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What Happened to the 2013 Atlantic Hurricane Season?

Nearly one year after Hurricane Sandy ravaged the East Coast, the 2013 Atlantic Hurricane Season has not produced a single land-falling hurricane in the U.S. Instead of having above-average storm activity, as the seasonal hurricane outlooks unanimously called for, the season has been quiet — notable for its inactivity.

The tropical season doesn’t officially end until November 30, but it would take a barrage of late-season storms to bring the season up to average levels, let alone above average, something that forecasters say is unlikely.

A computer model image shows the extent of dry air flowing westward from Africa on August 16. 
Click image to enlarge. Credit: WeatherBell Analytics.

“It’s not only quiet, but it’s got the potential to be near record quiet for the Atlantic Basin,” Chris Landsea, a meteorologist at the National Hurricane Center in Miami, said.

So far, there have been just 11 named storms, two of which have been hurricanes, and none that have been major hurricanes.

While pre-season outlooks rarely, if ever, have pinpoint accuracy, they don’t usually miss by such a large margin. In May, the National Oceanic and Atmospheric Administration (NOAA) projected that there would likely be between 13 and 20 named storms (with sustained winds of at least 39 mph). Of those storms, NOAA projected that between seven and 11 would achieve hurricane status (winds of at least 74 mph); and that three or four would become major hurricanes of category 3, 4 or 5 (winds of at least 111 mph).

By one measure, 2013 so far ranks as the 7th quietest season in the past 70 years. That measure uses an index known as Accumulated Cyclone Energy, which incorporates how many storms formed, how long they lasted, and how strong they became. If no additional storms were to form before the end of the season, 2013 would be the 4th quietest.

There has not been a major hurricane in either the North Atlantic Basin or the eastern Pacific this year, something that hasn’t happened since 1968, according to Philip Klotzbach, a hurricane researcher and seasonal forecaster at Colorado State University.

Subsidence and the Sahara

The scant number of storms is surprising given some of the favorable conditions that exist that would normally fuel tropical cyclones. The ocean waters throughout the North Atlantic are warmer than average, the trade winds are lighter, and there is no El Niño event in the Pacific to ramp up high altitude winds that can tear nascent storms apart.

Coastal homes in Texas' Bolivar Peninsula were wiped out by the storm surge from strong Category 2 Hurricane Ike in 2008.
Click image to enlarge. Credit: NOAA.

Forecasters say that three main features loom large for the inactivity: large areas of sinking air, frequent plumes of dry, dusty air coming off the Sahara Desert, and above-average wind shear. None of those features were part of their initial calculations in making seasonal projections. Researchers are now looking into whether they can be predicted in advance like other variables, such as El Niño and La Niña events.

Brian McNoldy, a senior research associate at the University of Miami, said that across the Atlantic this season “you had air sinking through a pretty large depth of the atmosphere.” Sinking air inhibits storm formation by causing air to become drier and more stable, thereby stunting the growth of thunderstorms that require moist, unstable air in order to thrive.

Tropical weather systems depend on a plentiful supply of warm, moist air to form and intensify, and when these storms ingest exceptionally dry air, as many of the storms have this year, they can choke to death in a matter of hours or days. For example, Tropical Storm Karen formed in the Gulf of Mexico, where landfall in the U.S. or Mexico is virtually assured, but died before reaching land because of the presence of dry air and strong wind shear.

Some of the dry air across the Atlantic Basin came from large areas of dusty air that originated in the scorching Sahara Desert. However, such outbreaks of dusty air are fairly typical during hurricane season. What has been unusual has been the broad expanse of sinking and drying air throughout the North Atlantic basin, McNoldy said.

This season, the dry air “made a huge difference” and “squashed all the other factors that looked good,” he said.

Klotzbach said the area where most tropical storms and hurricanes form had the driest mid-to-lower atmospheric conditions during the Aug. 1 to Sept. 25 period since reliable records began in 1970.

In addition to the dry air, Landsea and Klotzbach pointed to above-average wind shear as another key reason. Wind shear is the difference in wind speed and direction between the ocean surface and the mid-to-upper atmosphere. Strong shear can knock storms off balance, essentially tearing them apart and allowing dry air to enter their circulation.

Landsea said that NOAA’s seasonal outlooks focused on the other pieces of the puzzle that argued in favor of an above average to average season, namely the absence of El Nino and the presence of warm sea surface temperatures. The seasonal outlook won’t be correct every time, Landsea said.

Klotzbach, who along with William Gray pioneered the art of forecasting the severity of hurricane seasons, said future outlooks will need to incorporate more variables.

“We will be looking at ways to be able to incorporate more moisture data into our models, in hopes to not make a similar mistake in future years,” he said in an email interview.

Record Major Hurricane Drought Continues

The absence of a major hurricane in the U.S. this season means the continuation of a record-long streak. On Oct. 24, it will be exactly 8 years since the last major hurricane of Category 3 strength or greater made landfall. Scientists fear this streak of good luck is leading to more severe cases of “hurricane amnesia,” which can complicate emergency preparation efforts the next time a monster storm threatens.

Infrared satellite view of Tropical Storm Karen as the storm struggled to fight off wind shear and dry air on Oct. 4 over the Gulf of Mexico.
Click image to enlarge. Credit: NOAA.

“When it doesn’t happen often you certainly become a little more lax,” McNoldy said, noting that in the 8 years since Hurricane Wilma struck Florida, tens of thousands of people have moved to the Sunshine State, many of whom have never before experienced a major hurricane. These residents, McNoldy said, may be less willing to evacuate their homes before the next major storm strikes.

“People who have never experienced it . . . don’t really know what they’re in for,” McNoldy said.

Klotzbach said the “fear of complacency” grows as the major hurricane gap lengthens. “One statistic that people should remember is that on average, about 1 in every 3 major hurricanes makes landfall at major hurricane strength (in the U.S.)” he said. Klotzbach noted that since 2005, 22 major hurricanes formed in the Atlantic, yet none of them made landfall in the U.S. as major hurricanes.

Even without a major hurricane reaching land, the U.S. has seen its fair share of damaging storms in recent years. Hurricane Ike devastated the Galveston, Texas area in 2008 as a strong Category 2 storm, and Sandy was one of the strongest and most destructive storms to ever strike the Jersey Shore.

“I think anybody living along the Jersey coast or Long Island or in New York City would attest that they had a major event even though it wasn’t a major hurricane,” Landsea said.

Related Content
The Calm Before the Storm? Quiet August for Hurricanes
NOAA's Updated Forecast Calls For Busy Hurricane Season
2013 Hurricane Season Could Be Extremely Active: NOAA
As Hurricane Season Starts, U.S. Facing Heightened Risk
Ongoing Coverage of Historic Hurricane Sandy
Top 5 Most Vulnerable U.S. Cities to Hurricanes

Comments

By Joe Bastardi (16827)
on October 16th, 2013

The drop in mixing ratios over the tropics, which by the way is opposite the IPCC trapping hot spot theory, has been going on since 2007, about the time of the flip in the PDO. The dirty little secret that no one seems to want to acknowledge is that what has been going on in the Pacific has spread into the atlantic basin. 400mb levels over the tropics are much drier (implying lower wet bulbs, and forcing storms to have to work harder to develop their warm cores.. a developing cyclone pulls in all air, and dry air means lower wet bulbs)  In addition , the sudden flip to cold in the Arabian sea and Bay of Bengal caused an erratic Indian monsoon. This is something Dr John Lee at PSU taught in his tropical classes. I WAS NOT EXPECTING TO SEE THAT for several years, as Much of Lees idea occurred when the AMO was cold. It appears that the days of the warm AMO are now entering their last cyclically driven ( as per Dr Bill Gray) years. 

Keep in mind that what is more likely before we are out of this, the warm amo is bigger storms such as the 50s, but only the new naming criteria and satellites ( storms seen and named quicker in the middle of nowhere) is responsible for the increase in number.  But I believe like the 1950s, we are in a crucial period on the east coast as a cold PDO and warm AMO argues for US east coast hits. Remember, the benchmark years of 1938,1944,1954,1960 on the east coast were not high numbered years.

One more side item and I know you do not read what I write on weatherbell.com, otherwise you would understand what I am saying better, the last time we saw such low activity in the atlantic and Pacific together was 1977..the time of the great climatic shift where the PDO flipped to warm and many of us believe has been not taken into account to justify global rises in temps 1978-1997.  The shift, may create such imbalances that render the REASON for tropical cyclones, which is to help distribute heat out the tropics to the temperate regions, for a time not applicable.. in other words nature adapts. In this case, nature had reached a peak, and then the response to the peak was the naturally falling off. My theory on cooling is such that the shift in the amo to cool will once again cause the Pacific to respond ... become the big place for ACE and that should uptick again. This is not brain surgery, its simply observing what happened before.

The amazing thing this year Andrew was the SST distribution from Pacific to Atlantic was idea.. cool epac, warm atlantic.. In 1977 an el nino developed and the Atlantic was in a cold AMO.  The error I had was a) thinking the warmth of the ocean would overcome the dry air, it did eventually, but the wave train was shot.  By the way, Saharan dust is a cop out.  IT IS THE PRODUCT OF THE PATTERN…NOT THE CAUSE.  The Saharan dust is because of the abnormal build up of higher pressures, which is a sign of sinking, all of this a sign of the drying that is taking place, which takes us back to the IPCC trapping hot spot being debunked in front of our very eyes

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By Andrew
on October 16th, 2013

Thanks Joe for your thoughts on this, particularly your take on the Saharan dust. I have read some of your commentary at Weatherbell, as a subscriber there, and am well aware of your PDO flip hypothesis.

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By FishOutofWater (Pittsboro, NC)
on October 17th, 2013

This year’s southwest monsoon maybe the longest on record in India. Rainfall amounts in India were well above normal. The strong monsoon uplift entrained dry air lowering the absolute humidity of the troposphere in the northern hemisphere. The area most affected by the dry subsiding air was the tropical and subtropical north Atlantic basin.

Joe B is correct that the African dust is a symptom of the overall situation, not the cause of the low Accumulated Cyclone Energy (ACE) in the north Atlantic basin. However, the rest of his analysis is based on the denial of the continued uptake of heat by oceans associated with growing levels of greenhouse gases in the atmosphere. This is not a simple cyclical process. As the oceans heat up, ice is melting, the southern hemisphere’s thermohaline circulation is weakening and weather patterns are changing.

We will continue to struggle to predict how natural cycles will interact with changing ocean currents and climate change. The general predictions of climate change are correct, but predicting the details is problematic.

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By Camburn (North Dakota)
on October 20th, 2013

The uptake of warmth via the oceans caused by CO2 is probably not measurable without ARGO type measurements.  The XBT, bucket, intake etc had error bars that were large.

The ocean DOES respond to changes in the SW emission of the sun.

The trend to drier WB measurements in the atmosphere is troubling in that it defies what is currently understood.  This implies that our understanding of the drivers in regards to WB measurements needs extremely close examination.  The lack of topical storm/hurricane activity in 2013 continues to surprise, as the major models showed it should happen with our current understanding, but it most certainly did not happen.

By process of validation, the overall patterns observed since 2007 indicate that we need to totally rethink our understanding of longer term climate impacts.

This somewhat simple model is performing better than the IPCC consensus models.  We need to examine the parameters of both to see the cause/effect of what is not incorporated into the IPCC consensus models so they become potentially validated.

http://climateprediction.eu/cc/Main/Entries/2013/10/7_Still_confirming_forecast_of_Apr_2011_at_73_accuracy._IPCC_forecast_at_10._What_drives_Global_Warming_(Update_2).html

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By Scott
on October 21st, 2013

Yet next year, they will predict yet another “above average” hurricane season.  Maybe it will be, and maybe it won’t.  These guys are just throwing darts at a board when it comes to long range weather forecasts.  Stick to forecasting the next week, fellas.

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By Eric Peterson (Front Royal, VA 22630)
on October 22nd, 2013

“The general predictions of climate change are correct, but predicting the details is problematic.”

None of the “predictions” have been correct.

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By Jim (Sunset Beach, NC 28468)
on October 28th, 2013

Every year, same “above average” hype to secure attention and funding.  Media goes wild with dire warnings.  Almost every year, same staggering inaccuracy.  If I flipped a coin—literally—I’d have considerably more accurate predictions.  Somehow, the government allows you to keep your job with a 95% inaccuracy rating.  Never work in the private sector—you’d be unemployed after one season.  NWS & HNC, either get it right, or admit that you have no clue, shut up, and stop predicting.  Currently, you’re nothing but hype- and funding-mongers.

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By Antony Siese (Paget, Bermuda, DV 03)
on November 1st, 2013

It is unfortunate that so many are prepared to criticize and when there is a storm all the nay Sayers get their knickers in a twist.  You may not have been affected, but when you live in hurricane alley, one has a better appreciation of what the forecasters are doing.  Bermuda has been brushed by a storm this year,which closed the airport because of its’ proximity.
It is a bad season if one hurricane hits your area, but if you are not affected, please do not become complacent and thank God you have avoided a disaster.

Weather forecasting is NOT as exact science, but I thank these guys and gals for their forecasts and improve every year.

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By Rion Love (Aroostook County, Maine)
on November 18th, 2013

Perhaps that’s just it: as the climate continues to change, weather patterns become wild cards, and it has been nothing short of that here in northern New England. Might I remind all of the weak system that hit the Caribbean in JUNE and proceeded up the east coast as a tropical storm. I’m having trouble recounting on past tropical systems that have hit in June.
It appears this year, instead of the frequent late summer to autumn tropical systems, extratropical systems brought frequent hurricane-like conditions throughout late spring and early summer, skipped the hurricane season, and again proceeded in mid autumn.
I’m curious if there is any relation (I’m not an expert), there has been an intense increase in extratropical systems that, at least when they hit my area, make up for the lack of hurricanes in small but extremely severe outbreaks that are vaguely reported. June, July and October now mark “hurricane” season. Extremely humid and hot conditions now prevail in late spring and early summer, as opposed to the relatively mild and much drier conditions in many years back. When strong cold fronts from Canada collide with this air mass, the weather spirals. Intense thunderstorms with frequent rotation observed on radar are the norm now.
On June 1st the same system that destroyed towns in Oklahoma hit northern Maine. At the same time, the entire northeast was experiencing stifling heat and humidity. My area nearly had to evacuate the entire county when the storm hit. Hail the size of gulf balls, easily 75+ m/hr winds, the loudest and most frequent thunder I had ever experienced and constant cloud-to-ground lightning. Roof tops were ripped apart, farms were devastated. Then all the streams flooded as 3 inches of rain dropped in nearly an hour and a half. Next day, reports said two tornadoes were confirmed to have touched down and had been observed on radar. Nearly 600 yards of dense forest was completely flattened and torn up in two locations in northern Maine.
This pattern developed sevenfold throughout summer of 2013, as equally drastic conditions yet again slammed my area in early July,  late September, and early October. However, I also observed an unusually cool and dry late July all the way through August and into september. That is usually the time when summer really takes a grip of the area with high heat and humidity. It is also the time when we experience MOST HURRICANES. It intrigues me that 2013 has set record rainfall to claim the 2nd wettest year in Maine, only a few inches behind the 2011 season which also brought unseasonable heat and humidity.
Climate change is easily the responsible factor for all of this unusual weather. Does anyone have any further explanation? Are these occurrences linked or are their sources separate?

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By Wyss Yim (Hong Kong)
on January 6th, 2014

The main difference between 2012 and 2013 is the switching off of hot seawater from the submarine eruption of the El Hierro volcano in the Canary Islands in March 2012. This also helps to explain why sea ice is expanding again in the Arctic during 2013.

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