Research (Greg McCabe, Julie Betancourt and Michael Palecki) has shown that the -PDO/+AMO regime has a tendency to increase drought risk across the Southwest and Midwest U.S. during the warm season. The current U.S. soil moisture regime certainly recognizes the -PDO/+AMO influence on late summer soil moisture.

The NOAA/NHC storm surge forecast has increased to 15-20 feet near the TX/LA state line eastward along the southwest coast of Louisiana. The storm surge is 10-15 feet on the upper Texas coast and 10-15 feet central Louisiana coast. The forecast identifies a record storm surge for this location with catastrophic coastal damage extending well inland for low-lying land and also major loss of life for anyone along or just inland the coast.

Laura should easily reach category-3 hurricane intensity in the western half of the Gulf of Mexico midweek and possibly a category-4 hurricane prior to striking the northwest Gulf of Mexico coast early Thursday.

Tropical Storm Marco is a little stronger at 8AM EDT Saturday. However, a 30-40 knot southwest upper shear band is ahead across the central Gulf of Mexico. Marco will need to fight through that shear to survive. Tropical Storm Laura is forecast to track west-west-northwest across Hispaniola and Cuba over-the-weekend which is a tough course to follow to survive due to the high terrain. HOWEVER, if each storm survives these obstacles the super warm Gulf of Mexico could allow strengthening to a hurricane before eventual landfall in the north or northwest Gulf of Mexico.

The convective phase of the Madden Julian oscillation stretched across the eastern tropical Pacific Ocean and into the western Atlantic tropics (phase_8/phase_1) the past 7-10 days with moderate-to-strong intensity. The result is widespread tropical convection spawning many tropical events (4 in both the East Pacific and North Atlantic tropics including Elida, Fausto, Genevieve and Isaias plus several potent tropical disturbances). The latent heat release poleward of the tropical convection and the attendant tropical systems into the middle atmosphere of the middle latitudes amplified a high pressure ridge in the Western U.S. causing the California heat wave.

Occasionally, NOAA/CPC long-lead forecasts will produce relatively bold probabilities in extended-range forecasts. If so, risk managers interested in possible adverse climate conditions should take note. The NOAA/CPC outlook for meteorological summer (from last February) indicated an unusually wet probability (given the 3.5 to 6.5 lead time) across Virginia which has certainly verified given the historic rainfall observed in August.

On June 29, 2012 a derecho surged east-southeast from the Ohio Valley across the Mid-Atlantic region causing widespread wind damage resulting in the loss of 4,000,000 people without power. Yesterday a similarly intense derecho moved rapidly across the Midwest U.S. knocking out power to over 500,000 people.

Steady pulses of African dust continue to emit westward in the North Atlantic tropics suppressing tropics cyclone activity. However, the relative humidity/available moisture at mid-level atmosphere is increasing. The mid-level atmosphere increased humidity is very supportive of the tropics starting to percolate.

A La Nina Watch remains in-place for 1-3 months from now and there are some signs of La Nina diagnostics returning. Last week the Nino34 SSTA lowered to -0.8C. The SOI in July was in the positive phase and the subsurface cool water near the Dateline is new and expanding. Despite the loss of the APR/MAY cool subsurface there remains a chance of La Nina onset by early in quarter 4 of 2020.