Now that summer 2008 is officially half-over, I thought it would be interesting to see how my forecast from May is turning out. Aside from a very hot first two weeks of June, everything seems to be on track.
Here is a brief summary of my Summer 2008 forecast…
* Cold PDO, weakening La Nina, and wet soil across Midwest will be dominant forcing
* No 100+ days and few 95+ days
* Summer should move from cool and wet in June (relative to normal) to warm and dry in August (relative to normal)
One thing that has verified well so far is the idea that there will not be extreme (100+) temperatures in the Mid-South this summer. In fact, none of the big 3 cities in KY has been above 95 through July 17. Of course, there were no 95+ readings through July 17, 2007 either, and we all know how August 2007 turned out. Here are where temperatures stand relative to normal from June 1 – July 17. Note that while most of the Mid-South is warmer than normal at the half-way point, the past month (since June 16) has been cooler than normal.
Louisville (SDF): +2.9 (+0.2 since June 16)
Louisville (WFO): -0.6 (-3.3 since June 16)
Lexington: +0.6 (-2.0 since June 16)
Bowling Green: +1.3 (-1.1 since June 16)
As far as precipitation goes, most of the Mid-South is running 60-70% drier than normal for the summer so far, although a big part of that was the SE ridge that brought the early June heat. The dry start to summer has been more of a mesoscale problem than a synoptic problem, as there have been numerous fronts to cross the region. For whatever reason, the bulk of the actual precipitation has remained just north and east of central KY.
Louisville (SDF): 4.35″ (71% of normal)
Louisville (WFO): 3.93″ (64% of normal)
Lexington: 4.72″ (65% of normal)
Bowling Green: 4.15″ (60% of normal)
As far as the rest of the summer goes, there are no changes to the forecast I made in May. Last winter’s La Nina has weakened into neutral ENSO conditions and soil moisture remains high across the Midwest. Kentucky is the fulcrum of the seesaw that separates very wet (Midwest) from very dry (Southeast Appalachians) conditions. I don’t expect this soil moisture boundary to move appreciably the rest of the summer, although I would hedge dry if I had to make a choice. Climatologically, the period from mid-July to mid-August is the warmest time of year, so if we can bear the next 4-6 weeks, we’ll be on our way to the cooler weather of fall.