Wednesday, November 30, 2011

Highest Pressure in Decades Over The Northwest?

Do you feel the pressure?  Is it like the weight of the world is on your shoulders?  There may be a reason:  right now we are experiencing some of the highest atmospheric pressures in years and probably decades.

Take a look at the National Weather Service sea level pressure analysis at 7 PM (below).


A very strong high pressure area is centered over the Northwest and southwest Canada, with pressures greater than 1040 hPa over much of the region and a 1046 hPa center over southern BC.  1046 hPa is equivalent to 30.89 inches of mercury.  Folks, this is REALLY high sea level pressure.  At Sea-Tac the 9 pm pressure was 1042.6 hPa--and it is still going up!  There has been a huge pressure rise over the past 24h--roughly 20 hPa. The highest SLP I see at 9 PM is 1045.2 hPa at Lytton BC (elev 751 ft).

From experience I know these pressures are very unusual, but lets check the UW pressure archives.  Here are the hourly pressures at Sea-Tac airport since 1996.  Looks to me like the pressure last hour (9PM Wednesday is the final plotted red dot) was the highest during the entire record shown here (I confirmed by looking at the numbers).  So the highest pressure in 15 years!  That is impressive.

And the pressure is still going up!  The Portland International Airport has recorded a maximum barometric pressure reading of 30.76" (4:53am observation) which is tied for the second highest reading since records began at the airport in 1940 (thanks to Steve Pierce for this information). The bottom line is that we are experiencing truly unusual pressure right now...I wonder what this does to people with arthritis and sensitive joints.

 This push of high pressure over the Northwest is creating huge pressure gradients over the southwest U.S.  Here is the latest model prediction for tomorrow morning.  High pressure over us and a big pressure differences over Colorado, Utah, Nevada, California, and the offshore waters.


Very strong winds will be the result of these big pressure gradients, including gusts hitting 50-80 mph in places.   In fact, it has already started.  Take a look at the latest wind reports of greater than 45 mph over the western U.S.---quite a few of them.


And here are some recent reports from the National Weather Service office near Los Angeles.  Gusts as high as 69 mph so far.

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE OXNARD CA
802 PM PST WED NOV 30 2011

..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..

0557 PM NON-TSTM WND GST 1 NW SANTA CLARITA 34.42N 118.53W
11/30/2011 M67 MPH LOS ANGELES CA MESONET

67 MPH GUST AT SAUGUS RAWS LOCATED 1450 FT

0555 PM NON-TSTM WND GST 5 N SAN FERNANDO 34.36N 118.42W
11/30/2011 M64 MPH LOS ANGELES CA MESONET

64 MPH HOUR GUST AT CAMP NINE RAWS LOCATED AT 4000 FT

0753 PM NON-TSTM WND GST 8 ESE CASTAIC LAKE 34.60N 118.58W
11/30/2011 M69 MPH LOS ANGELES CA MESONET

69 MPH GUST AT WARM SPRINGS RAWS LOCATED AT 4930 FT


High pressure will bring us dry conditions and some sun...but air quality may decline.

17 comments:

Unknown said...

According to my one semester of "Elementary Meteorology" at MIT in the late 1950s, 1045 is insane.

Yikes.

Doug said...

Large power outages in LA due to high winds; 100mph in some cases.

http://latimesblogs.latimes.com/lanow/2011/11/powerful-winds.html

la takahashi said...

Hi Cliff,
Are the barometric measurements quoted corrected to sea level? Inquiring minds would like to know.

Thanks!

Big Wave said...

Those high winds squirting through the gaps...a huge hazard to drivers on those pass roads... There's a place up near Denali called Windy Pass where the same winds happen - on the north side with high pressure to the south. The folks in the little town of Healy are used to seeing 60 - 70 kts of wind when those conditions occur. Thanks Dr Mass!

Script Maven said...

High pressure tends to make arthritic joints feel better. It's the dropping barometer that makes them ache.

http://www.ehow.com/about_5368665_do-joints-ache-weather-changes.html

Jim S said...

Downslope winds along the Wasatch Front produced gusts in excess of 100 miles per hour in Centerville, UT this morning. A local disaster has been declared there due to wide spread downed trees and property damage.

W7ENK said...

The winds atop Mammoth Mountain NE of LA have been absolutely insane since last night.

Here's the Reno NV AFD from this morning.

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RENO NV
616 AM PST THU DEC 1 2011

UPDATE...

SCATTERED SNOW SHOWERS ALONG THE SIERRA CREST WILL DIMINISH BY LATE MORNING OR EARLY AFTERNOON AS DRIER AIR MOVES INTO MONO COUNTY. MAMMOTH MOUNTAIN WIND SENSOR AT 11000 FEET REPORTED SUSTAINED WINDS OF 140-150 MPH, BUT APPEARS GUST SENSOR CAN`T REPORTS WINDS OVER 150 MPH. ESTIMATING PEAK GUSTS OVER THE TOP OF MAMMOTH MOUNTAIN OF 170-180 MPH USING A 15-20 PERCENT INCREASE OVER THE SUSTAINED WINDS. ASIDE FROM THE TOP OF MAMMOTH MOUNTAIN, PEAK GUSTS OF 70-90 MPH WERE REPORTED ALONG THE CREST AND BELOW 10000 FEET.

http://www.wrh.noaa.gov/total_forecast/getprod.php?wfo=rev&pil=AFD&sid=REV&version=0

Yeah, and it's legit.

Check out the obs:
http://www.wrh.noaa.gov/mesowest/getobext.php?wfo=hnx&sid=MTH03&num=72&raw=0&dbn=m&banner=header

Insane!

W7ENK said...
This comment has been removed by the author.
orv said...

To put this in perspective, aircraft altimeters (which need to be adjusted to barometric pressure) generally max out at 31".

Sysiphus said...

According to weather historian Chris Burt, the record for Seattle is 30.83 in 1921: http://www.wunderground.com/resources/pressure_records.asp.

Not sure where he got that figure.

Ron said...

This is a rather interesting event. Typically high pressure of this magnitude is associated with an arctic air mass coming down from the Yukon. A 1045 mb High isn't very unusual over the Canadian prairie. But in this instance, the high pressure actually developed over the eastern Pacific and moved into the Pac NW. It is a reflection of the strength of the ridge of high pressure aloft.

Blake said...

And yet we still can't see the dang sun for the second day in row!

windlover said...

So when this high pressure leaves is it going to exit to the east? And if so, is there a low approaching the coast at the same time? And if so, how low is that low and how close to the coast witll it be? Just wondering, cause with that high of a pressure to the east and if we get a good low coming up the coast there could be some serious mountain wave winds in that senario, if it plays out, next week....

seamusmclean said...

I've noticed a huge number of students (as well as myself) having problems with migraines and vertigo this week. Looking around, it looks like high pressure is a common trigger for both migraines and vertigo. So at least that makes some amount of sense now, knowing this.

Tressa said...

My husband who has trouble with his ears is loving it. He can feel the pressure changes. he made a comment today about how good his ears feel. Now I can tell him why.

Ansel said...

Now if we could just get this kind if high once or twice a month this coming spring, I'll be satisfied!

M. M. Justus said...

I don't know about other effects, but you've explained why I'm having a migraine (one of my triggers is extreme barometric pressure, one way or the other, or wild swings).