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

 

Share

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.

 

Share

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.

Share

Subtropics rule the season

Hurricane Chris set the tone for the remainder of the Atlantic hurricane season

Hurricane Chris set the tone for the remainder of the Atlantic hurricane season

It has been a rather odd hurricane season so far. I say this because most of the activity, the stronger activity anyway, has developed well outside of the usual breeding grounds of the deep tropics.

Hurricane Chris, which formed back in the latter half of June, did so at 41.1 N latitude! That is incredible for so far north so early in the season.

Next up was hurricane Ernesto, the only hurricane to form south of 20 N latitude this season out of eight total hurricanes so far. However, Ernesto struggled to become a hurricane until right before landfall, another common trait this season as we’ll see with Isaac.

Gordon became the season’s third hurricane and again, well outside of the deep tropics, attaining hurricane status at 34.0 N latitude while heading for the Azores Islands.

Then there was Isaac. Several times during Isaac’s life span it looked as though it could become a powerful hurricane. Instead, Isaac struggled with dry air and the lack of an inner core all the way in to the north-central Gulf of Mexico. One private weather firm loudly proclaimed that Isaac could be another Katrina or worse! And yet the fourth hurricane of the season only managed to reach 80 miles per hour before making landfall in Louisiana. While Isaac was a large hurricane and caused significant flooding from surge and fresh water flooding, it was not a very convectively active hurricane with a well defined inner core. This kept the winds at flight level that were being measured by recon from reaching the surface. Fortunately for residents of the central Gulf Coast, Isaac was only a fraction of the intensity that we all know it could have been had environmental conditions been more favorable.

It took all the way until hurricane Kirk on August 30 to finally get a category two hurricane. And of course, this happened while Kirk was well out of the deep tropics, affecting only shipping interests.

Leslie also had promise to become a large and intense Atlantic hurricane but it too fell far short of that potential and spared Bermuda with only passing tropical storm conditions. Stronger winds and more pronounced effects were felt in Newfoundland but even here conditions were not as bad as what could have been experienced had Leslie been a much stronger hurricane.

Michael is the season’s only category three hurricane so far and guess what? It made it to this intensity at 29.6 N latitude while out over the open central Atlantic over water temps of about 80 to 81 degrees. That’s it. Just enough to get the small hurricane to really ramp up – and it maintained a strong eye feature for several days. Luckily, Michael was far from land and only padded the ACE index score for the season.

We are still tracking Nadine which has been on the map since the 11th of this month. Nadine became the season’s eighth hurricane on the 14th at 30 N latitude. This is remarkable and a sign that something is definitely “wrong” in the deep tropics this year.

I have heard everything from El Nino to mid-level dry air being responsible for the lack of intense cyclones in the deep tropics. I am sure researchers such as Dr. Philip Klotzbach at Colorado State University will be looking in to the source of this unusual pattern and I look forward to learning more about it myself at next year’s National Hurricane Conference in New Orleans. The obvious benefit here has been a substantial reduction in damage resulting from less intense hurricanes impacting land. What if Ernesto had become a 140 mph cat-4 at landfall along the Yucatan? What if Isaac had become another Katrina and brought 30 feet of surge instead of 12? We know the answers….it would have been horrible. Been there, done that. I am sure no one is complaining about the feeble nature to this season’s hurricanes. I hope too that people are curious as to why? Why would conditions be so hostile in the deep tropics? What was the root cause if it can be pin-pointed down to something that simple? Will this pattern continue for the next several seasons? While we can be thankful for the lack-luster performance of this year’s hurricanes thus far, I think understanding the mechanics of such good fortune (it’s relative, I know, as plenty of people are still cleaning up after Isaac) is important in case we see the reverse take place next season or next month for that matter.

In any case, it all boils down to this: the tropics have been strange this season and strange has meant fairly benign events for us to deal with. So far, it looks to stay that way for the next week at least. Although, once again, we will be looking for possible storm development out in the open central Atlantic, well north of the deep tropics which seem to be closed for repairs….

I’ll have more tomorrow.

Share

Tropics nice and quiet except for pesky Nadine

The Atlantic, Caribbean and Gulf are Mostly Quiet with the Exception of TS Nadine Near the Azores

The Atlantic, Caribbean and Gulf are Mostly Quiet with the Exception of TS Nadine Near the Azores

The Atlantic Basin is unusually quiet for this time of the hurricane season and I do not see that changing anytime soon.

We are tracking TS Nadine out near the Azores but that’s it and even Nadine is not that much of an issue.

Some people are blaming El Nino for the quietness, I do not think that the tropical Pacific is really all that warm compared to normal and we are certainly not in an official El Nino period as of yet. In fact, the central Pacific SST anomalies cooled by .30 degrees C in the recent week – and this is also not typical of an El Nino. So what is the reason behind the quiet time? It’s most likely the MJO phase which is currently not favorable in the Atlantic Basin. In other words, we are not in a pattern that supports upward motion in the tropics across the Atlantic, Caribbean or Gulf of Mexico. The lack of instability and generally unfavorable conditions are simply not allowing for any new development.

Looking at the long range models, I do not see any signs of change over the next week to 10 days either. We may escape September with no additional named storms in the Atlantic.

As for October? We’ll wait and see. Without a solid El Nino in place, it is possible that we could have a normal October with a couple of hurricanes developing somewhere – but that’s the key, where? Time will tell. For now, the tropics are of little concern and look to stay that way for quite some time.

Be sure to catch today’s video blog in our iPhone app as it covers these topics graphically. Also, we are anticipating a new update to the app within the next few days that I will address in tomorrow’s blog post.

Share