The Climate Impact Company North Atlantic basin seasonal activity forecast is updated. The seasonal activity forecast has increased dramatically propelled by the very warm North Atlantic basin and neutral ENSO to weak La Nina climate ahead. The activity forecast now indicates 24 tropical storms, 13 hurricanes, and 6 major hurricanes. The accumulated cyclone energy (ACE) index is revised sharply upward to 232. The ACE index projection is second highest on record, trailing only 2005 (245).

To evaluate AI forecasts, some preliminary verification results are recently available. The verification presented is for climate signal forecasts for the 6-10-day period from the past 30 days. Evaluated is the mean average error (MAE) for North Atlantic oscillation (NAO), Pacific North America (PNA) index, East Pacific oscillation (EPO), and West Pacific Oscillation (WPO).

The first high impact climate regime of summer 2024 develops before the arrival of the core of hurricane season. There is support, based on evolution of an intense marine heatwave east of New England, to apply the week 1-4 and week 5-6 ahead upper air and sensible weather forecasts from ECMWF to a long-term hot and dry pattern for the Ohio Valley and into the Northeast U.S. Corridor warranting drought development accelerated by persistent heat waves.

Late spring into early summer produces substantial flooding from extreme rains already occurring in Southern Florida and shifting into Texas later this week extending northward to the Midwest U.S. However, areas north and east of these heavy rain zones have the opposite problem likely to last well into the summer season, lack of significant rain and steady anomalous heat casual to increased drought risk from the Ohio Valley to the Mid-Atlantic States. By late summer, a shift in tropical rains should ease drought in the Ohio/Tennessee Valleys.