La Niņa is gone

By: Dr. Jeff Masters , 3:13 PM GMT on May 11, 2006

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The La Niņa of 2006 proved to be short-lived. Sea Surface Temperatures (SSTs) in the eastern Pacific near the Equator have returned to near-normal values over the past month, according to the latest El Niņo advisory issued today by the Climate Prediction Center (CPC). We are now in what is characterized as ENSO-neutral conditions (or El Niņo-neutral conditions), which means that there is neither an El Niņo nor a La Niņa occurring. This is the case about 45% of the time, and was true for March through December of 2005. The CPC expects El Niņo-neutral conditions to continue for at least the next 3-6 months, which means for all of hurricane season. The 2006 La Niņa was an unusual one, because it started very late--no La Niņa of similar magnitude has ever formed in the middle of winter, as this one did. However, the demise of this year's La Niņa came at the usual time such events end--April and May are the typical months for the demise of both La Niņa and El Niņo.

How will this affect the hurricane season of 2006?
So, what does all this portend for the upcoming hurricane season? It is well-known that the presence of a La Niņa usually means more Atlantic hurricanes, and stronger hurricanes, too. This is because the large-scale wind circulation that develops during a La Niņa keeps wind shear levels relatively low over the main development region for hurricanes in the tropical Atlantic. So, the demise of La Niņa is good news for those of you living in Hurricane Alley. However, before we get too cheerful about this, it is worth remembering that the unbelievable Hurricane Season of 2005 occurred in El Niņo-neutral conditions, and El Niņo-neutral conditions are expected for this hurricane season, too. So, let's look at some other factors that will influence this year's hurricane season.


Figure 1. Comparison of this year's May SST anomalies with last year's. Image credit: NOAA.

SST comparison--this year vs. last year
Let's compare last year's SST anomalies (the difference in temperature between observed and normal) with this year's, to see how things have changed (Figure 1). The key things to look at are the SSTs in the Caribbean and the tropical Atlantic between Africa and the Antilles Islands, since this is where 85% of all major hurricanes form. While SSTs are .5 to 1.5 degrees above normal--which is a lot!--SSTs are a full degree Centigrade cooler this year than last year at this time. This reduction in SSTs should keep this year's hurricane season from producing early major hurricanes, like Dennis and Emily of July 2005. However, once we enter the prime hurricane months of August through October, expect another above normal year for hurricanes and intense hurricanes. My worst-case scenario for 2006 is a year similar to 2004, which was awful, but modest compared to 2005. My best-case scenario is a year like 1995, which was still very active, but the Bermuda High set up much farther east and recurved most storms before they hit land. Of course, this would be bad for the northeastern Leeward Islands, which got pounded in 1995.

The Gulf of Mexico SSTs are much warmer this year than last, due in part to the record warm temperatures the U.S. experienced in January and April. This may allow for more intense that normal June systems to develop in the Gulf this year. However, remember that systems that develop in the Gulf usually only last a day or two, which doesn't give them much time to strengthen before they hit land. There has only ever been one major hurricane in June (Audrey of 1957).

The other item of interest is that the pattern of SSTs over the eastern Pacific is much different this year versus last year. Waters near the Equator were much warmer last year, thanks to the lingering effect of the El Niņo event early in the year. There is also a much warmer pool of water north of Hawaii this year. These differences may end up having a significant influence on this year's jet stream pattern, and where the Bermuda high ultimately sets up camp. The jet stream and Bermuda high determine how hurricanes are steered, but unfortunately we don't know enough about long-range influences of unusual SST patterns on the weather to be able to predict where this year's hurricanes are likely to be steered. The bottom line is that SSTs are cooler and have a much different pattern this year compared to last year, and thus we should not expect a continuation of last year's ridiculously hyperactive, once-in-a-lifetime hurricane season.

Outlook for the rest of May
SSTs are already warm enough to support hurricane formation in the Gulf of Mexico, and the entire tropical Atlantic. What is saving us are the strong upper level winds of the jet stream, which has been dipping far to the south and creating lots of wind shear. The jet stream is forecast to remain active and fairly far south for at least the next two weeks, which should maintain unfavorable levels of wind shear over the Atlantic for the remainder of May. As long as we're talking about tornado outbreaks in the southern U.S., such as we've experienced this week, we don't have to worry about hurricane formation in the Gulf of Mexico. Tornado outbreaks require a stong jet stream, which is the bane of a hurricane trying to form.

The other missing ingredient--at least in the Caribbean and tropical Atlantic--has been the lack of an initial disturbance to get a hurricane started. Africa has just begun to produce its usual summer parade of tropical waves, which frequently serve as the nucleus for a tropical storm. These tropical waves are coming off of Africa at about 2 degrees North Latitude, which is too close to the Equator to allow a hurricane to spin up. I'm not expecting any tropical development for the rest of May in the Atlantic due to high wind shear and the lack of proper initial disturbances.

It's another story in the Eastern Pacific, where wind shear is less and the remains of an old cold front coming off of North America could serve to trigger tropical storm formation as early as next week. The hurricane specialists at the National Hurricane Center begin rotating shift work on Monday May 15, which marks the official beginning of the Eastern Pacific hurricane season.

My next blog will be on Monday. I'll talk about air pollution some next week, since May marks the beginning of air pollution season, and next week is EPA's Air Pollution Awareness Week.

Jeff Masters

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663. RL3AO
3:50 PM GMT on May 15, 2006
662. TampaSteve
2:11 PM GMT on May 15, 2006
Whew...looks like Chanchu is starting to weaken...good news for Hong Kong and the China coast.
660. desertdisaster
1:28 PM GMT on May 15, 2006
During that time on the est coast...

Link
659. snowboy
1:14 PM GMT on May 15, 2006
I see our wavelet in the Atlantic is hanging on and continuing to move towards the Caribbean.
Member Since: September 21, 2005 Posts: 10 Comments: 2555
658. Cavin Rawlins
1:00 PM GMT on May 15, 2006
...TROPICAL WAVES...
TROPICAL WAVE ALONG 51W S OF 10N MOVING W 10 KT. SUSPECTED
SMALL SWIRL OF LOW CLOUDS ON WAVE AXIS NEAR 6N EMBEDDED IN ITCZ.
CONVECTION HOLDING TOGETHER OVERNIGHT INCREASING IN AMOUNT AND
CONCENTRATING NOW FROM 8N-10N WITHIN 120 NM OF WAVE AXIS.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
656. fredwx
12:25 PM GMT on May 15, 2006
Super Typhoon Chanchu is now moving NNW and is forecast to move northward reaching the vicinity of Hong Kong on the 17th about 1600GMT. The good news is that there will be only slight developent, if any, over the next 24-36hrs then Chanchu is forecast to weaken prior to reaching landfall. At 0600GMT Chanchu was at 922mb with max winds of 120 Kts.

Member Since: June 8, 2005 Posts: 221 Comments: 261
655. RL3AO
12:08 PM GMT on May 15, 2006
Wow, Chanchu down to 115 kts. Not looking good.
653. ForecasterColby
11:08 AM GMT on May 15, 2006
Chanchu looks awful, probably won't even be a major at landfall.
652. louastu
4:49 AM GMT on May 15, 2006
I am convinced that Chanchu is finished strengthening for now.
651. hurricane23
4:25 AM GMT on May 15, 2006
hey guys were really gonna get nailed with rain down here in south florida!here's the link to the gfs.Link
Member Since: May 14, 2006 Posts: 8 Comments: 13841
650. snowboy
4:13 AM GMT on May 15, 2006
I agree that 12 months is a short time, and way more data and analysis are needed but... some new influence seems to be allowing these storms to intensify so wildly.
Member Since: September 21, 2005 Posts: 10 Comments: 2555
649. franck
4:08 AM GMT on May 15, 2006
louastu..I think you're right. When we look at one of these storms we view it as a whole, but the life of a hurricane is right around the center.
Member Since: August 30, 2005 Posts: 0 Comments: 1150
648. kerneld
4:05 AM GMT on May 15, 2006
snowboy, you might be right, but I think 12 months is way to short a time to base an observation of a fundamental change in the weather systems.

atmosweather, thanks for confirming. There are tornado warnings on some coastal counties between Brownsville and Corpus Christie TX tonight. Earlier there was a huge amount of electrical activity inland before the rain. I think I will be in for a sleepless night.
647. snowboy
3:58 AM GMT on May 15, 2006
So now Chanchu has become a supertyphoon. That makes how many Cat4/Cat5's in the last year?! My gut feel is that if the stats were plotted, we could have an unprecedented number of superstorms in the last 12 months.

I am coming to the conclusion that something has fundamentally changed in the dynamics of the atmosphere to allow this wild intensification in storm after storm..
Member Since: September 21, 2005 Posts: 10 Comments: 2555
646. atmosweather
3:58 AM GMT on May 15, 2006
Yes it is a hook signature but so far there is no vortex.
Member Since: September 24, 2005 Posts: 33 Comments: 9265
645. kerneld
3:52 AM GMT on May 15, 2006
Is this a hook signature?
Wind has been very gusty down here near Brownsville.

644. Trouper415
3:47 AM GMT on May 15, 2006
Do not hit Hong Kong.
Member Since: September 22, 2005 Posts: 5 Comments: 637
643. louastu
3:29 AM GMT on May 15, 2006
Maybe the eye isn't being affected by the shear. If this is the case, then it is possible that it could still strengthen.
642. HurricaneMyles
3:24 AM GMT on May 15, 2006
I think that upper level low mentioned, that is providing the good outflow channel, is also causing the shear to the eastern side of the storm as atmos pointed out. And I agree with atmos that Chanchu is finished strengthening. Sat appearance has deteriorated in the last 12 hours, even though the eye has appeared to become better defined during the time aswell. Somewhat confusing to say the least, but I dont expect Chanchu to attain the 140kt intensity that the JTWC predicts.
Member Since: January 12, 2006 Posts: 5 Comments: 827
641. atmosweather
3:20 AM GMT on May 15, 2006
Wow squeak where do they come up with this stuff? Its almost comical.
Member Since: September 24, 2005 Posts: 33 Comments: 9265
640. louastu
3:08 AM GMT on May 15, 2006
Are you sure a tornado never touched down?

0121 NORTH CHARLESTON CHARLESTON SC 3285 7997 TORNADO REPORTED BY NORTH CHARLESTON FIRE DEPARTMENT VIA CHANNEL 5 TELEVISION STATION. (CHS)
639. squeak
3:08 AM GMT on May 15, 2006
The prog for #26 has an interesting note:

A. SUPER TYPHOON (STY) 02W (CHANCHU), LOCATED APPROXIMATELY 495 NM SOUTH OF HONG KONG, HAS TRACKED NORTHWESTWARD AT 04 KNOTS OVER THE PAST 06 HOURS.

B. STY 02W HAD CONTINUED TO SLOWLY TRACK WESTWARD AND IS JUST NOW STARTING TO SHIFT POLEWARD IN RESPONSE TO A WEAKNESS IN THE SUBTRO- PICAL STEERING RIDGE (STR) ANCHORED OVER SOUTHEASTERN CHINA. THE SYSTEM IS FORECAST TO TRACK NORTHWARD ALONG THE WESTERN PERIPHERY OF THE STR AND IS FORECAST TO MAKE LANDFALL BETWEEN TAUS 48 AND 72. THE AVAILABLE DYNAMIC AIDS, CONSISTING OF NOGAPS, GFDN, AFWA MM5, COAMPS, NCEP GFS, JGSM, JTYM, EGRR, TCLAPS AND WBAR ARE IN GOOD AGREEMENT WITH THIS SCENARIO.

C. STY 02W WILL ONLY SLIGHTLY INTENSIFY OVER THE NEXT 12 HOURS AND WILL MAINTAIN SUPER TYPHOON INTENSITY FOR THE NEXT 24 TO 36 HOURS AS THE SYSTEM REMAINS IN A FAVORABLE ENVIRONMENT OF EXCELLENT RADIAL OUTFLOW INCLUDING AN EASTWARD OUTFLOW CHANNEL PROVIDED BY AN UPPER LEVEL LOW LOCATED APPROXIMATELY 300NM EAST OF THE PHILIPPINES. AS THE SYSTEM APPROACHES LAND IT WILL UNDERGO RAPID DECREASE IN INTENSITY AND BEGIN TO UNDERGO THE EARLY STAGES OF EXTRA-TROPICAL TRANSITION.
638. StormJunkie
3:01 AM GMT on May 15, 2006
I am off to bed ya'll, but before I go let me tell you about some of that severe weather that lou mentioned. I am in the Chas SC area. We have been under several different tornado warnings to night. After the storm that triggered the original tornado warning I left my house to head over to see how my girlfriend faired. Well after picking her up we headed back to my house. I thought all was well, but little did I know that another tornado warning had been posted for a new cell. Anywho the long and the short of it is on our way home, we ran in to pouring rain and quarter sized hail. Worst part was as soon as this started we had just gotten on a 2 mile bridge. WHen we got over the bridge Ipulled in to a bank teller and sat it out. It was a great adrenaline rush, but I was scared as hell. I don't think a tornado ever actually touched down because the wind never got too bad, but it was an intresting night either way.

night
SJ

StormJunkie.com
Member Since: August 17, 2005 Posts: 26 Comments: 16874
637. atmosweather
2:54 AM GMT on May 15, 2006
The eastern semicircle is suffering from some easterly shear. She is not strengthening any more. I think she will hold at 130-135 kts before weakening steadily in the final 36 hours prior to landfall to a mid Category 3 storm.
Member Since: September 24, 2005 Posts: 33 Comments: 9265
636. DisneyEchoEarRich
2:49 AM GMT on May 15, 2006
Note that the latest predicted storm track shows it coming closer to Hong Kong than before... apparently they now think it is not going to take quite as much of a hard right turn as they thought earlier tonight.

Hong Kong is still well within the cone of probability and not in the clear yet, by a long shot.
635. RL3AO
2:48 AM GMT on May 15, 2006
634. louastu
2:45 AM GMT on May 15, 2006
Wow, I just checked the severe wether reports for today. Apparently it has been pretty active.

There have been 256 severe weather reports so far, including 14 reports of tornadoes, and 205 reports of hail.
633. atmosweather
2:38 AM GMT on May 15, 2006
I firmly believe that after looking at endless loops, shear forecasts and surface analysis for half an hour. She cannot move due north for another 3 days. Hong Kong will be spared of a major catastrophe.
Member Since: September 24, 2005 Posts: 33 Comments: 9265
632. snowboy
2:35 AM GMT on May 15, 2006
"Hong Kong will probably escape."

atmos, with all respect that sounds like wishful thinking this far out.
Member Since: September 21, 2005 Posts: 10 Comments: 2555
631. atmosweather
2:30 AM GMT on May 15, 2006
It appears Chanchu will take the bait and move NE before reaching the coast. Hong Kong will probably escape.
Member Since: September 24, 2005 Posts: 33 Comments: 9265
630. louastu
2:30 AM GMT on May 15, 2006
I saw your site turtle. I think it looks pretty good so far.
629. RL3AO
2:28 AM GMT on May 15, 2006
New advisory is out, Chanchu up to 135 knots, forcasted to peak at 140 knots.

628. snowboy
2:27 AM GMT on May 15, 2006
May 14, 2006: The Joint Typhoon Warning Center has set the initial intensity at 130 KNOTS as of Warning #25. Based on JTWC's intensity, Chanchu is now a SUPERtyphoon. All global models and forecasts from HKO, JMA, JTWC, CWB,and PAGASA take Chanchu toward or near HONG KONG within 2-4 days. Some weakening prior to landfall is possible. However, all interests in this are should be preparing NOW for the worst case scenario. It is becoming increasingly likely that Chanchu will be the strongest typhoon to ever strike Hong Kong in modern history.
Member Since: September 21, 2005 Posts: 10 Comments: 2555
627. squeak
2:21 AM GMT on May 15, 2006
Yes the latest model runs have diverged a bit and the more reliable ones have moved the landfall a bit to the west, but curving into HKG. Very very bad scenario.

I don't know how likely 155mph sustained winds are, with the colder water offshore, but does that really matter, when even 110mph sustained winds will be disasterous for the many skyscrapers there.
626. turtlehurricane
2:19 AM GMT on May 15, 2006
any of yall see my site? im gonna try bto make it a legitimate site over the next few months and eventually, make it its own domain
Member Since: July 22, 2005 Posts: 227 Comments: 469
625. TheLuckyTacoBlizzard
2:16 AM GMT on May 15, 2006
: ForecasterColby i see mail for you
624. ForecasterColby
2:15 AM GMT on May 15, 2006
That's the maximum significant wave height - or the average of the highest third of the waves. Actual maximums run around twice that.
623. RL3AO
2:14 AM GMT on May 15, 2006
Does anyone else find it ironic that the U.S. has to forcast and provide sat coverage for a storm about to him China/Hong Kong?
622. ForecasterColby
2:13 AM GMT on May 15, 2006
Snowman, it's not hard to make your own site. Start at Yahoo Geocities if you're interested - though their hosting doesn't support SQL (which is what my board runs on)
621. TheLuckyTacoBlizzard
2:12 AM GMT on May 15, 2006
WOW oh my gold


wave height at 141800z is 42 feet wow! run! dos that mean there 42feet sea going for Hong Kong wow not good
620. snowboy
2:10 AM GMT on May 15, 2006
Here's a Reuters Foundation AlertNet bulletin re Supertyphoon Chanchu. Current track has it making landfall as a Cat 4 just west of Hong Kong. Let's hope that this grim scenario doesn't play out as predicted.

******

Typhoon Chanchu is forecast to strike China at about 13:00 GMT on 17 May. Data supplied by the US Navy and Air Force Joint Typhoon Warning Center suggest that the point of landfall will be near 22.1 N, 114.0 E. Chanchu is expected to bring 1-minute maximum sustained winds to the region of around 250 km/hr (155 mph). Wind gusts in the area may be considerably higher.

According to the Saffir-Simpson damage scale the potential property damage and flooding from a storm of Chanchu's strength (category 4) at landfall includes:
Storm surge generally 4.0-5.5 metres (13-18 feet) above normal.
Curtainwall failures with some complete roof structure failures on small residences.
Shrubs, trees, and all signs are blown down.
Complete destruction of mobile homes.
Extensive damage to doors and windows.
Low-lying escape routes may be cut by rising water 3-5 hours before arrival of the centre of the storm.
Major damage to lower floors of structures near the shore.
Terrain lower than 3 metres (10 feet) above sea level may be flooded requiring massive evacuation of residential areas as far inland as 10 km (6 miles).

There is also the potential for flooding further inland due to heavy rain.

The information above is provided for guidance only and should not be used to make life or death decisions or decisions relating to property. Anyone in the region who is concerned for their personal safety or property should contact their official national weather agency or warning centre for advice.

*******
Member Since: September 21, 2005 Posts: 10 Comments: 2555
619. squeak
2:07 AM GMT on May 15, 2006
Sorry what I meant to say earlier was JTWC had it crossing 115E before making the turn (so did ALL the models, even the outliers). So the next couple hours whether it goes WNW, NW, or N, will be interesting, and also the next model runs and forecast (which is an hour from now). It will be much clearer whether it is more than a remote possibility that it will curve to the east and hit Taiwan instead.
618. squeak
2:01 AM GMT on May 15, 2006
JTWC just corrected #25:

CORRECTED STORM CLASSIFICATION TO SUPER TYPHOON.
617. turtlehurricane
2:00 AM GMT on May 15, 2006


my global hurricane site has the basics done, keep checking back on it because im gonna keep making it better

Link
Member Since: July 22, 2005 Posts: 227 Comments: 469
616. squeak
1:59 AM GMT on May 15, 2006
It's started the move north now.
615. snowboy
1:55 AM GMT on May 15, 2006
hey cool site there Colby! Chanchu looks menacing.
Member Since: September 21, 2005 Posts: 10 Comments: 2555
614. TheSnowman
1:27 AM GMT on May 15, 2006
I can't find any news to see if Hong Kong will be evacuating
613. TheSnowman
1:19 AM GMT on May 15, 2006
Colby Your Famous with your own Website!!!! Awsome man I never knew

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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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