The Windstorm of January 5-6, 1986

January 5-6, 1986 Level 8.4 Windstorm Data

Gust Velocity

# Times Occurred

Gust Level

47 mph



46 mph



45 mph



44 mph



43 mph



42 mph



41 mph



40 mph



39 mph



38 mph



37 mph



36 mph



35 mph



34 mph



33 mph



32 mph



31 mph



30 mph






Other Stats at a Glance (For Study Site)

Lowest Pressure

Avg Peak Above 29 mph

# Trees W/Major Damage


32.89 mph



This storm was completely monitored. The first large gusts, reaching 32 mph, happened right about 19:00 HRS on the 5th, with a quick escalation to 42 mph by 19:32 HRS, and reaching the peak velocity by 23:16 HRS. Gusts above 30 mph occurred until about 00:20 HRS on the 6th, with gusty 20-29 mph winds continuing all the way until 04:00 HRS. The National Weather Service reported that winds reached 120 mph at the 4,000' level over Western Washington.

The January 5-6, 1986 windstorm caught me by surprise, mainly because it didn't produce very sharp minimums in surface pressure. The central pressure of the low was around 994 mb as it neared Washington. However, as the low center was small, and it passed close to Cape Flattery, there was enough of a south-north gradient to kick up gale-force winds across Western Washington and Oregon. This kind of trend continued with the following blows--steep gradients but not-so-deep central pressures, certainly not deep when compared with the big windstorms. (Eventually, I'll graph out the surface pressure gradients for some of these storms, most probably the January 16-17 event, as a visual explanation of some of what triggers our high wind events.) This windstorm produced at least 18 brownouts at my location. My various weather record books include:

Journal Records:

January 7, 1986: Tuesday

5:40 AM: A windstorm hit for 5.25 hours early yesterday. It was as strong as the Thanksgiving windstorm of 1983. The peak gust, was again, 47 mph here (on the high side; Tacoma: 48, Everett: 44, Bellingham: 46, Bangor: 51). Tree damage was moderate and widespread. Right now I have counted 5 trees down, two with their tops off, and one maple lost a huge portion of its tip. No trees were lost in The Forest, two dead ones fell in Eric's Forest. A full report is still being compiled.

Weather Log Records:

January 5, 1986: Sunday

[This is what I could extract from very chaotic notes.]

7:15 PM: Strong winds have begun. Gusting to 30 mph.

7:32 PM: 29.78" steady. Wind gusting to 33 mph.

7PM Local Reports:
Everett--S18-28 knots
Tacoma--19-25 knots
Olympia--17-31 knots
Sea-Tac--29.72" falling slowly, 0.48" rain

7PM Marine Reports:
Hood Canal--30-40 knots
Bangor--44 knots
Alki Point--Gusting 38 knots
Astoria--Gusting 38 knots
Smith Island--Gusting 42 knots
Race Rocks--40-48 knots

7PM Pressure Readings:
SeaTac--1007 mb, Bellingham--1003 mb, Forks--999 mb,
Astoria--1013 mb, North Bend--1023 mb

8PM Local Reports:
Bellingham--Gusting 28 knots
Everett--Gusting 36 knots
Bremorton--Gusting 25 knots
Tacoma--Gusting 28 knots
Olympia--Gusting 16 knots
Sea-Tac--Gusting 32 knots, 29.76" rising

~8:00 PM: Weather radio alarm: Inland waters 25-40 knots, Strait of Juan de Fuca 30-45 knots, Coast 30-45 knots. Wind warning for land areas 20-35 mph WGT 45 mph. Winds gusting to 34 mph here.

9PM Local Reports:
Bellingham--25-35 knots
Everett--25-38 knots
Tacoma--28 knots
Olympia--16-20 knots
Sea-Tac--20-30 knots, 29.80" rising

10:00 PM: 29.86" rising rapidly. Winds gustin to 40 mph.

10:47 PM: Blackout for 3 seconds. Winds gusting to 38 mph.

10PM Local Reports:
Tacoma--30-42 knots
Olympia--Gusting 22 knots
Sea-Tac--Gusting 30 knots
Evergreen Pt. Floating Bridge--Gusting 45 knots

10PM Marine Reports:
Alki Point--Gusting 43 knots
Forks--Gusting to 35 knots

11:15 PM: Peak gust 47 mph.

11:16 PM: 29.90" rising. Gusting to 41 mph.

11:23 PM: Two transformer flashes! Gusting to 43 mph.

11:30 PM: Winds dimishing off south coast. Winds gusting to 43 mph here.

January 6, 1986: Monday

12:16 AM: 29.98" rising rapidly. Wind gusting to 39 mph.

12:20 AM: Weaking of wind noticable. Gusting to 30 mph.

12:30 AM: Stong winds appear to be finished. No 30 mph+ gusts.

4:00 AM: 30.22" rising

5:00 AM: 30.30" rising

Using a sample from the above weather logs, I'll take a quick look at pressure gradients. At 19:00 HRS, when the winds began to pick up across Western Washington and Oregon, the pressure at Forks was 999 mb, while far to the south, at North Bend, it was 1023 mb, making for a south to north difference of 24 mb. This is major. The Columbus Day Storm of 1962 produced a gradient of about 30 mb, and S to N gradients as low as 9-12 mb can produce strong winds, provided other conditions, such as a having a failry progressive storm, are favorable. The south to north axis of pressure is significant. This is the orientation of the West Coast mountain ranges. These mountains act as a sort of "mega-funnel" for winds flowing along the S to N axis. Basically, wind has a tendency to "follow the gradient" in a storm out to sea, where there aren't very large barriers to airflow. "Following the gradient" means that the wind generally moves along, or follows, areas of equal pressure. These areas of equal pressure are often drawn as roughly circular lines, or isobars, around the low pressure center, and are typically delineated in millibars. The airflow does have a slight curvature inward toward the low pressure center, but this is minor. When a low nears shore, the isohyets start cutting across mountain ranges, and the airflow following the isobars is impeded by the terrain. The restricted airmass then tends to follow the path of least resistance, which is down the S to N trending valleys and coastal strip toward the region of lower pressure. If a hypothetical low moves ashore along the Olympic Peninsula of Washington, the isobars will be nearly perpindicular to the mountain ranges south of the center. Airflow, in response to the imbalance created by the lower pressure to the north, will flow northward though the valleys. In essence, this airflow is moving 90º from the typical path of wind in a storm out to sea. The air is flowing across the gradient lines. This is called "jumping the gradient." In addition to producing SE to SW winds at the surface, when air jumps the gradient, it can have some influence on incoming cyclones. The airflow down the valleys, which draws from higher pressure fields to the south, is itself a developing tongue of high pressure at the surface. This zone of high pressure often shoots northward at enough of a clip to act as a block to the storm, and force a northward curvature to the low. This is partly explains why deep lows have a tendency to curve northward as they near shore, and then follow a track that is roughly parallel the coastline.

Examination of the January 5-6, 1986 Tree Damage

My final tally of tree loss for the study site is as follows: One living birch, Betula papyrifera, uprooted, and another partially uprooted. There were 9 trees snapped: three living alders (Alnus rubra), one thick Pacific madrona (Arbutus menzesii), one living bigleaf maple (Acer macrophyllum), one living birch (B. papyrifera), and 3 unidentified, but probably small, dead specimens (like the two noted down in Eric's Forest in the journal entry above). Six trees also lost their tops: four living alders (Alnus rubra), one dead alder, and one living bigleaf maple. Not all these trees I listed fell in the study site loctions, which is why the total listed in the stats above is different from the count of 17 listed in this paragraph. Most of the damage in the study sites is listed below, save for the two dead trees that broke in Eric's Forest.

It is noteworthy that no conifer trees were found with major damage from this windstorm (any would have been noted, and thus can be ruled out of being in the unidentified category), a reflection of their apparently greater resilience to gale force gusts in the 35-45 mph range over that of angiosperm varieties of trees. There is some record, however, of Douglas-firs losing large limbs, so this resilience is definitely being challenged at 35-45 mph wind speeds (in gusts). It is also noteworthy that there were hundreds, if not thousands, of trees in these woodlots that did not suffer much damage at all. It is likely that many of the trees that suffered probably had various kinds of weakness that made them more susceptable to the winds of this storm. Here are the ones I measured in detail (woodlots not listed escaped heavy damage from this storm):

Eric's Forest

Specimen #: 05JAN1986001
Location: East Side
Species: Red Alder, Alnus rubra
Damage: Top Snapped Off
Circumference: 14.5"
Diameter: N/A
Break Height: Over 20' (Est.)

Field Description: The top landed in Eric's Creek. Appeared healthy.

Conclusion: No clear reason for this tree to break when others of same species and in same area did not.

--- --- ---

Southern Woodlot

Specimen #: 05JAN1986002
Location: West Side
Species: Red Alder, Alnus rubra
Damage: Top Snapped Off
Circumference: 16.5"
Diameter: 5.25"
Break Height: 16-18' (Est.)

Field Description: The top is about 16' tall itself and has snapped in two upon hitting the ground. The longest section of the top is propped up by a hazelnut bush (Corylus cornata). The top proves to be dead, but it has not rotted yet, so is therefore still very strong; after repeated attempts kicking it, I gave up without so much as cracking it. The rest of the tree is still alive and green (or gray).

Conclusion: Tree most likely broke due to having a dead portion.


Specimen #: 05JAN1986003
Location: Extreme West Side
Species: Red Alder, Alnus rubra
Damage: Top Snapped Off
Circumference: 11.625"
Diameter: 3.7" (Avg.)
Break Height: 14-16' (Est.)

Field Description: The top is about 15' tall and has stuck in the ground like a spear. It is actually one fork of two on the tree. This one was the largest and healthiest of the two. The tree itself has its side opened (at the fork) and its heartwood is rotting badly. The other fork (the one still up) appears to be almost dead. The heatwood of the fallen top has only a slight discoloration and its lower branches are very healthy. The tip of it is dead, however. There is a strip of bark that is missing on the lower end of the top. It is 22" long and is 1-1.5" wide on the lower 12" and 1-2" wide on the upper 10". The wood in this area looks dead, but it has not yet rotted. There are two field sketches of this break.

Conclusion: Tree most likely broke due to heartwood rot, which was probably the product of bark damage.

Field Sketch: To the right, showing broken portion of tree's top. Bark just below the break, seen in the bottom center of the image, has been torn off in a past calamity, and this damage probably contributed to the tree's breaking.


Specimen #: 05JAN1986004
Location: N/A
Species: Paper Birch, Betula papyrifera
Damage: Snapped Low
Circumference: N/A
Diameter: 7.5"
Break Height: 6'

Field Description: This tree's heartwood is strong. A hazelnut (Corylus cornata) is holding the birch, which is about 25-30' long, nearly parallel to the ground.

Conclusion: No clear reason for this tree to break when others of same species and in same area did not.


Specimen #: 05JAN1986005
Location: West End
Species: Red Alder, Alnus rubra
Damage: Top Snapped Off
Circumference: N/A
Diameter: 5"
Break Height: 15' (Est.)

Field Description: Ten feet of this tree's top fell, hit a dead red alder and snapped the dead tree in half.

Conclusion: No clear reason for this tree to break when others of same species and in same area did not.


Specimen #: 05JAN1986006
Location: West End
Species: Red Alder, Alnus rubra
Damage: Top Snapped Off
Circumference: 24"
Diameter: 6"
Break Height: 15' (Est.)

Field Description: This alder was dead previous to the windstorm. Only a little rotted.

Conclusion: Tree most likely broke due to having a dead portion.


Southern Woodlot Notes: A Douglas-fir (Pseudotsuga menzesii) in a east-central location lost some big branches, but nothing of a major category (like a top). There were three: one with a 2.5" diameter and 10' long, one 1.875" diameter and 8' long, and one 0.75" diameter and 6' long. A red alder (Alnus rubra) in a central location also lost a large multi-forked branch measuring 3" in diameter and 8' long.

--- --- ---

Northern Woodlot

Specimen #: 05JAN1986007
Location: N/A
Species: Paper Birch, Betula papyrifera
Damage: Uprooted
Circumference: N/A
Diameter: 5.5"
Break Height: Ground Level

Field Description: This 25' tall birch uprooted and got stuck in surrounding trees. Tree is healthy. Took a dead 2" diameter scouler willow (Salix scoulerana) with it.

Conclusion: No clear reason why this tree was singled out by wind; maybe a weak root system due to failing competition with other trees.


Specimen #: 05JAN1986008
Location: N/A
Species: Red Alder, Alnus rubra
Damage: Snapped
Circumference: N/A
Diameter: 5"
Break Height: 4'10"

Field Description: This alder was healthy. At least 20' of it is on the ground. Trunk still attached to stump via a sharply bent section of wood about 2" thick at its deepest. Break shows that the alder tree suffered compressive failure (where the attached part of the trunk is) of the down-wind side, and then tensile failure on the windward side (the main break). This fracture has been illustrated.

Conclusion: No clear reason why this tree was singled out by wind.


Specimen #: 05JAN1986009
Location: N/A
Species: Paper Birch, Betula papyrifera
Damage: Partial Uprooting
Circumference: 26.675" and 42.5"
Diameter: N/A
Break Height: Ground Level

Field Description: This healthy brich had two trunks, hence the two circumferences. The tree was obviously leaning, having had some root damage, but was still tentatively supporting itself by the roots that remained.

Conclusion: No clear reason why this tree was singled out by wind.


Specimen #: 05JAN1986010
Location: East Side
Species: Paper Birch, Betula papyrifera
Damage: Snapped Low
Circumference: N/A
Diameter: 6.25"
Break Height: 6' Above Ground

Field Description: This tree was dead before the storm, and part of it were fairly rotted.

Conclusion: Tree most likely broke due to having a dead portion.


Northern Woodlot Notes: A 10" diameter paper birch that was broken by the November 14-15, 1981 windstorms, and suspended in a red alder bough (also 10" diameter) was forced to the ground in the January 5-6, 1986 windstorm. This long dead tree is now blocking a trail. A Douglas-fir (Pseudotsuga menzesii) on the extreme east end lost a 4' long branch with a 1-1.5" diameter (Estimated--the branch is stuck in a tree). It also shed four branches over 1' long in nearby Phillip Arnold Park. Douglas-firs in Phillip Arnold Park shed an enormity of twigs. At least 20 were torn from one tree.

--- --- ---

Trillium Forest

Specimen #: 05JAN1986011
Location: Central
Species: Bigleaf Maple, Acer macrophyllum
Damage: Part of Top Broken
Circumference: N/A
Diameter: 4"
Break Height: N/A

Field Description: This branch, in essence, was 15-20' long. The bough landed tip-first, and two branches from it speared the ground and sheared off the main body. Entire bough appeared healthy.

Conclusion: No clear reason why this tree was singled out by wind.


Trillium Forest Notes: A western hemlock (Tsuga heterophylla) on the east-central side lost a 3' long and 0.75" thick branch. This tree is part of a grouping of four, most of which didn't suffer greatly (two nearby hemlocks had been uprooted in the November 14-15, 1981 windstorms). Douglas-firs (Pseudotsuga menzesii) forest-wide lost lots of twigs and branchlets, though nothing of large size.

--- --- ---

Notes About Entire Field Study Area: A red alder (Alnus rubra) outside of any of the study woodlots, but near to the Southern Woodlot (and the Talbot Substation), was broken at the 5'4" level. The tree was 6.5" in dameter and 20" in circumference. The field sketch to the right depicts this broken tree. Wood on the tree's west side was rotting due to previous bark damage, and this is the probably why this tree broke in the windstorm. Another red alder in the vicinity, live but with a crescent-shaped cross-section also broke. It was 8" wide on one axis and 4" on the other, and about 35-40' tall. It's unusual shape may have contributed to the fall--though it must be noted that this tree endured many other windstorms in the past (such as Nov 1981 and Nov 1983). The field sketch below shows the cross-section of this alder. A dead red alder, also in the region, snapped at the 10' level: it had a 19.25" circumference and a 5.25" diameter. The wood had not rotted and was still quite hard. These trees are all outside the woodlots being examined, so aren't included in the main database. They are included here as supporting evidence to the idea that biological factors play a significant role in determining which trees break during typical winter gales.

--- --- ---


Discussion of January 5-6, 1986 Windstorm Tree Damage

As I progress through the storms of January 1986, and their tally of broken trees, there will be a developing discussion about the results. Just note that in six cases (46%) of tree breakage from the January 5-6, 1986 windstorm, the specimens were not healthy in some clearly visible aspect, often pertaining to damage to the heartwood or outer wood, or the tree simply having died at an earlier date. And it is arguable that those apparently healthy trees that succumbed to this storm may have been losing in the resource competition with neighboring trees--maybe they were being crowded out, and thus had weaker roots and trunks than the others. Even sticking with the 46%, with this storm, there's growing evidence that winter gales seem to be nature's way of "clearing out the deadwood," in essence, which is partly where the intent of this study is going. Also note the species that suffered breakage. Almost all of the trees detailed are either red alder or paper birch. Is this a suggestion that some trees are more susceptable to wind than others? I think it does, but to make the conlusion less ambiguous, I'd have to note the relative abundance of each tree species in the woodlots, which I haven't done to date (though I may take a closer look at this one day). Certainly, there were (and still are) far more alders and birches than, say, Douglas-firs and western hemlocks in the study stie. Some of these woodlots, like the Mine Woods and The Forest, are virtually devoid of conifers. The Trillium Forest has the highest density of conifers, but angiosperms still abound, especially bigleaf maple, which exists in pure stands in some locations. Other variables have to be weighed, too. A tree's relative resistance to wind can be a player in how susceptable it is to a particular storm--conifers, by nature of their dense array of needles, probably offer more resistance to wind during the winter months than do alders (and in the case of this study, which was in January, all the deciduous trees were barren of foliage). And most conifers are taller than their angiosperm cousins, which puts them more directly in the path of the wind. Nothing is simple in my crude attempt to quantify the effects of windstorms on trees.

Table 2: January 5-6, 1986 Windfalls Broken Down By Species



Percent of Total [1]

Alnus rubra



Betula papyrifera



Acer macrophyllum



[1] Total excludes the two dead, broken trees from Eric's Forest that weren't catalogued. They were likely either A. rubra, or B. papyrifera.

Last Modified: February 26, 2003
Page Created: September 22, 2001

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