Last 80F Day of the Year in Seattle

It is kind of sad.  

Today, accompanied by glorious heat and sun, was probably the last day above 80F until next spring. 

Fortunately, our last warm day was announced by something very special:   an amazing auroral display last night.

First, the temperatures.  Today's high temperatures got into the mid to upper 80s around much of western Washington (see map).  The light reds are 80F and above, dark reds 90 plus.  Sea-Tac got to 86F.  Amazing.

A number of locations around the area (like Sea Tac) achieved their record high temperature for the date, with high temperatures 15-20F above normal.

Why so warm?  Warm air associated with a ridge of high pressure and moderate offshore (easterly) flow, which kept the cool ocean air offshore (see winds and temperatures above Sea Tac below).  Easterly flow also caused warming as air subsided over the western slopes of the Cascades and Olympics.

The situation is about to change radically, and a front is poised to move in on Friday (see satellite image a 8 PM). And models promise strong onshore flow and a series of weather disturbances.  You won't have to water your lawn or bushes anymore.

Now why do I think our 80F days are over?  First, virtually all the ensemble forecasting systems, which run forecasts many times to get at uncertainties, shows a cool down over the next 8 days, with temperatures not getting much out of the 60s. The temperatures predicted at Seattle from the NOAA/NWS GFS model illustrates this below.

And after that, it is simply too late to get very warm, with the sun weakening and the nights getting longer.  To illustrate, this plot shows the record highs at Sea-Tac (yellow), based on daily records.  In September, the record highs can get to around 90F, but the bottom drops out during October, and after around October 12th, Sea Tac never has got to 80F.  Depressing, but true.

But our depressing future cool down is at least made more palatable by the stunning aurora of last night.  Here is an image provided by Greg Johnson of Skunk Bay Weather, on the north side of the Kitsap Peninsula.   A video link is here.