El Nino's Collapse Has Begun

The entire character of this winter has been characterized by a strong El Nino.  

El Nino impacts have included low snowpack over Washington State, huge snowpack and heavy precipitation over California, and warm temperatures over the Upper Plains states.

However, El Nino's days are numbered and its decline is proceeding rapidly right now. 

First, consider the critical measure of El Nino:  the sea surface temperatures in the central tropical Pacific (the Nino 3.4 area).  The warmth of this El Nino peaked in late November (about 2.1°C above normal) and is now declining fairly rapidly (currently at roughly 1.3°C above normal).

But the cooling is really more dramatic than that:  a LOT of cooling has been happening beneath the surface!

To demonstrate this, take a look at subsurface temperatures (the difference from normal) for the lowest 300 m under the surface for a vertical cross-section across the Pacific (below).   

On 8 January, there was a substantial warm layer extending about 100 m beneath the surface.

But look at the same cross-section on 27 February.  

Wow--what a difference!  The warm water has dramatically cooled, with only a thin veneer of warmth evident for much of the Pacific.   Rapidly cooling has occurred beneath the surface and this cool water is about to spread to the surface.

If you really want to appreciate the profound cooling take a look at the amount of heat in the upper ocean for the western tropical Pacific (below, the difference from normal is being shown).

A very, very dramatic change has occurred.  The heat content of the upper ocean peaked in late November and then plummeted.   Declined so much that the water below the surface is now COOLER than normal.

El Nino fans will be further dismayed to learn that models are going for a continuous decline....so much so that they predict a La Nina next year!

So why should folks care about this major decline in El Nino here on the West Coast?

El Nino results in a trough of low pressure centered to our south and west, something evident in the upper-level maps (for 500 hPa, about 18,000 ft) for February hown below. The blue colors indicate lower-than-normal heights/pressures.

But with El Nino weakening, a major pattern change is possible, and the latest model  forecast is for a major change, with a huge ridge (red color) over our region for March 13-20th.  

FINALLY, we may experience some real springtime weather.  Like highs in the mid-60s!  I can't wait.  Tired of one frosty morning after another!

Coldest Early March in a Generation, Large Improvement in Regional Snowpack

If it feels a bit chilly to you, you are not imagining it.   

And if you are worried about the snowpack, you can rest easy, there have been big gains since the start of the year.

First, temperature.  For many of you, this is the coldest early March in memory.  Consider the average high temperatures for the first five days of March in Seattle (see below).   We are experiencing the coldest start to March since the late 1980s.   

There is something else interesting in this plot:  the average high temperatures in early March have actually COOLED since the 1980s (the trend line is shown by the brown line).   

If you want to really get a chill up your spine, take a look at the minimum temperatures this morning (March 6).  Mid-20s over southern Puget Sound and single digits over northeast Washington.  Portions of central Oregon dropped below ZERO.   This is with longer days and a much stronger sun.

Then there is the issue of snowpack.   Well, good news.....there has been substantial recovery and more is on the way.

The current snowpack percentage of normal for Washington State (shown below), shows several watersheds (like the crucial Yakima) at 80% or more.  The western side of the Cascades is now at roughly 2/3 of normal.   And the Olympics, which was down to roughly 25% has doubled to 50%.

Oregon's snowpack is in excellent shape (see below), with many watersheds well over 100% of normal.

Just to show you how much things have improved, below is the situation over Washington on January 4th.    MUCH worse, with much of the state below 50% of normal snowpack. Huge improvement.

So with all this cold and snowy news, what do you think was on the front page of the Seattle Times this morning?   

Lack of snow and DROUGHT.  And without a single mention of El Nino, the key driver of the lack of snow earlier in the season.  I will leave it to you to speculate why they are doing this.  But it is not good.