June 28, 2012

Battling Extremes and the July 4th Forecast

It is startling to see such weather extremes so close together.

Here in the Northwest we are experiencing wetter and colder than normal conditions on most days, with some locations shivering under daily low temperature records.  Yesterday, temperatures plummeted to 37 at Shelton, 39 in Olympia, and 38 at Yakima.  In some cold hollows near the surface temperatures may have dropped close to freezing.  In late June.

At the same time, temperatures in Colorado have reached over 100F day after day, some all-time high temperature records have been reached, extreme drought is in place, and fires are descending the Front Range of the Rockies into populated areas.

Let me illustrate....here are places that have experienced record low temperatures across the U.S. yesterday--some over the southeast U.S. associated with a trough and clouds and the other over guess

In contrast, here are where the high maximum temperature records occurred--from Wyoming through, Colorado, Oklahoma, to Louisiana on the same day.

Lets look at the differences from climatology (the anomalies) for the past week.  First for maximum temperature.  Extraordinary cold from central CA into the Northwest, with some locations 9-15F below normal, which equally strong but warm anomalies east of the Rockies

These extraordinary warm anomalies are occurring in locations where precipitation has been nearly absent all spring.  Here are the precipitation anomalies for the last month...large areas have had 5% or less of normal precipitation.  No wonder wildfires started so early.  And yes, WE have had wet anomalies...with eastern Washington being particularly wet.  I wonder what that implies for agricultural interests there.

 The reason for all this contrasting weather is due to a highly persistent atmospheric flow pattern with a stubborn trough over the eastern Pacific and a big ridge over the Rockies and middle part of the country.  Here is the mean upper level (500 hPa) flow and the anomaly from climatology.  You can see the troughs on both coasts and the big ridge over the middle of the U.S.  The trough off our coast represents a very large anomaly from normal, if that makes you feel better

But I know what you really want to know, how does July 4th look?  Will this abysmal pattern ruin our fireworks and barbecues?  Here is the answer from the latest European Center model run.  The panel on the right is the average of their ensemble (many model run) system and one on the right is their best single prediction, both for the upper level flow (500hPa).  The SAME pattern is there-troughs over the coast, big ridge over the central U.S.

At least we won't have to worry about wildfires, air conditioning, or firework cancellations.  Just mold and mildew.


  1. Just watched some very fast forming and disappearing Kelvin-Hemholtz Wave clouds. I'm in Bellevue looking east. Very cool!

  2. K-H wave clouds - did I say looking east? I meant west!

  3. High dewpoints again Cliff. This is like the 3rd episode in the past month.

    How much rain would we have gotten if we had this pattern in November.

    At the NWS page, you can see the yearly charts. I caught Portlands, and its odd. Just by eyeballing the graph, on March 10th they had 21 inches. Now by the end of this month they might reach 40 inches.

  4. I believe that today marks my personal definition of the first day of summer...the forecast was for rain last night and today, but instead I awoke with blazing, too-bright sunshine in my eyes.

    The proof of the existence of Summer is finally upon us when forecasts go wrong in that particular way.

    John M in Sequim

  5. Are you sure that global warming won't result in more total water content in the atmosphere and thus MORE snow pack for the cascades? Seems that given the assistance of altitude temperatures will still be cold enough in the cascades to support plenty of snow. And the rest of the warming will provide more moisture to support more snow. Kind of like the increase in major snow events in the eastern U.S. Just because it's warming the globe doesn't mean that it's not still cold enough for snow.

  6. It seems that summers were fairly decent in warmth (on average, admittedly by my own shadowy memory) from about the mid 70's to about 2004 (excluding 1993 & 1999). (I am told the 60's were cool and wet, but I didn't live here until fall 1972.) Since 2004, our "warm season" has been distinctly cool with the exception of 2009.

    Is the PDO behind this, maybe?

    Absolutly amazing to me that some areas in the central and SW part of the country have only a few percent of mormal rain this year. Global Warming? The PDO? Or the randomness of which Mother Nature seems so fond?


  7. Not just the Rockies and Plains that are getting very hot weather.

    The Midwest, Mid-Atlantic, and Northeast are also getting extremely hot weather, 100+ AND humid in many places.

    I'm from Philadelphia and prefer summer weather their to Seattle weather, but not when it gets that hot. A little more balance would be good.


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