4/19/13 - A Temperature Roller Coaster Ride

Article By:  Lester Rhoads
Ohio Weather Blog Long Range Forecaster

We've been on a temperature roller coaster for the last several weeks and that looks to continue as we go through the rest of April and into May.  We were in the low 80s in Cincinnati yesterday and the low 40s today with even a few sleet and rain showers this evening!  What a change...  Well what are a few of the factors driving this pattern and why is it lasting so long?

First of all we are still in a pattern that favors blocking.  In the below graphs, note the AO and NAO and how they take another dive as we hit May.

As you can see, this means more strong cold fronts with 2-3 day warm up's ahead of each system and 2-3 days of a cool down behind each system.  Wash, rinse, and repeat.   The latest computer models indicate another trough coming in for next week around mid week with an associated cold front due in on Wed.  We then, will see another system next weekend and there is more beyond that taking us into the first week of May. 

The pattern also looks to remain active.  Take a look at the 11-15 day 500 MB height anomaly map for the 11-15 day period.

As you can see, a ridge builds into the Rockies with a trough along the East Coast and over SE Canada.  There is a weakness in the atmosphere that places the Great Lakes and Ohio Valley regions right in the cross hairs for continues storm system with warm up's and cool down's continuing for the next few weeks. 

For comparison, here is the 6-10 day from the ECMWF model.

The Euro produces a much colder pattern with a positive PNA type of pattern with the ridge centered further west and the trough is centered right over the Ohio Valley.  This is a much colder outcome here with a strong North Atlantic ridge.  This is not a negative NAO by the way.  So there you have it! 

Thanks for reading and I appreciate your feedback!