the phenomenon o extremely strong west or northwesterly winds will surge through the strait of juan...
TRANSCRIPT
The phenomenon
o Extremely strong west or northwesterly winds will surge through the Strait of Juan de Fuca, with the greatest speeds occurring near the eastern mouth of the Strait.A high amplitude upper level ridge extending
into Alaska and a shortwave trough over southwest BC causes upper level westerly winds over the Strait.
A strong pressure gradient from the western to eastern mouth of the Strait causes westerly winds at the surface.
The result
o Falling treeso Huge power outageso Dangerous seaso Extensive property damageo Loss of life
December 17, 1990 – The Elwha Storm
o Winds gusting over 60 mph from Edmonds to Whidbey Island
o Several fallen trees damaged cars and homeso The ferry Elwha sustained $3 million in damage after
being repeatedly slammed against the pier at the Port of Everett. The pier was also badly damaged.
o 25,000 homes lost powero Local marinas sustained millions of dollars in damage
December 17, 1990
Seattle Times and The Snohomish County Daily Herald
December 17, 1990
◄ NCEP 500 hPa reanalysis at 06Z on Dec 18. A high amplitude ridge extends into Alaska and a shortwave trough passes over southwest BC causing upper level westerly winds.
► Surface observation chart at 02Z on Dec 18 (during the hour of maximum winds). Smith Island is recording a 39 knot wind. A pressure difference of 4.6 hPa can be seen between the west entrance of the Strait and Smith Island.
December 17, 1990
…and when you have a ferry graphic, why not use it…
October 28, 2003 – The Ivar’s Storm
o Strong winds surged eastward through the Strait behind a strong Pacific front, producing wind gusts exceeding 60 mph from Edmonds to Whidbey Island.
o Nearly 100,000 people lost powero One death on Whidbey Island from a tree falling onto a
parked caro Partial destruction of Ivar’s restaurant at Mukilteo
Landing
October 28, 2003
Seattle Times
Ivar’s “rogue wave” mural…and the carp…
October 28, 2003500 mb heights overlaying an infrared satellite image from 4 PM PST on Oct. 28. A high amplitude ridge extends into Alaska and a short wave trough over southwest British Columbia causes upper level westerly winds in the Strait.
NCEP surface pressure reanalysis at 4 PM PST on Oct. 28. A 4-5 mb pressure difference from the western mouth to the eastern mouth of the Strait, causing a westerly wind at the surface.
October 28, 2003
The MM5 predicted winds near 40 knots (20 m/s) at the eastern mouth of the Strait 24 hours in advance of the storm.
October 28, 2003
Stations
Paine Field – KPAE Point Wilson – K53S Race Rocks – CWQK Smith Is. – SISW1Whidbey Is. – KNUW
Climatology – How often?
o Examine data from these stations. o Consider winds in the direction of 250° to 300° and
exceeding 30 knots.o Count the number of days in which this occurred over a
10 year period.
o How do the different stations compare?o Do we need to modify our parameters?o Do we have any problems with our data?o Which station(s) are a good gauge?
Answers?
Station IDs 994180 712024 690230 727937
Wind Speed (knots) Smith Is. # of Days Race Rocks # of Days Whidbey # of Days Paine Field # of Days30-34 82 447 28 035-39 29 68 6 040-44 1 14 3 145-49 1 2 1 0
50+ 0 0 0 0
total 113 531 38 1
January 1994 – December 2003UCAR30+ knots250° - 300°
Answers…
o The different stations show varying numbers of daysThis could be due to using the same parameters on
stations that are in very different placeso The data sets for some of these stations are incomplete.
We are working to fill those time gaps with our own archived data.
o Smith Island appears to be a good gauge due to its location and data quality.
What’s next?
o Organize a list of several dates where high winds were observed at multiple stations
o Look at synoptic patterns and categorize stormso Run composites on similar stormso Dissect our case studies, rerun models
o We want to know how many different ways these high winds can occur, what causes them.
o Which stations miss out and why?o Publish our results
Acknowledgments
o UW Department of Atmospheric Scienceso Professor Cliff Masso NOAA/NWSo Neal Johnsono UCAR/NCARo NDBCo NCDC
Contact information: [email protected] [email protected]