From Highs to Lows

As noted in my previous blog, the meteorology of much of the summer has been dominated by high pressure offshore, resulting in a warmer and drier-than-normal period.

But this week it all changed, with low pressure---also called troughing-- gaining the upper hand.

Consider the infrared satellite image earlier this morning (below).   A low center was positioned over southwest Washington, with a plume of moisture circulating around.

That moisture originated in the famous Southwest (or North American) monsoon.  The same monsoon that brought heavy rain and a dust storm to the Phoenix area.

But as this low moves out today, ANOTHER low is ready to move in!   The water vapor satellite imagery this morning shows the low lurking offshore.  A larger low.

A sequence of forecast upper-level (500 hPa, about 18,000 ft) weather maps provides the "lowdown" on the situation.

Tomorrow morning at 5 AM,  the low is off the southern Oregon Coast.

But by Sunday morning, it had moved northwestward to immediately west of the Olympic Peninsula.

A day later...still out there.

This is no "bomb cyclone".   The precipitation from this feature will stay offshore (see forecast totals through Tuesday morning below).

Temperatures won't impress either.... here are the forecasts for SeaTac. A bit cooler over the weekend with the low offshore.  No major heatwaves.

With a low offshore, the winds will be very modest over the region.  

Very bad for wind energy generation.  Very good for keeping wildfires down.

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