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.

Miraculously Isaias survived the trek across Hispaniola as a minimal hurricane and will now reorganize over the warm waters of the Bahamas to a category 2 hurricane by tomorrow. Isaias is forecast to turn north and north-northeast staying just off the East Coast of the U.S.

During the past 2 months an arc of persistent heavy rainfall has extended from the western half of the tropical Indian Ocean northeastward across parts of India and northeastward from there into China and more recently Japan. The moderate-strength and stalled Madden Julian oscillation is the catalyst.

A Northeast Corridor heat wave begins today. An Excessive Heat Watch is in effect for parts of southern New England valid through 8PM EDT Monday. Heat advisories are in effect for much of the remainder of New England south to the New York City area. Today’s hot weather is without high humidity. However, high dew points arrive tomorrow forcing widespread 105F heat index (or higher) which will last into Tuesday.