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10/17/2018, 3:07 pm EDT

Powerful Madden Julian Oscillation Could Cause Potent East U.S. Storm Late October

Here we go again…Amplified MJO Phase_1 for late October We won’t see Michael this time but another big East storm likely Fig. 1-3:  NCEP MJO forecast indicates STRONG phase_1 emerging in 10 days. In October MJO phase_1 climatology favors a warmer regime in the East with heavy precipitation Midwest to Southeast U.S.   Discussion: Late October looks stormy in the Southeast U.S. to Mid-Atlantic States. These areas have been hit hard by Florence and Michael during the late warm season and cannot take any more high wind and heavy rain events. Unfortunately, signs of a potent Southeast/Mid-Atlantic storm are ahead for later this month likely causing excessive rainfall, high wind and probably some heavy wet snow in the central/south Appalachians. The eye-opening projection validating the major storm concern is an amplified phase_1 of the Madden Julian oscillation (MJO) in 10 days and forecast by NCEP. The last amplified MJO phase_1 occurred during Michael’s evolution in the eastern Gulf of Mexico. MJO phase_1 means there is presence of enhanced vertical motion (convection) in the tropics promoting tropical cyclone activity during the warm season and interaction between the prevailing jet stream in the middle latitudes entraining tropical moisture made available by the MJO to the south to produce strong extratropical storms during the cold season. We’re entering the cold season so we’re more concerned with an extra-tropical storm rather than a hurricane this time around. The complicating factor is the well above normal snow cover across eastern Canada producing/sustaining an established cold pattern which settles into the East ahead of the proposed storm. The dramatic thermal contrast between subtropical warmth from the south clashing with a cold air mass departing snow covered Quebec to the north coupled with tropical moisture should cause a major storm. The mega-clusters (combining all forecast models) show the most likely upper air scenario as a cutoff storm system over the Southeast U.S. to Mid-Atlantic region the day before Halloween. In this set-up heavy rain/high wind affects the Mid-Atlantic region while the central/south Appalachians encounter heavy wet snow and cold air is propelled from eastern Canada into the deep southern states arriving with harsh wind. The Southeast is windy and turning colder. The setup for a 2 to 3 day storm is possible leading into Halloween. Fig. 4:  Mega-clusters (considering all forecast models) for late October indicate the most likely scenario is an intense-storm-producing upper trough across the Interior East which implicates a major rain/wind event for the Mid-Atlantic States and heavy snows in the Appalachians and a cold wind into the Deep South U.S.