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Another late season freeze for the northern Dakotas prolonging cold soil moisture temperatures followed by yeat another excessive rainfall event this week including severe weather episodes.

Discussion: The Great Plains agriculture belts continue to receive one adverse climate event after another and this week is forecast as no exception. First, cold soil moisture temperatures unable to recover with necessary rate of improvement due to widespread heavy soils receive another late season freeze in the Dakotas to Minnesota (Fig. 1). Widespread 29-31F temperatures are likely in this zone tomorrow morning. Some pockets of snowfall could also occur later today.

Fig. 1: NWS weather watch, warnings and advisories issued for the U.S. now.

Meanwhile another widespread excessive rainfall event featuring day after day of severe weather is projected this week for the Great Plains. NOAA/WPC projects as much as 10-15 in. of rain in Kansas in their 7-day forecast with several in. of rain (at least) forecast for most of the Great Plains (Fig. 2). The most robust short-term event is tomorrow when both a tornado outbreak (Fig. 3) and excessive rainfall event (Fig. 4) are forecast in the central and southern Great Plains.

Fig. 2: NOAA/WPC 7-day precipitation forecast indicates 10-15 in. across Kansas.

Fig. 3-4: A tornado outbreak is forecast in the southern Plains tomorrow while up to 7 in. of rain occurs in Kansas.

While a strong high latitude high pressure blocking pattern has contributed to heavy rainfall events through mid-May in the U.S. and Europe, the Madden Julian oscillation (MJO) is gaining top influence as a heavy rainfall contributor likely to last through May and into early June (Fig. 5-7).

Fig. 5: The most recent ECMWF 30-day MJO forecast projects MJO phase_1 into early June followed by a week or so of MJO phase_2.

Fig. 6-7: MJO P1 and P2 favor wet weather in the Central U.S.

Presence of MJO convection in the deep tropics raises the risk of early season tropical issues. A subtropical disturbance is forming now near the Bahamas while an impressive tropical wave has appeared off the coast of Africa (Fig. 8).

Fig. 8: An active Madden Julian oscillation (tropical convection near the equator including the coast of West Africa) leads to an environment supportive of early season tropical systems in the North Atlantic basin.