How Windy Will It Get?

February 2, 2006

That’s the million dollar question tonight, because tomorrow’s forecast is simple (the day before a storm is often quite uneventful), and all of next week is simple under a big ridge.  SO…what about Friday night/Saturday AM’s storm?

I think I’ve looked at every possible weather map and bit of information in the last 3 hours.

All 00z models are in agreement that the development taking place right now north of Hawaii becomes a very deep "bomb" as it heads northeast.  See yesterday’s discussion for an explanation of that term.  They all agree on a low pressure center landfall somewhere between the far NW tip of Washington and Central Vancouver Island.  The storm appears to reach it’s deepest central pressure when it’s west of Astoria (way west) around sunset tomorrow.  As it moves onshore it will be weakening slightly.  As with most deep lows in the Eastern North Pacific, it’s likely the models will be too weak with the central pressure.

This track is in the "danger zone" for deep low pressure centers.  That said, for a major windstorm in our area, we would expect the low to be a bit closer to the coastline (well inside of 130W longitude).   A damaging wind at the coast appears quite likely.  Widespread gusts to 70 mph IN the coastal towns are likely lets say in the 9pm-6am timeframe tomorrow night.  I think we may finally see some 90-100mph gusts on the headlands too.

The valley is a different story.  Once the isobars line up perpendicular to the valley, about the time the low is close to landfall up in BC, that’s when we should get our peak wind.  Sometime between midnight-8am.  Both versions of the UW-MM5 at 00z show around 14-16 millibars pressure difference from Eugene to Olympia as high pressure rapidly builds in behind the front.  That should produce gusts to 50 mph here in the metro area.  Any deviation to the right of the projected track or a deeper cyclone would mean a stronger wind.  Luckily we have 2 more model runs before tomorrow night to nail things down a bit more.

My gut feeling is that we’ll have just slightly stronger wind here in the metro area than those two surprise windstorms on Christmas & New Years, NOT a big 1995 storm, or even the January 2000 storm.

More tomorrow…Mark


Bombs & Sun

February 1, 2006

Nice break today, but just a tease of what’s coming next week.

Shortwave moving onto the coastline at 10pm, will be well east of here by daybreak.  Then we wait for a "bomb" to develop offshore Friday.  So what’s a "bomb"?

A meteorological bomb is basically a deep low pressure area that strengthens rapidly, often associated with damaging winds here in the Pacific Northwest.   To be a "bomb", the central pressure must fall at least 24 millibars in 24 hours.  Of course if that occurs close to the coastline, it would produce widespread damaging winds here in the Northwest, but for Friday models develop the system far offshore.  It needs to be watched, but for now I’m not concerned.

That will be the last system we see for quite awhile.  ALL models shows blocking ridging developing Sunday-Monday right on the West Coast.  They also all show it lasting in one form or another all the way through next week.  We’re headed back into blue skies, gusty east winds in the Gorge and Metro area, and warm mountains…very nice February weather ahead…Mark