Spring Interlude

Over the long Easter Weekend, mid to high clouds from a nearly stationary weather system just offshore visited the Cascadia region. Between patches of blue, wispy cirrus, and thicker blankets of cirrostratus drifted overhead, giving the skies a milky cast, such as shown in the above photo, taken at Alice Lake north of Squamish, BC. Though the persistent clouds reduced the intensity of the sunshine at times, temperatures in many areas climbed to their greatest values for the year to date. Photo taken on 08 Apr 2012.

Sunday and Monday turned out rather warm and quite spring-like. At times, altostratus and cirrostratus from the stalled front off the coast obscured the sun. However, with a tendency for offshore flow, and a southerly airflow around the semi-stationary low off of Northern California, the temperature warmed nicely in many locations.

After spending all weekend off of the Northern California coast, a cutoff low still remains offshore today, and appears to now be slowly drifting SE from its former quasi-stationary position. The system is very much weakened, with a 100.2 kPa central pressure as of the 1500 UTC Hydrometeorological Prediction Center surface analysis. The associated weak frontal system has now reached the Pacific Coast, with moisture streaming due north over Cascadia. However, only light precipitation is associated with the band and among somewhat scattered locations.

For the Easter weekend, a quasi-stationary low set up off of Northern California, quite easy to pick out in this visible satellite photo. The associated frontal band virtually stalled just offshore for a number of days, with mid and high clouds streaming over Cascade country. The southerly flow along the front, carrying air from the subtropics, contributed to the warmth. Also, a tendency for offshore surface flow, with E to NE winds, also contributed to warmer temperatures than during the week previous. Image taken on 09 Apr 2012 at 1130 PDT (1830 UTC) and is courtesy of the US National Weather Service.

Despite the frequent presence of clouds similar to those depicted in the Alice Lake photo above, the temperature at the Squamish Airport reached 19.4ºC (67ºF) at 1400 PDT on Sunday, and then bumped up to 20.6ºC (69ºF) on Monday, 09 Apr.

I heard from a local weather observer that his thermometer in Vancouver, BC, north of the airport, reached 20ºC, the highest so far this year. Last year, the first 20ºC reading did not occur until 13 May. So, it appears that this spring will not be quite as cool as that in 2011. Though, one brief warm spell may not be indicative of a longer-term trend.

Vancouver International had much cooler highs temps than places even a short distance from the water, almost certainly due to a tendency for a WNW to NW breeze to set up during the afternoon, at times reaching speeds of 28 km/h (15 kt) on Sunday, and 17 km/h (9 kt) on Monday. The highs were 12ºC (54ºF) and 15ºC (59ºF) respectively.

The thermometer at Abbotsford, however, more closely reflected the temperature that the weather observer reported, with a high of 19ºC (66ºF) on Sunday and 21ºC (70ºF) yesterday. In 2011, the temperature in Abbotsford did not reach or exceed 21ºC until 13 May. Places south, like Sea-Tac and Portland, had highs similar to those at Abbotsford and Squamish this past weekend. The former reported 21ºC (70ºF) yesterday, and the latter 20ºC (68ºF) on Sunday for the toastiest highs of this spring warm spell (so far).

The March Deluge of 2012

A shower drops snow and rain on the North Shore Mountains in the vicinity of Vancouver, BC, while sunshine bathes the lowlands. This is not an uncommon situation. The tendency for convective activity over the nearby mountains, while the valley remains mostly dry, is just one type of orographic phenomenon that contributes greater precipitation to the higher elevations. Vancouverites can enjoy sunshine while witnessing a deluge on nearby slopes. Photo taken from Iona Beach on 06 Apr 2012.

For Cascadia, March proved quite wet. In some regions, soaked is a better term, for new records for total monthly precipitation were set. So many stations set new all-time high totals, including many mountain-based RAWS sites, that it would make a very long list. Instead, focus will be on a few key locations. The persistent rains of March 2012 found much of Western Oregon. Portland Metro, the most populated region in the state, did not escape the deluge. According to the National Weather Service (NWS), Portland office, the Portland International Airport reported 200.4 mm (7.89") of rain in March, the wettest in a period of record that goes back to 1940. Vancouver, Pearson Field, just across the Columbia River, reported 198.4 mm (7.81"), the 3^rd most soaked March since 1890.

Further down the coast, Southwest Oregon received some phenomenal amounts of rain, as reported by NWS Medford. During the previous March (2011), numerous all-time records were set. Amazingly, a number of these fell in 2012.

One of the more amazing reports occurred at a station designated Port Orford 5E. Some 952.5 mm (37.50") of precipitation fell in March of 2012, breaking the all-time monthly record of 795.5 mm (31.32") set just the year before. Keep this in mind: 952.5 mm is fully 30.7 mm (1.20") of rain a day on average.

Sexton Summit, right near I-5 in the Klamath-Siskyou Mountains, reported 350.0 mm (13.78"), breaking the "old" March record of 290.6 mm (11.44") set way back in 2011.

Moving into Northwest California, NWS Eureka indicated that 305.3 mm (12.02") of rain fell at the forecast office. This makes for the wettest March in a record going back to December 1941. This broke the former record, again set in 2011, of 302.0 mm (11.89") by a mere 3.3 mm (0.13"). Still enough to put March 2012 on top, but maybe not with complete confidence when the potential for error in measurement is taken into consideration.

Further south, rainfall totals were not so spectacular. San Francsico reported 120.9 mm (4.76") of rain during March 2012. Though this is 45.7 mm (1.80") above normal, the total is well short of the 229.1 mm (9.02") record set in March 1958. In fact, the value for 2012 ranks 12^th in terms of wettest Marches in San Francisco, going back to July 1945.

California had a fairly dry "wet season," not atypical of La Nina conditions. There is a phenomenon known as the March Miracle in the Golden State. Sometimes during a dry water year, the jet stream dives south right at the end of the wet season in March, bringing in a series of juicy storms before the storm track starts its seasonal northward migration in the spring. A March Miracle can bring much-needed moisture to a parched California before the summer "dry" arrives. It appears that in 2012, California had a a partial March miracle. Oregon and extreme northern California received the bulk of the moisture this time around.

Looking at interior sections east of the Cascades, NWS Spokane indicated that numerous March total precipitation records were set in Eastern Washington and Northern Idaho. This included Spokane, which had 115.8 mm (4.56").

One interesting aspect of the Spokane record is that more precipitation fell at this location than dropped in Vancouver, BC, during March. Indeed, with a 111.6 mm (4.39"), Vancouver (again, the northern one) appears to have been "gypped" in terms of rainfall. Well, not entirely gypped: The total is almost exactly "normal", based on the 1971-2000 record. In any event, Spokane, in the Cascade rain shadow, is typically much drier than Vancouver during the cold season. Not in March 2012. This reality, and with much heavier precipitation totals down in Oregon, reflects the tendency that storms had during March 2012 to track into the Beaver State and head northeast into Eastern Washington.

Precipitation varies widely between locations that may not be particularly far apart, and this situation is no different in Vancouver Metro. Vancouver is partially rain-shadowed by the Olympics and the Vancouver Island ranges. Plus, rainfall tends to pick up in the vicinity of the North Shore Mountains. There is a well-known gradient of average precipitation going from White Rock to North Vancouver, with the latter receiving higher amounts. A friend of mine who has been keeping a long-term climatological record up on the shallow rise to the north of Vancouver International, reported 133.5 mm (5.26") for March 2012, significantly more than at the airport.

Measurement methodology, instrument type and also instrument siting has changed over the years, resulting in some error. This translates to uncertainty in any rankings mentioned above, especially when the values are close. Nevertheless, the takeaway message is that March 2012 brought with it some historical precipitation amounts in many parts of Cascadia. Other locations appear to have had at least a decent soaking with normal to above normal precipitation.

Many thanks to Steve Pierce who brought to my attention some of the March precipitation records.

Pacific Storm Lingers Into A Second Day

A frontal system moves ashore as the parent low slowly weakens in a semi-stationary position off of the Southeast Alaska coast. After passing over the North Vancouver Island coast yesterday morning, the front has finally reached the Vancouver Metro area and surrounds. Visible satellite photo taken at 0900 PDT 03 Apr 2012. Image courtesy of the US National Weather Service.

The frontal boundary has finally moved through the Vancouver Metro area. E winds of 17 km/h (9 kt) at 0800 shifted to NW 35 km/h (19 kt) gusting 46 (25) by 0900. The temp fell from a rather warm reading of 10ºC (50ºF) at 0700 to 6.1ºC (43ºF) by 0900. Steady light rain accompanied this transition, and the barometric pressure began to rise. On my drive in, I observed rain intensity that in my estimation approached moderate at times up on the hill around Queen Elizabeth Park and driving in to the University of British Columbia.

The semi-stationary cyclone is nearly at the same location as this time yesterday morning, perhaps a few degrees further north. Satellite photos taken this morning are quite similar-looking to those of the previous day. The low, however, is much weakened, with a central pressure at 0500 (1200 UTC) of 97.8 kPa (28.88" Hg), according to the HPC surface analysis.

Here are peak wind and gust speeds from this event for selected stations. Most maxima occurred on 02 Apr. However, winds have recently picked up along the frontal boundary in a few places, such as Abbotsford and Bellingham. These peaks are denoted in italics:

Peak Wind and Gust: km/h (knots) Deep Haida Gwaii Cyclone 02-03 Apr 2012 (PDT)
Loc	Wind	Dir	Time	Gust	Dir	Time
Port Hardy	44 (24)	ESE	0800	70 (38)	ESE	0800
Campbell River	59 (32)	ESE	1306	81 (44)	SE	1200
Comox	65 (35)	SE	1200	83 (45)	SE	1400
Victoria	37 (20)	SE	1100	56 (30)	SE	1100
Vancouver	41 (22)	ESE	1100	52 (28)	ESE	1100
Abbotsford	33 (18)	S	0900	44 (24)	S	0900
Bellingham	33 (18)	SE	0953	57 (31)	SSE	0817
Navy, Whidbey	48 (26)	SSE	0856	69 (37)	S	0739
Quillayute	35 (19)	S	1553	74 (40)	SSE	1552
Tofino	56 (30)	SSE	0900	80 (43)	SE	1100
Estevan Pt	69 (37)	ESE	1500	93 (50)	ESE	1400
Solander I	120(65)	ESE	0600	143(77)	ESE	0900

North Vancouver Island received the strongest winds with this storm, both on the coast and in the interior. Comox and Campbell River were hit with significant gusts in excess of 80 km/h (43 kt), but nowhere near the magnitude of the 12 Mar 2012 windstorm. Further south, yesterday morning's wind forecast did not pan out for either Vancouver Metro or Bellingham.

Quite cold air has moved in behind the front. At Quillayute, for example, the temperature fell from 8.3ºC (47ºF) at 0353, with winds S 15 km/h (8 kt), to 2.2ºC (36ºF) at 0653, with winds E 9 km/h (5 kt), this after a period of heavy rain (5.6 mm, or 0.22", in the hour ending 0453) and gusty westerly winds as the front swept inland. The temp fell further to 1.7ºC (35ºF) by 07:53, with light rain continuing. Tofino reported 3.9ºC (39ºF) at 0900.

An Intense Cyclone Over the Northeast Pacific Promises Some Bluster

An intense extratropical cyclone had developed over the Northeast Pacific and is now nearly stationary off the west shore of Haida Gwaii. The cyclone exhibits a dramatical-looking doubly-wound spiral, or occluded front, near the centre. The tightly wound nature of the low is an indication of a mature system. Occlusions can become quite long as they are stretched around a cyclonic centre in this manner. Water Vapour satellite mage taken at 0700 PDT 02 Apr 2012 and is courtesy of the US National Weather Service.

We had a beautiful, mostly sunny afternoon yesterday. A few showers popped up in the vicinity but nothing moved right over my neighbourhood. Under all that sunshine, the temp climbed to a relatively warm 10.9ºC (51.6ºF) at Vancouver International.

Now, a very intense low has developed in the Northeast Pacific. As of the 1200 UTC Hydrometeorological Prediction Center (HPC) surface analysis, the low center had reached 53ºN 138ºW, nearly due west of Haida Gwaii. An intense pressure gradient surrounded the core, with a central pressure of 95.6 kPa (28.23" Hg). A strong pressure gradient is also associated with the leading warm and cold frontal systems, both of which are nearing the coast of Vancouver Island. An intensifying southeast pressure slope is already over Southwest British Columbia. The frontal boundaries are moving rather slowly, and the low center even more so. In fact, the doubly-wound spiral at the storm's core is nearly stationary. The low is also vertically stacked, or mature, and has almost certainly passed peak intensity.

The deep low is the kind of extratropical cyclone that generates our big windstorms, when they track closer to the coast than the current system. Given the more distant track, the winds are not expected to reach historical proportions. Environment Canada is forecasting southeast winds climbing toward 50 to 70 km/h (27 to 38 knots) by tonight in Vancouver Metro. The US National Weather Service has a wind advisory out in the Northwest Interior, with wind gusts up to 80 km/h (43 kt) expected at places like Bellingham.

With the incoming fronts, Solander Island is reporting extreme wind speeds, but this is rather typical for the station. At 0700, winds were ESE 113 km/h (61 kt) mph gusting 143 (77). The pressure had dropped to 99.77 kPa (29.46" Hg). The Estevan Point lighthouse reported winds E 48 km/h (26 kt) gusting 80 (43) at 07:00, with a pressure of 101.16 kPa (29.87" Hg). Note the steep pressure differential between the two stations: 13.9 hPa. This reflects the strong pressure gradients around the massive low, reaching far out from the centre.

Here in Vancouver, we have low, gray skies, a gentle breeze and a somewhat mild on-patio temperature of 8.6ºC (47.5ºF) indicative of 7ºC (44.6ºF) out in the park across the street. The relative humidity is 72%, with a pressure of 30.15"—rather high and not particularly threatening. The Davis reads 102.21 kPa, actually up 0.1 hPa in the hour ending 07:45. This despite and incoming front. The sky promises rain, and the barometer sunshine. Not atypical for the area.

At the airport:

Vancouver International Observation 0700 PDT
WX/Sky	BKN028 OVC090	Vis	15.00
Wind	ESE 28 (15)	T/Td	7.7/2.2
SLP	102.19	Tdcy	-0.1
Vis mi, T/Td ºC, And km/h (kt), SLP kPa, Tdcy hPa/hr.

Even though winds in my neighborhood are somewhat light—with the mild shaking of the tree limbs, I estimate 10-15 km/h (6-8 kt) in gusts at times—wind speeds at the airport have been stronger. At 0500, SE winds reached 28 km/h (15 kt) gusting 37 (20). The temperature has been mild all night, with a low around 7.2ºC (45ºF). The thermometer at Estevan Point, by the way, indicated 8.3ºC (47ºF) at 0700, and at Solander 6.7ºC (44ºF). Both locations also showed little temperature change overnight.

Even further south, at Quillayute, the temp at 0753 is 8.3ºC (47ºF) and somewhat warmer than earlier this morning. Winds, however, are SSE and had reached 28 km/h (15 kt) gusting 48 (26) by the 0753 observation. This appears to be a response associated with warm frontal passage, which appears to have occurred around 0412 at this station based on a wind shift from SE to SSE and an acceleration of speed, accompanied by a slight warming of the temp. The cyclone's warm sector is not particularly toasty, with a temp of 8.9ºC (48ºF) being indicated by Buoy 46206 at 0700, and 46005 reporting 10ºC (50ºF) at 0150 before the cold front brought the temp down to 6.7ºC (44ºF) by 0550.

Given the relatively mild temp at Estevan Point, it appears that the warm front is at, or very near, this location. Cooler Solander is perhaps north of the triple-point.

SE to SSE winds have been fairly strong at the two above-mentioned buoys, but not at a major windstorm level. Buoy 46206 reported winds SE 55 km/h (29.5 kt) gusting 72 (39) at 0600, the highest so far, and 46005 reported 61 km/h (33 kt) gusting 76 (41) at 0150, in association with the cold front. Direction is not being reported. The sea surface temperature, by the way, is 7.7ºC (46ºF), and had likely contributed to cooling the warm sector, reducing its intensity.

Update 1507 PDT:

The beautifully wound up cyclone continues to very slowly move northward along 139ºW, and is now near 54ºN. The leading cold front has slowly progressed eastward over Vancouver Island, with the boundary now past Solander Island, and a decent stream of moisture passing over the central portion of the island. Moderate to heavy rain has been soaking Estevan Point for a number of hours now:

Time (PDT)	Rain Total (mm/hr)	Rain Total (in/hr)
1000	3.0	0.12
1100	6.6	0.26
1200	7.4	0.29
1300	5.3	0.21
1400	4.3	0.17

Wind speeds at Estevan Point have also increased markedly, with a report at 1400 of ESE 69 km/h (37 kt) gusting 93 (50), high-wind criteria speeds.

The near hurricane-force winds at Solander Island slowed dramatically after noon, when the frontal boundary arrived. Winds SSE 104 km/h (56 kt) gusting 120 (65) at 1200 became SSE 56 km/h (30 kt) by 1300, then shifted to due S at 56 km/h (30 kt) gusting 70 (38) by the end of the next hour. The pressure jumped from 99.71 kPa (29.44" Hg) at 1100 to 100.04 kPa (29.54" Hg) at noon, an hourly change of 3.3 hPa. The temp fell from 7.8ºC (46ºF) at 1100 to 6.1ºC (43ºF) by 1300.

Here in Vancouver, we have not seen any rain yet, and indeed had some sunbreaks earlier this afternoon. The temp has warmed dramatically to 13ºC (55.4ºF) as of the most recent observation at 1400. Winds, however, have slacked off from a maximum of ESE 41 km/h (22 kt) gusting 52 (28) at 1100. The latest report indicated ESE 24 km/h (13 kt). However, the pressure in the same observation indicated a 1.1 hPa fall in the past hour, down to 101.85 kPa (30.08" Hg). The barometric trend reflects the slowly approaching cold front.

Bellingham has reported a maximum gust, so far, of 54 km/h (29 kt) out of 130º at 1255, plus on two other occasions before this observation.

Some maximum gusts on the Washington coast (so far):

Location	Direction (º)	Gust (km/h & knots)	Time (PDT)
Tatoosh I	170	80 (43)	1323
Quillayute	150	67 (36)	1248
Destruction I	140	91 (49)	1015
Hoquiam	60	37 (20)	1034

Not much happening at Hoquiam, but places north are reporting gale-force gusts. 

Update 1945 PDT:

The Pacific front is crawling eastward and now has passed Estevan Point, based on recent METAR information. SE winds 65 km/h (35 kt) gusting 76 (41) at 1700 dropped to SE 24 km/h (13 kt) during the following hour, with the temperature falling from 8.3ºC (47ºF) to 7.2ºC (45ºF), changes that likely mark the passage of the front. Moderate rain also tapered off to light by 1900.

Tofino is now under the baroclinic hose, with steady moderate rain, along with mist, since noon. Winds have been strong, too, with speeds climbing to SSE 56 km/h (30 kt) gusting 70 (38) at 0900, and a SE gust to 80 km/h (43 kt) at 1100.

East winds finally shifted to south and southeast by 1453 at Hoquiam. Though speeds are not particularly strong, with a maximum gust of 25 mph out of 170º at 1653. The temp, however, climbed to a rather warm 13.9ºC (57.0ºF) at 1553. Partly sunny skies likely enhanced this warm sector temperature.

New gust maxima for the Washington coast:

Location	Dir (º)	Gust (km/h)	Gust (knots)	Time (PDT)
Tatoosh I	170º	100	54	1707
Quillayute	160º	74	40	1542
Destruction I	170º	89	48	1407

 Wind speeds appear to be tapering off in recent observations from all three of these locations, so the above values may be the peaks for this storm. The front may be weakening, along with the low. As of 1700 (0000 UTC), the HPC analyzed the cyclone's central pressure at 96.4 kPa (28.47" Hg), up nearly 1 kPa from the minimum.

Light rain recently reached Quillayute at 1853. Partly cloudy to sometimes clear skies visited the area for much of the day, with the front just offshore, carrying significant moisture into Vancouver Island.

Here in Vancouver, low, gray overcast skies dominate, with a light breeze rustling the trees. The temperature on the patio is 12.5ºC (54.5ºF), with the shade temperature away from the building likely around 11ºC (52ºF). At the airport:

Vancouver International Observation 1900 PDT
WX/Sky	BKN078 OVC085	Vis	15.00
Wind	E 20 (11) G 30 (16)	T/Td	11.1/2.8
SLP	101.28	Tdcy	-1.2
Vis mi, T/Td ºC, And km/h (kt), SLP kPa, Tdcy hPa/hr.

Winds have been easterly since 1600, and appear to be on a slow wane, with some oscillations upward, like 28 km/h (15 kt) at 1800. The temperature is also slowly dropping from 12.8ºC (55ºF) at 16:00. Looking at the satellite loop and the progress of the front, I suspect rain may reach here within a few more hours.