Fig. 1: Current Gulf of Mexico SSTA indicates rapid warming!
Discussion: Tropical cyclone season is approaching therefore close monitoring of the North Atlantic subtropics/tropics SSTA patterns is of increasing importance. Currently, the Gulf of Mexico is warming rapidly. The regional SSTA is +0.76C (Fig. 1) and about half of that anomalous warmth has generated during the past 2 weeks. The warming trend is certainly important as applied to any early season tropical disturbances. None are indicated in the 15-day outlook ALTHOUGH a precarious low-pressure area is forecast to form off the Southeast U.S. Coast next week. Of additional significance, the warmer Gulf increases the risk of stronger severe weather outbreaks across the Central and East U.S. as southerly flow from the Gulf carries more moisture which increases instability in air masses ahead of cold fronts.
ECMWF “monthlies” are issued on the 5th of the month. In today’s update, the model forecasts risk of extreme heat over the central Great Plains to Texas in June (Fig. 2) and the Northwest U.S. to central Great Plains in July and August (Fig. 3-4). The Northeast averages armer than normal while the Southwest and Southeast trend temperate for July and August.
Fig. 2-4: Current Gulf of Mexico SSTA indicates rapid warming!
Right now, widespread flooding is across central and east Oklahoma to southeast Kansas and southwest Missouri. The heavy rains continue today and flash flood risk expands eastward across the Missouri Valley/Mid-south U.S. (Fig. 5). The heavy rains and attendant flash flood risk shift east to near and south of Pittsburgh, PA tomorrow (Fig. 6).
Fig. 5-6: NOAA/WPC excessive rainfall/flash flood risk areas for today and tomorrow.
Early season population weight CDD forecasts are greater than normal (Fig. 7). The forecast trend is less warm for next week while this week and May 13-19 are similar to yesterday’s forecast. Despite a cold month (nationally) the April CDD count was above normal (44 vs. 30) for the U.S. driven by the southern warmth.
Fig. 7: The U.S. population weight CDD forecast utilizing all models, their consensus and comparing with 24 hours ago and the 10-year/30-year climatology.