A First Very Preliminary Look

Crown Weather

I wanted to give you my ideas on what the 2016 Atlantic Hurricane Season may be like based on the various current and forecast factors.

Let’s first start out with the current and forecast ENSO state:

Currently, we are well within El Nino conditions and this El Nino is forecast to continue through this entire winter into spring, 2016. Some of the forecast guidance suggests that the ENSO state will evolve into a neutral state by Summer, 2016 and possibly a La Nina towards Autumn, 2016. It should be pointed out that not all of the guidance suggests this and that some of the guidance suggests that El Nino conditions will remain in place through much of 2016.

There are two previous El Nino’s that are similar to this one – the first is the 1982 strong El Nino and the second is the strong El Nino of 1997. The difference between these two El Nino’s were that the 1982-83 El Nino lasted longer (well through 1983) while the 1997-98 El Nino flipped fairly quickly into La Nina conditions during 1998. This difference had large implications on each of those Hurricane seasons. The long lasting El Nino of 1982-83 led to a inactive 1983 hurricane season, however, with that said, there were 2 Gulf of Mexico hurricanes in 1983 as well as a US East Coast landfall of a tropical storm. On the other hand, the El Nino of the winter of 1997-98 flipped quickly into a La Nina during the summer and autumn of 1998. This led to a very active 1998 Atlantic Hurricane Season with multiple landfalls in the Gulf of Mexico, Caribbean and along the US East Coast.

Based on the latest data, I think that we will cool down from the current strong El Nino conditions to a neutral ENSO state during the Spring of 2016 and very possibly into a La Nina during either the Summer or Autumn of 2016.

Forecast Environmental Conditions During The 2016 Atlantic Hurricane Season: The extremely long range CFS model is forecasting lower than average wind shear across parts of the Gulf of Mexico and much of the Caribbean during June, July and August of 2016. On the other hand, the CanSIPS very long range model guidance forecasts near average amounts of wind shear across the entire Atlantic Basin during the 2016 Hurricane Season. The exception to this is during June into part of July when the CanSIPS model is forecasting above average amounts of wind shear across the Caribbean and the Gulf of Mexico.

Turning to the forecast surface barometric pressures during the 2016 Atlantic Hurricane Season, there is a pretty large difference between the CFS and the CanSIPS model guidance. The CFS model is forecasting lower than average barometric pressures across much of the western Atlantic, Caribbean and Gulf of Mexico during June, July and August of 2016. The CanSIPS model guidance, on the other hand, is forecasting above average surface barometric pressures across much of the Atlantic Basin during the 2016 Hurricane Season. The reason why this large difference is important is because if we do see lower than average barometric pressures across the Atlantic like the CanSIPS model is suggesting, then we would see a higher than average likelihood of robust thunderstorm development leading to low pressure development and a higher chance for tropical development. On the other hand, higher than average barometric pressures would squash thunderstorm development leading to lower chances for tropical development.

Finally, the forecast of sea surface temperatures show both the CFS and CanSIPS model guidance are pointing towards warmer than average sea surface temperatures across the entire Atlantic, Caribbean and Gulf of Mexico throughout the entire period from June to November, 2016. This means that there will be plenty of ocean water heat available to help any tropical disturbances to grow into tropical cyclones; that is if the wind shear environment is favorable for development.

Here Are My First Very Preliminary Thoughts On The 2016 Atlantic Hurricane Season: I think that there is 3 possible scenarios for the 2016 Atlantic Hurricane Season.

The first possible scenario is that it could be an extremely active season due to favorable wind shear conditions and warmer than average ocean waters across the Atlantic, Caribbean and Gulf of Mexico. This would be very different than this season where we saw unfavorable environmental conditions across the Caribbean and Gulf of Mexico throughout much of the 2015 Atlantic Hurricane Season. This possible extremely active season would likely be very similar to the 1998 and 2010 Hurricane Seasons with upwards of 15 to 20 named storms, up to 12 of those storms becoming hurricanes and 3 to 5 of those hurricanes becoming major hurricanes. Another cause for this first possible scenario is the idea that the current El Nino state quickly transforms into a La Nina by summer of 2016 leading to a global change in atmospheric conditions which would lead to a favorable to very favorable environment for tropical cyclone development across the Atlantic Basin.

The second possible scenario is that we could end up seeing a very inactive season in terms of the number of named storms much like what we saw in 1983. This would be caused by a much slower transformation from El Nino conditions with these unfavorable conditions lasting into much of the 2016 Atlantic Hurricane Season. Should this happen, we would see unfavorable conditions across the Atlantic, Caribbean and Gulf of Mexico, more so than what we saw during this season. A season like this would yield 5 named storms with 2 of those storms becoming hurricanes and 1 of those hurricanes becoming a major hurricane. It should be pointed out that if this ends up being a very inactive season, we could still see landfalling tropical storms/hurricanes on the US Coast. The 1983 Atlantic Hurricane Season, which was a very inactive one, still saw 2 Gulf of Mexico hurricanes and a tropical storm landfall on the US East Coast.

The third possible scenario is for a “normal” season in terms of the number of named storms with most of the activity occurring from September 15th to November 1st. The reason for this third possible scenario is that there is the possibility for a slower transition from El Nino conditions which would potentially lead to a globally unfavorable environment state in terms of Atlantic tropical development chances early in the season. This would then potentially turn around later in the season as we transition into a La Nina state.

At This Point, My Thinking Is That the first possible scenario of an extremely active season seems to be the most likely right now with a season very much like the 1998 Atlantic Hurricane Season. This means that potentially the Caribbean and Gulf of Mexico could be quite active, which is a huge change from what we have seen over the last couple of seasons. In fact, much like the 1998 Atlantic Hurricane Season, it would not surprise me, at this point, to see a hyperactive period of tropical storm/hurricane development between August 15th and October 1st during the 2016 Atlantic Hurricane Season.

The third possible scenario of a “normal”, but late starting Hurricane Season is the second most likely scenario with most of the activity occurring between mid-September and early November thanks to a lingering El Nino that doesn’t fade into La Nina conditions until late 2016.

What this means right now for all of you is that it may not be a bad idea to make some preparations now in the off season, including:

- If you are thinking of putting your house up on stilts to avoid flood damage, do it now. If you wait until spring or summer of 2016, it may be too late to hire construction crews to raise your home.

- Review your flood and wind insurance protection and make sure you are adequately covered.

- As always, restock your hurricane preparedness kit with items that may need to be replaced. Also, those kits can be used for any type of severe weather, so it’s good to always have it on hand in case of a weather emergency.

Finally, I want to emphasize that these are preliminary thoughts and that this forecast will likely change in the coming months. I will be monitoring all of the factors leading up to whether the 2016 Atlantic Hurricane Season will be active or in active and will keep you updated between now and June 1st, 2016.

Even more than one might expect, the 2016 Atlantic hurricane season is shaping up with both high- and low-end possibilities, based on preliminary thoughts released Thursday by a team at Colorado State University. The CSU project, founded by Dr. William Gray with Dr. Phil Klotzbach now serving as lead author, has issued seasonal outlooks since 1984 for the anticipated amount of hurricane activity in the Atlantic basin. In 1993 the group began issuing outlooks each December for the following year’s activity, but in 2011 those outlooks were dropped due to lack of any demonstrated skill. In its place, the CSU team now releases what they call a “qualitative discussion,” which highlights the factors at play and includes a more generalized sense of what we might expect.

Although it’s not presented as a quantitive outlook, the Thursday release (PDF) does include a set of four potential scenarios for 2016, each rated in terms of probabilities that we will see a given amount of seasonally-averaged accumulated cyclone energy (ACE). These scenarios hinge on two factors: how quickly the current El Niño will diminish, and how the Atlantic Multidecadal Oscillation/thermohaline circulation (AMO/THC) will evolve.

1. AMO/THC becomes above average in 2016 and no El Niño impacts remain (resulting in an ACE of ~ 170) – 25% chance
2. AMO/THC is above average in 2016 but some El Niño impacts remain (ACE ~ 120) – 35% chance
3. AMO/THC is below average and no El Niño impacts remain (ACE ~ 80) – 20% chance
4. AMO/THC is below average and some El Niño impacts remain (ACE ~ 50) – 20% chance

CSU relates the ACE values shown above to these general ranges of activity:

170 ACE – 14-17 named storms, 9-11 hurricanes, 4-5 major hurricanes
120 ACE – 12-15 named storms, 6-8 hurricanes, 2-3 major hurricanes
80 ACE – 8-11 named storms, 3-5 hurricanes, 1-2 major hurricanes
50 ACE – 5-7 named storms, 2-3 hurricanes, 0-1 major hurricane

The upshot is that we have a 45% chance of falling into one of the two more extreme scenarios: either #1 (a very busy season) or #4 (a very quiet season). Looking back at each of the last four years, CSU placed the combined odds of the highest- and lowest-end scenarios at only 20% to 25%. So if CSU is right, the Atlantic season of 2016 has an considerably better chance than the last four seasons of being either unusually active or uncommonly tranquil. Want more evidence for this split verdict? CSU points out the wildly contrasting outcomes for the Atlantic hurricane seasons that followed our two other “super El Niño” events since 1950 (1982-83 and 1997-98):

1983: Atlantic ACE = 17% of average
1998: Atlantic ACE = 182% of average

This stark difference is largely because the 1982-83 El Niño decayed gradually, holding on till midsummer, whereas the 1997-88 El Niño quickly shifted into a moderate La Niña by late summer. The most recent monthly outlook for El Niño, issued Thursday by NOAA, calls for a transition to ENSO-neutral conditions by late spring or early summer. Computer models are in agreement on this shift, though the timing varies somewhat. More often than not, a strong or very strong El Niño event is followed by La Niña in the next summer or autumn. It’s certainly possible that La Niña could be in place by late summer (see Figure 1 below), which would favor an active Atlantic hurricane season.

Figure 1. The December outlook issued by a collaborative group of forecasters at NOAA’s Climate Prediction Center and the International Research Institute for Climate and Society (IRI). The odds of neutral or La Niña conditions rise considerably by next summer. Image credit: NOAA/IRI.

How do El Niño and the AMO/TCH influence hurricanes?
In a relationship that’s well understood, El Niño tends to suppress Atlantic hurricane activity, mainly by enhancing upper-level wind shear, while La Niña favors more Atlantic activity by reducing wind shear. These factors come and go from year to year. Meanwhile, the ups and downs of the AMO/THC modulate hurricane activity over much longer periods by affecting sea-surface temperatures and other conditions over the tropical and subtropical Atlantic. “These changes are natural and have been occurring for at least the last 1,000 years,” notes a NOAA FAQ on the phenomenon.

The AMO/THC has shown large multidecadal trends over the last century, favoring reduced hurricane activity from the 1970s to the mid-1990s and increased activity from that point until the early 2010s. Over the last couple of years, the AMO/THC has slowed down, in tandem with a reduction in Atlantic hurricane activity. However, the AMO/THC can vary on the shorter term as well, so it’s not yet certain that we have entered a new multi-decade era of reduced activity--although Phil Klotzbach made the case for this in a paper published in Science this past September and summarized in a writeup by Klotzbach at Capital Weather Gang. (The Science paper can be accessed through a link at the bottom of the CWG article.) Even if we are indeed in a new era, shorter-term factors could strengthen the AMO/THC during a given year. This includes the train of weather features and oceanic effects that El Niño is expected to produce over the next few months from the Pacific to the Atlantic.

“The uncertainties related to the AMO for 2016 are enormous,” said Eric Blake (National Hurricane Center) in an email, “because we lack a reliable way to track the feature and because of possible effects of El Niño countering the longer-term cycle.”

CSU will issue its full seasonal outlooks for Atlantic hurricane activity in 2016 on April 14, June 1, and August 3. As one would expect, the skill of these outlooks steadily improves as the hurricane season nears. Even if it’s too soon right now to expect an accurate forecast for 2016, the latest thoughts from CSU make me even more eager to see how this very uncertain hurricane season will unfold.

Bob Henson

Figure 2. The largest patch of below-average ocean temperatures for 2015 (January - October) has been in the North Atlantic, where record-cold values have been observed southeast of Greenland. These values are consistent with a weaker Atlantic multidecadal oscillation/thermohaline circulation. Image credit: NOAA/NCEI.

Jeff Masters