Hurricane season 2005--why so active?

By: Dr. Jeff Masters , 7:31 PM GMT on August 01, 2005

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This will be my last blog entry until August 12; I'm vacationing far from the tropics (Yellowstone!) to appreciate some mountain weather.

Today's monthly summary of hurricane activity for July issued by the National Hurricane Center (NHC) states:

"The month of July saw unprecedented tropical cyclone activity in the Atlantic Basin...with the development of five named storms...Tropical Storm Cindy...Hurricane Dennis...Hurricane Emily... Tropical Storm Franklin...and Tropical Storm Gert. The previous record for named storms that formed in July was four. The two major hurricanes that developed during the month tied a record set in 1916. The July activity follows an unusually active month of June ...And the seven named storms that have formed thus far in 2005 represent a record level of activity for the first two months of the season."

Why has this hurricane season been so active? Part of the reason lies in a decades-long natural cycle in hurricane activity that in 1995 switched to a high-hurricane activity mode. Hurricane activity has been above normal since 1995, and will likely continue to be for the rest of this decade and the next.

Additionally, there are six key ingredients are necessary for tropical cyclone formation (you can read about these in full detail in the Tropical Cyclone FAQ. We'll focus on three of them in particular that have been highly conducive to tropical cyclone formation during this remarkable hurricane season of 2005.


Vertical Wind Shear
Hurricanes need low values of vertical wind shear between the surface and the upper atmosphere (the jet stream level, typically 35,000 - 40,000 feet high in the tropics). Vertical wind shear is the magnitude of wind change with height. High vertical wind shear can disrupt a tropical cyclone trying to form by literally tearing it apart. High wind shear also can weaken or destroy a healthy tropical cyclone by interfering with the organization of deep convection around the cyclone center. Typically, 20 knots (23 mph or 10 m/s) or less difference in wind speed between the surface and upper atmosphere is considered favorable for hurricanes. In June and July of 2005, wind shear values were 20 - 40% below normal for the Gulf of Mexico and Caribbean Sea, the primary genesis locations for the seven tropical cyclones that formed. Wind shear values this low are highly favorable for tropical cyclone formation (see plots below).



Figure 1. Average amount of vertical wind shear (in black) and observed wind shear (in blue) for 2005 for the western Caribbean. Credit: Colorado State University (NOAA/CIRA)



Figure 2. Average amount of vertical wind shear (in black) and observed wind shear (in blue) for 2005 for the eastern Caribbean. Credit: Colorado State University (NOAA/CIRA)

Sea Surface Temperatures
Hurricanes need ocean waters of at least 26.5C (80 F) through a depth of about 50 meters to form or maintain their strength. The warmer the water, the better, since a hurricane is a huge heat engine. Sea surface temperatures (SSTs) are at the highest levels ever observed in the Atlantic, for the 50 years we have records. As of July 31, typical tropical Atlantic SSTs were about 2F (1.1C) above normal.



Figure 3. The Sea Surface Temperature departure from normal (in degrees C) for July 31, 2005. A large area of above normal SSTs (yellows and light greens) covers virtually the entire North Atlantic Ocean. The cold wake of Hurricane Emily is still apparent between the Yucatan Peninsula and southern Texas. Credit: U.S. Navy.

Moist Air
Hurricanes need moist air in the mid-troposphere (5 km or 3 mi altitude). Dry air interferes with the development of the large thunderstorm complexes needed to get a tropical storm going. Until the last week of July, the air over the tropical Atlantic and Caribbean Sea has been very moist. Since then, several large dust storms have moved off of the coast of Africa, accompanied by copious amounts of dry air that has interfered with tropical storm formation. TOMS aerosol data shows a large area of dust covering the entire tropical eastern Atlantic today.

Is Global Warming to Blame?
How much, if any, of this year's activity is due to global warming? That's a difficult question to answer. The research published so far shows that global warming cannot be linked to an increase in the number of hurricanes. So, this season's exceptional number of storms is probably unrelated to global warming. However, there is considerable debate whether or not sea surface temperatures and hurricane intensity have been affected by global warming. It is possible that the remarkable intensity of the hurricanes seen so far this season can be partially blamed on global warming. However, much more research needs to be done on this subject before we can link global warming with hurricane intensity. I plan to write a detailed article on the subject later this season, after I've had time to read the new research linking hurricane intensity to global warming, due to be published in Nature magazine on Sunday, August 7.

Dr. Jeff Masters

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592. 147257
03:40 AM GMT op 04 Augustus, 2005
yeah ok youre right alec
Member Since: August 2, 2005 Posts: 7 Comments: 68
591. Alec
11:38 PM EDT on August 03, 2005
now using tape is useless in a major hurricanes because the force against the walls would peel the roof off if the windows broke
590. mobal
3:37 AM GMT on August 04, 2005
Well, they DO hade duct tape on the shuttle!
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589. outrocket
10:33 PM CDT on August 03, 2005
now,there is one purpose for duct tape I have found.The spinning vents to let heat from attic make wonderful alian looking flying objects as they spin up to over 100mph they let loose (along with taking shingle with them) and fly away. So cover them with 2 heavy duty garbage bags and tape then to base with a whole roll if neccessary.
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588. 147257
03:36 AM GMT op 04 Augustus, 2005
but i'm going to sleep

keep a eye on TS Harvey and coming TS Irene

over and out

cya tommorow :)
Member Since: August 2, 2005 Posts: 7 Comments: 68
587. Alec
11:36 PM EDT on August 03, 2005
security*

-that's my last correction for tonight
586. mobal
3:34 AM GMT on August 04, 2005
I have no idea 147257, I am in Reynosa MX. right now, WORKING.
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585. 147257
03:34 AM GMT op 04 Augustus, 2005
btw 147257 is a silly name just call me nicolai i thought i had to type a secuity password or something like that wasnt awake anymore
Member Since: August 2, 2005 Posts: 7 Comments: 68
584. Alec
11:34 PM EDT on August 03, 2005
good.
583. 147257
03:33 AM GMT op 04 Augustus, 2005
why is tape a waste of effort it protect you when windows break
Member Since: August 2, 2005 Posts: 7 Comments: 68
582. 147257
03:32 AM GMT op 04 Augustus, 2005
lol yeah but is my english good bad?
Member Since: August 2, 2005 Posts: 7 Comments: 68
581. mobal
3:31 AM GMT on August 04, 2005
147357, tape is a waste of effort.
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580. outrocket
10:29 PM CDT on August 03, 2005
tape is for the box you put your personals in and stack on shelf. As far as windows useless.
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579. Alec
11:29 PM EDT on August 03, 2005
it is. i just like spell checking people.
578. mobal
3:27 AM GMT on August 04, 2005
I moved here in 82, but im learning now. Lets do it. HOW?
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577. 147257
03:28 AM GMT op 04 Augustus, 2005
great i'm dutch so english isn't my best language so my teacher will be happy with you :) going to write letters and you can correct them :)
Member Since: August 2, 2005 Posts: 7 Comments: 68
576. outrocket
10:26 PM CDT on August 03, 2005
I really am starting to think MET may not be your field Alec...Ya know if you time it right you could host Jeopardy and uhhhh dock em money for spelling...
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575. 147257
03:26 AM GMT op 04 Augustus, 2005
tape is for the windows
Member Since: August 2, 2005 Posts: 7 Comments: 68
574. Alec
11:26 PM EDT on August 03, 2005
important*- yes i do. help people with spelling.
573. mobal
3:25 AM GMT on August 04, 2005
or tape
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572. outrocket
10:21 PM CDT on August 03, 2005
Yes Mobal it would,I have lived on coast all my life that is a needed blog.There is a good learning curve on being prepared,and alot here have moved to this area since frederic.The best people to give those blogs are ones who have been though them..I seemed to have learned a new trick somewhere for my house every storm since Camille..
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571. 147257
03:25 AM GMT op 04 Augustus, 2005
alec dont you have something better to do ? the importants thing is that people understand me :)
Member Since: August 2, 2005 Posts: 7 Comments: 68
570. Alec
11:24 PM EDT on August 03, 2005
thought*
569. 147257
03:22 AM GMT op 04 Augustus, 2005
hey outrocket i thougt you was going to join the irc channel posting here is fun but the refreshing of the site takes long by me bad routing and very bad internet
Member Since: August 2, 2005 Posts: 7 Comments: 68
568. Alec
11:21 PM EDT on August 03, 2005
doesn't*
567. mobal
3:17 AM GMT on August 04, 2005
outrocket, I think it would be a good blog, as long as that storm guy dosnt say to use cardboard.
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566. outrocket
10:18 PM CDT on August 03, 2005
thanks I did kinda make a fruit out of it...bad keyboard night here.
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565. Alec
11:17 PM EDT on August 03, 2005
well it didnt appear so scrap that last comment.
564. Alec
11:15 PM EDT on August 03, 2005
nevermind that last correction outrocket.
563. 147257
03:14 AM GMT op 04 Augustus, 2005
irc://irc.after-all.net/Forecasters wrong its irc://irc.after-all.org/Forecasters
Member Since: August 2, 2005 Posts: 7 Comments: 68
562. outrocket
10:13 PM CDT on August 03, 2005
Mobal...dont think so but the subject has been tossed around here a few times,is that what you do,or do you have questions on preparing?
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561. 147257
03:07 AM GMT op 04 Augustus, 2005
i set up the channel

/server irc.after-all.org

/join #forecasters

for explorer or mozilla

irc://irc.after-all.net/Forecasters

not sure if the internet link works but i will see it :)
Member Since: August 2, 2005 Posts: 7 Comments: 68
560. outrocket
10:11 PM CDT on August 03, 2005
wow the lost post showed up,after I rewrote question...maybe the server got into my coffee too...
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559. Alec
11:09 PM EDT on August 03, 2005
I think it is getting ready to develop. Certainly going to be going w or wnw around the southern end of a high. Most models show a weakness in the ridge so it may just go out to sea. But still wayyyyyyyy to far out to pinpoint the long range forecast.
558. outrocket
10:09 PM CDT on August 03, 2005
sorry alec...either I have had too much coffee or my keyboard has...LOL save your breath tonight..and what of system midway across near ITCZ?
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557. mobal
3:05 AM GMT on August 04, 2005
Has there ever been a blog here about hurricane prepareness? IE Plylox, wood size, time to leave etc....
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556. outrocket
10:05 PM CDT on August 03, 2005
good deal on test Alec..and only one f in last word so ya dont have to get me..I got a hanging f key,too much coffee in this keyboard...so what do you think of the blob near the ITCZ alec..midway across?
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555. Alec
11:05 PM EDT on August 03, 2005
infering*
554. Alec
11:04 PM EDT on August 03, 2005
distractions* GET IT RIGHT!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
553. Alec
11:04 PM EDT on August 03, 2005
exists*
552. outrocket
10:02 PM CDT on August 03, 2005
No...not inffering that at all,hey was young once..I mean ,distactions...lol
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551. 147257
03:00 AM GMT op 04 Augustus, 2005
So TD 9 excist ?
Member Since: August 2, 2005 Posts: 7 Comments: 68
550. Alec
11:00 PM EDT on August 03, 2005
Are you infering im a woman????better not. that calc final was pie. totally ripped it up cause i understood it.
549. outrocket
9:59 PM CDT on August 03, 2005
Thanks nicoliai...appreciate the inside on the language,,still though duthc lives at risk same as spainish and American..still should be recognized..
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548. 147257
02:57 AM GMT op 04 Augustus, 2005
strange you opened mirc?

first typ in the white box /server irc.after-all.org
then youre in the network you typ

/join #forecasters

this only a setup for a few hours but maybe i can setup one for weeks if people are interested
Member Since: August 2, 2005 Posts: 7 Comments: 68
547. mobal
2:56 AM GMT on August 04, 2005
Alec, I have to fly to FL. 8/22. Guy I ill be with is from Tampa. He's sick of Tropics too.
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546. outrocket
9:56 PM CDT on August 03, 2005
Alec..is there still 4 womens colleges in tallahassee...if so how did you ace that calc test????
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545. pirateotobx
2:57 AM GMT on August 04, 2005
link to latest on storm in east atlantic....
Link

Hopefully it will take the track and head out to sea.;-)
544. Alec
10:57 PM EDT on August 03, 2005
you see it that bad goldenhine???
543. 147257
02:56 AM GMT op 04 Augustus, 2005
youre wrong only Suriname Aruba Curacao Bonaire and the sss island speak dutch the rest is spanish ;)
Member Since: August 2, 2005 Posts: 7 Comments: 68
542. goldenhine
10:54 PM EDT on August 03, 2005
im waitin on that big super capeverde hurricane that takes a week to get here floyd hugo david andrew those kinda guys
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Dr. Masters co-founded wunderground in 1995. He flew with the NOAA Hurricane Hunters from 1986-1990. Co-blogging with him: Bob Henson, @bhensonweather

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