La Nina Strengthens...Again!

(With the dreaded La Nina cooking again, I thought a re-broadcast was appropriate.)

It’s funny. Every October, like clockwork, people start asking me what are the projections for our winter. Let’s face it…no one whats a repeat of last winter’s snowfall. Well, no one except Perfect North. Right, Chip? LOL

You see, La Nina ("little girl") is underway and it could foul up your winter plans! Perhaps more importantly, ice storms could be more frequent this winter.

La Nina Update

The latest update on this moderately understood weather phenomenon is out. La Nina continues to strengthen and will persist through the winter. The sea surface temperatures (SST) have dropped .5 degree over the last four weeks. It may not sound like much; but, we are talking about a vast ocean area over the equator. So, a La Nina Advisory has been issued.

For background, La Nina is unusually cold ocean water located in the eastern equatorial Pacific. Typically, a La Niña is preceded by a buildup of cooler-than-normal water just below the surface. Although not fully understood, weather factors bring that water to the surface. The interaction between the ocean and the atmosphere end up changing the global weather pattern.

Now, with so much detailed information on La Nina, I want to stick to the effects on the Tri-State. So, if you’re interested in more specific La Nina info, you can find it here.

Anyway, La Nina may dash every skier’s and snowman builder’s hope for a a fun and exciting Winter. On average, La Nina means a warmer than usual temperature profile with above average moisture. In plain terms, it's less snow and warmer weather. Let me take you deeper. My weather association, the AMS publishes an academic magazine every month called BAMS (Bulletin of the American Meteorological Society).

Tri-State Effects

A couple of Florida State researchers studied La Nina in 2001. They looked at 143 weather stations and came to these conclusions about the Ohio Valley, Midwest and Cincinnati:

The Ohio Valley receives less snow in early and midwinter during both El Nino and La Nina than in winters without them. The Midwest had the same trend, but only during midwinter. There is a wide range of effects on snowfall in the Midwest. For instance, Cincinnati snowfall totals declined by 2 to 5 inches during an El Nino or La Nina. But, parts of Michigan declined by 1-2 feet!

Now, if you consider Cincinnati’s average snowfall totals for the cold weather months:

November 1.3”
December 3.7”
January 7.8”
February 6.0”
March 3.8”

Up to five inches can really make a difference. Essentially, it wipes out an entire month of snowfall.

Here’s the real kicker to the story. During a La Nina episode, the jet stream or storm track shifts. The National Oceanic Atmospheric Adminstration notes, “It is inaccurate to label individual storms or events as a La Niña event. Rather, these climate extremes affect the position and intensity of the jet streams, which in turn affect the intensity and track of storms. During La Niña, the normal climate patterns are enhanced.”

This is an important point. Researchers know that both La Nina and El Nino don't always play fair. By that I mean, some years the statistics don't follow the pattern. Last year, with La Nina brewing, the Tri-State received above average snowfall. In December 2010 alone, we received over a 13.6" more snow than average. This will be an interesting winter to watch.