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TheForecast Post

A chronicle of American weather and climate  ·  Wednesday, 16 September 2026

Weather Trader Tropics MILEPOST 68

GFS 18z finally activates

Hurricane develops from tropical wave and transits the Atlantic

What the month did

August 2023 was the 10th-warmest August in the 132-year national record (1895–2026), at 74.4°F against a 1991–2020 normal of 73.1°F (+1.3°F).

August 2023 was the 43rd-wettest August in the 132-year national record (1895–2026), at 2.8in against a 1991–2020 normal of 2.7in (+0.1in).

NOAA/NCEI Climate at a Glance, contiguous United States. This is the observed record for the month, not a score of anything said in this piece — the forecast ledger begins 2026-08-17 and cannot reach earlier posts.

While the GFS 12z cycle was a ghost town with only minimal development in the tropics, the 18z update lights up a tropical wave in the next 48-hours and goes on to develop Hurricane Emily .

GFS 18z | +48 hours | 850 hPa Relative Vorticity

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Milepost
68 · laid 2023-08-15T23:22:56.999000Z
Source
https://weather.substack.com/p/gfs-18z-finally-activates
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