Recent helpful research published in the AMS Journal of Climate identifies deep layer soil moisture deficits as a potential catalyst to future drought (and flash drought during the warm season). Northern hemisphere summer has ended BUT there area significant deep layer soil moisture shortages likely to cause Southwest U.S. drought to expand to the central and southern Great Plains. Similarly, emerging deep layer soil moisture anomalies in Southwest/West-central Russia foreshadow intensifying drought ahead.

La Nina is intact and plenty of subsurface eastern equatorial Pacific Ocean cool water is present to sustain La Nina. Forecast models indicate La Nina peaks later this year. Interestingly, a reversal toward a weak El Nino next summer is also indicated.

Meanwhile another area of concern has evolved in the southwest Gulf of Mexico. NOAA/NHC indicates tropical cyclone risk is 40% within the next 48 hours and >60% after 48 hours. The midday GFS develops this system into a tropical cyclone Friday by midday just north of the central Bay of Campeche. Unclear is whether this system sits in the west-central Gulf of Mexico into early weekend or drifts north toward Louisiana.

Sally is slowly organizing in that the associated convection is becoming more concentric. The interaction between the convection east of Sally and the Florida coastline has eased and dry air entrainment off the Yucatan Peninsula has also dissipated. Northwest shear across Salley is still present but weaker. The environment improves as Sally shifts west and west-northwest and intensification to a hurricane is likely today.

Tropical Disturbance 96L has emerged in the western Bahamas and will drift west-northwest bringing heavy rains to southern Florida this weekend and re-emerge over very warm surface water in the eastern Gulf of Mexico Sunday night beginning to intensify to a tropical cyclone.

The expected broad wetter-than-normal climate pattern across Australia driven by an evolving La Nina appears to develop in the latest NCEP CFS V2 weekly rainfall forecast.

An anticipated below normal U.S. electricity demand for summer 2020 due to the effects of Covid-19 on U.S. industry did not materialize as demand exceeded expectations due to the anomalous heat. U.S. meteorological summer 2020 ranked 4th hottest in the 126-year climatology. Arizona and all of southern New England observed the hottest JUN/JUL/AUG on record. Only Missouri, Oklahoma and Arkansas observed near normal summertime heat with all other states hotter than normal.

There is a significant change in the ENSO outlook: Stronger La Nina for late 2020 into early 2021. The catalyst to this stronger La Nina forecast is the previously proposed influence (on ENSO) by an evolving negative Indian Ocean Dipole (-IOD). The -IOD pattern warms the (already very warm) eastern Indian Ocean and western Pacific Ocean tropics while cooler-than-normal waters dominate the equatorial Pacific east of the Dateline.

The number of drier soil moisture regions outweighed the wetter regimes by 14 to 8 in August 2020. In North America a drier trend became established over the Southwest U.S. centered on the 4-Corners region. The Ohio Valley also trended drier. Canadian dryness extended to New England although drought in Western Canada eased.

An Excessive Heat Warning is issued for the southern half of California and an upgrade from a watch to a warning for the northern half of California is due by tomorrow. Excessive heat warnings are the highest state of alert for the California electricity markets. The projected population weight CDD for Sep. 4-10 for the Pacific region is 104 which is slightly higher than the 102 observed Aug. 14-20.

Negative phase Indian Ocean Dipole is forecast to develop the next 1-3 months. Coupled with La Nina a wet Australia climate ahead is likely. 2010 and 1998 were -IOD years with La Nina present during quarter 4. The result was a very wet climate across northern and eastern Australia.