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Tropical TS Isaias

Tropical Storm Isaias Discussion Number 6
NWS National Hurricane Center Miami FL AL092026
1000 PM CDT Wed Oct 07 2026

Aircraft data and satellite trends indicate Isaias has continued
intensifying this evening. The center of the tropical cyclone is
embedded underneath a small central dense overcast with very cold
tops associated with deep convection. Upper-level outflow is
observed in all quadrants, though it remains somewhat restricted to
the southwest due to moderate vertical wind shear. Data from the Air
Force Hurricane Hunters indicates the central pressure has fallen to
988 mb, and on the last fix they reported a circular eyewall open to
the southwest. Based on these developments, the initial intensity is
raised to 60 kt.

Aircraft fixes indicate the center is still moving toward the
east-northeast (070/8 kt). The system is expected to accelerate
northeastward tomorrow and then northward on Friday within the flow
between a deepening trough over the south-central United States and
a strengthening subtropical ridge over the western Atlantic. This
steering pattern is forecast to bring the center of Isaias to the
northern Gulf Coast late Friday night into early Saturday. There
were no major changes to the guidance suite, with the AI-based
models generally faster and farther right than the physics-based
models. The NHC forecast continues to lean more heavily on the
better-performing corrected consensus (HCCA) and Google DeepMind
(GDMI) aids, remaining on the faster and right side of the guidance
envelope. The inland track at 60-72 h was shifted westward as more
models now show Isaias becoming captured by the cutoff low over the
southeastern United States.

Continued strengthening is expected during the next day or so as
Isaias moves over very warm waters in a moist environment with
moderate vertical wind shear. Given its small size and formative
inner core, rapid intensification is a distinct possibility, and the
NHC forecast lies on the high end of the intensity guidance. The
shear is predicted to markedly increase on Friday while Isaias
approaches the northern Gulf Coast, but the system is expected to
remain a dangerous hurricane through landfall. Gusty winds are
expected well inland after landfall given the anticipated expansion
of the wind field and fast forward speed of the storm.

Hurricane, Storm Surge, and Tropical Storm Warnings have been
issued with this advisory for portions of the northern Gulf Coast.
 
...ISAIAS BECOMES A HURRICANE...

Dropsonde data from an Air Force Reserve hurricane hunter aircraft
indicates that Isaias has become a hurricane, with maximum sustained
winds of 75 mph (120 km/h) with higher gusts. The minimum central
pressure measured from another dropsonde launched in the eye was
982 mb (29.00 inches).
Who knew that the first hurricane of the season will be a I-storm.
 
The change on IR over the last few hours is drastic. This being a MH in twelve hours wouldn't surprise me.
I would agree with that. I am curious to see how strong this one can get before the shear takes over for sure. I wonder if it can stay "east" enough long enough to maintain a cat 2 at landfall.
 
I would agree with that. I am curious to see how strong this one can get before the shear takes over for sure. I wonder if it can stay "east" enough long enough to maintain a cat 2 at landfall.
Something to consider regarding the shear. The storm is and will be moving with the direction of the mid-level shear and will get upper-level enhancement from divergent flow aloft as it approaches the coast. There is a great deal of dry air to the west, though. Tricky intensity forecast for sure.
 
Underwelming pass so far wind wise, but pretty substantial pull north of the COC.

Edit: But huge spike in temp. My guess is the LLC and the MLC are still slightly disjointed and preventing rapid strengthening. IR kind of shows this.
 
Underwelming pass so far wind wise, but pretty substantial pull north of the COC.

Edit: But huge spike in temp. My guess is the LLC and the MLC are still slightly disjointed and preventing rapid strengthening. IR kind of shows this.
Unless TT is running slowly, it hasn't reached the core yet. No?
 
Winds catching up.
635
URNT15 KNHC 080445
AF301 0509A ISAIAS HDOB 42 20261008
043630 2311N 09141W 6947 03065 9885 +119 +107 105029 030 /// /// 03
043700 2312N 09140W 6940 03079 9901 +110 //// 116033 037 /// /// 05
043730 2314N 09139W 6939 03087 9912 +109 +102 129029 031 /// /// 03
043800 2315N 09138W 6946 03081 9921 +106 +095 135033 033 /// /// 03
043830 2316N 09137W 6933 03101 9928 +101 +100 143038 041 /// /// 03
043900 2317N 09135W 6934 03107 9941 +096 //// 144043 045 /// /// 05
043930 2318N 09134W 6942 03098 9950 +090 //// 149053 056 /// /// 05
044000 2318N 09132W 6962 03077 9948 +093 //// 157053 055 /// /// 05
044030 2319N 09130W 6929 03117 9949 +097 //// 156055 057 /// /// 05
044100 2321N 09129W 6954 03092 9954 +095 //// 155062 069 /// /// 05
044130 2322N 09128W 6938 03118 9976 +080 //// 137057 070 /// /// 05
044200 2324N 09128W 6949 03105 //// +072 //// 135052 056 /// /// 05
044230 2326N 09127W 6935 03131 //// +070 //// 134047 052 /// /// 05
044300 2327N 09126W 6949 03117 //// +067 //// 129044 049 /// /// 05
044330 2329N 09125W 6938 03134 //// +063 //// 124042 043 /// /// 05
044400 2331N 09125W 6940 03137 0026 +064 //// 126042 043 /// /// 05
044430 2333N 09125W 6938 03144 0024 +069 //// 125042 044 /// /// 05
044500 2335N 09126W 6946 03137 0018 +078 //// 122039 043 /// /// 05
044530 2337N 09126W 6945 03137 0008 +083 //// 117038 040 /// /// 05
044600 2338N 09126W 6955 03132 //// +076 //// 114034 040 /// /// 05
 
Definitely strengthening, 79knts at the surface and a very impressive 23.6C at 850mb in the eye.

recon_NOAA2-0609A-ISAIAS_dropsonde4_20261008-0510.png
 
Something to consider regarding the shear. The storm is and will be moving with the direction of the mid-level shear and will get upper-level enhancement from divergent flow aloft as it approaches the coast. There is a great deal of dry air to the west, though. Tricky intensity forecast for sure.

I agree. I don't envy anyone trying to forecast intensity here. I mean it's always a mess(track is the easy part...) if we remember past forecasts but there's a wide range of possibilities

Lili went from a strong Cat 4 to a weakening rapidly Cat 1 in the final 12 hours before landfall(at the end of a 3 year streak of no hurricane landfalls...) but there's also the other extreme of Michael which in both cases nobody saw coming

Like anyone who thinks they know what landfall intensity will be is kidding themselves
 
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