A Very Wet May, But Summer Ahead

May 29, 2013

Last night’s soaking put us into a tie for 3rd place here in Portland.

MarkRain_PortlandToday

As of 4pm we’ve seen 4.68″ 4.71″  so far…strangely enough that’s the same total from May 2010 (I think I added wrong initially), that was a gruesome late spring!  Here are the top 5:

MarkRain_MayWettest

Even stranger, this May total is just a quarter-inch away from the entire February, March, & April combined total!  Those were some very dry months.

I think I mentioned 2-3 weeks ago that we’d see payback for all that dry weather and sunshine…

So what happens next?  It’s as if a switch is going to go off and we go dry again.  Get ready for a return to summer, and this time it’ll be “real” summer weather (next week) because it’ll be June.

Why a dramatic change?  The cool upper-level troughiness and moist westerly flow will be replaced by an upper level ridge either over us or just to the west (reminds me of late winter and most of spring).  As we head into summer this pattern is usually dry with just varying degrees of onshore flow or flat onshore/offshore gradients.  Take a look at the rise in 850mb temps over the next week on the 12z GFS:

tseries_850t_000-384_Portland

The 12z ECMWF is similar, although it appears the cold trough late next week is a big outlier (the blue line is the operational run):

tseries_850t_000-360_Portland

850mb temps peak out around +15 or so next Tuesday/Wednesday/Thursday.  That should easily push us up into the low-mid 80s!  Our 7 Day is a little cooler because I’m a little gun-shy after some episodes earlier this spring.  Or maybe I’m just getting old and conservative with a cold-bias?  The new 18z GFS is even warmer with 6 days at +15 or warmer starting next Tuesday…Summer!

The ground is very wet right now, but should dry quickly the next 3-4 days with warmer temps.  I was out in my (overgrown) yard today…wow, lots of weeding, mowing and weed-whacking on the way.  But it sure is GREEN out there!  Can’t wait to get outside in the sunshine and warmer temps, even if it involves a lot of work.

Chief Meteorologist Mark Nelsen