ECM Weeklies: WET weather drives Central cool. MJO supports the cool, defeats the Atlantic tropics. El Nino approach has stalled, does this mean the tropics will be busier? Discussion: The ECMWF “weeklies” confidently project cool and wet weather across the Central/East-Central U.S. the next 2 weeks (through (Aug. 27). The forecast is supported by an amplifying Madden Julian oscillation (MJO) in the Indian Ocean/Maritime Continent which correlates to the cool pattern (driven by rainfall). In 14 days daily mega-clusters indicate upper level ridge areas affecting the Northwest and Northeast Coast leaving the Central U.S. susceptible to the wet weather that may cause cool temperatures to last to week 3 (Aug. 28-Sep. 3). Breaking down the Northwest and Northeast ridge areas will be difficult due to their link to very warm SSTA patterns just off the coastal areas. So…the forecast theme is wetter, therefore cooler in the Great Plains into early September while anomalous warmth risk is greatest Northwest and Northeast. Given the increasing influx of moisture to the U.S. pattern extreme heat risk lowers. Although the weekly CDD values remain above normal (nationally) mainly due to the warm influence lingering Northeast, the overall trend in weekly CDD’s for later this month into early September was lower today. MJO shifting into the Indian Ocean and toward Maritime Continent should increase a tropical cyclone risk in the Indian Ocean and produce another wave of tropical systems in the West Pacific later this month. Tropical cyclone development support in the tropical North Atlantic stays poor into early September. As mentioned earlier today the approaching El Nino is running out of gas as subsurface warm water in the equatorial East Pacific is fading. The likely scenario (now) is the warming approaching the Dateline in the subsurface must be pushed eastward back into the East Pacific to ignite any El Nino risk. Such a scenario would take until Nov. 1 to generate an El Nino. The immediate concern of stalled El Nino development is the implications of no El Nino during tropical cyclone season and implications on the amount forecast. Most forecasters, including NOAA last Thursday have lowered their seasonal forecasts due to a cool tropical North Atlantic and approaching El Nino. However, very recent trends indicate no El Nino which collapses any upper shear in the tropical North Atlantic and trade winds lower allowing some warming of the ocean surface. As indicated by a colleague the wet soils in the Mid-Atlantic region raise the risk of minor wind speeds downing trees and causing power outages. If a tropical system moves into Virginia/Pennsylvania widespread downed trees in an over-achieving manor. Palmer Drought Severity Index (PDSI) is “very moist” to “extremely moist” over northern Virginia to south-central Pennsylvania and eastern Pennsylvania.