Major Hurricane Isaias

[NavarreDon]

I enjoyed sharing snowstorms. This, not so much. I hope all will be well. 

Thanks Jason!


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[CampergirlFL]

Link to pier camera on Perdido Key

https://www.earthcam.com/usa/florida/pensacola/pier/


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[ROOSTA]

CWOP KFLPENSA690

Summary	High	Low	Average	Total
Temperature	78.2°F	69.8°F	73.9°F	—
Dew Point	73.1°F	67.7°F	70.8°F	—
Humidity	98%	82%	90.1%	—
Precipitation Rate	0.14in/hr	—	0.08in/hr	—
Precipitation Accumulation	—	—	—	0.39in*
Wind Speed	68.5mph	5.6mph	25mph	—
Wind Gust	79mph	7.4mph	29.1mph	—
Wind Direction	—	—	ENE	—
Pressure	29.38in	29.1in	—

 

As for timing... ahead of scheduled LF  

[RU848789]

1 hour ago, NorthHillsWx said:

What a beast. Who saw this coming a week ago 

While he didn't predict this storm, per se, about a week ago, Greg Postel on TWC had a great discussion about how the huge frontal system that was progged to sweep through the SE US last weekend would stall over the very warm GOM and that pressures and low shear looked favorable for tropical development this week.  

[Radtechwxman]

Temps near coast in upper 60s. That's pretty stable for hurricane. Cool and much drier air. May see quite a bit of weakening before it fully comes on shore

[Chinook]

Pensacola Naval Air Station gust to 51mph

[Seminole]

Starting to see multiple tornados around the Nature Coast 

https://radar.weather.gov/station/KTLH/standard

[NavarreDon]

Conditions are rapidly deteriorating in Wright Fl as the northern eyewall bears down. TS sustained with gusts over 50 ATM.




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[SnoSki14]

13 minutes ago, Radtechwxman said:

Temps near coast in upper 60s. That's pretty stable for hurricane. Cool and much drier air. May see quite a bit of weakening before it fully comes on shore

There's not enough time for substantial weakening. 

[MANDA]

Not that it is going to make a huge difference but you can clearly see the western edges of the circulation starting to "flatten" as shear is now starting to take hold.

[Maggie Valley Steve]

3 minutes ago, NavarreDon said:

Conditions are rapidly deteriorating in Wright Fl as the northern eyewall bears down. TS sustained with gusts over 50 ATM.




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Stay safe down there Don. We're thinking about you from WNC.

[olafminesaw]

[ROOSTA]

Even as far removed from the hurricane. The FL peninsula is prone to quick spin-ups as the feeder band traverses inland areas. 

[NavarreDon]

Stay safe down there Don. We're thinking about you from WNC.

Thanks Steve!


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[40/70 Benchmark]

6 minutes ago, olafminesaw said:

Matt is a helluva writer...does baseball and weather.

[yoda]

BULLETIN
Hurricane Isaias Advisory Number  13
NWS National Hurricane Center Miami FL       AL092026
400 PM CDT Fri Oct 09 2026
 
...CONDITIONS DETERIORATING QUICKLY WITHIN THE STORM SURGE AND
HURRICANE WARNING AREAS...
...RESIDENTS SHOULD BE SEEKING SAFE SHELTER...
 
 
SUMMARY OF 400 PM CDT...2100 UTC...INFORMATION
----------------------------------------------
LOCATION...29.2N 87.0W
ABOUT 90 MI...145 KM S OF PENSACOLA FLORIDA
ABOUT 125 MI...195 KM SSE OF MOBILE ALABAMA
MAXIMUM SUSTAINED WINDS...115 MPH...185 KM/H
PRESENT MOVEMENT...N OR 10 DEGREES AT 17 MPH...28 KM/H
MINIMUM CENTRAL PRESSURE...959 MB...28.32 INCHES

[MANDA]

Assuming it does not degrade that northern eye wall will mean business when it reaches the coast in the next 2 hours or so. Actual landfall should occur between 10 and 11 pm.

[yoda]

Hurricane Isaias Discussion Number  13
NWS National Hurricane Center Miami FL       AL092026
400 PM CDT Fri Oct 09 2026
 
Deep-layer shear from the southwest has increased to 30-40 kt, and
the hurricane's structure is responding accordingly. WSR-88D radar
data shows that the structure is becoming increasingly asymmetric,
with very intense convection mainly confined to the northern
eyewall. Tail Doppler radar data from the NOAA P-3 has also shown
that the circulation is becoming tilted with height. That said,
some impressive winds were measured at flight-level--136 kt by the
Air Force Reserve at 10,000 feet and 126 kt by NOAA at 8,000 ft.
While these winds themselves would normally support a higher
intensity, several dropsondes released in the eyewall showed that
there is a sharp drop-off of winds at the ocean surface, with
layer-averaging suggesting a surface intensity of 90-95 kt. In
addition, recent Doppler radar data from Mobile show winds of
100-110 kt at about 10,000 feet in the northern eyewall. Combining
all this data together, the maximum surface winds appear to be
around 100 kt, although it's very likely that Isaias will be a
gustier-than-normal hurricane when it makes landfall.
 
Isaias has turned northward and is accelerating with a current
motion of 010/15 kt. The track guidance has honed in on a landfall
over the western Florida Panhandle near the Pensacola area sometime
this evening. A northward motion is expected to continue through
Saturday, bringing Isaias's center through Alabama, followed by a
northeastward trajectory across the Tennessee and the central
Appalachians on Sunday. The circulation is expected to dissipate by
hour 60.
 
The high-resolution hurricane regional models (HAFS-A, HAFS-B, and
HWRF), as well as the statistical-dynamical models (SHIPS and LGEM)
indicate that Isaias is likely to be at or near major hurricane
strength at landfall this evening. After landfall, fast weakening
is expected, with some caveats. As mentioned previously, Isaias is
likely to be a gusty hurricane, and its fast motion could bring
strong hurricane-force gusts well inland. Simulated satellite
imagery from global model guidance indicates that Isaias is likely
to transition to a post-tropical cyclone over Alabama by Saturday
afternoon, although it could still be producing
tropical-storm-force gusts, especially in areas of higher terrain.
 
 
Key Messages:
 
1. A life-threatening storm surge is expected from the Mouth of the
Mississippi River to Suwannee, Florida. Residents under evacuation
orders should leave immediately and follow advice from local
officials.
 
2. Extremely dangerous and damaging hurricane force-winds are
expected over portions of the Florida Panhandle, southern Alabama,
and southern Mississippi where a Hurricane Warning is in effect.
Residents in these areas should have a safe room to ride out the
storm and prepare for long-duration power outages.
 
3. Damaging wind gusts are likely over a large portion of the
southeastern United States from western and northern Georgia and the
southern Appalachians, westward over much of central and northern
Alabama, southern middle Tennessee, and Mississippi, especially in
areas of higher terrain. Residents should secure loose outdoor
items, avoid driving high-profile vehicles, prepare for power
outages, and be aware of the potential for falling trees.
 
4. Isaias will bring areas of heavy rainfall to the central U.S.
Gulf coast and much of the Southeast through the weekend.
Considerable flash and urban flooding, along with significant river
flooding, will be possible. Landslides are also possible across the
Southern Appalachians.
 
5. The tornado potential will continue through tonight. The greatest
risk will be east of the center, particularly across the Florida
Panhandle into southern Georgia. This risk will continue spreading
north-northeast across parts of the Southeast on Saturday.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  09/2100Z 29.2N  87.0W  100 KT 115 MPH
 12H  10/0600Z 31.2N  86.8W   75 KT  85 MPH...INLAND
 24H  10/1800Z 33.4N  87.2W   40 KT  45 MPH...POST-TROP/INLAND
 36H  11/0600Z 35.6N  86.1W   30 KT  35 MPH...POST-TROP/INLAND
 48H  11/1800Z 38.1N  82.5W   25 KT  30 MPH...POST-TROP/INLAND
 60H  12/0600Z...DISSIPATED
 
$$
Forecaster Berg

[beanskip]

Latest pass 953.7 so looks like it's probably topped out strength-wise, unsurprisingly.

 

[Nomz]

18 minutes ago, 40/70 Benchmark said:

Matt is a helluva writer...does baseball and weather.

go sox

[vortex95]

3 hours ago, OHweather said:

Judging by radar, the shear is starting to impact the southwestern eyewall a bit more. At the moment convection in the northern and eastern eyewall is still quite robust and the inner core is holding up well. Per recon the pressure and winds have seemingly leveled off for a few hours now. I’m guessing we see a few more hours of relatively steady state intensity before shear and dry air start taking a more substantial toll on the inner core. 

For a few hours now, the core has been "halved" on radar in terms of an eyewall.  I realize there is some attenuation, but if the eyewall ring was complete and intense, we'd easily be seeing a closed ring starting a few hours ago.

Ever seem intense TC at extreme range of radars?  The eye and a solid eyewall show up very well even 200 nm away!

So dry air and shear are have impacted the inner core, however, this has not impacted the central pressure or winds much at all!

This shows that the relationship between sig shear and dry air and a HU is complex and it is definitely not one-size-fits-all!  As discussed earlier, why did Lili, Opal, and Dennis weaken so much after a solid RI period in and environment not as strongly baroclinic overall than Isaias?  Actually, think about Katrina!  It went from 150 kt to 110 kt from peak onshore to landfall in ~24 hr with a ton of dry air ingested into the core and quite ragged convective structure compared to Isaias right now.  And Katrina was way larger than Isaias, so you would think it could resist dry air intrusions better.  Also, Katrina was in Aug.  The mean atmosphere as to being conducive for a strong TC that time of year is significantly better than Oct!  You don't have troughs of this magnitude cutting across the nrn Gulf in Aug!

That being said, the upper level outflow plume for Isaias is outstanding.  That unquestionably is a factor here as to keeping it from weakening.

[Nomz]

Significant tornado threat looks to be pretty stunted for the next few hours. Nearly zero SBCAPE is making it inland, and storms are getting choked out before they can come ashore. Already happened to a few cells coming up Apalachee Bay. 

[jm1220]

5 minutes ago, vortex95 said:

For a few hours now, the core has been "halved" on radar in terms of an eyewall.  I realize there is some attenuation, but if the eyewall ring was complete and intense, we'd easily be seeing a closed ring starting a few hours ago.

Ever seem intense TC at extreme range of radars?  The eye and a solid eyewall show up very well even 200 nm away!

So dry air and shear are have impacted the inner core, however, this has not impacted the central pressure or winds much at all!

This shows that the relationship between sig shear and dry air and a HU is complex and it is definitely not one-size-fits-all!  As discussed earlier, why did Lili, Opal, and Dennis weaken so much after a solid RI period in and environment not as strongly baroclinic overall than Isaias?  Actually, think about Katrina!  It went from 150 kt to 110 kt from peak onshore to landfall in ~24 hr with a ton of dry air ingested into the core and quite ragged convective structure compared to Isaias right now.  And Katrina was way larger than Isaias, so you would think it could resist dry air intrusions better.  Also, Katrina was in Aug.  The mean atmosphere as to being conducive for a strong TC that time of year is significantly better than Oct!  You don't have troughs of this magnitude cutting across the nrn Gulf in Aug!

That being said, the upper level outflow plume for Isaias is outstanding.  That unquestionably is a factor here as to keeping it from weakening.

Yep, I'm looking out my window at it 1000 miles away. 

[EasternLI]

[lee59]

Looks like the southern  part of the storm is being ripped apart somewhat.

[mob1]

Looks like the more consistent and stronger winds will move into the coastal areas between Pensacola and Panama Beach in the next 30-60 minutes. 

[vortex95]

3 hours ago, WEATHER53 said:

Most here  know way more than me so I ask questions but there is No Doubt that 80% of the discussions yesterday had this  ripped apart by shear. In fact and once again it’s strengthened and will maintain intensity at landfall which used to be a definite rarity 

The thing is the models shows the thing getting ripped apart clearly, the primary HU models as well (HAFS) Why wouldn't you think that w/ the shear increasing to 40 kt and that much dry air present? 

There have been other cases like Isaias,, but also cases where unexpected rapid weakening occurs as well (Katrina and LIli are prime examples).  So you can't fault ppl for driving the point home.  We have a strong baroclinic situation here, so one wouldn't just ignore than.

I would not say rapid intensification not long before landfall used to be definite rarity.  That is recency bias largely.  Since 1995, we have been in an active phase of the AMO for favorable Atlantic TC activity.  Also, we are much better in determining absolute intensity now, esp. for the stronger HUs b/c of things like the GPS dropsonde, which did not come into use until 1998, and the SFMR, which did not exist on recons until 2004.  This advancement in tech has allowed us to diagnose *much* better extreme winds that we could not directly measure before.  Prior, it was largely just FL winds at 700 mb, but that serves only as a proxy and does not work all the time. So in recent decades we are seeing things we never could detect before, but were always there.

Also, and this is a biggie, through the 1960s, if a hurricane was thought be 100 kt or stronger, many recons wouyld not penetrate the eyewall and get into the eye for direct measurements.  They would fly only as close enough to get a solid radar scan of the eye, and then turn away.  So many HUs were underestimated by 1 or even 2 categories at times in the first decades of the recon era!

[NavarreDon]

Northern eyewall is upon us!




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[vortex95]

2 hours ago, Maestrobjwa said:

And during a super niño, no less. Isaías vs Niño and I is kicking butt and basically said "Shear? What shear?" lol And as others have pointed out, having not having any other storms in the Gulf probably helped this outcome...wow.

You can have major HUs in very strong El Nino years.  Debby in the western Atlantic was Cat 4 in Sep 1982.  Bob in Aug 1991 just off Hatteras was a Cat 3 that went on to hit New England.   Erika in the western Atlantic in Sep 1997 was almost a Cat 4. Joaquin near the Bahamas in Oct 2015 was almost a Cat 5.  So Isaias occurring here is not atypical overall given the strength of El Nino.  The key is that frequency of major HUs in very strong El Nino years is down relative to avg and there is lack of long-tracked Cabo Verde classics.
 

[NJwx85]

Half canes are very common in these setups due to the downsloaping effect. Essentially the air is comparatively much drier over land and naturally gets wrapped around due to the counter clockwise flow. A very intense tight core sometimes can overcome this. That combined with the shear is why it’s weakening now or at the very least leveling off and that has been clearly in the tropical guidance for a few days now.