Thursday, October 23, 2014

A windy weekend expected

In yesterday's blog post, we talked about the potential for the remnants of Tropical Storm Ana to head to the Inland Northwest early next week.  In that blog, we briefly mentioned a possible wind storm on the weekend, before Ana arrives.  Let's take a look at some details of this event.

First, we'll look at the overall set up.  Here's the GFS model forecast for rain (shading) and sea-level pressure (red lines).

The forecast shows a deep low pressure center off the West coast Friday afternoon.  The precipitation extending across northern Oregon into central Idaho is associated with the warm front that will move into our area.  By this time, strong winds will be developing along the southern Oregon coast.

Overnight, the low deepens and moves north.  Here's the forecast for Saturday morning.

GFS Forecast SLP (red contours) and precipitation (shading) for Saturday morning 25 Oct
Now the low pressure is down to 990mb, and impressive low.  The warm front has lifted up to the WA/BC border.  The tightly packed pressure lines (red contours) indicate wind strength.  The tighter the packing, the stronger the winds.  Over the Inland Northwest, winds will be from the east on Saturday, blowing into the low.  Along the Oregon Coast it will be extremely windy.

By Saturday afternoon (below), the low moves onto the Olympic Peninsula and fills to 995mb.  

GFS Forecast SLP (red contours) and precipitation (shading) for Saturday afternoon 25 Oct

And by Sunday morning, the low will be in southeast British Columbia.

GFS Forecast SLP (red contours) and precipitation (shading) for Sunday 26 Oct

It's this Saturday night and Sunday morning period where the winds could be rather strong across the Inland Northwest.  On the one hand, the pattern for this storm is one that is common for strong winds, with the low moving by just to the north of the US/Canadian border.  On the down side, it's moving through at night, which tends to inhibit winds somewhat.  But in this case, that probably won't matter.

Now let's look a bit closer at the details.  First, here's the University of Washington WRF model forecast for Saturday.

This shows forecast gusts of 70+ mph along the central Oregon coast.  Not good beach umbrella weather.

And here's the WRF forecast for wind gusts Saturday evening:

The area of red and orange in southeast Washington is a forecast of up to 57 kts, or 65 mph.  Now, before you say "glad I don't live in southeast Washington", this is just one model forecast.  The next model run (tonight) could move that area of strong winds to a slightly different area, such as Tri Cities, or Pullman, or Spokane.  At this point, it's too early to tell exactly where the strongest winds will occur, and just how strong they'll be.

As for Tropical Storm Ana, the GFS and ECMWF models are still showing solutions similar to yesterday's blog.  Here's the GFS forecast for Tuesday afternoon:

GFS Forecast SLP (red contours) and precipitation (shading) for Tuesday 29 Oct
We'll write more about this Friday evening.

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