Sunday, December 16, 2012

Impending Storm... Noon Update

Well, I went to bed last night thinking I created this blog at a good time... We had an impending wind storm, so lots of material right? Well now, this has turned into a SERIOUS event. Before we were talking on par with the Dec 14, 2006 storm (Hanukkah Eve Storm) which produced 50-80 mph gusts in the interior valleys, with the strongest up near Seattle. We now may be talking something more serious than that... But don't just take my word for it, here's the recently updated High Wind Warning from the PDX NWS...


URGENT - WEATHER MESSAGE
NATIONAL WEATHER SERVICE PORTLAND OR
930 AM PST SUN DEC 16 2012

ORZ005>007-010-WAZ022-039-040-170600-
/O.CON.KPQR.HW.W.0019.121217T0200Z-121217T2000Z/
LOWER COLUMBIA-GREATER PORTLAND METRO AREA-
CENTRAL WILLAMETTE VALLEY-NORTHERN OREGON CASCADE FOOTHILLS-I-
5 CORRIDOR IN COWLITZ COUNTY-GREATER VANCOUVER AREA-
SOUTH WASHINGTON CASCADE FOOTHILLS-
INCLUDING THE CITIES OF...ST. HELENS...HILLSBORO...PORTLAND...
OREGON CITY...GRESHAM...TROUTDALE...SALEM...MCMINNVILLE...SANDY...
SWEET HOME...LONGVIEW...KELSO...VANCOUVER...BATTLE GROUND...
CAMAS...WASHOUGAL...TOUTLE...ARIEL...COUGAR
930 AM PST SUN DEC 16 2012

...HIGH WIND WARNING REMAINS IN EFFECT FROM 6 PM THIS EVENING TO
NOON PST MONDAY FOR MUCH OF THE INTERIOR LOWLANDS AND FOOTHILLS
OF THE CASCADES...AS WELL AS CLARK COUNTY AND THE NORTH AND SOUTH
WILLAMETTE VALLEY...

A HIGH WIND WARNING REMAINS IN EFFECT FROM 6 PM THIS EVENING TO
NOON PST MONDAY.

* WINDS: WINDS WILL INCREASE LATE THIS AFTERNOON AND
  EVENING...WITH SOUTH WINDS 25 TO 40 MPH...WITH GUSTS 45 TO 60
  MPH EXPECTED THIS EVENING. AFTER MIDNIGHT...WINDS WILL TURN
  SOUTHWEST TO WEST 30 TO 45 MPH WITH GUSTS 50 TO 60 MPH. THE
  STRONGEST WINDS WILL BE IN LARGE OPEN AREAS...AND HIGHER HILLS
  EXPOSED TO SOUTHWEST TO WESTERLY WINDS.

* TIMING: INCREASING THIS EVENING...STRONGEST WINDS ARE EXPECTED
  BETWEEN 11 PM TONIGHT AND 6 AM MONDAY.

* IMPACTS: POWER DISRUPTIONS ARE LIKELY. WITH SATURATED
  GROUND...WINDS OF THIS MAGNITUDE MAY TOPPLE TREES AND CAUSE
  DAMAGE. HIGH PROFILE VEHICLES TRAVELING ON INTERSTATE 5...
  205... 84...AND OTHER HIGHWAYS SHOULD BE PREPARED FOR STRONG
  WINDS.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A HIGH WIND WARNING MEANS A HAZARDOUS HIGH WIND EVENT IS EXPECTED
OR OCCURRING. SUSTAINED WIND SPEEDS OF AT LEAST 40 MPH OR GUSTS
OF 58 MPH OR MORE CAN LEAD TO PROPERTY DAMAGE.


This is now a serious situation, but what made the NWS so sure of a much stronger storm? That would  be the 12z model runs from this morning. The WRF-GFS is a model developed at UW, which is tailored to help predict PNW weather. Using it I'm going to walk you through this storms TIMING, IMPACT  and DEVELOPMENT Here's the 4km (resolution) surface pressure model.


Notice the lines so close together over our area? Those are isobars, which show differences in pressure... The tighter they are, the stronger the wind. This image is from hour 18, which corresponds to 10pm tonight, right before the peak winds. The low has made landfall around 972mb at this point. Below is the wind gust model from the same time...


Not super impressive yet, gusts of 25-35 KTS (30-40 MPH), but check out the SLP and Wind gusts for hour 21, just 3 hours later...


After the low is inland, the isobars oriant slightly differently, allowing for the strongest winds (now out of the SSW) to slam our area. Widespread 35-40 KTS (40-50 MPH) with areas down in the south valley towards Salem reaching 50 KTS (60+ MPH). Also note the area just off of Astoria which is shaded white. That is an area of gusts that are out of the range of the model (which goes up to 70 KTS or 80 MPH) which suggest 80-100 MPH winds just offshore. 

SO, what does all of this mean? We have a storm moving in that WILL do damage, best to prepare now for it. I will update the blog later as more details become apparent, and as actual observations begin to roll in. I will also open up a section for any blog followers with personal weather stations to comment with their OBS... Thank you, and you should hear from me soon.




No comments:

Post a Comment