Happy New Year!

TWZ: 2015 In Review

What a year! Yes, this blog has only been around since June, but I am continually amazed at just how far and wide TWZ has grown in just a few short months. In a very small amount of time, TWZ has reached so many people and catered to visitors from vast parts of the globe. That’s a kind of growth I never imagined to be possible. Thank you so much for coming along on this adventure and I can’t wait to see what 2016 will bring about for this young, but thriving community. Here’s hoping that you learned a few things about the atmosphere above our heads in 2015 and that 2016 continues to spark your interest in “all things weather”.

Be sure to follow the link below for an in-depth look at TWZ’s stats for 2015!

Click here to see the complete report.

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The Weather Explained

What is El Niño?

I have no doubt in my mind that you have at least heard the term “El Niño” before. Chances are if you have watched a news story about some meteorological happening over the past several months the phenomenon very likely was at least mentioned. El Niño in my opinion tends to be a catch-all reason behind crazy meteorological events according to the media, especially over the past several weeks and months. While some of that hype is legitimate (this year’s El Niño event will likely go down as one of the strongest on record), as with other phenomena within the field of meteorology (and in this case within the field of climatology), the situation is a bit more complex. So what exactly is El Niño and why does it seem to do some strange things to the weather, both nationally and locally? Also, what’s up with that name? I’m no climatologist, but hopefully I’ve got some answers for you.

El Nino
NOAA

In order to understand a little bit more about El Niño, you first have to understand the difference between meteorology and climatology. They are two separate, but related fields. The differences between the fields can often become blurred, especially in short news stories that simply don’t have the time or space to explain the difference. Meteorology typically deals with the day-to-day happenings of the weather overhead. When trying to determine what outfit to wear on a specific day, you are going to find the information you need within the field of meteorology. Climatology on the other hand deals with much longer-term meteorological events and patterns. If you wanted to know the general type of clothing to wear during a particular season of the year, climatology is where you’d find that answer (for example, we wear heavy jackets in the winter and shorts in the summer here in Southwest Virginia, but that could be very different in other parts of the country and the world). Meteorology can go to about a week or so out in terms of accuracy, but everything beyond that point lies within the realm of climatology. Think of meteorology as current events and climatology as history class. When viewed through that analogy, you can get an idea of the differences and similarities of the two fields. Any good meteorologist must have a solid handle on the climatology of the particular area for which he or she is forecasting. For example, the majority of the snowfall we receive during the winter months here in Southwest Virginia typically arrives in late January through the month of February. With that information in the back of your mind, if you see a forecast model output churning up a foot of snow for our area in late November/early December, you can take that solution with a very healthy dose of salt simply because the history says that we just don’t see that kind of snow this early in the season. Of course, the atmosphere is very complex and that’s not to say we couldn’t see a freak snowstorm during that time period. History just says that scenario is rare and history is a very good place to start with a forecast.

El Niño is considered a climatological phenomenon due to the fact that it takes place over several weeks and months. The temporal reach of El Niño is quite impressive, but the geographical reach of the event is even more so. The long-term impacts of the pattern have the power to change and influence the short-term weather pattern over our heads. It’s truly fascinating when you think about the happenings of the atmosphere as an interconnected, global system. One change in a particular area can set off a chain of events that can affect locations around the world. While El Niño typically gets all of the love within the media, it is just one of many of this particular type of phenomena known as teleconnections. According to the American Meteorological Society, a teleconnection can be defined as follows:

“A linkage between weather changes occurring in widely separated regions of the world.”

El Niño is part of a much bigger family of large-scale weather patterns that take place over several weeks and months. The North Atlantic Oscillation (NAO) and Arctic Oscillation (AO) are just a few of the different teleconnections that impact the United States each year, along with El Niño (which is technically known as the El Niño Southern Oscillation, or ENSO for short). Teleconnections are caused by various different things. For example, the Madden Julian Oscillation (MJO) is caused by groupings of clouds over a particular area of the Indian Ocean. ENSO is caused by changes in ocean temperatures along the equator spanning all the way from the Indonesian islands to the western coast of South America. That may not seem like a big deal, but this change in ocean temperatures leads to some major differences from the normal weather patterns of the area.

The term “El Niño” is Spanish for “the Christ child”, which is fitting considering that the phenomenon tends to take shape around the Christmas season. Once formed, an El Niño event can last for months, and in some cases well over a year. During the early 20th century meteorologists discovered some interesting changes in the atmospheric pressure over parts of the Pacific Ocean every few years. The scientists eventually traced these changes in pressure back to ocean temperatures, specifically off the coast of Peru. Fishing has always been a large contributor to the Peruvian economy due to the cold, nutrient-rich waters that lie just off the coast; a perfect combination of ingredients for a thriving fish community. These cold waters lead to a general area of higher atmospheric pressure over Peru and it’s coast, meaning that the westernmost portion of the country doesn’t typically see a whole lot in the way of precipitation. In other words, pleasant fishing conditions are typically the norm for Peru. El Niño messes with that happy norm however. The phenomenon leads to a shift in winds which ultimately leads to warmer waters off the Peruvian coast. This warm water allows for air to rise which in turn lowers the atmospheric pressure overhead. The one overriding rule of meteorology is that rising air equals precipitation in some way, shape or form, and that rule holds true here as well. Peru, which is normally a fairly dry place, becomes home to rain and thunderstorms during an El Niño period. Warmer waters also mean less fish and a big hit to the Peruvian economy (another topic for another time, but clearly the weather can have a big impact on more than just what you should wear on a specific day). The effects of El Niño may begin with Peru, but they certainly reach to other places of the world.

The warming trend that El Niño brings to the Pacific basin allows for an alteration of the typical Pacific jet stream pattern of the northern hemisphere. Lower pressure off the Peruvian coast allows for the Pacific jet stream to take a dive towards the south. Here is a pretty good diagram that shows the differences El Niño can bring about as opposed to “normal”:

jet stream
NWS Blacksburg

Ripples of energy ride along the Pacific jet meaning more precipitation than usual for the southernmost portion of the U.S. You also can see in this diagram the term La Niña, which is essentially El Niño, but in reverse. La Niña events don’t typically get as much love within the media as their El Niño siblings, but they certainly have widespread effects too. A La Niña event leads to warm ocean temperatures on the opposite side of the Pacific, leading to a whole new set of widespread changes to weather patterns around the world. This is why most teleconnections have the term oscillation in their names. There are varying degrees of ENSO (along with other teleconnections), with conditions typically oscillating back and forth between each phase or ending up somewhere in the middle each year. Here is another diagram that shows how both phases of ENSO (El Niño and La Niña) typically cause the Pacific jet stream to interact with the northern Polar jet stream and what that means for the United States:

elnino;lanina
NWS Blacksburg

 

Here is a basic rundown of each phase’s effects within the U.S.:

  • El Niño:
    • Wet conditions for the bottom half of the country
    • Cool conditions from Texas to Florida and into the Mid-Atlantic
    • Warm conditions for the top half of the country
    • Dry conditions for the Ohio Valley and parts of the Northern Midwest
  • La Niña:
    • Dry conditions for the bottom half of the country
    • Warm conditions from Texas to Florida and the Mid-Atlantic
    • Wet conditions for the Ohio Valley
    • Cool conditions from Washington state to about Minnesota
    • Wet conditions for the Pacific Northwest

These are of course just generalizations that give us a good idea of what to expect during each respective phase of ENSO. The atmosphere is a constantly changing beast where several factors must be taken into consideration when trying to compile an accurate forecast, but hopefully this gives you an idea as to the general impacts ENSO can have on the United States. It is also important to know that these generalizations show each phase’s offset from the climatological norm. For example, during an El Niño event, parts of Florida are typically cooler than conditions that have been recorded over the past 30 years or so for those same parts of Florida. Florida would see cooler than the average conditions during that particular time of year when an El Niño event is taking place.

The fact that we have these generalizations is telling to how much we still have to learn about the El Niño Southern Oscillation. What makes an El Niño (and transversely, a La Niña event) event occur every 2-7 years at seemingly random intervals? Why is the interval between events sometimes longer or shorter than the ones experienced in the past? Why do some events exceed others in strength and longevity? These questions just speak to the fact that while we have come a very long way in terms of learning about the atmosphere over our heads, we still have a long way to go.

Hurricane Patricia
Hurricane Patricia before slamming into the Mexican mainland. (NOAA)

While we are still learning about El Niño’s inner workings, it is obvious that the event has serious potential to mess with the “normal” workings of the atmosphere above us. I mentioned before that this year’s El Niño will likely be one of the strongest we’ve ever seen. Considering this, it would come as no surprise that this year’s Pacific hurricane season was one of the worst on record (16 hurricanes, 11 major hurricanes, and 10 Category 4-5 hurricanes, all of which are new records). Hurricane Patricia was the strongest hurricane to ever make landfall, with sustained winds of around 200 MPH right before it moved inland over Mexico. All of this can be attributed to the fact that hurricanes thrive over warm ocean water, which this year’s El Niño was more than happy to provide. While the Pacific season was filled to the brim with strong storms, the Atlantic season on the other hand was fairly calm when compared with previous years. This is a fairly common trait of an El Niño event, where warm waters needed for hurricane development just aren’t as prevalent within the Atlantic basin. This feature shows how connected the global system can be and the impacts a small change can have on two very distant locations.

While El Niño can certainly cause some funny things to happen weather-wise here in the U.S., it probably shouldn’t be the catch-all term that it can be within the media today. We have to take into account the entire atmosphere as a whole. With that being said, you hopefully now have a better grasp of just what that term means and how it can bring vast changes to the United States and areas around the world. The next time you hear the term in a media report, just remember that the phenomenon is a climatological event known as a teleconnection that can help shape the meteorological happenings over our heads. While there is still a lot to learn, we do know that El Niño is typically characterized by abnormally warm ocean waters along the Pacific basin, specifically off the Peruvian coastline. These warm waters cause changes in the usual atmospheric pressure of the area which leads to changes in weather patterns around the world. We’ve already seen some incredible weather events that were caused by this year’s El Niño event and only time will tell what more “the Christ child” could have in store over the coming months and into the future.


What questions do you have about the weather? Get in touch with me through the About page and I will do my best to answer them! Thanks for tuning in as always!