El Niño on its way out – to be replaced by….?

The strong El Niño that we heard so much about over the past several months is beginning to weaken (has been for a few weeks) and will soon be just a faded memory.

Current data and computer model forecasts overwhelmingly favor the continued demise of the current El Niño which was one of the strongest on record. Once this happens, what will replace it? The answer to that question is not as clear but has possible huge implications on the upcoming hurricane season for the Atlantic.

First, a quick re-cap of what El Niño is.

Current look at SST anomalies across the tropical Pacific and the tropical Atlantic

Current look at SST anomalies across the tropical Pacific and the tropical Atlantic

The easiest way to understand the El Niño phenomenon is to think of an abnormal warming of the Pacific along the Equatorial region – usually extending from the coast of South America (where El Niño gets its namesake) westward in to the tropical Pacific. How far west and how much warming then determines the extent of the effects from said event. In the case of the current El Niño, some areas peaked out at roughly 3.0 degrees C above average – quite a significant deviation from normal.

Now things are changing. The warm episode is fading as much colder water in the subsurface continues to gather in the west Pacific, slowly moving eastward and closer to the surface. Once the trade winds return to normal across the region, this cold water will have a chance to over take the El Niño and finish it off for good. It’s just a matter of time.

Latest subsurface analysis showing the growing pool of cold water in the western Pacific

Latest subsurface analysis showing the growing pool of cold water in the western Pacific

As you can see by the computer model chart, the signal is very strong that El Niño will be gone by summer. How far gone and whether or not the Pacific does in fact swing the other way remains in question but most of the reliable long-term guidance at least suggests the possibility of La Niña conditions setting in by fall. Why does this matter? Hurricanes, that’s why.

We should all know by now that El Niño typically equals a quieter, less intense Atlantic hurricane season. This is due to strong wind shear generated across the deep tropics and other factors that act to kill off developing storms before they can get too strong. This doesn’t mean everyone is safe during an El Niño but the intense hurricanes on the Atlantic side are often kept at bay.

Latest IRI/CPC model output chart which clearly shows the demis of the current El Nino

Latest IRI/CPC model output chart which clearly shows the demise of the current El Nino

Conversely, La Niña presents us with the opposite effect. Shear is typically very low across the deep tropics and tropical seedlings have a much better chance of becoming strong hurricanes at some point. It should be pointed out that La Niña does not necessarily mean someone will get hit by a nasty hurricane. On the whole, La Niña tends to have more dreaded landfalls and so it tends to stick out more – especially compared to warm events or El Niño.

Looking at the average of the dynamic models, it would appear that El Niño is on its way out and could be replaced by La Niña conditions by late summer early fall – just in time for peak hurricane season in the Atlantic.

It wouldn’t be fair to not mention that there are other large-scale factors than can shape a hurricane season. The mere absence of El Niño can certainly change things and allow for more development but it is just one piece of the overall puzzle – a large piece, but not the only one.

Water temps off the coast of Africa have warmed considerably in recent weeks, something that will need to be monitored closely as we get in to the Atlantic hurricane season

Water temps off the coast of Africa have warmed considerably in recent weeks, something that will need to be monitored closely as we get in to the Atlantic hurricane season

Atlantic sea surface temperatures will also be a huge factor and right now, especially off the coast of Africa, those temps are running above the long term average. This can change, heck, it’s only February, but these are the puzzle pieces we keep an eye on in the off-season.

By mid-April, we will get a solid look at what to expect as Dr. Phil Klotzbach and his team from Colorado State University issue the first quantitative forecast for the Atlantic Basin. I can assure you that the state of the Pacific – whether it be El Niño or La Niña – will weigh heavily in to his predictions. Once we get to June, the outlook becomes more clear and again we’ll have an update from the team at CSU.

For now, it appears that the writing is on the wall. La Niña may be coming and if so, we just might have more to track than we have in quite some time.

I’ll have more on this topic in a few weeks as more data and other information becomes available.

M. Sudduth 12:55 pm ET February 11

Hurricane Guillermo tracking in general direction of Hawaii, Atlantic remains inactive

Track map of hurricane Guillermo in the Pacific

Track map of hurricane Guillermo in the Pacific

You’ll be hearing quite a bit about Pacific hurricane Guillermo over the next several days. The track forecast suggests that it could impact Hawaii sometime next week but that is not a certainty, not by any means.

Right now, Guillermo is a category one hurricane with 90 mph winds. Overall, the environment looks favorable for additional intensification and it could become a major hurricane over the weekend.

Water temperatures around Hawaii are running above the long term average due to a spike in northern Pacific sea surface temps this year. However, warm water alone is not enough to bring a hurricane in to Hawaii. The NHC notes on their most recent forecast discussion that upper level winds are likely to be less favorable in the latter part of the forecast period, causing the hurricane to weaken quite a bit before reaching Hawaii. This weakening would also have an impact on steering as well.

If Guillermo weakens and loses a lot of its deep convection, then it is prone to bending back to the west more with time, steered by lower level winds. If this happens sooner rather than later, there is a good chance that Hawaii is only grazed by a passing tropical storm to the south. Obviously, this can change and it really depends on how strong the shearing winds are and when they begin to adversely affect the hurricane. For now, interests in Hawaii should simply be monitoring the progress of Guillermo as it tracks over open water.

Meanwhile, in the Atlantic Basin, all is quiet. The NHC has lowered the chance for development of invest area 94L to 10% over the next several days. None of the global models show the tropical wave surviving the hostile environment of the tropical Atlantic. There is still way too much African dust and drier more stable air in place for anything to have a chance out that way.

Looking down the forecast road, it appears that while several tropical waves emerge from Africa as we begin August, none ever make it past about 40 degrees west longitude before being eaten up by shear or dry air. This is almost exactly what was expected to happen this hurricane season though it is hard to imagine that nothing will ever develop in the deep tropics. Sooner or later, a small window of opportunity will open, even if only for a few days, and we’ll see one or two Atlantic hurricanes. For now, such is not the case and is likely to remain that way for the next several days.

I’ll have more here over the weekend concerning Guillermo in the Pacific.

M. Sudduth 1:40 PM ET July 31


New depression forming in the SW Gulf while 94L develops in east Atlantic

Remnants of TD 7 in the SW Gulf

Remnants of TD 7 in the SW Gulf

Early morning satellite imagery shows that what was once TD 7 is coming back to life again in the southwest Gulf of Mexico. The NHC is indicating a 70% chance of it becoming a tropical depression again before it moves inland this weekend.

Computer models suggest a WNW to NE track towards Mexico as a tropical storm or category one hurricane (SHIPs model shows it reaching hurricane intensity). The overall circulation is fairly small and will only affect a limited area of the southwest to western Gulf and I do not see much impact for Texas. However, it is possible that some of the northern rain bands will move in to south Texas over the weekend. The main threat will be very heavy rains for Mexico with the possibility of a strengthening tropical storm at landfall. The NHC has tasked a recon plane to investigate the area later today if conditions warrant.

Meanwhile, we have a new area of interest just off the African coast that certainly bears watching. It has been designated as invest 94L and should steadily develop as it moves westward over the deep tropics.

All of the global computer models indicate that it will develop and it is likely to become a hurricane at some point since conditions are becoming more favorable along its path. This will be one to watch very closely as we move through the week next week. For now, it is in its early stages of development and we’ll just monitor how it develops over the weekend.

In the east Pacific, Hector has dissipated and there are no other areas of concern brewing in that region. I’ll post another blog here later this afternoon or early evening and will cover all of the goings on in the tropics thoroughly in the video blog to be posted in our app early this afternoon.

East Pacific remains busy as we monitor a large distubance in the Gulf/Caribbean

The east Pacific hurricane season has been quite busy so far with three named storms; one of them becoming a major hurricane.

It looks as though another tropical depression is forming not too far off the coast of Manzanillo. The good news here is two-fold. First, the system is only experiencing marginally favorable conditions to develop so it should not ramp up very quickly. Second, computer model guidance suggests that it will not track in to Mexico but rather turn back to the north and northwest over the next couple of days. While it could strengthen in to a tropical storm, none of the intensity models indicate a very strong system. Obviously, interests along the Pacific coast of Mexico will need to monitor this feature closely until it starts moving away.

Meanwhile, I am watching a large area of showers and thunderstorms that has developed over the southeast Gulf of Mexico and portions of the northern Caribbean Sea. The NHC mentions that there is a surface trough in the region which is simply a weak area of low pressure that acts like a focusing mechanism for unsettled weather. Upper level winds are not completely hostile but they’re not particularly favorable either. Water temps are plenty warm and this will lead to a continuation of the shower and thunderstorm activity that we currently have in place.

HPC Precip Forecast

HPC Precip Forecast

Computer models indicate that the disturbance is likely to remain in the region and move slowly northwest throughout the remainder of the week. The result will be periods of stormy weather for the Florida peninsula. In fact, the precip forecast from the HPC shows the potential for several inches of rain to fall across south Florida (see graphic). Beyond that, I do not see much in the way of potential for the system to become a tropical storm although this scenario cannot be ruled out. As long as the disturbance remains disorganized and lacking of a well defined low level center, it will not do much more than be a large rain maker.

Elsewhere, invest 95L, over the cold waters of the North Atlantic, is a non-issue except for shipping interests. The storm system had some potential yesterday to develop in to a more tropical type storm but that window has since closed.

I’ll post another update here tomorrow with more info on the Pacific and Atlantic at that time.

How’s that La Niña going?

Subsurface Temps of the Tropical Pacific

Subsurface Temps of the Tropical Pacific

So far this winter, the La Niña that has been in place since last fall continues to hold strong. As the graphic from the Bureau of Meteorology in Australia indicates, subsurface temperatures across the tropical Pacific remain much colder than average over a large area. There is a growing region of subsurface warmth beginning to pool in the western Pacific but it lacks a real mechanism to drive it eastward- a so-called westerly wind burst. We typically don’t see those unless there is a significant pressure change across the Pacific and that shows up in the SOI or Southern Oscillation Index. When it is substantially negative, and persistently so, the trade winds often slow or even reverse, allowing the warm water gathering in the western Pacific to migrate eastward.

The latest update from the BOM also points out that long range climate models suggest a gradual warming of the tropical Pacific as the La Niña fades. This means it is likely that we’ll see a return to more average, or neutral ENSO conditions (ENSO stands for El Niño Southern Oscillation) by the time summer arrives in the Northern Hemisphere. There is also the possibility that the warming will continue and a weak El Niño could set in by next fall. I do not see any evidence yet to suggest that a strong El Niño is coming. However, this time of year, it is difficult to predict what will happen several months down the road but the large subsurface cold pool coupled with a fairly strong SOI signal over the past 30 to 90 days tells me that La Niña is going to be the rule for a few more months at least.

Why does any of this matter? Aside from the effects outside of the hurricane season, which are far too detailed to get in to in this post, we typically see a more active hurricane season when El Niño is not present. This is due to the stronger and more numerous instances of wind shear, the change of wind speed and/or direction with height, over the deep tropics. El Niño events promote this negative impact to tropical cyclones where as La Niña events usually do not.

For now, the La Niña pattern will continue but we’ll watch for signs that it is breaking down and then we’ll see how much warming takes place in the tropical Pacific. The end result could have an impact, one way or another, on the upcoming Atlantic hurricane season. I’ll post more about the ENSO state next month.