flight shows strengthening as it flies through the storm; if it does, then we might be setting up for a bout of rapid intensification overnight as I believe that is the best window in terms of wind shear (and diurnal max). 

[olafminesaw]

Landfall right along the FL/AL line seems like the best bet right now

[wncsnow]

2 minutes ago, olafminesaw said:

Landfall right along the FL/AL line seems like the best bet right now

I like 50-75 miles east of there similar to Google. The 12Z GFS and ICON moved east.

[Prismshine Productions]

I like 50-75 miles east of there similar to Google. The 12Z GFS and ICON moved east.

Another result of that:

Further east delays the shear weakening

Sent from my SM-S176V using Tapatalk

[olafminesaw]

Whoa 

[beanskip]

Wow latest recon finding about 10mb lower pressure than the previous one. 

[Tyler Penland]

6 minutes ago, beanskip said:

Wow latest recon finding about 10mb lower pressure than the previous one. 

This morning's recon was having some data issues, wonder if they just missed it or the data was bad. If not Isaias we're about to see some big wind increases as winds catch up to that pressure drop.

[hawkeye_wx]

The pressure dropped by several mb because the center of circulation has suddenly tightened up.

[hawkeye_wx]

The latest dropsonde says 997 mb.

[NorthHillsWx]

Incredible organization since this morning’s flight. The inner core is well on its way to becoming established. Very tight core too

[olafminesaw]

Yeah the center is squarely under the convective burst ongoing at the moment, would expect another substantial drop on the next pass

[hawkeye_wx]

The latest hurricane models, like the HAFS, have backed off on the strength as Isaias struggles with dry air advection from the west all the way through the gulf.

[GaWx]

12Z UKMET is at its strongest of any run so far at landfall with 979 mb at 12Z on Sat at AL/MS border. Then it heads N along the border followed by NNW/NW into MS. The center is in NW MS as of GA/AL gametime. Tornadoes look like a problem in much of N FL/AL/GA while heavy rain and strong winds hit N MS/Memphis area Sat afternoon/evening due to the tightest gradient in that area at that time. Interesting.

[NorthHillsWx]

Significant strengthening ongoing this pass 

[Interstate]

He is starting to wrap up.

[SnowenOutThere]

Seems to be right on the verge of becoming a hurricane based on the latest pass. No new pressure measurement so they may have missed the center. 

[40/70 Benchmark]

https://forecastmaven.com/forecasts/easternmassweather/isaias-poses-imminent-threat-to-gulf-coast-by-early-saturday-am-as-first-hurrica/

Isaias First Call:

 

[WxWatcher007]

What a difference a few hours make. From a broad and weak low to a clearly aligning and tighter center. Winds are responding almost immediately. If it can avoid dry air entrainment as it organizes today, I would favor a peak at major status.