Low Departed With Showers to Follow

Infrared satellite photo taken at 0800 PDT 01 Apr 2012. The remnants of yesterday's extratropical cyclone have moved well inland. A patch of cold clouds just moving ashore in Oregon is associated with a weak shortwave trough that promises to bring showers to Cascadia through the day. The next strong system can be seen developing west of the 140ºW line. Image courtesy of the US National Weather Service.

The wraparound band swept past the Lower Mainland in the early morning hours on this first day of April. The METAR from Vancouver International indicate that winds SW 7 km/h (4 kt) at midnight shifted to WSW 11 km/h (6 kt) by 0021, then WNW 28 km/h (15 kt) by 0100. Rain intensified at the time, and the temperature began a gradual drop from 41ºF to eventually reach 36ºF by 0432. Maximum winds occurred around 0400, with WNW 39 km/h (21 kt). A gust of 54 km/h (29 kt) followed, at 0432. Heavy rain arrived by 0445, a rare intensity for the airport. With the 0500 report, the rain had tapered off to moderate, then light in the next hour.

In terms of peak wind speeds in the surrounding area, wind-prone Race Rocks reported WSW 67 km/h (36 kt) gusting 80 km/h (43 kt) at 0600, Victoria Gonzales Heights reported WSW 39 km/h (21 kt) gusting 54 km/h (29 kt) and Sheringham reported W 52 km/h (28 kt) at 0400. Sand Heads reported NW 41 km/h (22 kt) at 0400, Victoria a mere WNW 24 km/h (13 kt) at 0300, and Bellingham--typically with weak response during westerly wind events--nevertheless reported a peak gust of 44 km/h (24 kt) from a 270º direction. Abbotsford, inland and somewhat sheltered from many westerly surges, only reported a peak wind speeds of WSW 20 km/h (11 kt) at 0533. At Abby, light rain at 0635 became light rain/snow mix by 0655, with the temperature down to 1ºC (34ºF) and dew point 0ºC (32ºF) during the 0700 regular observation. Lowland snow in April is always an interesting treat, but in terms of wind speed, this storm did not have a strong showing over much of the region, save for a focused area on the coast south of North Bend, Oregon.

Yesterday's cyclone fell apart as it moved inland and effectively became absorbed early this morning. New lows have since developed along the leading frontal system over the Intermountain Empire. A weak shortwave trough is expected to bring renewed showers to Vancouver, BC, by this afternoon, and earlier in locations south.

Update 1931 PDT:

As the bent-back front swept through the Puget Lowlands, wind speeds climbed fairly high in places, with METAR data showing gale-force gusts at a few stations.

Winds at Sea-Tac reached SW 48 km/h (26 kt) gusting 67 (36) at 0553 this morning. The heavy gusts arrived during a time of rapid pressure rise, with rates reaching 2.3 hPa/hr by 0653. Everett reported peak winds of S 44 km/h (24 kt) gusting 65 (35) at 0353, followed by a 2.8 hPa/hr pressure rise in the hour ending 0453. A gust of 67 km/h (36 kt) occurred out of 190º at 0406. Bremerton reported winds of SSW 41 km/h (22 kt) gusting 56 (30) during the 0535 observation, with a gust to 59 km/h  (32 kt) at 0515. Tacoma McChord reported maximum winds of 33 km/h (18 kt) gusting 46 (25) at 0253, with a maximum gust of 48 km/h (26 kt) out of 200º at 0301. Olympia had winds escalate to SSW 24 km/h (13 kt) gusting 44 (24) at 0254.

Both Tacoma and Olympia escaped the heavier gusts that occurred just to the north. However, the South Sound had rates of pressure rise similar in magnitude to the reports from the Seattle-Everett area, with a 2.1 hPa climb at Olympia in the hour ending 0354. The isallobaric effect could not have been the only player in the reported wind speeds. Pressure gradients likely were a key contributor, but I have not checked the values for this storm.