Latest forecast suggests no El Nino in sight

Latest CPC/IRI ENSO forecast chart

Latest CPC/IRI ENSO forecast chart

It’s approaching mid-June and the latest info from the Climate Prediction Center and International Research Institute (CPC/IRI) suggests that El Nino is not going to happen this hurricane season.

First, what is El Nino and why is it an issue? Well, basically, it is the abnormal warming of the tropical Pacific along and near the Equator. This warming tends to throw off the typical weather pattens and usually equates to a below-average Atlantic hurricane season. This is due to stronger upper level winds, or shear, that streaks across the tropical Atlantic and Caribbean, cutting off the tops of developing hurricanes. In the absence of El Nino, we often experience a busy Atlantic hurricane season, especially if the tropical Atlantic sea surface temps are themselves running above average – as is the case this season.

For reasons not well understood, El Nino comes and goes every few years. In between we have neutral periods where the water temps are more or less average. Then we have La Nina or an abnormal cooling of the tropical Pacific. That phenomenon also has its own set of interesting side-effects which are better explained another time. For this season, we are looking at a neutral pattern setting up and remaining in place.

The latest data and forecast from the CPC/IRI suggests less than a 10% chance of seeing El Nino develop during the August/September/October peak time of the Atlantic hurricane season. This should act to allow for prolofic development once we reach mid-August and beyond, especially considering the warmer than average SSTs in the Atlantic.

This chart gets updated a couple of times per month and I’ll post another write up on the state of the ENSO or El Nino Southern Oscillation towards the end of the month. In the meantime, the tropics are nice and quiet with no areas of concern noted in either the east Pacific or the the Atlantic.

M. Sudduth

 

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Where is the El Niño?

August SST anomalies in the tropical Pacific

August SST anomalies in the tropical Pacific

Earlier in the year, it seemed almost a certainty that El Niño would develop in the tropical Pacific. As we moved through the spring and summer, the tropical Pacific began to warm and it looked like we were well on our way to seeing an El Niño develop. Then, it just stopped.

In recent weeks, the tropical Pacific has actually cooled significantly, especially in the

October SST anomalies in the tropical Pacific. Notice the cooling along the Equator

October SST anomalies in the tropical Pacific. Notice the cooling along the Equator

central Pacific. Just compare the two SST anomaly maps from August and now. You can clearly see a substantial decrease in SST anomalies across the tropical Pacific.

So what happened? It’s hard to say. The latest report from Australia’s Bureau of Meteorology site addresses the retreat in SST values across the region that was warming up until recent weeks. It seems that the pressure pattern across the Pacific changed and the abnormally weak trade winds picked up, cooling the sea surface rather quickly.

Sub-surface temperatures in the tropical Pacific. Notice the distinct cooling in recent weeks

Sub-surface temperatures in the tropical Pacific. Notice the distinct cooling in recent weeks

It is also very interesting to note that the sub-surface temperatures also have declined in dramatic fashion since the late summer. While there was a growing pool of warm water since the spring, it suddenly cooled and now we have a noticeable large area of cooler than normal sub-surface water across a large section of the Pacific. This means that the chances of seeing a true El Niño are getting quite slim.

Why is El Niño even an issue? Well, aside from the weather patterns that El Niño tends to have an influence on globally, if we look at the Atlantic hurricane season specifically, there tends to be a suppression of overall activity. This is mainly due to the increase in tropical convection over the Pacific which is due to the increase in sea surface temperatures because of the El Niño. Persistent tropical convection over the Pacific will usually mean stronger upper level winds and sinking air across the tropical Atlantic. These two negative factors limit the amount of development typically seen in the Atlantic main development region. It’s interesting that the end result seems to have been present this season. In other words, we have seen a limit to the numbers of hurricanes that have developed in the deep tropics. In fact, the ONLY major hurricane to form did so well outside of the typical breeding grounds and was very short-lived.

I do not understand why we had the effects of El Niño without the El Niño itself. Perhaps the atmosphere was responding as if there was an El Niño coming on even though the tropical Pacific was not quite there yet. Who knows? It’s all so complex and there are many interactions between the ocean and atmosphere that it’s difficult at best to know the real reasons behind some of this.

The bottom line is that El Niño has been put on hold, or so it would seem. It may be that it never fully takes root and this could have an effect on the upcoming winter season and most certainly the 2013 Atlantic hurricane season. None of the reliable climate models indicate an El Niño for the early part of 2013 and one could reasonably assume that there won’t be an El Niño during the peak of next year’s season in August-September-October. And yet, even with the near-El Niño observed this season, the Atlantic still has managed to produce eight hurricanes total. This is above the 100 year average. And, on the topic of abnormal sea surface temps, the tropical Atlantic was thought to have been cooler than normal this season. It wasn’t and still isn’t. In fact, a good deal of the tropical Atlantic is running nearly 1 degree C above normal right now. I guess there is a lot we still do not understand about our oceans and the atmosphere.

I’ll have another post here later this afternoon to address the current goings on in the tropics and what we might expect with 98L.

 

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Favorable MJO pulse could lead to more development but not where we would expect

ECMWF indicating a more favorable MJO pulse coming for the Western Hemisphere

ECMWF indicating a more favorable MJO pulse coming for the Western Hemisphere

It’s October and climatology would suggest that we would be looking in the western Caribbean or Gulf of Mexico for the best chance of development right now. While this may be the favored region, the tropical Atlantic is not quite ready to shut down just yet and we may actually see something develop out that way over the next several days.

Right now, the MJO pulse for enhanced upward motion and tropical convection is still weak and centered over the west Pacific. However, it looks as though the MJO will strengthen and begin to shift eastward around the tropics, heading in to the Western Hemisphere soon.

Add to this an existing area of low pressure associated with a tropical wave over the deep tropical Atlantic and we may yet see another named storm before all is said and done. The arrival of the favorable MJO pattern could be the spark needed to get this disturbance, actually labeled as 98L, to spin up and be some thing to track.

Looking at the various global models, the GFS seems to be the most ambitious with development though it does not take place until about a week out. I am leery about putting too much faith in any model that indicates development that far out in time. However, considering the favorable conditions that look to be present, I would not rule out the possibility that we will in fact see 98L slowly come together over the next several days.

In addition, it looks like the steering pattern will more typical of summer than fall and as such, 98L may track fairly far to the west over time and not turn out to the open Atlantic like Nadine and Oscar did. I suggest that interests in the Lesser Antilles pay close attention to 98L over the next week. It is possible that some impacts will be felt in the islands but to what extent, it’s hard to say.

Elsewhere, 97L remains off the coast of the Southeast U.S. and is bringing showers and some thunderstorms to the Bahamas but that’s going to be the limit of the impact from this system. Upper level winds will preclude any significant additional development.

In the east Pacific, TS Olivia will track south of west in the coming days and fizzle over the cooler Pacific waters. In fact, the Pacific is quite a bit cooler than the major climate models were predicting for this time of year, a sign that the much talked about El Nino has not come to pass. This may have an impact on the remaining weeks of the Atlantic hurricane season since El Nino conditions typically thwart late season Atlantic/Caribbean development. There are no other areas of interest in the east Pacific to monitor right now.

For those who have our iPhone app, be sure to catch today’s Hurricane Outlook video which will be posted within the hour. I’ll go over in extensive detail all of the topics in the blog post plus take a look at the state of the ENSO and how much the Pacific has cooled in recent weeks. I’ll have more here tomorrow.

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TD7 not much of a threat while Ernesto will live on…in the east Pacific

Conditions across the tropical Atlantic are just not very favorable right now. There is simply too much mid-level dry air and pockets of unfavorable upper level winds are widespread. For these reasons, it looks as though, once again, the global models will be correct in forecasting what will likely turn out to be a very weak system in TD7.

Looking at the latest satellite photos, there is very little convection and the envelope of energy with the depression is fairly small. As the NHC noted on their early morning discussion, this makes it vulnerable to effects such as dry air and shear more so than a larger, more potent circulation would. I do not see TD7 being much of a problem for anyone unless of course there is a sudden and unexpected change in the environmental conditions ahead of it. I doubt it.

Meanwhile, something remarkable is going to happen. Think about this…the tropical wave that became hurricane Ernesto has traveled from Africa, all the way across the tropical Atlantic, through the gauntlet of the eastern Caribbean Sea, made landfall twice in Mexico and is now poised to emerge in the east Pacific where it can live another day. That’s right, Ernesto, or at least a bulk of its energy, is about to finish quite an incredible trek across the mountainous terrain of Mexico to cross in to the east Pacific. Now, it will not be named Ernesto if it does in fact regenerate, which is very likely to happen. Instead, it will take on the next name of the east Pacific, Hector. It is quite rare to have a tropical cyclone cross over land from one distinct basin to another. What’s even more interesting about this, there is a possibility that the regenerated system could eventually affect the Baja region. Who would have thought this to be the case a week ago or more when we were tracking something that, at one point, could have ended up making landfall anywhere from Florida to Texas. Now, it’s eventual final landfall could easily be along the Pacific coast of Mexico. Needless to say, folks in that region need to monitor what happens and I’ll post updates about it here along with video blogs in our HurricaneTrack app throughout the upcoming weekend.

The remainder of the Atlantic is somewhat busy with invest area 93L off the coast of Africa. Here again we see that conditions are only marginal for development and the global models show next to nothing over the next week to 10 days anywhere in the Atlantic, Caribbean or Gulf. I am not sure if it’s climatology (i.e. we are simply still just a little too early in the season to see prolific, sustained development) or if something else is going on related to the growing El Nino in the Pacific. I’ll take a closer look in today’s video blog to be posted in our app this afternoon. What ever the reason, it’s great news for coastal dwellers who will not have to deal with any hurricanes this weekend for sure and probably all of next week as well.

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Is there an El Nino in the cards for 2012? Perhaps, but not looking as likely.

The mark of a busy hurricane season usually has one element missing from it: El Nino. That is to say, El Nino conditions in the Tropical Pacific tend to suppress Atlantic hurricane activity. This is due mainly to strong upper level winds that cut across the breeding grounds for hurricanes, thus limiting their numbers and intensities. However, one must remember infamous exceptions to this rule such as Andrew in 1992, an El Nino year. There are others as well which remind us of the adage “it only takes one”.

What about neutral years? What defines a neutral year anyway? Basically, when we see the sea surface temperature (SST) anomaly in the Tropical Pacific between .50 Celsius above or below normal, it is a neutral year (ENSO neutral). The scale is not tipped in one direction or another. Easy enough, right?

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