Event analysis · October 2026

Hurricane Isaias: the post-event peak-gust footprint

We published this post-event research footprint within days of landfall. It is free to download and share under CC BY 4.0.

Get the Isaias footprint
Map of Downstream's post-event peak-gust footprint for Hurricane Isaias across the Florida Panhandle and southern Alabama. The strongest gusts, in dark navy, lie west of the landfall point toward Pensacola. Landfall
105 mphat landfall near Destin, 9 October
6,700 mi²of land with hurricane-force gusts
1.5 millionpeople in gusts of 60 mph or more
Satellite image of Hurricane Isaias over the eastern Gulf of Mexico approaching the Florida Panhandle, its cloud shield spread north and east of the center.
Isaias approaching the Gulf Coast, 9 October 2026.

Why the west side was strongest

Isaias was not a textbook hurricane. The strongest gusts, 114–117 mph, were measured around Pensacola, 20–35 miles west of the track. That is normally the weaker side of a storm moving north, so a standard parametric vortex puts the peak winds in the wrong place.

On approach, the National Hurricane Center analyzed 35–45 mph of southwesterly wind shear, and radar showed the storm tilting with height. After landfall, NHC described damaging gusts “in a band wrapping around the western side of the circulation.”1

Aircraft measured 145–157 mph at 8,000–10,000 ft, and dropsondes found a sharp drop-off toward the surface. The west-side band resembles a “sting jet,” in which strong winds aloft appear to have been brought down to the surface in a narrow band as dry air disrupted the circulation.

West of the center
120mph
East of the center
91mph

The side a standard parametric model makes stronger

90th percentile within 12 miles · Sentinel-1 SAR2

How we built the footprint

We used five datasets. Each takes the wind field from the one above and corrects the part it measures best.

  1. A

    NHC best track and a CLE15 vortex

    We use NHC’s post-event best track together with the Chavas, Lin, and Emanuel (2015) model of the hurricane wind profile.3

    Measures best: track, intensity, size

    Passes ona symmetric vortex on NHC’s track

  2. B

    HAFS-A

    NOAA’s hurricane model, on a 1.2-mile storm-following grid, gives the shape of the field around the center. Track and intensity stay NHC’s.

    Measures best: asymmetry

    Passes onthe same vortex, made lopsided

  3. C

    Sentinel-1 SAR

    A satellite radar image at 6:53 PM CT measured ocean-surface wind on 0.3-mile pixels. Land and areas outside the swath come from HAFS-A, adjusted to match the SAR where both exist.

    Measures best: observed wind over water

    Passes onobserved over water, filled over land

  4. D

    HRRR

    We use NOAA’s HRRR weather model to turn our wind into peak 3-second gusts over land and water.

    Measures best: gusts over land and water

    Passes onpeak gusts on every 1 km cell

  5. E

    153 stations

    Airport, buoy, Texas Tech tower, mesonet, and NWS reports inside NHC’s 34-kt radius. The 22 that failed count as lower bounds, and 81 more outside the radius constrain the outer field.

    Measures best: ground truth and scaling

    Resultone scaling on the modeled wind, with the SAR kept as observed

Roofs likely damaged, by peak gust
Share of roofs likely damaged by peak gust in Hurricane Isaias. Under the Downstream footprint it rises from under 1% below 90 mph to 9% at 120 to 130 mph. Under a parametric model on the NHC best track it peaks near 4% at 60 to 80 mph and falls below 1% above 90 mph. 0% 2% 4% 6% 8% 10% 40 60 80 100 120 140 Peak 3-second gust, mph Parametric model on NHC best track Downstream footprint Share of roofs likely damaged by peak gust in Hurricane Isaias. Under the Downstream footprint it rises from under 1% below 90 mph to 9% at 120 to 130 mph. Under a parametric model on the NHC best track it peaks near 4% at 60 to 80 mph and falls below 1% above 90 mph. 0% 2% 4% 6% 8% 10% 40 60 80 100 120 140 Peak 3-second gust, mph Parametric model on NHC best track Downstream footprint
115,687 roofs with clear NOAA post-storm imagery · 10 mph bins · bands are 95% intervals · footprint as issued 11 October, before the imagery

Roof damage rises with the footprint’s gusts

We scored NOAA’s post-storm aerial imagery of 115,687 roofs for likely damage. None of it was used to build the footprint, so it is an independent check.

Under our footprint, the share of roofs likely damaged rises with the gust, to 9% at 120–130 mph. Under a parametric model on the NHC best track, it peaks at 60–80 mph and then falls. Only the wind field differs.

87% of the damaged roofs lie west of landfall, where the footprint puts the strongest gusts.

How the footprint compares with stations

On the coast the footprint captures the west-side band. Inland, in northern Santa Rosa County, it underestimates the band by roughly 20–30%. East of the track it may overstate the contrast.

Seven stations, peak gust, mph
Seven stations, observed peak gust against the footprint. The footprint is close at the three coastal stations in the Pensacola band, 20 to 34 mph low at the three inland stations, and 21 mph low at Blue Mountain Beach east of the track. 70 80 90 100 110 120 130 140 3 ESE Oriole Beach 117 reported · 134 at 10 m 124 Santa Rosa Sound 116 reported 124 Texas Tech tower near Navarre 105 reported · 120 at 10 m 114 Milton / Whiting Field airport 114 before it failed 91 1 WNW Allentown 101 reported · 116 at 10 m 82 7 NE Chumuckla 95 reported · 109 at 10 m 79 3 NNE Blue Mountain Beach 110 reported 89 Seven stations, observed peak gust against the footprint, 70 to 140 mph. 70 80 100 120 140 3 ESE Oriole Beach 117 reported · 134 at 10 m 124 Santa Rosa Sound 116 reported 124 Texas Tech tower near Navarre 105 reported · 120 at 10 m 114 Milton / Whiting Field airport 114 before it failed 91 1 WNW Allentown 101 reported · 116 at 10 m 82 7 NE Chumuckla 95 reported · 109 at 10 m 79 3 NNE Blue Mountain Beach 110 reported 89
Observed, at 10 m where availableStation failed, true peak higherFootprint
StatisticValue
RMSE16 mph
Within ±25%69%
Median ratio to observed, 10 stations ≥ 100 mph0.94

These stations were also used for calibration, so this is an in-sample check of shape.

Land at or above 96 mph
West of 86.5° W
392mi²

maximum 125 mph

East of the track
5mi²

maximum 98 mph

Download the footprint

The link arrives by email after a short sign-up. The footprint is free under CC BY 4.0: you may use it commercially, show it to clients, and combine it with your own event response, as long as you credit Downstream.

Cite as: Downstream Earth Analytics, Hurricane Isaias post-event peak-gust footprint (2026), CC BY 4.0.

If you compare it with a client’s claims, we would like to hear what you find.

Get the Isaias footprintGet in touch

A research product, provided as is, without warranty.

Pen-and-ink drawing of a weather station mast with a cup anemometer and a wind vane on a dune, sea oats bending in a wind from the left.

Sources

  1. NHC Hurricane Isaias Discussions 13 (4 PM CT 9 Oct) and 14 (10 PM CT 9 Oct); NHC best track AL092026.
  2. NOAA/NESDIS/STAR SAR ocean winds, Sentinel-1C, 23:52:56 UTC 9 Oct 2026. Contains modified Copernicus Sentinel data 2026. Statistics computed by Downstream.
  3. Chavas, D. R., N. Lin and K. Emanuel (2015), A model for the complete radial structure of the tropical cyclone wind field. Part I: Comparison with observed structure, Journal of the Atmospheric Sciences 72, 3647–3662.

Data: NOAA HAFS-A and HRRR forecasts, NOAA Open Data Dissemination; Iowa Environmental Mesonet ASOS archive; NDBC; Texas Tech University StickNet; NWS Local Storm Reports and the NWS Mobile/Pensacola Public Information Statement (3:37 AM CT 10 Oct). Station statistics cover all 107 working stations at or above 40 mph inside NHC’s 34-kt radius. All figures are from Downstream’s technical memo of 2026-10-11.

Pen sketch of a shore neighborhood at sunrise, hip-roofed houses and palms above a beach.

Get in touch

We love feedback. If you’re working through interesting problems in wind risk, let’s chat.

ted@downstream.earth
marketing@downstream.earth

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