Tuesday, March 31, 2009

Endless cold and strong winds at Camp Muir

The extraordinary cool March continues.... the climatology (red-average max, blue-average min) at Seattle versus observed temperatures shows the sad situation (image). During the last month only 3 days have reached or exceeded the normal maximum temperature, while over half the days have had minima below the normal lows. We should have highs in the mid-50s now.An underlying cause of the cold air has been the persistence of a certain atmospheric configuration, with a ridge over the eastern Pacific and a trough somewhere over our region--and this pattern is not going away soon (see example for later this week). This very persistent pattern results in a cold northerly flow and embedded troughs aloft (weather disturbances) that move in this northerly flow giving us intermittent cold precipitation. Last spring was also very cool...and I had some fun with the "barbeque index" last year to quantify the cold (the barbeque index is the number of days in spring reaching at least 60F, last year had the least number of such days from mid-March to mid-June since 1918!). Another major anomaly this year is Spokane's snow...with added snow this week, this is that city's snowiest winter on record. There was a strong pressure gradient at the surface at this time.

The next question you have is why is this happening? La Nina years have a higher frequency of such configurations...and this has been a La Nina year...so perhaps some of the blame can rest with the colder than normal sea surface temps over the tropical Pacific that are associated with La Nina. But even with that said, the cold pattern this year has been unusually persistent.

One of you (Mbeebe) noted the strong winds at Camp Muir...at 10,000 ft on Mt. Rainier.. this morning with winds gusting to 140 mph. Check the following link to see the winds at this site (
http://www.nwac.us/products/OSOMUR). Now it was windy in the lower mountain stations....but nothing like this. The strong winds accompanied a strong frontal passage this morning (see surface pressure, wind and near surface temp plot attached for 10 AM), in which the winds switched to northwesterly as a trough pushed through (image). The computer wind prediction (sustained not gusts) for 10 AM shows strong NW winds..but far less than occurred. Clearly, the observed trough aloft was strong than predicted---assuming the Camp Muir obsevations are reliable.

5 comments:

GHSCSHWEATHER said...

Hey Cliff,

The 00z NAM run from tonight is showing a fairly widespread snow event for tomorrow morning. Any thoughts?

andycottle said...

Hey Cliff, I noticed on radar that a fast moving CZ blew through here earlier this morning, but then moved from south to north later this afternoon and reaching it`s usual spot.....central sound. Was I seeing that right?

mainstreeter said...

On This Day, March 31, In 1992, Seattle, Washington Closed Out Its First Snowless Winter Ever. Further South, Las Vegas, Nevada Recorded 4.80 Inches Of Rain During The Past Month Which Set 2 Records. The First Record Was The Wettest March Ever With An Old Record Of 1.83 Inches Set In 1973 And The Second Record Was The Wettest Month Ever With An Old Record Of 3.39 Inches Set In September Of 1939. The Normal Rainfall For Las Vegas Is Only 4.19 Inches.

Lance said...

Cliff,

What are the chances of us experiencing a spring similar to last year's? Also, does a cold spring usually bring a cool summer, if my memory serves me correctly, the summer of 2008 wasn't too shabby.

Liembo said...

What is the period that the ming/max/average wind for Camp Muir is calculated? The whole hour? Minimum 81 mph over the course of a whole hour?