Developing La Nina Is Old News!

Many meteorologists including myself have written about the state of the winter El Nino and the strong probability that ENSO would transition to an infant La Nina in spring/summer of 2017 for a while now.  Main news sources give the impression at this transition out of El Nino as something new.  I tweeted a preliminary La Nina outlook based on CPC analogs BACK IN NOVEMBER!

Recently, NOAA stated in their newest bulletin, very accurately, that El Nino was finished as of June 9th. These transitions don't occur instantly. The transition away from El Nino toward La Nina has been ongoing for months.

The region used in determining the state of the equatorial Pacific is the ENSO 3.4 region.

All Nino regions (especially the key Nino 3.4 region) temperatures have been falling since the start of the year.

This animation showing the ocean temperatures vs normal values show this perfectly. See the cooler water on the right side (east).

A larger spherical look at the ocean temperatures show the transition even better starting in January. The last image is what the mature La Nina looked like in January of 1999.

According Bob Hensen at Weather Underground, a recent study found that about a 1/3 of first year La Nina events returned of persisted for a second year. This behavior seems to be more frequent over the last 150 years.  It is possible that La Nina could linger into 2018.

It takes months for the effects of any ENSO state (El Nino, neutral or La Nina) to be reflected in the atmosphere. So its very difficult to predict at this time what the winter will be like for specific locations. But we can perform some basic albeit general statistical comparisons between snowfall and La Nina.

Using the ERSSTv4 ocean temperature dataset, a list of La Nina strengths can be determined. Hat tip to Eric Webb.

Based on these years and rankings, I matched up our Cleveland snowfall for these La Nina years. Here is what I found.  The majority of these years had ABOVE NORMAL SNOWFALL in Cleveland!

This is no guarantee of above normal snowfall during the winter of 2016-17 as there are other factors yet to be determined. 

Last year, I posted my thoughts on the upcoming winter (2015-16) around Labor Day. Expect some more detailed thoughts on the effects of La Nina on the upcoming winter of 2016-17 around the same time this year.  Until then, let's enjoy summer!

Precipitation and El Ninos: West Coast Rains Not Always A Lock

Not all El Ninos are alike. We've heard this time and time again. Sea surface temperatures are never exactly alike. Jet stream position varies. Overall winter temperatures vary too as does the location of above and below normal precipitation. We remember the El Nino of 1997-98 that produced heavy rains out west.  But that's not always the case.

We examine the top El Ninos according to the ONI Index from this site. We only examined the El Ninos that are ranked MODERATE, STRONG AND VERY STRONG.

THE STRONGEST EL NINOS (1997-98 and 1982-83)  

Storm track kept heaviest precipitation along the west coast and in the southeast.  At or below normal precipitation around the Great Lakes.

STRONG EL NINOS - RANK #3, #4 AND #5

Storm track is still strong in the deep south with a southerly shift out over the Gulf of Mexico with above normal precipitation.  Aside from the winter of 1957-58, precipitation along the west coast is less in these years. Still below normal precipitation across much of the Great Lakes.

MODERATE EL NINOS

Southern storm track is still strong but weaker during the winters of 1986-87 and 1963-64. Storm track shifted much further north into the Ohio Valley and Mid-Atlantic during the winters of 2002-03 and 2009-10 with heavy wet snows. During many of these winter, well below normal precipitation was observed along the west coast especially during the winter of 1963-64

Contrary to what you hear, its not a guarantee that El Ninos always produce heavy precipitation events across the west coast and the Pacific Northwest. It does appear that the chances are greater with stronger El Ninos per the ONI Index.  The southern storm track seems to be more consistent--with varying intensities--in each of top El Ninos. 

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A few side notes:

* Another modulator of the El Nino and storm track is the mode of the PDO (Pacific Multidecadal Oscillation). The winters of 1957-58, 86-87, 87-88, 97-98, 2002-03 and this year so far all have PDO values strongly positive.

* Yet another area of the Pacific that may have ties to the evolution of El Nino is the Pacific Meridional Mode located between the equator and Baja California. The link between the two is being studied. Here is a paper published in 2014.  Looking at the data from late summer through fall during early El Ninos, late 1957, 1986, 2009, 2015 (and partly 1982 although it was trending cooler) all had positive values (above normal water temperatures).

Do we see some matches above for this winter?  Hmmmm.

Yes, Big El Nino Brewing But Not All El Ninos Are Alike: 2015 vs 1997

You have probably heard about the BIG EL NINO or SUPER EL NINO or some phrase like that. If not then you will soon enough. Eventually EL NINO will trend on social media by the end of September. You heard it here first.

But hold on. Doesn't Big El Nino mean mild winter?  Not necessarily. See the differences between the last BIG El Nino in July 1997 and July 2015.  Also, notice the differences in the North Atlantic ocean temperatures? This is why the winter 2015-16 outlook is not an "El Nino shoo-in". Not all El Ninos are alike. (See my post on the different El Ninos and what they mean for our weather)

When will we know enough to make an educated assessment on the upcoming winter?  Probably by the end of September. Stay tuned...

How Does This Early El Nino Start Compare To Others? Implications.

Last year at this time (Spring 2014) the talk of a "Super El Nino" was at the forefront of weather circles. The resultant El Nino later in the year surely didn't fit the hype for a variety of reasons.  This year's close El Nino cousin is a little different.  I believe the "hype" is more warranted this go-around.

Here is a great El Nino animation from NASA showing its evolution.

Using the ONI (Oceanic Nino Index), I logged all El Ninos since the early 1900s.  The ONI is a 3 month overlapping sea surface temperature anomaly index of the Nino 3.4 region, the area used in defining the ENS state.

In determining how different this evolving El Nino is compared to past events, I used the actual NON-OVERLAPPING monthly Nino 3.4 sea surface temperatures anomalies for each early stage El Nino event starting in March and continuing through December. My goal was to see any slight variation in ocean temperature that was smoothed by the 3-month overlapping ONI.  Note: Many of these El Nino events continued into the following year not shown here.

The first chart below shows El Nino events from 1982 to early 2015.

Some key points:  This year's event has started MUCH FASTER and earlier than the historic El Nino events in 1997 and 1982. 

The 1986-87 event peaked in summer then slowly dropped by fall after a similar start.

The current El Nino is well ahead of all of the events from the early 1950s through the late 1970s. Some of these El Ninos were weak. 1965 and 1972 was strong.

The El Ninos of the late 1920s, 30s and 40s were late bloomers showing little sign of El Nino until mid fall.

The early 20th century El Ninos had more erratic evolutions. Even the strong El Nino of 1918 struggled until fall/early winter.

Of all 23 El Ninos I charted, only the El Nino of 1905 had WARMER ocean temperatures in May compared to this year's event. That year peaked at 1.5 in September.

So in summary...

*  El Nino headlines need historical perspective.  Don't be quick to compare this event to the 1997 event per the model projections.

*  The 2015 El Nino is building faster than any El Nino since 1905

* The rapid rise in ENSO 3.4 ocean temperatures this early in spring historically usually means the El Nino will sustain itself through the summer. The major El Ninos of 1997, 82 and 72 started off slower. A big start doesn't necessarily mean 2015 will be another 1997 or 1982.  In fact, the warmth is more centralized. The warmth in '82 and '97 sloshed eastward by summer.

Warmth so far this year has two lobes, one central near dateline and another eastern closer to South America.

* The moderate El Ninos (SST 3/4 between 1.0 and 1.5) in 1987, 72, 65, 57, 30, 25, 23, 18, 05 and 1902 all sustained El Nino status through December per the ENSO 3/4 ocean temperatures.

What does all of this mean for the summer, fall and upcoming winter?

* The next 2-3 months will be critical in determining how this El Nino will impact our (US) weather this summer and especially fall.early winter.  The position of the warmth will be a big factor.

*  How much cool water near Australia relative to the ENSO 4 and 3/4 region temperatures will be HUGE in driving the westerly wind bursts necessary in sloshing more warmth to the east keeping the El Nino machine going.

Next week, we'll dive more into why the COOL WATER NEAR AUSTRALIA is so critical in the development of El Nino

End of Winter Right? Not So Fast

Northern Ohio has not had a string of days above 40 degrees similar to what we will enjoy this week since the week of Christmas. That stretch went from December 22nd to December 28th (44, 52, 59, 41, 49, 54 and 47).  While it feels great as it melts off the majority of the snow cover (big piles will stay around a while), the pattern is still ripe for more cool air relative to the averages for this time of year.

To be clear, mid March sun is much stronger than mid January sun.  The average temperature for March 8th is 44 degrees. The average temperature on March 23rd is 50.  So temperatures in the 30s or lower 40s would be considered below average. It's all relative to the season in question. It's not arctic but its not considered spring.

One of the components that we use in formulating longer range outlooks of 8-14 days is the EPO.  Its a measure of the pressure patterns in the eastern Pacific Ocean (EPO region in red boxes---excuse my crude drawing). I also included the WPO which is another favor in evaluating the pressure pattern (further west) over the Pacific Ocean.

This winter (since January), high pressure has settled over Alaska and western Canada/western US while low pressure developed south northern of Hawaii. Notice the trough and cold across the eastern US.  When the EPO is negative, this favors cold and snow east; milder temps and dry west.

The EPO has bounced back positive recently.  The trough in the east and the cold have retreated north as the ridge slid east.

By the 3rd week of March, it will more than likely drop negative again which will strongly favor colder than normal temps in the east again.

I CAUTION EVERYONE. THIS DOES NOT MEAN HIGHS IN THE 10s AND 20s WITH BELOW ZERO TEMPERATURES SIMILAR TO WHAT WE SAW IN FEBRUARY!



Notice how the temperatures spike later this week (dates are on the bottom) then drop below normal starting mid week next week on the graph below. See how temperatures fall but only into the 30s.

The bottom line:  Below normal temperatures around the 20th of March means temperatures below 50 degrees.  So highs in the 30s up through the mid 40s would classify. Not arctic cold but NOT SPRING...yet.

Signs of Colder Air Returning Before Christmas

You live by your long range outlook sword and die by it.

This past summer and fall, we hinted that the variables present across the globe were conducive for a colder/snowier winter ahead. November big start out of the gate was a big sign that winter will be cold and snowier than average.

This brings me to the present "break" in the arctic air.

High temps across the eastern US trend slightly above normal by the weekend. Typically when November temperatures average as cold as last month did, bounce-backs are not that uncommon in December.

What has me concerned is the Typhoon in the eastern Pacific. Two models have it recurving back to the northeast next week with it eventually getting absorbed into the Alaskan low which boosts the western ridge making eastern US troughs/colder intrusions that much easier.

The American Model also shows the recurvature by December 10th

 The European is the only outlier with a more westerly track.

Remember the old Typhoon Rule? It states that when Typhoons recurve north and east near Japan, this signifies the overall pattern is conducive for below normal temperatures across the eastern US. See my post a few weeks back on this HERE.

The PNA pattern is showing a strong tendency toward positive which indicated the ridge is rebuilding in the west which drops the trough/colder air east.

I ran a composite of all December years where the PNA index was PLUS ONE OR HIGHER and MINUS ONE OR LOWER. You can see how these correlate strongly to extreme temperatures cold and warm.

PNA at -1 or Below correlates to MILDER EAST

PNA at +1 or Higher correlates to COLDER EAST

Sure enough, the European and Canadian models both develop the beginnings of an eastern trough by December 16-17.

So unless the typhoon tracks further west and doesn't recurve and the PNA pattern (which has trended colder across the US for a while now does a complete 180 degree flip), I would expect temperatures to trend colder the week before Christmas with higher chances of lake effect snow.