Thunderstorms and a Winter-Like System Approaches the Pacific Northwest

A wet, winter-like frontal system is now approaching the Northwest and will arrive on Friday, but before I discuss it, let's consider the substantial thunderstorm activity that struck the regional mountains on Wednesday.

The weather radar image around 2 PM Wednesday showed a strong thunderstorm over the northeast Olympics and a line of convective showers over the eastern slopes of the Cascades.

The Seattle Space Needle panocam showed the extensive scale of the Olympic Peninsula thunderstorm:

And the Space Needle cam also indicated a line of storms over and east of the Cascades.

The Wednesday thunderstorms were associated with hundreds of lightning strokes, as illustrated by a one-hour sample during the mid-afternoon on Wednesday:

Why is there so much lighting on Wednesday afternoon?    

The air above us was unusually unstable, meaning that a rising parcel of air would tend to accelerate upward if lifted.   A measure of such potential instability is called CAPE (Convective Available Potential Energy), and values of CAPE were unusually high over the region (see plot below).

High for the Northwest, but the folks in the Midwest would laugh.

Convection tends to release at the surface warms, but yesterday the process was aided by increasing westerly winds (from the west), which provided strong upslope flow over the high terrain.  It helps to give the air a kick upwards to get the instability going.

Finally, a wet, winter-like system is now approaching our region, as illustrated by the latest infrared satellite image (below).  Looks like winter!

The total forecast precipitation over the region through Sunday morning is substantial (see below), and should both moisten the surface, add to the water supply, and reduce wildfire potential.

The "Super" El Nino Will Weaken Super Fast

There is a lot of folk wisdom about the current El Nino situation.

The flame that burns twice as bright burns half as long.

Fast ripe, fast rotten.

Up like a rocket, down like a stick.

The higher you climb, the harder you fall.

The media, such as the Seattle Times, have been breathlessly describing the currently developing El Nino, with many applying the unscientific "super" prefix.   Some have suggested devastating impacts (see below).

The latest forecasts paint a different picture.  

El Nino will develop rapidly this summer/fall but will weaken quickly during the winter.

This rapid decline is important, since the winter is the period with the greatest impact of El Nino on the meteorology of the Northwest.

Let me demonstrate this to you.

The latest forecast of the NOAA CFS model (below) predicts a peak warming of the tropical Pacific in October-November to around 2 °C (major El Nino), followed by a rapid cooling to 1°F (moderate El Nino) by January-February.

Looking at a collection of many forecast models (below) provides a similar picture:  a substantial weakening of El Nino during the winter.

The bottom line of these forecasts is that some of the over-the-top predictions by the media and others regarding a super El Nino causing severe weather impacts may be a bit over the top.

Finally, looking at the current short-period forecasts, it appears that we have a wet/cooler than normal period ahead, as shown by the NOAA predictions below.

The latest UW forecast model predictions for precipitation totals through Sunday morning (below indicate a nice wetting across Washington State.  A lot more precipitation is predicted during the next 10 days.