Friday, July 27, 2012

Atmosphere May Be Showing El Nino Signs in Precipitation Placement

The latest GEM 144 hour accumulated precipitation forecasts displays a very El Nino-like pattern, with little precipitation in the Midwest and a lot of wet weather on the East Coast.

As is typical in El Ninos, precipitation is favored over the East Coast into the Gulf of Mexico coast, with little precipitation over the Ohio Valley and Midwest. The image above very well shows the pattern described, with a wet pattern holding out over the East Coast. But is the atmosphere showing an El Nino in other indices?

The Southern Oscillation Index, or SOI, is rapidly dropping, characterizing an El Nino pattern. El Ninos are detected when the SOI is below -8, and as shown above, the SOI is below -10.
A look at the 30 day average of the SOI, used in the graph above, shows that the 30 day average has shot up to a value of positive 2. Positive values above 8 indicate a La Nina. This is fairly confusing for the atmosphere, because sea surface temperatures are positive, while the SOI is in fairly neutral territory. This will become interesting to monitor as we progress into the fall months to see if the atmosphere can sort itself out.

So while the precipitation appears to support an El Nino pattern, the SOI is in disagreement, and it will likely take a good month to see the SOI sort itself out.



Anonymous said...

So, Andrew. Do you see any relief to the drought that blankets the midwest? Indiana needs 9 to 10 inches of rain to stop it. I thought El Nino would bring us some rain in the fall but not so much in the winter. Will we have to cross our fingers and hope that spring will have normal rainfall?

mike paulocsak said...

Hello Andrew! Hope your feeling better.One thing i noticed is that the state of Ohio is getting wetter.We had a good ammount of rainfall in the past couple of weeks.Last evening i had over an inch of rainfall from thunderstorms.I personally think the pattern of dryness we have been in all summer is changing in Ohio.It will be interesting to see if it continues.Take care!

ERN WX said...

I like what I see. I decided to spend the last few days in PA to fish and storm chase. Perfect. Tstm movin thru, now that I am back. Lots of rain, wind, and even 2 rainbows. Weak Nino for winter and the CPC is acting like they have lost their minds. Andrew, did you see what they are forecasting?????????? Rediculous. NO SENSE WHATSOEVER............ WARM ALASKA=cold CONUS.

Andrew said...

Anonymous: I am not seeing any relief in the long term. However, in the short term, a continued northwest flow may cycle storms around the Indiana area over the next while.

Mike: I am feeling much better, thank you for the concern. Ohio is indeed getting wetter as showers and storms cycle through thanks to the northwest flow. I see a wet pattern continuing in the short term.

ERN WX: A warm Alaska does indeed signal high pressure over the area, leading to a colder CONUS. However, there remains those little details that the CPC may be picking up that I may not be. Time will tell.