Madden Julian Oscillation Eastward Shift Should Break East U.S. Cold

Fig. 1-4: The January 2025 U.S. temperature anomalies so far, the 15-day U.S. temperature anomaly forecast by ECM ENS, the La Nina temperature anomaly climatology for the U.S. in February, and 15-day MJO forecast.

Discussion: So far, January 2025 is very cold east of the Continental Divide with coldest anomalies over North Dakota, Kansas, and West Virginia (Fig. 1). The outlooks for the remainder of January maintain chill as indicated by ECM ENS in the overnight 15-day outlook (Fig. 2). Climate Impact Company projects 1060 HDD for January making the mid-winter month the coldest January of this century. However, the overnight outlooks, by all dynamic models, are not as cold as recent days. One reason is the eastern shift of a moderate to strong convection phase of the Madden Julian oscillation (MJO) from tropical Africa (now) across Maritime Continent late this month. The MJO shift through the eastern Indian Ocean tropics to north of Australia and West Pacific tropics is indicated by the MJO 115-day forecast phase_3, phase_4, and phase_5 (Fig. 3). When MJO enters the phases listed during mid-winter a milder Pacific maritime influence is generated on U.S. climate. The arctic air across the U.S. will take time to erode. However, by February the U.S. pattern should shift toward a typical late meteorological winter La Nina climate as the East turns warm and the Northwest gains the colder climate (Fig. 4).