What is El Nino & Why Should We Care About it? | NBC 10 Philadelphia
NBC10 First Alert Severe Weather Central

NBC10 First Alert Severe Weather Central

What is El Nino & Why Should We Care About it?

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    NEWSLETTERS

    El Nino is a huge area of extra warm water in the Tropical Pacific. Ocean temperatures always vary, but this is a large and persistent area that can stretch from the coast of South America all the way to the Phillipines. That’s a lot of real estate and a lot of energy. It can influence weather in many parts of the world, including ours. And the one developing now could rival 1997-98 as the strongest El Nino ever recorded.

    The animation below shows how the El Nino has quickly evolved into a monster. The redder the colors, the more extreme the temperature change from average (called “anomalies”). And, as you can see, it is still strengthening.

    SUPER EL NINO=SUPER QUIET HURRICANE SEASON

    As we head toward the beginning of August, we keep getting closer to the peak months of hurricane season. August, September, and October represent the peak, with September at the top of the list historically. Anyone with interests at the shore tends to become more focused on the tropics. But there has been only a small increase of tropical activity in the Atlantic Basin (Gulf of Mexico, Caribbean, and North Atlantic). A tropical disturbance in the far East Atlantic is being watched as of this writing. Here is the satellite loop: http://www.goes.noaa.gov/dml/eumet/nhem/eatl/rb.html

    It doesn’t seem to make sense, but we can largely thank the Pacific Ocean for decreased activity in the Atlantic-specifically, the “Super” El Nino that is developing there.

    El Nino’s biggest influence is obviously in the Pacific, especially the Tropical Pacific. This leads to tremendous amounts of thunderstorms. The strong upper-level winds from some of these storms cross into the Tropical Atlantic, creating extra “wind shear." Wind shear, or big changes of wind direction or speed as you go higher in the atmosphere, helps prevent Tropical Storms from forming, or weaken ones that have already formed. On the other hand, all that warm water in the Tropical Pacific leads to more storms, and helps make for stronger tropical systems. There are a lot of “Super-typhoons” when there’s a strong El Nino. This year is no exception.

    Take a look at the tropical tracks for the Atlantic and Pacific so far this season from http://weather.unisys.com/hurricane/index.php (Unisys has had the best historical tropical tracking information since the internet’s early days).

    The Atlantic has had three named storms already, but all formed close to the U.S., weren’t around long, and none became hurricanes. The “Super” El Nino effect is the lack of action in the tropics, from the Caribbean to Africa. Let’s see how much forms there as we go into the historical peak of the season.

    The East Pacific (map #2) shows a lot of activity for that part of the world, with three major hurricanes already. And in the Western Pacific (map #3) they’re off to a big start. Even though this is the most active part of the world, the storms are much more frequent and stronger than usual.

    OTHER FACTORS SUPPRESSING ATLANTIC HURRICANES

    El Nino isn’t the only thing helping to suppress the 2015 Atlantic Hurricane Season. While much of the Pacific Ocean has water temperatures WAAAY above “normal," a lot of the Atlantic is colder than normal. That is especially true for what is known as the “Main Development Region (MDR)” from just east of the Caribbean straight to the African coast.

    Also, the drier Africa is, the lower the chance of tropical development in the MDR. Some of the most powerful hurricanes in history have developed in the MDR. A lot of dust from the Sahara desert is a result of dry conditions over the continent. That dust helps prevent tropical formation. The graphic below shows how extensive the Sahara dust is. It also shows the blobs of thunderstorms moving east to west across Africa. Those “tropical waves” are usually much bigger than the current ones.

    Finally, the lower atmospheric pressures are in the MDR, the more likely tropical storms are to form. Pressures are higher than normal. The “Bermuda HIGH” is closer to the tropics, leading to higher pressures.

    SO NO ATLANTIC HURRICANES, RIGHT?

    No, I’m not saying that. It just looks like an overall “quiet” season in the Atlantic. But as we say, “All it takes is ONE to make it a bad season." In 1972, a strong El Nino was underway, and there was only one hurricane that even came close to the U.S., and that one was barely strong enough to be a hurricane. But its name was Agnes, which caused so much flooding in Pennsylvania that it became the worst natural disaster in the state’s history.

    IT’S ABOUT ODDS….

    As you know, there are few guarantees in weather forecasting. But people still make plans based on weather forecasts. In this case, your odds of good weather for a tropical vacation this year are better than they may be next year. I checked, and many post El Nino years were very active in the Tropical Atlantic.

    The good odds this year also applies to the Pope’s visit in September, the historical peak of hurricane season. Let’s hope the strong El Nino, cold ocean, Saharan dust, and higher pressures continue….