The

VANCOUVER TORNADOVANCOUVER TORNADOof

JANUARY 10 2008JANUARY 10 2008JANUARY 10, 2008JANUARY 10, 2008

David ElsonDavid ElsonNOAA/National Weather Service Forecast Office, Portland OR

Oregon-AMS meeting, November 20, 2008

A brief tornado climatology…A brief tornado climatology…1950-2006tornado

Plots from Severe Plot v2.0

A brief tornado climatology…

Some commonalities exist:

A brief tornado climatology…

• Tornadoes in western Oregon and Washington are usually

Some commonalities exist:

post-frontal.

• Moderating marine air at surface coupled with cooling aloft create favorable lapse ratesaloft create favorable lapse rates.

• Not until frontal passage do shear profiles support rotation in storms. Why is this?...y

A brief tornado climatology…

Google

12 PM PST KPDX NAM BUFR Forecast Sounding12 PM PST Sounding modified with surface observations

NAM Sounding

Modified Sounding

Sfc T/Td 48°F / 45°F 52°F / 48°F

CAPE 238 J/kg 912 J/kg

Lifted Index 0.98 -2.12

Equilibrium Level 15,713 ft asl 23,868 ft asl

0-3 km SRH 174 m2/s2 204 m2/s2

Horizontal Convective Rolls – A key source of rotation

Image source: Daniel Tyndall, Department of Meteorology, University of Utah

0.5o Reflectivity 19:04Z – 21:47Z

Low Level Low Level Reflectivity CoreReflectivity Core

0.5 deg0.5 degReflectivity Reflectivity

20:14Z20:14Z2300 ft2300 ft

2.4 deg2.4 degReflectivity Reflectivity

20:14Z20:14Z4800 ft4800 ftHook EchoHook Echo 2300 ft2300 ft 4800 ft4800 ftHook EchoHook Echo

Mean FlowMean Flow

Storm MotionStorm Motion

6.0 deg6.0 degReflectivityReflectivity

14.6 deg14.6 degReflectivityReflectivityReflectivity Reflectivity

20:14Z20:14Z10,200 ft10,200 ft

Reflectivity Reflectivity 20:14Z20:14Z

24,000 ft24,000 ft

1.5° Velocity 18:59 UTC – 20:02 UTC

1.5° Velocity 18:59 UTC – 20:02 UTC

1.5° Velocity 18:59 UTC – 20:02 UTC

1.5° Velocity 18:59 UTC – 20:02 UTC

0.5° Storm Relative Motion

20:02 UTC 1900 ft

3.4° Storm Relative Motion

20:02 UTC 4500 ft

1.5° Velocity 20:02 UTC

The supercell at it’s peak…

0.5 degReflectivity 20:14 UTC

2.4 degReflectivity 20:14 UTC0 5° S R l i M i20:14 UTC

2300 ft20:14 UTC

4800 ft0.5° Storm Relative Motion

20:14 UTC 2300 ft

6.0 degReflectivity 20:14 UTC

14.6 degReflectivity 20:14 UTC

10,200 ft 24,000 ft3.4o Storm Relative Motion

20:14 UTC 6200 ft

The End ResultThe End ResultRated an EF-1 (90-110mph winds)winds)Track length of around 10 milesMostly light damagey g g• +200 trees (largest 50”

diameter, and six 36” in diameter)

• 30-40 homes damagedProperty damage totaled $525kZERO deaths/injuries

What does this say about the future?

History tells us tornadoes are rare in the Pacific Northwest, but do show a preference for select inland valleys.p y

Unstable post-frontal wintertime air masses, which have been associated with past tornadoes, are a regular occurrence in the P ifi N h Pacific Northwest.

Terrain appears to play a significant role in the development of tornadoes especially in creating favorable sheartornadoes…especially in creating favorable shear.

Two of the 3 most significant tornadoes in the region touched down within a few miles of each other in west Vancouver.

History and Terrain both suggest that the lower Columbia River Valley east of the Tualatin Mountains is likely to see m r (b t till i fr q t) t r d i th f t rmore (but still infrequent) tornadoes in the future.