We may be seeing some benefit from a stretch of solidly El Nino-like readings in the Pacific Southern Oscillation Index (SOI) during the past week and a half. From Saturday December 8 through Monday Dec 17, the SOI had an average value of -27.43. That is solidly in the El Nino camp.
Here are the daily SOI values calculated by the Australia Bureau of Meteorology (BOM): Dec 8 -21.07; Dec 9 -31.71; Dec 10 -48.84; Dec 11 -45.72; Dec 12 -40.79; Dec 13 -32.02; Dec 14 -20.03; Dec 15 -9.50; Dec 16 -4.05; and Dec 17 -20.55.
As a refresher--SOI readings that are in the "minus" category imply a sustained higher barometric value over Darwin, Australia compared with the island of Tahiti in the central and western Pacific. NOAA, the Australia BOM and other weather agencies focus on the central Pacific findings for determination of El Nino or La Nina, due to the greater ocean depth in these regions. Higher pressures west versus east indicate that the trade wind pattern will also be west-to-east, thus sending more Pacific moisture at the subtropical latitudes toward North America--including the southern Plains.
As noted at the beginning of this blog, some benefit from this ocean engine could be heading our way. Forecast maps for the week between Christmas and New Year's Day are showing a higher likelihood for precipitation in the southern Plains and the western Midwest--enough of a chance that our call for precipitation during next week in these areas is normal to above normal. That's the first time in a couple months at least that normal to above normal precipitation has been featured.
The two big questions, of course, are 1) how much actual moisture will develop; and 2) if this type of pattern is truly the beginning of a major change going into midwinter, or if it's a one-time event. But one thing that is for sure is--this is the best chance that the Plains wheat belt and the western Corn Belt have had since before Hallowe'en to get even a slight bit of drought relief.
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