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

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

Share this Blog
79
+

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

Reader Comments

Comments will take a few seconds to appear.

Post Your Comments

Please sign in to post comments.

or Join

Not only will you be able to leave comments on this blog, but you'll also have the ability to upload and share your photos in our Wunder Photos section.

Display: 0, 50, 100, 200 Sort: Newest First - Order Posted

Viewing: 640 - 590

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | 49 | 50Blog Index

Ah.. no problem
Member Since: Posts: Comments:
Quoting 634. Tropicsweatherpr:


On this I agree. I have a few of those downcasters on my ignore list.
Yep is getting annoying and i can't enjoy the blog.
Member Since: Posts: Comments:
Quoting 618. SuperStorm093:


You can call it nonsence, if the season starts to pick up. But just as that one guy on here before, we are going to need a hurricane once every like 6 days and MAJOR every 3 weeks. thats not happening.
I supect in a matter of a few weeks we will have 3 named storms at once, and at some point two majors at once.
Member Since: Posts: Comments:
I think Utor will become a super typhoon in two days time.
Member Since: Posts: Comments:
Quoting SunriseSteeda:


One day, I'll wander through the blog archives and work up some stats on the average time of the season that we start seeing "This season is a bust!". And then compare them to what actually happened later ;-)


reason i lurk and rarely post anymore..
Member Since: Posts: Comments:
SuperStorm093.

People please stop arguing with this fella.I don't know who are the bigger fools in this situation the people who keep arguing with him or him or perhaps both.He's not going to get this in his head no matter how much you argue with him.It's not going to work.
Member Since: August 14, 2010 Posts: 10 Comments: 16362
Quoting 630. Gearsts:
I have people in ignore and you go and quote them! Please DON'T quote trolls.


On this I agree. I have a few of those downcasters on my ignore list.
Member Since: Posts: Comments:
I see a favorable GOM and Caribbean Sea tracking cyclones in late August it no September as high pressure begins to dominate the western Atlantic and eastern US allowing a zone of lower pressures to exist across Caribbean Sea and GOM. Models are showing better upward vertical motion coming into the Caribbean and MDR and East Atlantic regions come late August and I say tropical activity begins around August 16th. This will not be a dull season, and the upper level low over Cuba moving westward is showing signs that this region of the Atlantic will become more favorable for hurricane development. Be patient as this will likely be the only lull in activity until early October.
Member Since: Posts: Comments:
Quoting 615. Tornado6042008X:
I know this is a random question but why does the underground hurricane archive show Andrew hitting Florida as a category 4 hurricane instead of a category 5? And didn't it hit Louisiana as a category 3 hurricane?
 
And I highly doubt that Andrew made it all of the way across and exited Florida as a category 4 hurricane.

!

 
Maybe someone forgot to update it.
Member Since: Posts: Comments:
Things can quickly change across the tropics as we are now near the REAL season. I fully expect things to really get going soon.
Member Since: Posts: Comments:
Quoting 539. CybrTeddy:


Given it hasn't developed a single tropical cyclone in the Atlantic and has done very poorly at forecasting genesis of tropical cyclones in the western pacific I'd say they're both becoming quite as useless since their upgrades this year.
I have people in ignore and you go and quote them! Please DON'T quote trolls.
Member Since: Posts: Comments:
Quoting 611. hurricane23:


please stop with this nonsence.. you do realize about 80% of hurricane season is still to come.


One day, I'll wander through the blog archives and work up some stats on the average time of the season that we start seeing "This season is a bust!". And then compare them to what actually happened later ;-)
Member Since: Posts: Comments:
Tropical Storm Utor will be a hurricane soon
Member Since: Posts: Comments:
Quoting SuperStorm093:


You can call it nonsence, if the season starts to pick up. But just as that one guy on here before, we are going to need a hurricane once every like 6 days and MAJOR every 3 weeks. thats not happening.


Have u ever experienced a major? Plenty of time to get close to the numbers predicted which i might add isnt important as it just takes 1 over your area. Things will begin to change across the tropical atlantic next week as overall conditions should improve across the basin.
Member Since: Posts: Comments:
626. Skyepony (Mod)
11W UTOR
Member Since: Posts: Comments:
Just saying, I am having a hard time believing that both the EURO and the GFS would be wrong.
Member Since: Posts: Comments:
Quoting opal92nwf:
If a storm doesn't form by August 25th, then I don't know what I will do with myself.


It'll happen. Just give it time.
Member Since: Posts: Comments:
Large monsoonal low pressure system can be seen between 10-20n: and 30-40w, with slight cyclonic turning in a rather convection less environment subdued to the monsoon trough, or ITCZ. Dry air is a big hinderance towards development while wind shear is rather low in the region, but increases towards 55w. Eastern Caribbean Sea becomes more unfavorable as a large upper level anticyclone tries to move into the Caribbean Sea it's westerly upper level winds cause some severe shear over the islands of the lesser Antilles. Upper level low moving over western Cuba is bringing the Shear with it slowly, as a strong upper level anticyclone builds into the Gulf and northwestern Caribbean Sea, where shear is lower and SSTs are warmer. Monsoon low over or near Panama will continue to move northwestward with time, but development is not expected as it travels over land. However if it emerges into the Northwestern Caribbean Sea and GOM it's potential for development becomes rather high as shear continues to die down. Again development chances are low first 48 hours, but becomes more and more possible near day five.
Member Since: Posts: Comments:
Quoting 615. Tornado6042008X:
I know this is a random question but why does the underground hurricane archive show Andrew hitting Florida as a category 4 hurricane instead of acategory 5? And didn't it hit Louisiana as a category 3 hurricane?

!


Weather Underground's season maps do not take into consideration post-season changes. Andrew was upgraded to a Category 5 Florida landfall a decade after it dissipated.

They're actually pretty unreliable. I suggest using Wikipedia's.
Member Since: July 6, 2010 Posts: 113 Comments: 31409
Quoting 601. TropicalAnalystwx13:
I seriously hate hurricane season lulls so much...
Time for a friday evening bike ride!!
Member Since: Posts: Comments:
Quoting 610. Stormchaser121:
Would yall quit getting into these childish arguments?? Please?


All cornbread all the time gets boring. It adds a little if you dash in some sugar now and then.
Member Since: Posts: Comments:
Quoting 615. Tornado6042008X:
I know this is a random question but why does the underground hurricane archive show Andrew hitting Florida as a category 4 hurricane instead of a category 5? And didn't it hit Louisiana as a category 3 hurricane?

!-- -->!-- -->!-- -->!-- -->!-- -->!-- -->!-- -->

 

I was wondering that too.
Member Since: Posts: Comments:
Quoting 611. hurricane23:


please stop with this nonsence.. you do realize about 80% of hurricane season is still to come.


You can call it nonsence, if the season starts to pick up. But just as that one guy on here before, we are going to need a hurricane once every like 6 days and MAJOR every 3 weeks. thats not happening.
Member Since: Posts: Comments:
If a storm doesn't form by August 25th, then I don't know what I will do with myself.
Member Since: Posts: Comments:
616. Skyepony (Mod)
Quoting 604. SuperStorm093:


How did it do so far this year.


Middle of the pack for Dorian..(final ave model error in nm 0hr,24hr, 48hr & etc..)
NVGM 32.2 53.1 76.3 133.6 185.0 250.8

Not real great on Chantal..
NVGM 28.0 97.5 154.7 226.7 251.2 -
Member Since: Posts: Comments:
I know this is a random question but why does the underground hurricane archive show Andrew hitting Florida as a category 4 hurricane instead of a category 5? And didn't it hit Louisiana as a category 3 hurricane?
 
And I highly doubt that Andrew made it all of the way across and exited Florida as a category 4 hurricane.

!

 
Member Since: Posts: Comments:
614. ackee
Well for those who are saying the seasons is a bust pretty much Do have a strong point the GFS have been on and off with development interesting show no development nearing the end of the month while the EUro has been right so far showing No development. THE FIM is not a reliable model and personal I would not put much faith on that model ultimately mother nature will have the final say
Member Since: Posts: Comments:




Member Since: September 23, 2005 Posts: 14 Comments: 10870
612. ackee
Well for those who are saying the seasons is a bust pretty much Do have a strong point the GFS have been on and off with development interesting show no development nearing the end of the month while the EUro has been right so far showing No development. THE FIM is not a reliable model and personal I would not put much faith on that model ultimately mother nature will have the final say
Member Since: Posts: Comments:
Quoting SuperStorm093:
well 12z pretty much dropped the CV systems, I am telling you, LOTS of people are going to bust high this season with numbers, and the ECMWF doesnt show any developments expect a curve RIGHT off the coast.


please stop with this nonsence.. you do realize about 80% of hurricane season is still to come.
Member Since: Posts: Comments:
Would yall quit getting into these childish arguments?? Please?
Member Since: Posts: Comments:
609. whitewabit (Mod)
Quoting 600. CybrTeddy:
I seriously can't wait for school to start back up for Florida kids...


in all states ..
Member Since: Posts: Comments:
Quoting 606. Skyepony:


UTOR's size & land should slow it down..

LOL you know I remember my post being snatched down real fast when I was out of line.What about LargoFl's?.
Member Since: August 14, 2010 Posts: 10 Comments: 16362
Quoting TropicalAnalystwx13:
I hate hurricane season lulls so much...


*sigh, rolling eyes* tell me about it
Member Since: Posts: Comments:
606. Skyepony (Mod)
Quoting 598. Tornado6042008X:
I see a pretty good chance of RI there.


UTOR's size & land should slow it down..

Member Since: Posts: Comments:
Quoting 570. Camille33:

off topic stay on topic!!


What if the next question was "Are there military positions where I can exercise my passion for weather?".


Too many are too quick to jump the gun and spend time (like I am now) to admonish what they see as trollism. Does no one notice that one distracts ones own self and others by doing so?

If everyone would read a post, decide to engage in it, or not, and move on... wait, isn't that what we are doing?

Sorta like Yahoo's news feeds, where every 7th "article" headline is really an advertisement disguised as an article... I simply recognize it for what it is, and keep skimming. It costs very little time to do this. I don't go all blog-commando on Yahoo for contaminating my "news" with "ads" :-) That costs time for myself and others!

Member Since: Posts: Comments:
Quoting 602. Camille33:

Dr.M trust it he says it is a reliable forecasting cyclone model!!


How did it do so far this year.
Member Since: Posts: Comments:
Quoting 601. TropicalAnalystwx13:
I seriously hate hurricane season lulls so much...


Can't even look at any model candy either, they don't show anything, which makes it way worse.
Member Since: Posts: Comments:
Quoting 595. SuperStorm093:


We cannot trust the NAVGEM model.

Dr.M trust it he says it is a reliable forecasting cyclone model!!
Member Since: Posts: Comments:
I seriously hate hurricane season lulls so much...
Member Since: July 6, 2010 Posts: 113 Comments: 31409
I seriously can't wait for school to start back up for Florida kids...
Member Since: July 8, 2005 Posts: 259 Comments: 23560
Quoting 595. SuperStorm093:


We cannot trust the NAVGEM model.
The US NAVY?
Member Since: Posts: Comments:
Quoting 590. TropicalAnalystwx13:
Tropical Storm Utor is well on its way to becoming a typhoon.

I see a pretty good chance of RI there.
Member Since: Posts: Comments:
Quoting 569. Levi32:


Placement in relation to the land mass destroyed it on this run, but with no trackable low pressure area yet, models are going to flip around. Nothing's guaranteed either way. I think this blog could use a dose of conservatism. Following individual model runs leads to ruin.
Member Since: Posts: Comments:
Quoting 589. Camille33:

look off cozumal here
That is what has been a topic here. Does that go west or north or what?
Member Since: Posts: Comments:
Quoting 593. Camille33:


no fim but this model look interesting!


We cannot trust the NAVGEM model.
Member Since: Posts: Comments:
Member Since: Posts: Comments:
Quoting 591. unknowncomic:
When will they get the FIM to run as quick as the GFS? Any answers?


no fim but this model look interesting!
Member Since: Posts: Comments:
18z drops everything. E. atlantic still doesnt have anything forming in it on the GFS run. is the GFS seeing something we are not?
Member Since: Posts: Comments:
When will they get the FIM to run as quick as the GFS? Any answers?
Member Since: Posts: Comments:
Tropical Storm Utor is well on its way to becoming a typhoon.

Member Since: July 6, 2010 Posts: 113 Comments: 31409

Viewing: 640 - 590

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | 49 | 50Blog Index

Top of Page

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.