U.S. Rains, MJO and El Nino

Headline: Texas drought eroding due to heavy rains ahead supported by MJO episode. North of that wet zone, unclear on where and how much rain occurs. Kansas drought may spread northeastward. MJO event likely to trigger El Nino in June.

Fig. 1-2: So far in May, the East-central Great Plains/Missouri Valley are trending drier. The ECM ENS 10-day rainfall forecast soaks Texas and the Ohio Valley.

Discussion: There is concern that the Great Plains drought will expand east-northeast toward Iowa/Northern Missouri and possibly reach Illinois during early summer. The May soil moisture change (so far) supports that claim (Fig. 1). The 10-day rainfall forecasts feature buoyant amounts across Texas where ECM ENS forecasts extreme rainfall (Fig. 2). The Texas drought is easing. To the north of this wet zone easing Texas drought, forecasts are uncertain how much heavy rain can infiltrate northern latitudes and if any of that rain can strike the core of the current drought in Kansas. ECM ENS favors moderate rain in the northwest Great Plains and heavy rain in the Ohio Valley. The wet weather forecasts have the support of an equatorial Pacific Ocean transient Madden Julian oscillation episode. The latest 15 day forecast yields progression of MJO across the west and central equatorial Pacific which supports wet subtropical/tropical influence on the Central and East U.S. climate pattern (Fig. 3). The east shifting MJO episode has significant GLOBAL climate implications. If the MJO can produce negative southern oscillation index (-SOI) which is forecast by all models although the SOI of the past several days was robust positive, El Nino warming of the entire eastern equatorial Pacific is likely and onset of El Nino in June likely (Fig. 4). During the trend toward El Nino the past 2 months, SOI is reluctant to go full throttle negative phase (typical of approaching El Nino). The 15-day SOI forecast is quite aggressive (in the negative phase) and implies a significant shift out of lingering La Nina climate and into El Nino climate is possible as mid-2023 approaches.  Currently, El Nino warm waters are present off the northwest coast of South America shifting westward to the Nino3 region (Fig. 5). The emerging MJO episode during the next 2 weeks should cause that warming to shift westward toward the Dateline.

Fig. 3: Madden Julian oscillation 15-day forecast by all models indicates a moderate convection phase shifting across the equatorial Pacific.

Fig. 4: Southern oscillation index is forecast to shift into a long duration moderate negative phase due to an east-shifting Pacific MJO.

Fig. 5: East-shifting MJO across the equatorial Pacific during the next 2 weeks is likely to cause the El Nino warming in the eastern equatorial Pacific to spread westward toward the Dateline and initiate El Nino 2023.