An Active Atlantic Hurricane Season Still Predicted by NOAA, CSU, and TSR

By: Dr. Jeff Masters , 4:07 PM GMT on August 09, 2013

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As we stand on the cusp of the peak part of hurricane season, all of the major groups that perform long-range seasonal hurricane forecasts are still calling for an active 2013 Atlantic hurricane season. NOAA forecasts an above-normal and possibly very active Atlantic hurricane season in 2013, in their August 8 outlook. They give a 70% chance of an above-normal season, a 25% chance of an near-normal season, and 5% chance of a below-normal season. They predict a 70% chance that there will be 13 - 19 named storms, 6 - 9 hurricanes, and 3 - 5 major hurricanes, with an Accumulated Cyclone Energy (ACE) 120% - 190% of the median. If we take the midpoint of these numbers, NOAA is calling for 16 named storms, 7.5 hurricanes, 4 major hurricanes, and an ACE index 155% of normal. This is well above the 1981 - 2010 average of 12 named storms, 6 hurricanes, and 3 major hurricanes. Hurricane seasons during the active hurricane period 1995 - 2012 have averaged 15 named storms, 8 hurricanes, and 4 major hurricanes, with an ACE index 151% of the median.


Figure 1. Tropical Storm Dorian on July 25, 2013, when the storm reached peak intensity--sustained winds of 60 mph. Formation of early-season tropical storms like Chantal and Dorian in June and July in the deep tropics is usually a harbinger of an active Atlantic hurricane season. Image credit: NASA.

NOAA cites five main reasons to expect an active remainder of hurricane season:

1) Sea Surface Temperatures (SSTs) are above average in the Main Development Region (MDR) for hurricanes, from the coast of Africa to the Caribbean. As of August 9, SST were 0.4°C (0.8°F) above average.
2) Trade winds are weaker than average across the MDR, which has caused the African Monsoon to grow wetter and stronger, the amount of spin over the MDR to increase, and the amount of vertical wind shear to decrease.
3) No El Niño event is present or expected this fall.
4) There have been two early-season tropical storms in the deep tropics (Tropical Storms Chantal and Dorian), which is generally a harbinger of an above-normal season.
5) We are in an active hurricane period that began in 1995.

Colorado State predicts a much above-average hurricane season
A much above-average Atlantic hurricane season is on tap for 2013, according to the seasonal hurricane forecast issued August 2 by Dr. Phil Klotzbach and Dr. Bill Gray of Colorado State University (CSU). The CSU team is calling for 18 named storms, 8 hurricanes, and 3 intense hurricanes, and an Accumulated Cyclone Energy (ACE) of 142. The forecast calls for an above-average chance of a major hurricane hitting the U.S., both along the East Coast (40% chance, 31% chance is average) and the Gulf Coast (40% chance, 30% chance is average). The risk of a major hurricane in the Caribbean is also above average, at 53% (42% is average.)

Analogue years
The CSU team picked five previous years when atmospheric and oceanic conditions were similar to what we are seeing this year: cool neutral ENSO conditions and slightly above-average tropical Atlantic sea surface temperatures. Those five years were 2008, a very active year with 16 named storms and 4 major hurricanes--Gustav, Ike, Paloma, and Omar; 2007, an active year with 15 named storms and two Category 5 storms--Dean and Felix; 1996, an above average year with 13 named storms and 6 major hurricanes--Edouard, Hortense, Fran, Bertha, Isidore, and Lili; 1966, an average year with 11 named storms and 3 major hurricanes--Inez, Alma, and Faith; and 1952, a below average year with 7 named storms and 3 major hurricanes. The average activity during these five analogue years was 12.4 named storms, 7.2 hurricanes, and 3.8 major hurricanes.

TSR predicts an above-average hurricane season: 14.8 named storms
The August 6 forecast for the 2013 Atlantic hurricane season made by British private forecasting firm Tropical Storm Risk, Inc. (TSR) calls for an active season with 14.8 named storms, 6.9 hurricanes, 3 intense hurricanes, and an Accumulated Cyclone Energy (ACE) of 121. The long-term averages for the past 63 years are 11 named storms, 6 hurricanes, 3 intense hurricanes, and an ACE of 103. TSR rates their skill level as good for these August forecasts--47% - 59% higher than a "no-skill" forecast made using climatology. TSR predicts a 58% chance that U.S. land falling activity will be above average, a 26% chance it will be near average, and a 16% chance it will be below average. They project that 4 named storms will hit the U.S., with 1.8 of these being hurricanes. The averages from the 1950-2012 climatology are 3.1 named storms and 1.4 hurricanes. They rate their skill at making these August forecasts for U.S. landfalls just 9% - 18% higher than a "no-skill" forecast made using climatology. In the Lesser Antilles Islands of the Caribbean, TSR projects 1.4 named storms, 0.6 of these being hurricanes. Climatology is 1.1 named storms and 0.5 hurricanes.

TSR's two predictors for their statistical model are the forecast July - September trade wind speed over the Caribbean and tropical North Atlantic, and the forecast August - September 2013 sea surface temperatures in the tropical North Atlantic. Their model is calling for warmer than average SSTs and near average trade winds during these periods, and both of these factors should act to increase hurricane and tropical storm activity.


Figure 2. Comparison of the percent improvement over climatology for May and August seasonal hurricane forecasts for the Atlantic from NOAA, CSU and TSR from 1999-2009 (May) and 1998-2009 (August), using the Mean Squared Error. Image credit: Verification of 12 years of NOAA seasonal hurricane forecasts, National Hurricane Center.


Figure 3. Comparison of the percent improvement in mean square error over climatology for seasonal hurricane forecasts for the Atlantic from NOAA, CSU and TSR from 2003-2012, using the Mean Square Skill Score (MSSS). The figure shows the results using two different climatologies: a fixed 50-year (1950 - 1999) climatology, and a 2003 - 2012 climatology. Skill is poor for forecasts issued in December and April, moderate for June forecasts, and good for August forecasts. Image credit: Tropical Storm Risk, Inc.

FSU predicts an above-average hurricane season: 15 named storms
The Florida State University (FSU) Center for Ocean-Atmospheric Prediction Studies (COAPS) issued their fifth annual Atlantic hurricane season forecast on May 30, calling for a 70% probability of 12 - 17 named storms and 5 - 10 hurricanes. The mid-point forecast is for 15 named storms, 8 hurricanes, and an accumulated cyclone energy (ACE) of 135. The scientists use a numerical atmospheric model developed at COAPS to understand seasonal predictability of hurricane activity. The model is one of only a handful of numerical models in the world being used to study seasonal hurricane activity and is different from the statistical methods used by other seasonal hurricane forecasters such as Colorado State, TSR, and PSU (NOAA uses a hybrid statistical-dynamical model technique.) The FSU forecast has been one of the best ones over the past four years:

2009 prediction: 8 named storms, 4 hurricanes. Actual: 9 named storms, 3 hurricanes
2010 prediction: 17 named storms, 10 hurricanes. Actual: 19 named storms, 12 hurricanes
2011 prediction: 17 named storms, 9 hurricanes. Actual: 19 named storms, 7 hurricanes
2012 prediction: 13 named storms, 7 hurricanes. Actual: 19 named storms, 10 hurricanes

Penn State predicts an above-average hurricane season: 16 named storms
A statistical model by Penn State's Michael Mann and alumnus Michael Kozar is calling for an active Atlantic hurricane season with 16 named storms, plus or minus 4 storms. Their prediction was made using statistics of how past hurricane seasons have behaved in response to sea surface temperatures (SSTs), the El Niño/La Niña oscillation, the North Atlantic Oscillation (NAO), and other factors. The statistic model assumes that in 2013 the May 0.87°C above average temperatures in the MDR will persist throughout hurricane season, the El Niño phase will be neutral to slightly warm, and the North Atlantic Oscillation (NAO) will be near average.

The PSU team has been making Atlantic hurricane season forecasts since 2007, and these predictions have done pretty well, except for in 2012, when an expected El Niño did not materialize:

2007 prediction: 15 named storms, Actual: 15
2009 prediction: 12.5, named storms, Actual: 9
2010 prediction: 23 named storms, Actual: 19
2011 prediction: 16 named storms, Actual: 19
2012 prediction: 10.5 named storms, Actual: 19

UK Met Office predicts a slightly above-average hurricane season: 14 named storms
The UKMET office forecast for the 2013 Atlantic hurricane season, issued May 13, calls for slightly above normal activity, with 14 named storms, 9 hurricanes, and an ACE index of 130. In contrast to the statistical models relied upon by CSU, TSR, and NOAA, the UKMET model is done strictly using two dynamical global seasonal prediction systems: the Met Office GloSea5 system and ECMWF system 4. In 2012, the Met Office forecast was for 10 tropical storms and an ACE index of 90. The actual numbers were 19 named storms and an ACE index of 123.


Figure 4. Total 2013 Atlantic hurricane season activity as predicted by twelve different groups.

NOAA predicts a below-average Eastern Pacific hurricane season
NOAA's pre-season prediction for the Eastern Pacific hurricane season, issued on May 23, calls for a below-average season, with 11 - 16 named storms, 5 - 8 hurricanes, 1 - 4 major hurricanes, and an ACE index 60% - 105% of the median. The mid-point of these ranges gives us a forecast for 13.5 named storms, 6.5 hurricanes, and 2.5 major hurricanes, with an ACE index 82% of average. The 1981 - 2010 averages for the Eastern Pacific hurricane season are 15 named storms, 8 hurricanes, and 4 major hurricanes.

NOAA predicts a below-average Central Pacific hurricane season
NOAA's pre-season prediction for the Central Pacific hurricane season, issued on May 22, calls for a below-average season, with 1 - 3 tropical cyclones. An average season has 4 - 5 tropical cyclones, which include tropical depressions, tropical storms, and hurricanes. Hawaii is the primary land area affected by Central Pacific tropical cyclones.

West Pacific typhoon season forecast not available this year
Dr. Johnny Chan of the City University of Hong Kong usually issues a seasonal forecast of typhoon season in the Western Pacific, but did not do so in 2012 or 2013. An average typhoon season has 27 named storms and 17 typhoons. Typhoon seasons immediately following a La Niña year typically see higher levels of activity in the South China Sea, especially between months of May and July. Also, the jet stream tends to dip farther south than usual to the south of Japan, helping steer more tropical cyclones towards Japan and Korea.

Quiet in the Atlantic this weekend
There are no Atlantic threat areas to discuss today, and none of the reliable models for tropical cyclone formation is predicting development during the coming seven days. However, there are some indications that the atmosphere over the tropical Atlantic will become more conducive for tropical storm formation beginning around August 15. The Madden Julian Oscillation (MJO), a pattern of increased thunderstorm activity near the Equator that moves around the globe in 30 - 60 days, may move into the Atlantic then, increasing tropical storm formation odds. At the same time, the computer models are indicating an increase in moisture over the tropical Atlantic, due to a series of tropical waves expected to push off of the coast of Africa. There will also be several eastward-moving Convectively-Coupled Kelvin Waves (CCKWs) traversing the Atlantic during that period. These atmospheric disturbances have a great deal of upward-moving air, which helps strengthen the updrafts of tropical disturbances. Formation of the Eastern Pacific's Hurricane Gil and Henriette were aided by CCKWs. These same CCKWs will cross into the Atlantic and increase the odds of tropical storm formation during the period August 15 - 20.

Have a great weekend, everyone!

Jeff Masters

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Quoting 1684. LargoFl:
blob in the gulf near florida is falling apart now.....
Sure is
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Quoting 1683. washingtonian115:
My daughter is leaving in a few days.She's going to Delaware for college.Hubby and I will drive her up there.Probably won't see her until Christmas break.
First year or returning student?
Member Since: August 1, 2011 Posts: 28 Comments: 8031
Quoting 1681. GTstormChaserCaleb:
Good luck! :)
I agree with you GT, and by the way , when does MJO kick in?
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1687. yqt1001
While this is ongoing in the Pacific...



Here we are talking about some 10% AOI that has basically no chance of developing. I could only imagine how miserable this blog would get in a year like 2009 when all the activity is in the Pacific. :P
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Quoting 1674. LAbonbon:


Are you going to school there? If so, lucky you. Lovely area.
Yup, it's a beautiful area. Campus is really pretty too, but the view of mountains are limited because of trees unless you get out of campus :)
Member Since: August 1, 2011 Posts: 28 Comments: 8031
1685. FOREX
Quoting 1682. VR46L:
Which feature on the Sat image of the Gulf is the most interesting In your opinion folks

A. Western Gulf

B Central Gulf

C eastern Gulf





central
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1684. LargoFl
blob in the gulf near florida is falling apart now.....
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Quoting 1666. Bluestorm5:
In a hotel outside Asheville, NC now. I am moving into dorm tomorrow and spend the next several days backpacking and other outdoor activities around Western NC! Can't believe I'm not going back to Raleigh for awhile...
My daughter is leaving in a few days.She's going to Delaware for college.Hubby and I will drive her up there.Probably won't see her until Christmas break.
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1682. VR46L
Which feature on the Sat image of the Gulf is the most interesting In your opinion folks

A. Western Gulf

B Central Gulf

C eastern Gulf



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Quoting 1675. ricderr:
In 7 days there might be a Tropical Storm


in 7 days i might be the powerball winner....ta da da boom!
Good luck! :)
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Good morning/afternoon.

I am under a flood advisory as the remnant moisture from Gil is bringing light to moderate showers to portions of Hawaii. Typically, Hawaii receives some leftovers from former tropical cyclones annually. They could bring added showers, wind, and surf.

Member Since: July 21, 2011 Posts: 83 Comments: 7167
Many of you new people must think some of us are just a bunch of jokers with our humor...Trust us....When things get hot and serious we change our tune...Many of us have been in ground zero and the tone will change...For now we try to keep things jovial.
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1678. Patrap
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Quoting 1670. seer2012:


Low pres. center over the CV islands(inferred)


You think NHC might start tracking it anytime soon?
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@1664: What other model support is there?
@1665: 2010 is a recent year...and we were on C
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1675. ricderr
In 7 days there might be a Tropical Storm


in 7 days i might be the powerball winner....ta da da boom!
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Quoting 1666. Bluestorm5:
In a hotel outside Asheville, NC now. I am moving into dorm tomorrow and spend the next several days backpacking and other outdoor activities around Western NC! Can't believe I'm not going back to Raleigh for awhile...


Are you going to school there? If so, lucky you. Lovely area.
Member Since: June 26, 2013 Posts: 0 Comments: 1817
1673. LargoFl
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Quoting 1665. opal92nwf:
I do have to admit, no storms until late-August is pretty quiet, especially compared to recent years.

???? No storms????

we are still almost 2 storms ahead of normal.

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1671. ricderr
when a hurricane approaches..they shut off electricity im sure maybe water as well huh.




no to both...however you have a very good chance of losing power and restoration can be weeks away.....water due to flooding...if you haev no electricity and are on well water...no way to pump it....and in many cases...water treatment plants may be flooded...therefore a boil water order will be in place....

while many post very good hurricane plans.....if you live in a hurricane prone area....while not a necessity....one of the best things you can invest in....is a generator
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Low pres. center over the CV islands(inferred)
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Quoting 1654. GTstormChaserCaleb:
High Resolution FIM-9:



This is getting interesting.

Hmmmm....
Member Since: September 2, 2011 Posts: 0 Comments: 1148
1668. LargoFl
nasty cell up around Jacksonville now.....
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new tropical wave is getting kill by this dry air.
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In a hotel outside Asheville, NC now. I am moving into dorm tomorrow and spend the next several days backpacking and other outdoor activities around Western NC! Can't believe I'm not going back to Raleigh for awhile...
Member Since: August 1, 2011 Posts: 28 Comments: 8031
I do have to admit that for after July, no storms until late-August is pretty quiet, especially compared to recent years.
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In 7 days there might be a Tropical Storm and not out of the question this seasons first hurricane somewhere in the GOM:

Lower Resolution FIM-X:

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With the below normal ACE in western Pacific and E.Pacific this year i have the fear with the Atlantic,the signs are starting to line up, and with the low ACE in those parts, the Atlantic can take the protagonist this year and explode in the near future ..the pattern favor this..thats my fear..


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1662. LargoFl
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jbs clip is out. florida is in the middle of his corridor of disaster. also mentioned record cold north pole and lack of tornados as well as lowering his ace forecast for this yr. good luck all
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Quoting 1658. aislinnpaps:
Yes, it's definitely going to storm. The electric just went out for a couple of seconds. Glad I have dinner cooking now before it does hit.


Where (approx.) are you located?
Member Since: June 26, 2013 Posts: 0 Comments: 1817
Quoting 1654. GTstormChaserCaleb:
High Resolution FIM-9:



This is getting interesting.


Darn it. I was hoping the FIM9 would show something different than the other two. Of course, Kori will be in later doing a Snoopy dance.
Member Since: June 26, 2013 Posts: 0 Comments: 1817
Yes, it's definitely going to storm. The electric just went out for a couple of seconds. Glad I have dinner cooking now before it does hit.
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Quoting 1622. pottery:


Really, I have no doubt about that.
But not in August, and not as many as predicted.


August will have at least three storms by the end of the month.
Member Since: October 21, 2008 Posts: 246 Comments: 3947
1656. TxLisa
Quoting 1634. LargoFl:
one thing on that list..oil lamps...I would never have thought of those..i bought 2 battery operated lanterns...maybe the oil lamps would last longer huh.........
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1655. LargoFl
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High Resolution FIM-9:



This is getting interesting.
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1653. barbamz

Mainz/Germany goes Florida, lol. Some more impressions of summer at the banks of Rhine River, which was inundated just two months ago, at my new blog.
I have to leave for the evening and hope, everybody has a nice weekend, too.
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1652. pottery
Quoting Socalmargie:
why do people keep trying to scare people.. nothing is gonna happen


Well, I wouldn't go that far....
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Quoting 1646. GTstormChaserCaleb:
Kinda cute that Ana threw herself out in front so Bill could explode into the massive hurricane he became.

Those were my lurking days and some one said it was like a strip tease lol.
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We are now under a dangerous thunderstorm alert. The horses in the pasture across the road are all huddled together. AND, there are rain drops on my deck. YES!
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1649. pottery
Quoting LargoFl:
when a hurricane approaches..they shut off electricity im sure maybe water as well huh......im thinking now..toiletries etc...not to get gross here but flushing 2-3 weeks afterwards might be a problem huh...amazing how one storm can change EVERYTHING YOU DO huh...hope one never does come here...like living in the pioneer days..you have to fend for yourself in every way huh....just awful.

Nasty Truths ! :):))

Pour a bucket of water into the tank, or directly down into the bowl.
Works just fine.

A couple of containers (bathtub, drums anything) of water is a must, obviously. Swimming pools are the ultimate water storage systems. But not for drinking.
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1647. LargoFl
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Quoting 1631. GTstormChaserCaleb:
TD 3 which later became Hurricane Bill was also surrounded by dry air.

Kinda cute that Ana threw herself out in front so Bill could explode into the massive hurricane he became.

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Quoting 1636. mitchelace5:
I live here in Broward. And with the POSSIBILITY of tropical threats this year, I have a gas stove, food, LOTS of water, and plywood and shutters.


Lots of gas meters get damaged during hurricanes. I saw many that were damaged during Katrina. Lots of folks who had gas couldn't rely on it.
Member Since: June 26, 2013 Posts: 0 Comments: 1817
1644. LargoFl
when a hurricane approaches..they shut off electricity im sure maybe water as well huh......im thinking now..toiletries etc...not to get gross here but flushing 2-3 weeks afterwards might be a problem huh...amazing how one storm can change EVERYTHING YOU DO huh...hope one never does come here...like living in the pioneer days..you have to fend for yourself in every way huh....just awful.
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1643. Patrap
GOM Sea Height Anomaly

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1642. Patrap
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1641. Patrap
Hurricane Preparation 2013

It's time to dust off that family disaster plan, or in many cases, create one.

Keeping your family safe during a hurricane starts with proper planning. One in six Americans live along the eastern seaboard or the Gulf of Mexico, making hurricane preparation a must for many and their families.








Evacuation Considerations for the Elderly, Disabled and Special Medical Care Issues



Your Evacuation Plan


Disaster Supplies Kit


NOAA Alert Weather Radio's


"Think outside the Cone"
hurricanebuddy.com

History teaches that a lack of hurricane awareness and preparation are common threads among all major hurricane disasters. By knowing your vulnerability and what actions you should take, you can reduce the effects of a hurricane disaster.
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Thank you! :D
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About

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.