NWS Seattle is still
watching a potential windstorm situation for Monday. One model brought the
low over Portland, which would have a completely different outcome, but the
other models continue bringing a strong low across Vancouver Island. The latest
WRF-GFS, 12:00 UTC 14 Dec 2012, brings a 97.7 kPa (28.85" Hg) cyclone ashore very near
Estevan Point. Interestingly the gradient near the center is not very
strong—probably indicating a mature low—but is quite tight further south and
west. The strongest winds for Vancouver may be to the rear of the low as a
westerly surge. This scenario appears somewhat similar to 25 Sep 1999, though
the modeled low is deeper in this case suggesting that the potential for damaging winds is a bit higher. 08:38 PST.
09:34 PST: I took a
closer look at the WRF-GFS model and my own regression modeling. Note that my regression
model is preliminary. If we assume the low has a central pressure around 97.5
kPa and tracks across northern Vancouver Island, then my model predicts an
average peak gust for Victoria, Vancouver and Abbotsford of 41 kt (76 km/h).
Since peak gusts tend to vary between the stations, the average could contain an instance
of 48 kt (89 km/h) or higher, my own minimum cutoff for "high wind"
that allows for some error in measurement. Some examples of high-wind
generating cyclones with a central pressure at landfall around 97.5 kPa include
04 Feb 2006 with an 3-station average peak gust of 42 kt (78 km/h) and 11 Dec
2006 with 49 kt (91 km/h). Both these storms produced high-wind criteria gusts
in the Lower Mainland and/or Greater Victoria.
The WRF-GFS indicates
that the highest winds for Vancouver may occur as the low passes inland to the
north of the station in a classic westerly surge event that may climb to 35 kt
(65 km/h), which may bring gusts upwards of 45 kt (83 km/h), arriving around
15:00 PST on 17 Dec. Again, quite similar to 25 Sep 1999. This westerly surge may be linked to the passage of a well-developed bent-back front. As the low tracks toward The Island, easterly winds could
climb to 25 kt (46 km/h) Sunday night on the 16 Dec.
Interestingly,
the NWP model suggests that the pressure in Vancouver could fall as low as 98.0 kPa
(28.94" Hg) around 04:00 on Monday. My own regression model predicts a
minimum around 99.0 kPa (29.23" Hg). Some of the difference may be due to
the track, which is nearly due east in the case of the expected storm and generally
ENE to NE on average which is reflected in the regression model. Probability,
however, is on the side of the higher minimum-pressure prediction, and perhaps
one might expect a minimum at Vancouver between these two values. 09:56 PST.
Very interesting--this bears watching as more info becomes available. I am glad the overhanging tree beside me was recently cut down.
ReplyDeleteOne thing that I forgot to mention in the post--I am a bit concerned that the ground here in Vancouver is quite saturated, with the soil gone to mud and standing water in places, and more rain on the way for tonight. With water-logged soils, trees are more likely to uproot in a strong wind.
DeleteGreat blog post! Very interested from Federal Way, Washington. I couldn't seem to find the info anywhere, but is this blogspot authored by Wolf Read?
ReplyDeleteYep, that is me. Thanks for the kind words. I am planning a new post on this upcoming storm either later tonight, or more likely tomorrow morning.
DeleteAh, very cool; huge fan of your Storm King page. I still remember the day I stumbled on it almost a decade ago and have had it bookmarked on every browser on every computer since. Can't wait for the blog post!
DeleteThanks much. I am always glad to hear that someone is using the information of The Storm King.
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