Looking Ahead to July in the Atlantic

July is the bridge to the heart of the hurricane season in August, September, and October

July is a transition month across the tropical Atlantic. Although a third more tropical systems form in July than in June, fewer do so near the United States, typically giving us more time to prepare if they head our way.

July also historically sees fewer U.S. and Florida tropical impacts than any other month of hurricane season besides November.

It’s why July is one of the better months of the hurricane season to avoid a tropical vacation cancellation. Although nothing is guaranteed during hurricane season, the doldrums of July don’t last long and by mid to late August, hurricane season activity abruptly increases.

Looking ahead to the first week of July, the Atlantic appears characteristically quiet. After a very sluggish start to its hurricane season, the eastern Pacific awoke this week with its first named storms of 2023 – Adrian and Beatriz. The Atlantic and eastern Pacific see-saw so when the eastern Pacific is busy, the Atlantic is typically quiet. This should stay the case for the next week or two.

Further out into July, there are some indications that the Atlantic may reawake, especially toward the end of the month. The European ensemble modeling system’s extended range forecast suggests a noticeable uptick in tropical activity (as measured by the Accumulated Cyclone Energy or ACE) above climatology beginning around third week of July.

European Centre for Medium-Range Weather Forecasts (ECMWF) monthly forecast for Accumulated Cyclone Energy or ACE for each tropical ocean basin the week of July 24-30, 2023. Green bars show the forecast weekly average from 101 different model simulations. Orange bars indicate the 20-year climatology. Light orange boxes over the oceans show significant differences between the ACE forecast and climatology. For the Atlantic, the forecast indicates a statistically significant uptick in tropical activity the third week of July. Credit: ECMWF.

This is consistent with extended range forecasts from other modeling systems like the Climate Forecast System (CFS) – the GFS’s long-range cousin – which show a decrease in wind shear later in July, perhaps from the apparent passage of another active Convectively Coupled Kelvin Wave or CCKW, which can both promote storminess and dial back hostile wind shear.

But for now we have little to worry about in the Atlantic. Increasing wind shear should keep a low-pressure area south of Bermuda from developing while shear and dust will plague the deep tropics into the 4^th of July holiday week.