The fall transition of 2012 occurred during the period of 12-14 Oct 2012, just after the 50th anniversary of the Columbus Day Storm (AKA Typhoon Freda), with the arrival of two moist frontal systems, followed by a strong extratropical cyclone after the weekend closed:
15 Oct 2012: Monday
1540 PDT: A short-term forecast
issued by the National Weather Service, Seattle, at 1533 indicates
thunderstorms moving east into the Olympics, Strait of Juan de Fuca and the
Chehalis Valley. They expect the thunderstorms to reach Seattle within an hour.
Small hail, heavy rain and gusty winds may accompany these showers. Environment
Canada indicates the possibility of thunderstorms here in Vancouver this evening,
so it appears we are under the lightning gun as the vigorous cold front moves
ashore. There is also a wind warning for Victoria, for strong SE winds shifting
to W after frontal passage, with the possibility of gusts to 90 km/h, perhaps
even up to 100 km/h. Here in Vancouver, SE winds are expected to reach 60 km/h
at times, before shifting to west 50-70 km/h.
Based on the latest
Water Vapor (WV) satellite loop, the low pressure center is just south of the
southern tip of Haida Gwaii, with the leading front now coming ashore on
Vancouver Island. The most enhanced cloud-tops, which have a granular, almost
ropy structure, indicate the presence of numerous convective cells reaching
down the coast from Vancouver Island to Southern Oregon.
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| Visible satellite photo of the developing extratropical cyclone, center just south of Haida Gwaii. Time 22:30 UTC on 15 Oct 2012. Image courtesy of the National Weather Service. |
Quillayute reported a
thunderstorm with heavy rain at 15:18, and some 5.3 mm (0.21") of
precipitation fell between 1453 and 1537. Winds were not particularly strong
during the thunderstorm, with gusts to 29 km/h (16 kt). Hoquiam has not
reported a thunderstorm, but heavy rain occurred around 14:50, after which a
wind shift occurred: from ESE 16 km/h (9 kt) at 14:53 to SSE 34 km/h (18 kt) by
15:01. Gusts climbed to SSE 53 km/h (29 kt) by 1539. A thunderstorm with light
rain struck Astoria around 1509, followed by S gusts to 69 km/h (37 kt) by
1509.
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| This infrared image from the same time as the visible photo above reveals strongly enhanced cloud tops, stretching SE over Cascadia like giant fingers, associated with deep convection (about 10 km, or 35,000 feet) ahead of the extratropical cyclone's cold front. Most of the thunderstorm activity was confined to the coast, though heavy showers did strike some inland stations. For example, both Eugene and Salem reported heavy rain, with hourly totals around 5-6 mm (0.20-0.25"). Image courtesy of the National Weather Service. |
We have a dark gray
sky with light rain falling right now, with a patio temp of 13.8ºC, RH 83%,
unsettled winds perhaps up to 15-20 km/h at times and a pressure of 29.63" (100.34 kPa), falling at a decent clip. Vancouver International began
reporting light rain showers around 1345, with E winds of 16 km/h gusting 27
(9 kt G 15). The 1500 report indicated light rain showers with temp 13ºC
(55ºF), dew point 11ºC (52ºF), wind ENE 11 km/h (6 kt) and pressure 100.63 kPa
(29.72" Hg), falling 1.9 hPa/hr. Victoria at 1500 reported moderate rain
and mist, with temp 12ºC (54ºF), dew point 11ºC (52ºF), wind NNE 10 km/h (5 kt)
and pressure 100.55 kPa (29.69"), falling 1.9 hPa/hr.
The 2100 UTC HPC
surface analysis indicated a 98.0 kPa central pressure for the extratropical
cyclone, with a position almost due south of Haida Gwaii at latitude 51ºN. The
weather situation is evolving rapidly. 1605 PDT.
1902 PDT: Not a
whole lot of excitement happening here so far. Just a steady light rain
outside, with somewhat unsettled winds. The patio temp is 13.2ºC. The most
exciting thing, perhaps, is the pressure fall, which has been fairly fast at
times.
Vancouver
International reported a drop of 2.7 hPa to 100.13 kPa (29.57" Hg) in the
hour ending 1700, followed by an additional 1.8 hPa in the next hour. East
winds picked up to 24 km/h gusting 34 at 1800 (13 kt G 18). Moderate rain
occurred at 1748, dropping back to light by 18:00. It appears that the threat
of a thunderstorm is probably over, with the more enhanced cloud tops off to
the east, based on the WV satellite loop.
The extratropical
cyclone center has passed the southern end of Haida Gwaii and is now racing ENE
toward the mainland. Buoy 46147, near Haida Gwaii's Khungit Island, reported a
wind shift in the past few hours, from SE 58 km/h (31 kt) at 1500 Alaska
Daylight Time to W 47 km/h gusting 87
(25 kt G 47) by 1600 and then WNW 67 km/h gusting 90 (36.5 kt G 49) by
1700, with a pressure jump from 97.15 kPa (lowest pressure; 28.69" Hg) to 97.65 kPa (28.84" Hg), or 5.0
hPa, in the hour ending 17:00. Out in the Hecate Strait, buoy 46185 reported SE
winds of 76 km/h gusting 101 (41 kt G 55) at 1700 Pacific Daylight Time,
followed by SE 72 km/h gusting 93 (39 kt G 50) by 1800. The pressure continued
to show a falling trend, down 3.1 hPa/hr to 97.28 kPa (28.73" Hg), as of the most recent
observation, 1800. Note the SE winds as well: The low center has not yet passed
north of Buoy 46185.
Sandspit had winds
shifting from NNE around 1737-1807 to N by 1815 and then NNW by 1832
finally to NW by 1900 as the low tracked south of the station. Wind speeds
have generally been in the 40-50 km/h (22-27 kt) range, with gusts as high as
66 km/h (36 kt). A steady heavy rain fell during the entire wind shift, with
the temp slowly falling from 11ºC (52ºF) to 9ºC (48ºF). 1928 PDT.
16 Oct 2012: Tuesday
0823 PDT: (Vancouver, BC) Buoy
46185 had a classic bent-back attack after my last entry yesterday. At 1900
PDT, wind became SSE 50 km/h gusting 67 (27 kt G 36.5), with the temperature
climbing to 12ºC (54ºF) from 11ºC (52ºF). The pressure reached its minimum of
97.14 kPa (28.69" Hg), quite low. Then, by 2000, the wind had shifted to
W, with a speed of 72 km/h gusting 96 (39 kt G 52). The temp dropped back to
11ºC (52ºF) and would fall further in the next hour to 10.5ºC (51ºF). More
importantly, the pressure jumped 3.5 hPa to 98.17 kPa (28.79" Hg) in the
hour ending 2000, to be followed by an even stronger climb of 6.8 hPa to 98.77
kPa (28.99" Hg) in the next hour. Winds tapered off after the initial
surge. This is a classic pattern for a station that falls under the tip of a
extratropical cyclone's bent-back occlusion. Sometimes a city like Victoria or
Vancouver is on the receiving end of a strong wraparound band. For many stations, the
strongest wind speeds on record have occurred in association with this feature. Here is
the wind, gust and sea-level pressure plot for 46185:
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| Wind speed in knots (blue line), gust (red line) and sea-level pressure in inches (green line) for Buoy 46185. The signature of the 15-16 Oc 2012 extratropical cyclone is quite evident in the sharp wind and pressure response on the right-hand side of the chart. The first escalation in wind occurred out of the SE as the low center approached the station. The second surge, not quite as dramatic, arrived out of the W and is associated with the storm's strong bent-back front. Extremely fast pressure rises accompanied this feature, resulting in a V-shaped pressure trace that is reminiscent of a hurricane. Chart courtesy of the National Data Buoy Center. |
1040 PDT: Looking
locally, the storm did not quite meet forecast expectations. At Vancouver
International, peak winds reached W 47 km/h gusting 56 (25 kt G 30) at 0700,
with a maximum gust of 58 km/h (31 kt) reported at 0600. The westerly surge
arrived around 0300, and slowly escalated. These wind speeds were not even
close to the maximum 61 km/h gusting 74 (33 kt G 40) that occurred after a dry
upper trough moved through overnight on 01-02 Oct 2012.
Victoria International reported maximum winds of W 34 km/h gusting 45 (18 kt G
24) at 03:00, nothing like the forecast 90 km/h (even 100 km/h in one warning).
Even wind-favored Gonzales Heights only managed WSW 52 km/h gusting 69 (28 kt G
37) at 2300 with a peak gust of 76 km/h (41 kt) at midnight.
Abbotsford
reported peak winds of SSW 34 km/h (18 kt) at 0500, with a maximum gust of 40 km/h
(22 kt) at 0500 and 0700.
Bellingham reported SSE 39 km/h gusting 52 (21 kt G
28) at 2053, with a maximum gust to 58 km/h (36 kt) at 2019.
Nothing really
spectacular happened rainfall-wise with this storm. Bellingham reported 5.6 mm
(0.22") in the 24 hours ending 0453. Vancouver had 3.6 mm (0.14")
yesterday, with Victoria reporting 10.1 mm (0.40") and Abbotsford a
soaking 17.0 mm (0.67"). Quillayute had 25.9 mm (1.02") in the 24
hours ending 0453, a good soaker but still far from any record. Sea-Tac had 7.9
mm (0.31") in the same time period, and Portland 11.2 mm (0.44").
The 15-16 Oct 2012 extratropical cyclone, though it did not bring a big storm to the major population-centers of Cascadia, nevertheless made for an interesting opening to the 2012-13 storm
season. 1104 PDT.
