Summer 2011 Forecast

This summer's forecast is a somewhat tougher call to make than past summers, such as last summer's hot forecast (which we weren't hot enough in forecasting!). A weakening La Nina, combined with a rare treat of a wet and warm (but volatile) Spring are setting the stage for what I feel will be a cooler summer than last year (that's an easy call), but one that could provide flooding challenges to parts of the Ohio Valley and Northeast through the Summer season.

First, the wet Spring start that we've experienced.  It has been awfully wet -- on the scale of historic in some parts of the Ohio Valley and Northeast this Spring season.  A snapshot of 30 days through last Wednesday shows some parts of the Mid South getting more than 400% of average rainfall.   No wonder the Mississippi River is at historic levels in the Deep South.

A few years fit the synoptic pattern overall -- either in temperatures, precipitation, or upper atmosphere.   The "best" fit years so far that I've 1954 (upper atmosphere and temperatures), 1977 (temps plus precipitation), and 2006 (temps and precipitation).    There is a decent similarity in those years to a wetter than average Ohio Valley and Northeast, with a dry Plains.   It's not perfect but for our backyard it's a decent enough blend to use.

2006 and 1977 were years that featured neutral ENSO conditions.    With a weakening Nina trend this year, I have placed a bit less stock in ENSO conditions than I would if the trend were strengthening towards a Nino or Nina...that should not happen this year.

In terms of temperatures, it shapes up as a warmer than average summer in the South based on a blend of these three years -- with the warmest temperatures in the Plains and Ozarks, across to the Mid South.  The Northeast and Northwest are cooler than average overall.   We tend to average out to just a notch or two below average for the summer overall.   It doesn't mean it's going to be a cold summer...

One of the common themes in these years is that one month ends up rather wet and cool compared to the other months in the summer.  We may have two months where temperatures are typical or even slightly above average and one of the months where temperatures are a few degrees below average with unsettled, humid, rainy weather.   Unfortunately, each of our three years provides us one bad month -- just not the same month (1954 was August, 1977 was June, and 2006 was also June).

This means there's a bit of a risk factor in our summer forecast as that if July ends up cooler and wet we bust in two months of the three.    Our thinking is the year shapes up a bit more similarly to 1954 in terms of weather pattern overall based on similarity in the atmospheric pattern to date...seasonal to start, rainy to end.  However, with stats backing up June being a rainy month (1977 and 2006) I could whiff on this prediction.    Figuring out when the rainy stretch of the summer takes shape is arguably the lowest confidence call of the forecast.

A few things are a bit more certain though:

1) We won't have 50+ 90 degree days this year.  I think Philly ends up right around average and am forecasting 27 90+ degree days for the year.

2) The hottest relative to average will probably occur around the 4th of July and we could flirt with upper 90's in that timeframe.  When we get warm, it will be quite warm.   In other words, think typical summer outside of a few weeks of murky and stormy weather.