First strong Pacific front of the season. Surprisingly good forecasts on such fronts are now common.

Yesterday, the first strong Pacific front of the season moved out of the Pacific.

There are some fascinating subtleties about how Pacific fronts like this interact with our regional terrain….let me show you!

Radar imagery at around 8am yesterday (Wednesday) shows rainfall from the front to the WA and North West WA coast. Green indicates light rain, yellow moderate and red indicates heavy rain. Umbrella warning.

By mid-afternoon, the front moved through and the wind on the coast had shifted from the South (from the South) to the Northwest. As a result of this wind shift, a rain shadow begins to develop over the northern Sound as northwest winds move down the northeast flank of the Olympics (I’ve indicated the rain shadow with a red arrow).

Several hours later, the air was pushed eastward at low level across the Strait of Juan de Fuca, with strong upward motion at the leading edge of the marine air flow entering the strait. Air is forced upward at the leading edge of the marine airflow creating an enhanced precipitation arc (yellow to red)

And after the main rain front moved through, the Puget Sound Convergence Zone formed over the northern Strait as air moved north and south around the Olympic convergence point over Puget Sound.

A visible satellite image of the front around 1pm is shown below. The red line is the approximate location of the front, unstable cold air behind (area with white cloud elements over the ocean)

What’s very interesting to me as a modeler, someone who simulates the atmosphere using complex physical models, is that predictive models have achieved this in recent years. the day before.

Let me show you. A high-resolution forecast made the day before produced simulated clouds very similar to those observed (see below).

An even higher resolution forecast from the previous day showed the main rain band ahead and, surprisingly, the rain arc moving north of the Sound.

And yes, the high-resolution forecast accurately predicts the location and timing of the Puget Sound convergence zone.

The advances in high-resolution weather forecasting are astonishing. How can we do that?

Vast satellite-based observational resources provide a good depiction of what is happening across the Pacific in three dimensions. High-resolution weather forecast models will then simulate detailed interactions of air from the Pacific Ocean with our complex regional terrain.

We have come a very long way in the past few decades, providing much better forecasts and helping to warn/protect people in the area.

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Announcement: Free public lecture at Kane Hall on October 10: Global Warming, Jet Streams, and Cold Waves

You are all invited to attend an excellent public lecture by Professor Jonathan Martin on how global warming affects the jet stream and cold air outbreaks.

This will be a timely and interesting lecture for non-meteorologists and is given in honor of UW Professor Peter Hobbs.

The talk will take place at 7pm in Kane Hall 210.

If you want to go, please register online This:

Parking is available (at a modest cost) in the UW Central Parking Garage, located just below Kane Hall. Or take the light rail (UW stop is a 5-10 minute walk away).