MJO across Pacific in the Medium-range; Soaks Mid-South States While East Turns Warmer

U.S. Rainfall Needed to Neutralize Palmer Drought Severity Index
04/25/2023, 8:52 am EDT
Dramatic Cooling Gulf of Mexico While North Atlantic Outer Tropics are Very Warm
05/02/2023, 8:56 am EDT
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Highlight: MJO soaks Mid-south U.S. Much warmer 11-15-day GFS forecast.

Fig. 1-3: Latest 14-day MJO forecast and 12Z GFS medium-range precipitation amount update.

Discussion: Market interest in the Great Plains drought is paramount right now. First, the influence of drought on U.S. wheat is of great concern AND second, a widening drought is accompanied by increased heat risk particularly for the SPP region likely extending to ERCOT for summer 2023. For now, the drought forecast looks less threatening as evolution and eastward shifting of another convection phase of the Madden Julian oscillation (MJO) is ahead (Fig. 1). As MJO shifts into the equatorial West Pacific and reaches the Dateline, anomalous warm SSTA strengthen this feature. The influence on U.S. climate is to reverse the cool regime in the East this week to a somewhat warmer pattern in the medium range while cooling down the West States. At midday, the 12Z GFS was prohibitively warm across the eastern half of the U.S. with warmest anomalies centered on Chicago. The MJO forecast also supports excessive rain in the southern Plains and Mid-South States for the medium range (Fig. 2-3). The warmer extended range appears in the adjusted population weight CDD forecast at midday (Table 1). May 12-18 is firmly indicating much higher CDD vs. HDD count (Table 2).

DatesCDD Forecast12-Hr Change24-Hr Change10-Year NML30-Year NML
Apr. 28-May 4


May 5-11



May 12-18




Table 1: The 12Z GFS U.S. population weight CDD forecast compared to 12 and 24 hours ago.

DatesHDD Forecast12-Hr Change24-Hr Change10-Year NML30-Year NML
Apr. 28-May 4


May 5-11



May 12-18




Table 2: The 12Z GFS U.S. gas population weight HDD forecast compared to 12 and 24 hours ago.