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02 FEB Wind Event
Overview of the 02 February 1999
Eastern Washington and Northern Idaho Wind Storm
Don Moore - WFO Spokane
INTRODUCTION
Strong winds developed over eastern
Washington and Northern Idaho on 02 Feb 1999. Wind speeds of 50 mph were common
across many locations in Eastern Washington and Northern Idaho, with over 70
mph wind gusts recorded in Spokane. As a result, numerous trees and powerlines
were toppled. In addition, structural damage to many homes and businesses was
reported. KXLY news also reported 8000 to 10000 of AVISTA's customers were without
power during the height of the wind storm. To gain an understanding of the cause
and extent of the wind damage, an overview of model data, satellite data, and
surface observations will be presented. In addition, reports of damage receieved
by NWS Spokane will also be presented.
SYNOPTIC ENVIRONMENT
An upper level low was heading
east into the coast of southern BC and shearing apart at 12 UTC 02 Feb 1999
(Fig. 1). Meanwhile 500 mb short wave trough was moving
east toward western Washington. Strong 850 to 700 mb warm air advection over
eastern Washington ahead of the short wave trough was producing snow from Spokane
and Collville east into the Idaho Panhandle. The snow ended over the area by
late morning as strong subsidence associated with the 500 mb short wave spread
into the area. (Fig. 2).
A strong jet, with 250 mb winds
in excess of 120 kts at 12 UTC, was situated to the south of the low over Washington.
Once the shortwave trough moved through northeast Washington, the 250 mb jet
increased to 160 knots (Fig. 3).
Wind speeds in the mid to low levels
over Washington were also exceptionally strong with 850 mb wind speeds near
50 kts at 12 UTC (Fig. 4). The surface pressure gradient
was also exceptionally tight as an area of low pressure moved southeast through
British Columbia (Fig. 5).
Surface Conditions
Surface wind speeds over the east
slopes of the Cascades began to increase considerably by late morning. Sedge
Ridge RAWS reported a wind gust of 95 mph while Washington Pass Raws reported
a wind gust to 55 mph. Wind gusts began to slacken off by early afternoon over
the Cascades. Meanwhile, over eastern Washington wind speeds increased dramatically
through early afternoon. By 2200 UTC, most locations over Eastern Washington
reported wind gusts over 45 mph including Spokane Felts Feild (SFF) where a
wind gust of 63 mph was recorded ( Table 1).
The stiff sustained winds were
a result of a very tight pressure gradient. However, it is likely the higher
wind gusts that caused most of the damage were a result of mid level winds
accelerating down to the surface. One indication of this is a number of surface
observations reporting rapidly a falling pressure, followed by a rapidly rising
surface pressure, and then another rapidly falling surface pressure. Water
Vapor imagery also indicates that this type of phenomena may be occuring (Fig.
6). Visible imagery also clearly shows the impact of subsidence associated
with the short wave trough (Fig. 7).
Damage Reported
Wind damage over Douglas and Northern
Grant County began to occur before noon and by early afternoon in Spokane and
Coeur D'Alene. The most common type of damage was due to fallen trees and downed
power lines. Power outages were reported in most towns across the Basin along
with the Palouse and Spokane and Coeur D'Alene areas. Outages ranged from just
a few hours in Lewiston to over 12 hours around Spokane and Coeur D'Alene. More
serious types of damage such as blown off roofs and trees falling on structures
were generally confined to Spokane and Coeur D'Alene areas (
Table 2). The fact that the ground was wet and soft from recent rain and
snow along the Spokane River Valley likely aided in producing the large number
of downed trees and power lines.
Table 1 - Maximum
Surface Wind Speeds across KOTX CWA
Values in red meet high wind criteria
|
Observations |
Maximum Wind Speed (kts)
|
Time (UTC) |
WA
Zone 32/ ID Zone 26 |
|
|
Lewiston (LWS) |
40 Gust to 45
|
2153 |
Lewiston (LWS) |
32 Gust to 56 |
2235 |
WA
Zone 33/ ID Zone 03
|
|
|
Pullman (PUW) |
31 Gust to 54 |
2356 |
WA
Zone 34 |
|
|
Ephrata (EPH) |
46 Gust to 63
|
1856 |
WA
Zone 36/ ID Zone 02
|
|
|
Spokane (GEG) |
39 Gust to 47 |
1956 |
Spokane (GEG) |
31 Gust to 53 |
2135 |
Spokane (SFF) |
26 Gust to 63
|
2045 |
Otis Orchards (spotter) |
Gust to 73
|
2012 |
Coeur D'Alene (COE) |
38 Gust to 61
|
2115 |
Foss Maritime (north side
of Lake Coeur D'Alene) |
Gust to 67 mph
|
2235 |
WA
Zone 37
|
|
|
Deer Park (DEW) |
31 Gust to 48 |
2053 |
WA
Zone 38
|
|
|
Nespelem (RAWS) |
25 Gust to 45 mph |
2054 |
WA
Zone 42 |
|
|
Washington Pass (RAWS) |
26 Gust to 55 |
1957 |
Douglas Ingram (RAWS) |
17 Gust to 35 |
2030 |
Leecher (RAWS) |
20 Gust to 48 |
1954 |
NCSB (RAWS) |
33 |
2058 |
First Butte (RAWS) |
16 Gust to 34 |
1856 |
WA
Zone 43
|
|
|
Kramer (RAWS) |
21 Gust to 37 mph |
2056 |
WA
Zone 43
|
|
|
Douglas (RAWS) |
26 Gust to 44 mph |
2040 |
ID
Zone 04
|
|
|
Mullan Pass (MLP) |
Gust to 46 mph |
0108 |
Other
Observations |
|
|
Rattlesnake Ridge |
82 Gust to 97
mph |
2335 |
Grey Back (RAWS) |
Gust to 79 mph
|
1911 |
Sedge Ridge (RAWS) |
Gust to 95 mph
|
1721 |
Hanford (HMS) |
41 Gust to 64
mph |
2356 |
Table 2 - Reports
of Wind Damage across KOTX CWA
Damage reports were not received in counties not included
|
Location of Damage
|
Damage type |
Approximate Time
|
WA
Zone 32/ ID Zone 27 |
|
|
Lewiston/Clarkston Vicinity
|
A few downed trees and breif
power outages. |
Late Afternoon |
WA
Zone 33/ ID Zone 03 |
|
|
Whitman County |
Many trees and Power lines
downed.
A few blocked roads due to debris.
Power outages of at least 10 hours. |
Late Afternoon |
WA
Zone 34 |
|
|
Grant County |
Entire roof blown off a mobile
home near Ephrata.
Trees and Power Lines downed.
|
Late morning into early afternoon.
|
WA
Zone 35 |
|
|
Adams County |
Parts of roofs blown off
buildings, mainly northeast sections of Adams County.
|
Late afternoon into early
evening. |
Lincoln County |
Shingles blown off roofs.
Metal roofs partially blown off barns and other structures.
|
Late morning into early afternoon.
|
WA
Zone 36/ID Zone 02 |
|
|
Spokane &
Coeur D'Alene |
Parts of roofs blown off
buildings.
Business signs blown apart.
Many traffic light poles were turned and caused to be facing the wrong
direction.
Numerous trees down, 2 known large trees blown onto homes. Numerous power
lines down.
Power outages impacted over 8000 people, some for over 12 hours.
Roads blocked by debris, as many as 12 intersections at one time.
|
Noon into mid afternoon.
|
WA
Zone 37 |
|
|
Deer Park and vicinity |
A few trees downed into power
lines.
|
Noon into mid afternoon.
|
|
|
Webmaster
US Dept of Commerce
National Oceanic and Atmospheric Administration
National Weather Service
Spokane Weather Forecast Office
2601 N. Rambo Rd.
Spokane, Washington 99224
Tel: (509) 244-0110
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