Even though it is January, there are clues that we can look for when trying to figure out how busy the upcoming Atlantic hurricane season may be. One of those clues is the state of the El Niño.
As we know, El Niño or the abnormal warming of the tropical Pacific, tends to suppress Atlantic hurricane activity due to a number of factors. For a good deal of 2014, it looked as though a rather substantial El Niño event was going to unfold – it failed to do so. However, the tropical Pacific did warm quite a bit and in fact, most of the warmest water on the globe was found in the Pacific during last year’s hurricane season. This is a big reason why the east Pacific was so very busy and the Atlantic was not.
As of early January, the tropical Pacific was only slightly warmer than usual with a noticeable decline in sea surface temperatures in the east Pacific, just west of Central America. In fact, as far as I can tell, we are not even in an official El Niño right now as the thresholds have not been met. This is not surprising if we look at some other aspects of a traditional El Niño event.
One of those aspects is the SOI or Southern Oscillation Index. Typically the more negative it is, the more likely we are to see El Niño conditions prevail in the atmosphere AND in the oceans. What’s the trend over the past 90 days been? A slow and steady rise in the SOI. As the chart shows, October was -8.2, November was -8.0 and December was -7.6 with the current daily value showing +4.4. What does this mean? In short, it means that the pressure pattern is such that the trade winds are not all that weak across the tropical Pacific and thus the El Niño is being held back if not stopped completely.
More evidence of the collapse of the El Niño can be seen via the temperature depth anomaly chart from the Climate Prediction Center. This shows us what the temperature profile is of the tropical Pacific from the surface down several hundred meters. Clearly you can see the loss of the warm pool as the animation progresses over the past several weeks. In fact, cooler anomalies are showing up in the eastern Pacific at a depth of around 110-150 meters. Unless more warm water begins to migrate eastward (from left to right on the chart) then the warming of the tropical Pacific will be very slow if not stopped entirely.
So what does this all mean as far as impact on the 2015 hurricane season? While it’s too early to be confident about the demise of the El Niño, the most recent forecasts indicate that the odds of neutral conditions are beginning to outweigh El Niño as we get in to the Atlantic hurricane season which begins in June. This is very important because a cooler tropical Pacific would likely mean less upward motion in that region compared to what we saw in 2014 and this could lead to a better chance for Atlantic development, even if only a little. Remember, 2014 was not too far off from being an average season and so any increase in activity this year would seem to most people as being quite busy, especially considering how slack things have appeared to be since 2012.
There are many other factors to consider as we enter the 2015 Atlantic hurricane season but the state of the ENSO is a big one and thus far, it appears that it will not be much of a negative influence. Obviously, the climate models can and do make gross miscalculations and we could end up with a raging warm episode by late summer. However, with other signals leaning in the direction of a non-El Nino event shaping up, I tend to think that the forecast will be pretty accurate and that we will not have an El Nino during the 2015 hurricane season. We shall see…
I will post an update to this information in early April, right before the National Tropical Weather Conference which is being held in South Padre Island again this year. By then, we’ll be within 90 days of the hurricane season getting started. I’ll have other topics posted before April of course but that’s the next logical time to take a look at the ENSO state again. Until next time, stay warm!
M. Sudduth 9:26 AM ET Jan 14