Monday, April 4, 2011

Super high SOI signalling dramatic weather ahead?

The Southern Oscillation Index is based on the difference in surface pressure between Darwin, AU and Tahiti related to the tendency up or down.  Negative numbers and/or falling tendency signals a progressive (west to east) weather pattern.  In this case the index soared to 74, the highest I have seen, signaling an amplified (north-south) and often a blocked pattern.  The chart below shows that this occurred on April 1st. 
SOI soars to 74 on April 1st
Data Source: The Long Paddock
Computer models are showing no specific events today here in Central NC and VA on April 14-15.  This is not a surprise as models have been simply terrible through this La Nina episode.  I think that the GFS shows an interesting intense storm in the Plains that would be a headline maker if its true.
April 14 GFS - Very cold airmass dominates the east.
Count the number of sub 1000mb storms on the map!

One clue that the cold air mass affecting the east beginning at the middle of this month has a lot of merit is the strong warming event in the Stratosphere advancing from Siberia to the Pole.  Such an event acts like a plunger pushing arctic air into the middle latitudes.  Unfortunately cold air surging into the the typical gyrations of spring further south is a recipe for severe storms, frosts, and freezes.
Sudden Stratospheric Warming (SSW) advances toward the Pole.
Source: NOAA Climatic Prediction Center

So, interesting days lie ahead.  You can definitely that I will be paying close attention to weather developments and will keep you informed.

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