Friday, July 7, 2017

A Very Dry Start to Summer

For much of the Northwest, it hasn't rained since mid-June, when we had an unusually heavy one-day deluge of over an inch (see accumulated precipitation at Seattle Tacoma Airport over the past four week, red is observed, blue is normal).  Interestingly, because of that one-day amount, the last four weeks had nearly normal rainfall!
A map of the total precipitation over the past two weeks shows less than .1 inches over most of the western U.S., with most locations getting nothing.

The departure from normal shows .75 to roughly 2 inches below normal over western Washington.  The departures from normal are not large because we get very little precipitation this time of the year.
In fact, we are now entering the driest time of the year in the Northwest, with the lowest precipitation amounts the last week of July and first week of August (see climatology for Seattle)

 The models are forecasting little or no precipitation for the next few weeks.
For example, the 21-member NOAA/NWS GEFS ensemble (many forecasts made to explore uncertainty) show virtually nothing for the next 192 hours.

 The even larger NAEFS (US plus Canadian) ensemble shows the same thing  through the 21st (second panel)
 And the larger European Center ensemble indicates no precipitation or a few hundredths (gray colors) during the next ten days.  The bottom panel is the ensemble average... maybe a slight misting on Monday.

With above normal temperatures and no rain, the demand for water in Seattle has increased substantially (see Seattle SPU graphic)--see the red line.

This year has certainly been one of contrasts:  the wettest winter for many and now a very dry early summer.

9 comments:

Unknown said...

Amazing that water consumption is nearly 1/3 less then the average w0 years ago despite the population growth in Seattle.

Unknown said...

Oh and my PWS in Kent's East Hill had 0.022" of rain on Monday (7/3).

Michael DeMarco said...

Watch for lightning.

sunsnow12 said...

June 2017 precip Sea-Tac: 1.52" actual vs. 1.57" average. Not remotely "very dry".

You know how averages work Cliff and you know our "very dry" summer climate. Furthermore it is common for the majority of one month's precip to fall in a few days - particularly in the summer here. What happens if we get a thunderstorm in late July that drops .75" on Seatac in a half hour? Right there we just went over the average for the entire month. In 30 minutes.

Maybe I'm missing something here but I like it better when you are the one fighting back against provocative and questionable headlines like, oh, I don't know, "A Very Dry Start to Summer". Can you characterize any normal summer (or July) here differently?

AnneScott said...

I hate this feast or famine type weather we have had the past couple of years. It goes from months of relentless rain and gloom to drought with little variation.Having a few days of rain in between the sunny stretches (as is usually the case in a normal summer) would be perfect otherwise it get too parched out there and we run into fire related issues such as extreme fire hazards,campfire bans,recreation closures and smoke choking the air. Many climatologists have said that one of the effects of climate change on Pacific Northwest weather is hotter, drier summers and wetter winters with more heavy rainfall and we have certainly seen a bit of a preview of what "normal" might be like in the future ( minus the cold, snowy winter).

Andrew Lincicome said...

Why should we watch for lightning Michael DeMarco?

Kenna Wickman said...

We just had some tractor work on our place, clearing the blackberries and a patch of broom and some Willow. 3 large burn piles - 10 X 10. We burned one of these the day we made it and it was frustrating and needed a blower to get it all. We waited 2 weeks of this dry weather. But not the same deal. Had flames going up 25' and one had to stand back some 50' from the fire due to the radiant energy. These burned completely within an hour.

Thecatguy93 said...

Hey sunsnow, Cliff said a very dry start to our "summer", and he's 100 percent correct. It has not rained since summer officially started. If no rain does not constitute "very dry", then please enlighten us as to what does. I don't understand why people argue for the sake of arguing.

Yaela said...

seems to me to be cooler this July than in recent years. Is that right?