EL NINO WATCH: Possible Effects In Iowa

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El Nino

El Nino is once again making headlines in the weather community, and many of the natural questions of what this means for Iowa’s weather are springing up.

El Nino conditions can sometimes produce profound effects on Central Iowa, yet other times its effects are barely felt in Iowa. Even though Iowa weather still maintains a fair degree of independence from El Nino, let’s take a look at what is usually the case.

First, a little explanation is in order. El Nino is not currently “happening,” and it is not a guarantee that it “will happen” this year. To clarify, El Nino refers to the warming of sea surface temperatures of the waters of the Eastern Pacific off the coast of South America (Ecuador/Peru).

Right now, all the commotion surrounding El Nino is from the increasing likelihood that El Nino conditions will develop in that area sometime later this summer or early fall. There is enough information from long-range models that forecasting agencies like the Climate Prediction Center can forecast a greater than 50% chance El Nino will develop later this year, with some models putting it closer to 65 or 70%.

Even with the indications that El Nino conditions are developing, forecasting conditions 6 to 8 months down the road is still fairly inexact so timing – and maybe more importantly – the possible strength of these conditions remains murky.

With that said, what are some of the impacts on Iowa’s weather during an El Nino?

Knowing what we just explained about El Nino not really taking hold until fall, I wouldn’t look for any Spring or Summer impacts at this point. Winter is more likely where we would feel an impact – if we feel one at all.

El Nino’s effects are usually most clearly felt on the coasts and in the South, along the gulf coast. The Midwest tends to be more of a mixed bag, with Iowa almost indifferent at times to El Nino conditions.

On average, Iowa tends to see slightly warmer winters during El Nino conditions, combined with normal to just a hair above normal precipitation.  We’re talking a difference of about +1 degree difference from 3 month running average temperatures in Des Moines, with just slightly more pronounced warming near the Minnesota border.

Things can be a bit more pronounced during an exceptionally strong El Nino. During some of the stronger El Nino winters, the temperatures tend to run more along the lines of +2 to +3 degrees above normal and maybe an extra 0.75” of precipitation (measured in liquid equivalent, not snow).

Thus, El Nino is typically thought to be associated with slightly warmer, and maybe slightly wetter winters in Iowa, with still some typical cold snaps and snow storms mixed in. HOWEVER….

The last time El Nino conditions occurred was the 2009-10 winter season. You may recall that as the winter Des Moines saw 69.0” of snow, good for 3rd snowiest winter in Des Moines ever, and only 3” shy of the record. In terms of liquid equivalent, Des Moines was around +2.50” or 50% above normal from Dec 1 until the snow stopped in mid-March.

Temperatures also were stuck below normal most of that season due to all of the snow, so a typical “El Nino forecast” of a milder winter went sorely off the rails and serves as a reminder that El Nino’s impact tends to be fairly faint in Central Iowa.

It is certainly something that will be monitored over the coming months, but it is also important to remember that there will be plenty of factors between now and then, and possibly even during an El Nino season that could win out and have a much bigger impact on Central Iowa’s weather.

The latest discussion of El Nino conditions from the Climate Prediction Center can be found here.

Another good overview of El Nino impacts in Iowa and around the country is here.




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