Timing Thursday's Rain

Record highs are noted by the asterisk. We come close to breaking record highs for Monday once again.

Redding Time Lapse 12/11/15

El Nino

This year’s milder start to the cold weather seasons can be attributed to a climate feature called El Nino. This climate pattern pushes a clever twist on the atmospheric pattern across the globe by altering typical seasonal patterns. Let’s discuss what exactly an El Nino is:

Let’s take this story far from southwestern Connecticut and let’s start near the equator on the Pacific Ocean near Peru and Ecuador.

The normal weather pattern for this region is very different from what we are used to here in Connecticut. The “jet stream” over us moves air from west to east, but down there, their version of our jet stream is called the “trade winds” which pushes air from east to west. Quite the opposite!

In a normal scenario, the deep waters near Ecuador and Peru will warm because of its location near the equator (the warmest climate region on earth). The trade winds will then push the warm water across the Pacific Ocean. When the warmer waters push out of the way, the colder water under the warmer water ends up warming and the process repeats. Warmer waters encourage evaporation and could lead to storminess. Therefore, the western equatorial Pacific region normally finds warm waters and rainy weather. Whereas the eastern Pacific near Ecuador and Peru can often be drier.

During an El Nino event, the trade winds slow down or completely reverse direction. This no longer pushes the warmer water to the western Pacific and the warmer water pools along the eastern Pacific near South and Central America. With the water unable to move west – the evaporation and stormy weather shifts from western Pacific to the eastern Pacific. Uh oh!

In turn, this “pooling” of warmer water and increased moisture into the air can be caught into the southern jet stream which then forces wet weather and storms to develop along California and the southern United States!

When the rainy and stormy weather reaches the Gulf of Mexico or the Atlantic Ocean, they can continue to trigger storms that eventually then ride up along the eastern coast. This could bring some close calls to wet weather here in southwestern Connecticut – and since storms from the south are typically “warmer” than storms from the north [because they are closer to the warmer climate] – it makes for a tricky forecast.

Tricky? Why? Well as these storms move north – they can actually be influenced by the cooler weather up north! That means we can see some close calls between rain and snow, too! And not just near-misses.

Also, warmer water warms the air above it. In winter-time, this warmer air surges farther north than normal and colder Canadian air has a harder time dipping down into the United States – thus limiting cold air outbreaks. However, this doesn’t mean cold outbreaks would be non-existent! It just means that chances for outbreaks decrease in El Nino events.

According to the National Oceanic and Atmospheric Administration (NOAA), this year’s El Nino can rank as one of the top three strongest El Nino events in recorded history since 1950.

Based on the strength of the El Nino – it is expected to peak during our winter – which is summer in the southern Hemisphere, where the water will be warmest near Peru and Ecuador. It is forecast that weakening is likely to take place in our late spring with a neutral pattern by our early summer.

So could this mean a milder winter for us?

Source: Climate Prediction Center, NOAA 

It looks likely! According to the NOAA Climate Prediction Center, the three-month temperature outlook for December, January, and February shows at least a 40% chance for above seasonal temperatures here in southwestern Connecticut.

It already seems to be the case here in southwestern Connecticut for autumn since it was the 2nd warmest autumn on record – falling behind 2011. Looking at December, we already had a week where temperatures were above seasonal, too!

Given that this year’s El Nino is fairly strong through observation of the water temperatures and observed effects so far, now I ask you:

Would you say that there is a likely possibility that the next few months could be warmer than seasonal?

And that, folks, is what it’s like to think like a meteorologist – to examine, to infer, to analyze, and to hypothesize based on what we know – just to create a vision of what could be.

Enjoy the weather!

Meteorologist Mike Rizzo

@meteor_mike

fb.com/MikeRizzoWeather

Redding Time Lapse December 2, 2015