Tuesday, May 26, 2015

"When it Rains, it Pours" and the Summer Outlook.

One of the most popular questions the meteorologist gets coming out of an extremely cold/snowy winter is "What does this mean for summer -- will it be really hot?"
The short answer to that question is that one really doesn't have anything to do with the other unless the overall weather pattern has been unchanged for months.
The longer explanation takes into account many other factors and is set forth in this blog. :)

To get things started, let's take a look at the past 50 years or so and find out the result of comparing winters and the their following summers. In a majority cases, winter that were exceptionally cold were followed by summers neither too cold or too hot, rather just average. (We can call it a Goldilocks Summer, see graphic to the right.)

There seems to be a slight advantage for equal chances of a cold, warm, or average summer when winter averages warmer. (See graphic to the left.)

Looking to our past can be interesting but it hardly determines a certain outcome in either case. A better indicator to a seasonal outlook is to look at the overall global weather pattern, specifically the current status and forecast for El Nino and La Nina. It usually gives us a good idea of whether or not our weather pattern will remain consistent or start to change. Here is an example...
Headed into last winter conditions were cool and wet and there was a hint that El Nino was going to emerge and change our weather pattern to milder and drier for the cold season. Without any strong signals that El Nino was in fact developing, it became very clear that we would endure a lot of cold and snow/rain.
That wet/cool weather pattern has continued into the Spring this year but it has also begun to change a bit to the warmer side but remaining wet. In fact, El Nino has helped to steer the jet stream further south into the Heartland, and tap into rich Gulf of Mexico moisture. This has aided in exasperating the flooding situation in Texas and Oklahoma.
Heavy downpours have already been increasing in frequency across part of the United States over the past several decades. A warmer environment can hold more moisture. It's plausible that areas warming more than others on a larger scale are apt to see increased heavy rainfall events. Here is what research shows concerning the Lower 48. The next graphic to the right is a closer look at the frequency for the state of Kentucky itself.

Heavy Downpours

No comments:

Post a Comment