General Storm Data
Minimum Pressures and Peak Gradients
Table 1, below, lists the lowet barometric pressures achieved
during the January 16, 2000 storm for 11 Pacific Northwest locations. This
storm had a strong double-dip signature at most of these stations. For many
inland stations, the first dip, which appears to have been from the cyclone's
leading front, was the strongest. For most of the coastal stations, the
second dip, which appears to be the time of the low center's closest approach,
was the sharpest, leading to apparent time disparities in the data. For
Bellingham, the two dips had the same magnitude, and the earliest occurrence
is noted below--the station also reported 29.49" in the hours 12:00
to 14:00. The pressure minimum times for Arcata -> North Bend -> Medford
-> Eugene -> Salem -> Portland -> Seattle -> Bellingham mark
the arrival times of the leading front fairly well, and the pressure minimum
times for Astoria -> Olympia -> Quillayute mark the closest-approach
times for the low center. Note the 01:00 minimum pressure at Eugene, and
the position of the leading front in the satellite picture shown in Figure
2, above.
Some of the lowest pressures on or near land occurred along the Western
Washington coast, with Buoy 46029 near the Columbia River Bar reporting
29.10" (985.5 mb), Buoy 46041 near Cape Elizabeth 29.08" (984.8
mb) at 12:00 HRS PST, DESW1 Destruction Island 29.13" (986.3 mb) at
12:00 and TTIW1 Tatoosh Island 29.15" (987.2 mb) at 14:00.
Source: Pressure data is from the National Climatic Data Center,
Unedited Surface Observation Forms (Arcata), University of Washington archived surface observations (most stations), and the National Data
Buoy Center historical meteorological data (North Bend CARO3 C-MAN station
used in place of OTH). |
Location |
Lowest
Pressure
"Hg |
Time of Lowest Pressure
PST |
California: |
|
|
Arcata |
29.51" |
22:00 HRS, 15th |
Oregon: |
|
|
North Bend |
29.38" |
00:00 HRS, 16th |
Astoria |
29.32" |
07:00 HRS, 16th |
Medford |
29.45" |
00:00 HRS, 16th |
Eugene |
29.41" |
01:00 HRS, 16th |
Salem |
29.42" |
02:00 HRS, 16th |
Portland |
29.44" |
03:00 HRS, 16th |
Washington: |
|
|
Quillayute |
29.20" |
13:00 HRS, 16th |
Olympia |
29.43" |
11:00 HRS, 16th |
Seattle (Sea-Tac) |
29.43" |
05:00 HRS, 16th |
Bellingham |
29.49" |
06:00 HRS, 16th |
|
|
|
AVERAGE |
29.41" |
|
|
Table 2, below, lists the maximum pressure gradients achieved
during the January 16, 2000 storm for 10 Pacific Northwest measures. In
a long-standing ASOS tradition, reporting of sea-level pressure became spotty
right at the critical maximum gradient times for a number of measures. Astoria
stopped reporting all data after 11:00 in what appears to be a system failure
(maybe due to power outage) that reached beyond the station, for the Columbia
River Buoy also quit reporting during the same hour. Quillayute's weather
robot decided that reporting barometric pressure wasn't necessary during
the first two hours of critical pressure rise as the storm passed to the
north. Thus, maximum gradients using these stations are the highest from
the available data--they may have been higher, for pressure "blackouts"
occurred right near peak gradients times. It is no small thing that sea-level
pressure was rarely missed back in the good old days when weather monitoring
was done by humans and surface observation forms were filled by hand. The
ASOS situation has shown no signs of improvement as of the writing of this
paragraph (01-2003).
Some of the coastal gradients are decent, but none are records. Many
windstorms have exceeded the +23.8 mb (+0.70") OTH-UIL reading. Inland,
he EUG-PDX value of +6.5 mb (+0.19") was short of the +8.0 to +10.0
mb (+0.23" to +0.30") that is usually required for destructive
winds in the Willamette Valley. The PDX-SEA value of +7.4 mb (+0.22")
is similarly short, as is the SEA-BLI reading of +6.3 mb (+0.19").
The PDX-BLI gradient was +12.5 mb (+0.37") at 16:00 HRS, again a bit
short for a truly damaging gale.
Source: Pressure data is from the National Climatic Data Center,
Unedited Surface Observation Forms (Arcata), University of Washington archived surface observations (most stations), and the National Data
Buoy Center historical meteorological data (North Bend CARO3 C-MAN station
used in place of OTH). |
Location |
Max Gradient hPa |
Time of Max Gradient
PST |
Coast: |
|
|
ACV-OTH |
11.8 |
06:00 HRS, 16th |
OTH-AST [1] |
13.7 |
11:00 HRS, 16th |
AST-UIL [2] |
11.8 |
14:00 HRS, 16th |
ACV-AST [1] |
21.6 |
10:00 HRS, 16th |
OTH-UIL [3] |
23.8 |
14:00 HRS, 16th |
Interior: |
|
|
MDF-EUG |
11.8 |
14:00 HRS, 16th |
EUG-PDX |
6.5 |
11:00 HRS, 16th |
PDX-SEA |
7.4 |
13:00 HRS, 16th |
SEA-BLI |
6.3 |
19:00 HRS, 16th |
AST-DLS |
-12.9 |
10:00 HRS, 16th |
|
Table 2 Notes:
[1] AST pressure data missing near the peak gradient period. The listed
value could be low.
[2] AST and UIL pressure data missing near the peak gradient period.
The listed value could be low.
[3] UIL pressure data missing near the peak gradient period. The listed
value could be low. |
Pressure Tendencies
Table 3, below, lists the maximum hourly pressure falls
and rises achieved during the January 16, 2000 storm for 11 Pacific Northwest
stations. Nothing particularly unusual here. Peak hourly falls of -2.1 to
-3.1 mb (-0.06" to -0.09") and climbs of +2.3 to +3.4 mb (+0.07"
to +0.10") are fairly standard for big storms in the Pacific Northwest.
This cyclone had much weaker tendencies than many windstorms on record for
the region.
Welcome to the Information Age, era of twitchy machines. Peak gusts reached
66 mph at Astoria by 10:00 HRS PST, and peak sustained winds 35 mph at 11:00.
Then the station stopped reporting, which resulted in the storm's pressure
climbout phase being unrecorded. Astoria did not go back online until 14:00
on January 17th. Quillayute stopped reporting pressure from 15:00 to 16:00,
a critical time period when the barometer jumped 10.0 mb (0.30") in
a three-hour span that could have contained a higher value than the +3.4
mb (+0.10") at 18:00. Olympia did not report pressure for four consecutive
observation periods from 12:00 to 15:00, which is the time period of initial
climbout, though, in looking at the late maximum barometric rise at Sea-Tac,
the +2.8 mb (+0.08") at 18:00 for Olympia is probably the correct maximum
value.
Source: all pressure data is calculated from hourly readings obtained
from the National Climatic Data Center, unedited surface observation
forms. |
Maximum Pressure Tendencies for the January 15-16, 2000
Storm |
Location |
Max
Hrly
Fall
hPa |
Time of
Max Fall
PST |
Max
Hrly
Rise
hPa |
Time of
Max Rise
PST |
California: |
|
|
|
|
Arcata |
-2.1 |
14:00 HRS, 15th |
+2.8 |
07:00 HRS, 16th |
Oregon: |
|
|
|
|
North Bend [1] |
-2.5 |
22:00 HRS, 15th |
+3.0 |
07:00 HRS, 16th |
Astoria [2] |
-3.1 |
02:00 HRS, 16th |
MM |
MM |
Medford |
-3.0 |
00:00 HRS, 16th |
+3.2 |
08:00 HRS, 16th |
Eugene |
-3.9 |
01:00 HRS, 16th |
+3.3 |
11:00 HRS, 16th |
Salem |
-2.6 |
01:00 HRS, 16th |
+2.7 |
13:00 HRS, 16th |
Portland |
-2.5 |
02:00 HRS, 16th |
+2.3 |
18:00 HRS, 16th |
Washington: |
|
|
|
|
Quillayute [3] |
-3.0 |
01:00 HRS, 16th |
+3.4 |
18:00 HRS, 16th |
Olympia [4] |
-2.1 |
01:00 HRS, 16th |
+2.8 |
18:00 HRS, 16th |
Seattle (Sea-Tac) |
-2.4 |
02:00 HRS, 16th |
+2.7 |
19:00 HRS, 16th |
Bellingham |
-2.3 |
04:00 HRS, 16th |
+2.6 |
20:00 HRS, 16th |
|
|
|
|
|
AVERAGE [5] |
-2.7 |
|
+2.9 |
|
|
Table 3 Notes:
Also see the above discussion.
[1] The -2.5 mb hourly fall is the last of two occurrences.
[2] Astoria stopped reporting after 11:00 HRS PST, just after pressures
started to climb.
[3] Quillayute didn't report sea-level pressure from 15:00-16:00, the
time of initial pressure climb.
[4] Olympia didn't report sea-level pressure from 12:00-15:00, the time
of initial pressure climb.
[5] Average rise assumes an estimated maximum climb of +3.0 mb at Astoria. |
Peak Wind and Gust
Table 4, below, lists the peak wind and gust for eleven
key stations in the Pacific Northwest, their direction, and their time of
occurrence. "Peak Wind" is a 2-minute average, and "Peak
Gust" is a 5-second average. By my own personal methodology, a wind
event rates the term "windstorm" when the average peak gust of
these eleven stations reaches 39.0 mph (gale force) or higher. This ranking
favors those storms that follow a northward path close to the U.S. Pacific
Coast, and for good reason--such storms affect the largest land area, and
therefore are potentially the most destructive. The January 16, 2000 cyclone
followed such a path, with damaging winds striking many points along the
way.
With an average peak of 52.5 mph, the January 16, 2000 event ranked as
a high-end moderate windstorm. Moderate windstorms have an average of 45.0
to 54.9, and major windstorms are those that reach or exceed 55.0. Only
a handfull of storms have made the majors, including December 12, 1995 with
60.5, November 14, 1981 with 65.9 and October 12, 1962 with 80.5. It should
be noted, however, that the peak gust measure for the earlier storms was
different. Peak instant gust was noted up to about 1995, with the
December 1995 storm's average containing a mixture of intant gusts at some
stations and the new ASOS 5-second peak. ASOS hadn't been fully implemented
in the Pacific Northwest by December 1995--that took until mid-1996.
Peak gusts recorded during the January 16, 2000 storm are all 5-second averages. There is a difference between peak instant gust of the
past and the 5-second peak of the modern era. A 5-second average could contain
a peak intant reading that is significantly higher--maybe even by a factor
of 1.2 (20%), depending on the amount of turbulence at the site. Multiplying
the 52.5 average peak gust for the January 16, 2000 storm by 1.2 yileds
63.0, which would put the 2000 storm deeply into the major windstorm category.
The disparity probably is not this strong--an adjustment of 1.05 to 1.10
(5 to 10%) is probably more realistic, as airport-based anemometers tend
to be subjected to fairly steady winds due to their typically good exposures.
These lower adjustments would put the January 16, 2000 storm in the range
of 55.0 to 58.0 for comparison to events like the Columbus Day Storm and
November 14, 1981. December 1995 is more tricky, due to the mix of measures--it is
probably in the range of 62.0 to 65.0 when adjusted for the difference in
peak gust measure.
In the Willamette Valley, the January 16, 2000 windstorm struck the Portland
and Salem area fairly hard, while barely reaching gale-force at Eugene.
The trend toward higher gusts northward in the Willamette Valley is a fairly
typical one for classic-path windstorms, but the disparity usually is not as
strong as seen during the 2000 storm. Often the difference between Salem
and Eugene is about 5 to 10 mph, not a whopping 21. With Corvallis showing
a peak of 44 mph, it seems that much of the South Valley was spared the
heavy gusts seen in the north.
The Seattle area stations, including Boeing Field, Renton, the University
of Washington, and West Point, received gusts between 52 and 57 mph, fairly intense for the region. This puts the January 16, 2000 storm slighty
above the 48 to 56 mph gusts recorded during the more recent December 27,
2002 storm.
Sources: National Climatic Data Center, undedited surface observation
forms. |
Location |
Peak
Wind
mph |
Direction
Pk Wnd
degrees |
Obs Time of
Peak Wind
PST |
Peak
Gust
mph |
Direction
Pk Gst
degrees |
Obs Time of
Peak Gust
PST |
California: |
|
|
|
|
|
|
Arcata |
29 |
200º |
23:48 HRS, 15th |
47 |
130º |
21:20 HRS, 15th |
Oregon: |
|
|
|
|
|
|
North Bend |
39 |
180º |
05:55 HRS, 16th |
51 |
180º |
05:55 HRS, 16th |
Astoria [1] |
35 |
180º |
10:56 HRS, 16th |
66 |
170º |
10:09 HRS, 16th |
Medford |
21 |
210º |
06:56 HRS, 16th |
39 |
210º |
06:56 HRS, 16th |
Eugene |
29 |
170º |
06:56 HRS, 16th |
39 |
170º |
08:14 HRS, 16th |
Salem |
36 |
160º |
08:56 HRS, 16th |
60 |
160º |
08:11 HRS, 16th |
Portland |
37 |
180º |
09:55 HRS, 16th |
59 |
190º |
10:14 HRS, 16th |
Washington: |
|
|
|
|
|
|
Quillayute [2] |
29 |
180º |
13:49 HRS, 16th |
45 |
210º |
17:13 HRS, 16th |
Olympia [3] |
30 |
170º |
11:56 HRS, 16th |
54 |
160º |
10:44 HRS, 16th |
Sea-Tac |
36 |
200º |
14:56 HRS, 16th |
52 |
200º |
14:36 HRS, 16th |
Bellingham |
47 |
160º |
15:53 HRS, 16th |
66 |
170º |
15:54 HRS, 16th |
|
|
|
|
|
|
|
AVERAGE |
33.4 |
181º |
|
52.5 |
177º |
|
Table 4 Notes:
[1] Highest wind and gust at Astoria before station stopped reporting
after 11:00.
[2] No reports from Quillayute from 15:00-16:00.
[3] An apparent power failure stopped peak wind (PK WND) reports from 12:00
to 15:00, wind and gust still noted. |
|