Why so many U.S. hurricanes the past two years?

By: Dr. Jeff Masters , 4:51 PM GMT on December 05, 2005

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Before I answer the title question, let's talk about Epsilon. This hurricane refuses to die, despite cold waters and high wind shear. The latest model projections continue to keep it as a hurricane for at least two more days, which would make 2005 break the record for most number of hurricane days (50, set in 1995) and most number of days with a named tropical storm (120.5, set in 1995). Beyond three days from now, I really don't see how the storm can survive, since wind shear levels will increase to more than 50 knots, which will surely tear the storm apart. Nothing else is brewing in the tropics, although there is a marginal possibility of something developing north of Panama a week or so from now.

Why have so many hurricanes hit the U.S. in 2004 and 2005?
The 1995 - 2003 hurricane seasons were quite active, but only 3 of 32 (9%) major hurricanes that formed in the Atlantic made landfall in the United States, much below the climatological average of 30% for the entire 20th century. This lack of hurricane strikes occurred because a trough of low pressure was frequently located over the East Coast during these years, and the flow of winds through the trough tended to recurve hurricanes northeastward out to sea before they could strike land. However, in 2004 and again in 2005, this trough was mostly absent, and an unusually strong ridge of high pressure was in place which tended to steer hurricanes into the U.S. and not allow recurvature. Seven of 13 (54%) major hurricanes that formed in the Atlantic made United States landfall as major hurricanes during 2004 and 2005.

So, what caused this unusually strong ridge of high pressure to develop over the eastern U.S.? According to Dr. Bill Gray's hurricane forecast team at Colorado State University, this ridge formed in response to a strong warming of the ocean in the central North Pacific. Figure 3 shows the difference in Pacific sea surface temperatures during August-October 2004-2005 from August-October 1995-2003. Central North Pacific sea surface temperatures were up to 1.3C (2.3F) warmer in 2004-2005 compared to 1995-2003, leading to a deflection of the jet stream dowstream of the warm pool. The jet stream assumed a standing wave pattern, resulting in a ridge of high pressure over the central Pacific, trough of low pressure over the western U.S., and high of high pressure over the eastern U.S. It was this ridge of high pressure over the eastern U.S. that steered so many storms into the country during 2004-2005. Why did the ocean warm in the central North Pacific, and will that warm pool remain in place for the 2006 hurricane season? That is unknown.

Tune in tomorrow, when Dr. Bill Gray's forecast team releases their 2006 hurricane season forecast.



Figure 3. August-October 2004-2005 sea surface temperatures minus August-October 1995-2003 sea surface temperatures. Note the large warming of 1.3 degrees C in the central North Pacific. Image credit: Dr. Bill Gray's hurricane forecast team at Colorado State University.


Jeff Masters

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450. wonderness
7:01 PM GMT on December 06, 2005
The hot spot in the Pacific may be related to the upwelling of Global Ocean Circulation (THC or called the Gulf Stream in the northern Atlantic). The downwelling sites east and southwest of Greenland act as vacuum to pull water around the world. If the Gulf Stream (surface water headed north) is slowing so also would be the upwelling process in the north Pacific (deep water rising to become surface water and surface water pulled back to the Atlantic).
449. TampaSteve
6:04 PM GMT on December 06, 2005
Folks...remember that we had a period of a few weeks earlier this season where there were massive plumes of very dry air crossing the Atlantic from those African dust storms, which inhibited tropical development. Absent that, we may have had even more storms this year.

Can't wait to see what 2006 will bring...
448. FLCrackerGirl
3:26 PM GMT on December 06, 2005
NEW BLOG UP
Member Since: August 12, 2004 Posts: 47 Comments: 597
447. billsfaninsofla
2:37 PM GMT on December 06, 2005
good morning everyone... so we still have Epsilon?

hi Hurricane... hope you enjoy your vacation!
Member Since: September 5, 2005 Posts: 0 Comments: 5652
446. tornadoty
12:31 PM GMT on December 06, 2005
Real quickly before I leave:

If hurricanechaser's hypothesis is right (read his blog), then the approaching front may be aiding in its strengthening.
445. ForecasterColby
12:18 PM GMT on December 06, 2005
Convection closing, time for a new Epsilon.

Banding features looking really nice too.
444. ProgressivePulse
12:09 PM GMT on December 06, 2005
I am going to quote the NHC because it is how I feel and well simply put it says it all. "I HAVE RUN OUT OF THINGS TO SAY...AND THIS ONE WILL BE SHORT." HOW HOW HOW HOW and it looks like it wrapping around again and rebuilding the convection. HOW lol?
Member Since: August 19, 2005 Posts: 5 Comments: 5452
443. ForecasterColby
11:13 AM GMT on December 06, 2005
Still a 'cane at 5AM, looking better again (lol)
442. hurricanechaser
10:22 AM GMT on December 06, 2005
Thanks so much Melli for the very thoughtful sentiments.:)

I stayed up to see if the NHC would keep Epsilon at Hurricane intensity which they did. It is currently a 75 mph hurricane holding on in more or less a steady state.

I was going to post my expectations for Epsilons future intensity but decided to update my blog instead.

I hope everyone has a great day.:) I will once again be sleeping in while I'm on vacation this week.:)
441. melli
8:59 AM GMT on December 06, 2005
hurri, enjoyed your 3hr post. its why we are here.
melli
440. hurricanechaser
7:46 AM GMT on December 06, 2005
hey Jeff...I just left Corys blog..lol
439. theboldman
7:42 AM GMT on December 06, 2005
lol man a human typewriter thats lol
Member Since: September 8, 2005 Posts: 25 Comments: 2
438. hurricanechaser
7:24 AM GMT on December 06, 2005
LOl..mr. Jeff..actually I was writing that long post..to long I gues..I'm a slow typist. It took me almost three hours to write my last blog.:) lol
437. theboldman
7:22 AM GMT on December 06, 2005
haah tony you are a convicted lurker how does it feel lol
Member Since: September 8, 2005 Posts: 25 Comments: 2
436. hurricanechaser
7:20 AM GMT on December 06, 2005
Haydn,

I got fascinated by hurricanes when Diana brought hurricane force winds to me in Wilmington N.C. in September of 1984. I became somewhat obsessed with them at the impressionable age of 14.

One of my favorite memories is from my very first major hurricane experience in large category three Fran where I was in the right front quadrant NE of landfall on September 5th 1996. We got 120 mph gusts.

That same year in July, we got a direct hit from ctegory two Bertha.

In 1998, category two Bonnie hit us.

In 1999, it was 65 mph wind gusts as Dennis passed offshore a large category two hurricane, followed by category two Floyd that brought 100 mph gusts.

Then I began chasing storms in August of 2004.

Almost got swept away by storm surge on Hwy. 12 in the Outer Banks as hurricane Alex brushed by with hurricane force gusts.

Then a much weakened hurricane Charley in Wrightsville Beach, N.C. with 90 mph gusts.

I chased Jeanne in Daytona Beach , Fl. but I missed her and ony got 65 mph gusts.

This year I intercepted Dennis in extreme SW Alabama where I got hammered by 100 mph gusts in the small but intense eyewall.

I got as far as Extreme South Hattiesburg for Katrina after having to cancel my reservations in Gulfport because I was sick and left a day later. We got 120 mph gusts 55 miles inland. Roofs flyng off, kangaroo store being systematically dismantled with large metal debris cascading through the air, and trees being uprooted and cut in half around me. This footage was shown on Fox News and CNN with a personal interview which launched my chasing carrer.

Then Ophelia as a strong category One along Outer Banks and was trapped by storm surge once again in 86 mph gusts.

Then Wilma in Everglades City when we saw 115 mph gusts and a 4 to 5 foot storm surge that surrounded my car in a matter of minutes and me and another chaser just made it to a hotel that was the only possible place to go.

All in all...

Its a tough call between Fran, Katrina, and Wilma all category three when I experienced them.

Sorry I wrote so much..I just realized how long it is.:)





435. hurricanechaser
7:00 AM GMT on December 06, 2005
Epsilon may just retain hurricane intensity as its holding on...its borderline right now...heres the latest Infrared.:)

Link
434. hurricanechaser
6:59 AM GMT on December 06, 2005
Sorry Hay,
I just saw your post as I was signing off.;)
433. haydn
6:55 AM GMT on December 06, 2005
I guess I'll an answer to my question later. Goodnight.
432. theboldman
6:54 AM GMT on December 06, 2005
haha i dont think so lol ok night tony
Member Since: September 8, 2005 Posts: 25 Comments: 2
431. haydn
6:53 AM GMT on December 06, 2005
Hurricanechaser, what has been your most interesting experience? From the way you write, it sounds like you have been in several storms.
430. hurricanechaser
6:53 AM GMT on December 06, 2005
LOL Jeff...and you may have gotten a hurricane force gust with Hugo.

Have a goodnight everyone.:)
429. hurricanechaser
6:52 AM GMT on December 06, 2005
ok. I gotta try and get some sleep but I hope you each have a great night.:)

Take care Jeff, Snow, Hay, and the others.:)
428. theboldman
6:51 AM GMT on December 06, 2005
the only wind storms that come are the strong fronts and were i live i am sheltered from most of the wind maby a 20 mph gust will blow by my house lol but down in the valley it will be sustained at 20 gusting to 40 l0o
Member Since: September 8, 2005 Posts: 25 Comments: 2
427. theboldman
6:50 AM GMT on December 06, 2005
never that i can recall
Member Since: September 8, 2005 Posts: 25 Comments: 2
426. haydn
6:50 AM GMT on December 06, 2005
That is my biggest experience. It wasn't gusts. The winds were constant. I may be guessing about the 60mph winds. That was 17 years ago and I didn't have a way to measure the winds. I'm recalling what my father told me. If another weak storm like Tammy comes, I would like to go to the coast to see the waves.
425. hurricanechaser
6:48 AM GMT on December 06, 2005
I'm curious Jeff....have you experience hurricane force wind storms out there on the west coast or a strong earthquake?
424. hurricanechaser
6:46 AM GMT on December 06, 2005
alot of people don't realize that 60 mpoh gusts in saturated grond can uproot alot of trees and create life threatening conditions in the process. Its a blessing you had no rainfall with those gusts.
423. haydn
6:45 AM GMT on December 06, 2005
Ditto on the definition of MJO.
422. hurricanechaser
6:45 AM GMT on December 06, 2005
WOW!...is that your biggest tropical event to date?

not a good place to be in 60 mph gusts.
421. haydn
6:43 AM GMT on December 06, 2005
60 mph winds and no rain ... I thought our pine trees were going to snap. I lived in a double wide then. I did not like the thought of waking up to pine needles. ... I slept through most of it. My dad stayed up most of the night. Columbia got pounded though it was inland. People there got 120 mph winds.
420. theboldman
6:42 AM GMT on December 06, 2005
man im in sacramento and i have never heard of MJO nut know of the pinapple express thats storms that for by hawaii and bring a warmer rain with high snow levels
Member Since: September 8, 2005 Posts: 25 Comments: 2
419. hurricanechaser
6:42 AM GMT on December 06, 2005
Thanks for the very informative post.:)

Based upon what you just wrote and what I read in your link it appears very rational to expect such a correlation.
418. snowski
6:40 AM GMT on December 06, 2005
MJO--simply put--is intense tropical rainfall from the Western Pacific dumping moisture on the U.S. West Coast by the "Pineapple Express." Last Dec-Jan we had a huge MJO event (followed by additional episodes Feb-March) which dumped incredible anmounts of snow on the Southern Rockies.

We skiers love that. Thus my original question of whether the current warm SST anomaly in the Central N Pacific could trigger an MJO event. Since MJO by definition is a initiated by tropical Pacific moisture, I was wondering whether the warm Central N Pacific SST anomaly Dr. Masters noted in this thread could trigger an MJO.
417. hurricanechaser
6:39 AM GMT on December 06, 2005
Hey hay (oops..lol:),

Did you get any effects from Hugo in 1989?
416. hurricanechaser
6:38 AM GMT on December 06, 2005
I agree with your sentiments Skyepony. All of them.

Have a goodnight.:)
415. haydn
6:37 AM GMT on December 06, 2005
I live in the SC midlands. Tammy broke a small drought. I don't mind the weak systems that bring in the rain.
414. hurricanechaser
6:37 AM GMT on December 06, 2005
Honestly I'm torn because I get paid to cover major landfalling storms but I don't want the damage much less physical harm to others. This season has had a big impact on my perceptions of Hurricanes.

All in All..Id rather be poor.
413. theboldman
6:36 AM GMT on December 06, 2005
yeah who does maby if we chant loud ebough we will scare it away lol
Member Since: September 8, 2005 Posts: 25 Comments: 2
412. Skyepony (Mod)
6:36 AM GMT on December 06, 2005
not disappointed~ i payed the $5 for the entertainment value the blogs have provided alone. We're all a little chaotic, to love the beauty of these storms the way we do. Spats are inevitable, it's all good. The more minds that input though, the better we see & the blog is made better. No real need to run off those that can't admit an error. It's all wrote down, anyone can read it all & see. Keep discribing eppy for me through the night. i look forward to reading it tommarow~might be a pivital night~ to see what happens to her when she's cut from the extatropical energy source~peas out~
Member Since: August 10, 2005 Posts: 192 Comments: 38651
411. haydn
6:36 AM GMT on December 06, 2005
I just checked a picture of Epsilon. The convection seems stronger around the eye, but dry air is lurking in the SE.
410. hurricanechaser
6:34 AM GMT on December 06, 2005
LOL..hay and Jeff...I don't want to see one either.:)
409. hurricanechaser
6:33 AM GMT on December 06, 2005
However, I can't comprehend another season like this one and I personally see an above average season with 15 to 18 named storms which is whast I wrote in my blog a couple of weeks ago.

It is very unlikely to have two seasons back to back exhaust the 21 name list and I expect we won't get that far next season hopefully.:)
408. haydn
6:32 AM GMT on December 06, 2005
I agree with no La Nina.
407. haydn
6:31 AM GMT on December 06, 2005
Current maps of Pacific sst don't show any changes yet.
We'll have a bettr picture in Feb or March.
406. theboldman
6:31 AM GMT on December 06, 2005
ok i have made my point wait no La Nina
Member Since: September 8, 2005 Posts: 25 Comments: 2
405. theboldman
6:31 AM GMT on December 06, 2005
no La Nina no La Nina no La Nina no La Nina no La Nina
Member Since: September 8, 2005 Posts: 25 Comments: 2
404. hurricanechaser
6:28 AM GMT on December 06, 2005
Each timje a La nina has occured...there has been an increase in the typical numbers of Atlantic Basin storms but doesn't by itself guarentee an above normal season.

It does however make it more likely since it dramaticallly affects the strength of the westerly winds in the upper levels that try to mitigate against tropical cyclone development.

A La NINA combined with the well above normal Atlantic sea surface temperatures and a continued presence of lower surface pressures during next season could make for another very active season to sday the least. Right now, its difficult to predict a La Nina more than 3 to 6 months in advance.
403. haydn
6:27 AM GMT on December 06, 2005
I couldn't imagine. I helped load trucks to send to Mississippi after Katrina. I used to enjoy seeing storms come. After seeing pictures of the devastation, I have changed my mind.
402. theboldman
6:27 AM GMT on December 06, 2005
oh crud no la nina tell that female water wind thing to bug off
Member Since: September 8, 2005 Posts: 25 Comments: 2
401. hurricanechaser
6:24 AM GMT on December 06, 2005
La Nina creates extremely favorable conditions for Atlantic Basin storm formation because this cooling of the East Pacific off of Peru reduces the intensity of the upper level winds that blow from west to east against the typical direction troopical waves are moving from the east to the west.

El Nino conditions do the opposite with a major increase in the westerly wind shear all across the atlantic basin precluding much tropical cyclone development.

This year was a neutral ENSO cycle which by definition creates aveage upper level westerlies.

Just imagine if we had La nina conditions during this season.
400. haydn
6:23 AM GMT on December 06, 2005
La Nina?? That means there will be more storms in the Atlantic. I don't want to see a repeat of this season.

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

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