The December 15, 1977 Windstorm

compiled by

Wolf Read



In the late night of December 14th and into the morning of the 15th, 1977, strong winds pulled through Northwest California, across much of Oregon and into Southwest Washington as an intense low moved ashore near Hoquiam and into the Puget Lowlands. Based on pressure observations at Hoquiam, this cyclone had a central pressure of at least 982 mb at landfall--a fairly powerful storm. The low appears to have been deepening all the way to landfall: at 17:00 on the 14th, buoy 46002, some 300 miles off of Southwest Oregon, showed a pressure of 988.7 mb (a strong pressure surge of 8.5 mb/hr one-hour after this minimum indicates that the low center passed very close to this station), and buoy 46005, about 300 miles off of Southwest Washington, showed 985.0 mb at 22:00 on the same day. Despite the storm's strength, most interior sections were spared high wind criteria gusts (58 mph or more)--the coast was reserved for this special treatment.

This cyclone brought with it thunderstorms. Weather observers at Arcata, Brookings, Sexton Summit (with snow!) and Roseburg all noted lightning during the nighttime hours.

Though Washington was generally spared the strong wind assault that befell Oregon, a different attack struck the Puget Sound area: record high tides [1]. As the cyclone swept inland, minimum barometric pressure coincided with high tide in the Sound region.The combination left the Puget Sound deeper than any previous record at some tide gauges, including a 14.8 foot maximum in Elliott Bay (14.6 feet was the old record from December 5, 1967) and 15.7 feet in Poulsbo's Liberty Bay (old record 15.5 feet). Damage to waterfront property, which included flooded buildings, basements and broken seawalls, occurred from Olympia to Comano Island.


General Storm Data

Table 1, below, lists the barometric minimums for the December 15, 1977 storm at selected sites. Barometers over Northwest Oregon and Western Washington indicated quite low readings, but a number of Pacific Northwest windstorms have produced lower values. Of interest is the long period of time that barometers stayed around their minimums, as indicated in the notes section. This is a reflection of not only a fairly broad low, but also one that moved fairly slowly. The unusually high tides were likely exacerbated by the long period of low pressure over Washington.

Source: Hourly data are from the National Climatic Data Center, unedited surface observation forms.


Location

Lowest
Pressure

Approx Time
of Lowest Pressure

California:    
Arcata

29.60"

21:00 HRS, 14th

Oregon:    
North Bend

29.31"

01:00 HRS, 15th

Astoria

29.00"

07:00 HRS, 15th

Medford [1]

29.41"

23:00 HRS, 14th

Eugene [2]

29.26"

04:00 HRS, 15th

Salem [3]

29.16"

05:00 HRS, 15th

Portland

29.14"

06:00 HRS, 15th

Washington:    
Quillayute [4]

29.04"

08:00 HRS, 15th

Olympia

29.06"

08:00 HRS, 15th

Sea-Tac [5]

29.09"

09:00 HRS, 15th

Bellingham [6]

29.10"

08:00 HRS, 15th

     
AVERAGE

29.20"

 

Table 1 Notes:

[1] Last of two hourly reports in a row with the same reading.

[2] Last of two hourly reports in a row with the same reading.

[3] Last of two hourly reports in a row with the same reading.

[4] Last of two hourly reports in a row with the same reading.

[5] Last of three hourly reports in a row with the same reading.

[6] Last of three hourly reports in a row with the same reading.


Table 2, below, lists the maximum gradients for some standard measures during the December 15, 1977 cyclone. Gradients south of the low's track were quite strong. Double-digit measures (ahead of the decimal) for EUG-PDX and PDX-SEA are rare, and quite respectable. Any measure of +30.0 mb (+0.89") or higher is major. This storm was definitely not lacking in the extreme gradient department!

Source: Hourly data are from the National Climatic Data Center, unedited surface observation forms.


Location

Max Gradient, mb

Approx Time
of Max Gradient

Coast:    
ACV-OTH

+13.5

01:00 HRS, 15th

OTH-AST

+21.2

08:00 HRS, 15th

AST-UIL [1]

+7.9

16:00 HRS, 15th

ACV-AST

+30.0

08:00 HRS, 15th

OTH-UIL

+21.8

09:00 HRS, 15th

Interior:    
MFR-EUG

+10.0

04:00 HRS, 15th

EUG-PDX

+10.3

13:00 HRS, 15th

PDX-SEA [2]

+12.3

17:00 HRS, 15th

SEA-BLI [3]

+3.3

19:00 HRS, 15th

AST-DLS [4]

-7.1

08:00 HRS, 15th

Table 2 Notes:

[1] Max negative gradient -1.9 mb at 01:00 on the 15th.

[2] Max negative gradient -1.1 mb at 23:00 on the 14th.

[3] Max negative gradient -1.8 mb at 05:00 on the 15th.

[4] Max positive gradient +4.5 mb at 16:00 on the 15th.


A key measure for storms that track across the Olympic Peninsula and/or South Vancouver Island is the PDX-BLI gradient. Though the December 15, 1977 storm came in just south of the Olympics, I've included it in Table 3, below. The 1977 windstorm ranks about 11th on this incomplete table.

Sources: National Weather Service, Eureka, Portland and Seattle offices, METAR reports, and the National Climatic Data Center, unedited surface observation forms (for historical storm pressure data).


PDX-BLI Gradients For Big Storms in History

Storm

Peak Grad, mb

Time/Day

Oct 21, 1934

+22.7

15:00 HRS, 21st

Dec 12, 1995

+22.0

21:00 HRS, 12th

Jan 20, 1993

+21.5

11:00 HRS, 20th

Nov 24, 1983

+17.8

14:00 HRS, 24th

Oct 12, 1962

+17.7

00:00 HRS, 13th

Nov 13-14, 1981

+17.0

11:00 HRS, 14th

Jan 16-17, 1986

+16.9

23:00 HRS, 16th

Mar 25-26, 1971

+15.1

12:00 HRS, 26th

Feb 12-13, 1979

+15.0

05:00 HRS, 13th

Jan 19-20, 1964

+14.3

17:00 HRS, 19th

Dec 14-15, 1977

+14.0

17:00 HRS, 15th

Oct 26-27, 1950

+13.8

04:00 HRS, 27th

Dec 22, 1955

+13.2

15:00 HRS, 22nd

Dec 27, 2002

+12.1

11:00 HRS, 27th

Nov 15, 1981

+12.1

17:00 HRS, 15th

Apr 13-14, 1957

+11.3

18:00 HRS, 14th

Dec 21, 1955

+10.2

20:00 HRS, 21st


Pressure Tendencies

The December 15, 1977 windstorm brought with it a decent "pressure couplet" over much of Western Oregon and Washington. Strong pressure surges (+3.0 mb and higher) were occurred from about North Bend to Salem and northward. Table 4, below, shows the maximum hourly changes in pressure for eleven key stations in the Pacific Northwest.

Though this storm made barometers move with some vigor, these values are representative of the typical results from a good high-wind generating cyclone. No records were broken on December 14-15, 1977. This doesn't mean the numbers are weak--they just don't stand out against the major storms of history, such as Columbus Day 1962.

Of interest is a double pressure surge that showed up at a number of stations, after the low had passed. Figure 1, below the table, plots hourly pressure tendency in millibars against the hourly pressure readings in inches for Salem, OR. The two spikes in the hourly pressure tendency show up well. Apparently, the first surge marked the passage of a moderately-defined cold front where temeprature and dew point fell about 5 and 10 degrees F respectively, and the second surge the passage of the upper trough, or, likely for places a bit further north, a strong bent-back occlusion in association with the upper trough. A similar plot for Astoria is provided in Figure 2, below. For Astoria, the second surge was the strongest, and at +5.8 mb/hr (0.17"), is noteworthy. West gusts in excess of 70 mph accompanied that strong pressure jump--the mark of an intense bent-back occlusion.

Source: Microfilm copies of the unedited surface observation forms, obtained from the National Climatic Data Center.


Maximum Pressure Tendencies for the December 15, 1977 Storm

Location

Max
Hrly
Fall
mb

Time of
Max Fall
PST

Max
Hrly
Rise
mb

Time of
Max Rise
PST

California:        
Arcata [1]

-2.4

13:00 HRS, 14th

+2.1

00:00 HRS, 15th

Oregon:        
North Bend

-2.7

21:00 HRS, 14th

+3.1

04:00 HRS, 15th

Astoria

-2.6

22:00 HRS, 14th

+5.8

14:00 HRS, 15th

Medford

-2.4

22:00 HRS, 14th

+2.1

01:00 HRS, 15th

Eugene

-2.7

21:00 HRS, 14th

+2.6

14:00 HRS, 15th

Salem

-2.3

23:00 HRS, 14th

+3.4

14:00 HRS, 15th

Portland [2]

-2.5

23:00 HRS, 14th

+3.4

15:00 HRS, 15th

Washington:        
Quillayute

-2.1

00:00 HRS, 15th

+2.8

15:00 HRS, 15th

Olympia

-2.0

23:00 HRS, 14th

+4.2

17:00 HRS, 15th

Seattle (Sea-Tac)

-2.2

23:00 HRS, 14th

+3.0

19:00 HRS, 15th

Bellingham

-2.0

01:00 HRS, 15th

+3.0

20:00 HRS, 15th

         
AVERAGE

-2.5

 

+3.2

 





Table 4 Notes:

[1] The -2.4 mb hourly fall at Artcata is the last of two occurrences, the other instance having occurred at 12:00.

[2] The +3.4 mb hourly rise at Portland is the last of two occurrences, the other instance having occurred at 09:00. See text above for more details on this double pressure surge.


Table 5, 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 1-minute average, and "Peak Gust" is an instant reading. 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. The December 15, 1977 windstorm surpassed this threshold, and just made it into moderate windstorm category. Moderate windstorms have an average of 45.0 to 54.9, and major windstorms are those that reach or exceed 55.0. Only a handful of storms have made the majors, including December 12, 1995, November 14, 1981 and October 12, 1962.

Of interest was the particularly strong winds associated with the cyclone's bent-back occlusion, as indicated by the major west winds at Astoria. With the bent-back trailing the low, this explains the much later timing of peak winds at Astoria when compared to other Oregon stations. Hoquiam also felt the bent-back occlusion, with maximum winds of west 32 mph gusting 45 at 15:55 on the 15th, with a peak gust of 49 at 15:35. Arguably, Sea-Tac was also pounced by the bent-back, with the late arrival of the winds in that region, though they lacked the strong westerly component seen at Hoquiam and Astoria.

Source: Hourly data are from the National Climatic Data Center, unedited 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

25

220

21:27 HRS, 14th

39

230

22:21 HRS, 14th

Oregon:            
North Bend

31

240

03:55 HRS, 15th

60

210

03:08 HRS, 15th

Astoria

39

270

13:55 HRS, 15th

74

270

13:23 HRS, 15th

Medford

32

220

00:15 HRS, 15th

47

220

00:27 HRS, 15th

Eugene

32

220

05:55 HRS, 15th

48

210

06:02 HRS, 15th

Salem [1]

29

170

11:55 HRS, 15th

47

170

10:17 HRS, 15th

Portland

35

210

07:55 HRS, 15th

56

200

06:33 HRS, 15th

Washington:            
Quillayute

18

280

18:56 HRS, 15th

33

280

14:41 HRS, 15th

Olympia [2]

25

180

13:55 HRS, 15th

38

180

10:09 HRS, 15th

Sea-Tac

35

200

19:29 HRS, 15th

48

210

19:32 HRS, 15th

Bellingham [3]

15

200

22:53 HRS, 15th

19

200

22:53 HRS, 15th

             
AVERAGE

28.7

219

 

46.3

216

 

Table 5 Notes:

[1] Peak wind is last of three occurrences, with the other two happening at 04:55 and 10:55 on the 15th.

[2] Peak gust is the last of two occurrences, with the other happening at 09:44 PST.

[3] Peak wind is last of two occurrences, with the other happening at 12:58 out of 180 degrees. Peak gust estimated from peak wind via a standard 1.3 gust factor.


References

[1] High tide reported in NCDC's Storm Data publication for December 1977.


Last Modified: February 26, 2004
Page Created: February 23, 2004

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