Dr. Jeff Masters' WunderBlog

La Niña drawing to a close

Posted by: Dr. Jeff Masters, 3:39 PM GMT on February 27, 2012

+37

La Niña, the cooling of the equatorial Pacific waters off the coast of South America that has dramatically affected our weather for most of the past two years, is almost done. Sea surface temperatures (SSTs) over the tropical Eastern Pacific in the area 5°N - 5°S, 120°W - 170°W, also called the "Niña 3.4 region", have warmed rapidly over the past two weeks, and were 0.4°C below average on February 27. This is slightly warmer than the -0.5°C threshold to be considered La Niña conditions, and is the first time since early August that La Niña conditions have not been present. It is likely that SSTs will continue to warm during March and April, and NOAA's Climate Prediction Center is predicting that they will declare an official end to La Niña sometime between March and April. A moderate to strong La Niña began in the summer of 2010, weakened briefly during May - July 2011 to neutral status, then re-intensified to a borderline weak/moderate La Niña from August 2011 - January 2012.

Figure 1. Comparison of the sea surface temperature departure from average from January 4 and February 22, 2012, over the tropical Eastern Pacific. During January, a large region of the ocean was more than 0.5°C cooler than average, meaning a La Niña event was present. Beginning in mid-February, waters warmed rapidly from east to west along the Equator, signaling and end to the La Niña event. Image credit: NOAA.

The forecast: neutral or El Niño conditions by fall
The period March - May is the typical time of year that El Niño or La Niña events end, and it is common for the opposite phenomena to take hold by fall. Since 1950, there have been twelve La Niña events that ended during the first half of the year; during six of those years (50%), an El Niño event formed in time for the August - September - October peak of hurricane season. The official forecast from Columbia University's IRI and NOAA's Climate Prediction Center calls for a 31 - 32% chance of an El Niño event during the 2012 Atlantic hurricane season. El Niño conditions tend to suppress Atlantic hurricane activity by creating high levels of wind shear that tends to tear hurricanes apart. Given the relatively high chance of an El Niño event this fall, plus ocean temperatures over the tropical Atlantic that are cooler than we saw in 2011 and 2010, I doubt we'll see an Atlantic hurricane season as active as the ones in 2010 and 2011 (nineteen named storms both years, third busiest seasons on record.) The demise of La Niña also means that global temperatures should begin to approach record warm levels by the end of the year. The cool waters of a La Niña event keep global temperatures cooler than average.

Figure 2. Computer model forecasts of El Niño/La Niña made in mid-February 2012. The forecasts that go above the red line at +0.5°C denote El Niño conditions; -0.5°C to +0.5°C denote neutral conditions, and below -0.5°C denote La Niña conditions. Most of the computer models are predicting neutral or El Niño conditions during the fall peak of the Atlantic hurricane season. Image credit: Columbia University's IRI.

I'll have a new post by Wednesday.

Jeff Masters

Categories: Climate Summaries

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751. jamesrainier 2:37 PM GMT on February 29, 2012
Harrisburg, IL: One person is dead as the search and rescue process continues in the southern Illinois town. The southeastern portion of the town reported major damage. According to local news station KFVS, 35 to 40 homes were destroyed and semi trucks were overturned. Power outages were also reported, and roads were blocked by debris. http://www.weather.com/outlook/weather-news/news/ articles/wed-storm-reports_2012-02-29 Member Since: June 1, 2010 Posts: 0 Comments: 111

753. GeorgiaStormz 2:40 PM GMT on February 29, 2012
a little clearing over the moderate risk area: Member Since: February 11, 2012 Posts: 0 Comments: 7528

754. jamesrainier 2:46 PM GMT on February 29, 2012
http://www.csmonitor.com/USA/Latest-News-Wires/20 12/0229/Deadly-tornadoes-hit-Branson-Mo.-Illinois- and-Kansas Branson, Mo. One person is dead, dozens are injured and some are trapped in their homes after a powerful storm system bearing a string of tornadoes battered Branson, a tourist hub, and a mobile home park in southwest Missouri. Three deaths more were reported Wednesday morning in Harrisburg, Ill., by local TV station, KFVS12. Harveyville, Kansas, was also struck by a tornado causing injuries and extensive damage. ...the storm left a trail of destruction in downtown Branson, scattering the area with debris and uprooted road signs, and heavily damaging buildings in the city's famous theater district. Branson is one of the Midwest's major tourist attractions, drawing millions each year to its theaters and amusement parks Member Since: June 1, 2010 Posts: 0 Comments: 111

755. AussieStorm 2:48 PM GMT on February 29, 2012
Two new TVS in KY. click for larger images Member Since: September 30, 2007 Posts: 5 Comments: 13788

756. jamesrainier 2:48 PM GMT on February 29, 2012
NATIONAL WEATHER SERVICE PADUCAH KY 844 AM CST WED FEB 29 2012 THE NATIONAL WEATHER SERVICE IN PADUCAH HAS ISSUED A * TORNADO WARNING FOR... CENTRAL CHRISTIAN COUNTY IN SOUTH CENTRAL KENTUCKY... NORTHERN TODD COUNTY IN SOUTH CENTRAL KENTUCKY... * UNTIL 930 AM CST. * AT 843 AM CST...TRAINED WEATHER SPOTTERS REPORTED A FUNNEL CLOUD 6 MILES NORTH OF HOPKINSVILLE. A TORNADO MAY DEVELOP AT ANY TIME! DOPPLER RADAR SHOWED THIS TORNADIC STORM MOVING EAST AT 45 MPH. * LOCATIONS IN THE WARNED AREA INCLUDE... ALLEGRE AND CLIFTY. NATIONAL WEATHER SERVICE LOUISVILLE KY 844 AM CST WED FEB 29 2012 THE NATIONAL WEATHER SERVICE IN LOUISVILLE HAS ISSUED A * TORNADO WARNING FOR... NORTHERN GRAYSON COUNTY IN SOUTH CENTRAL KENTUCKY... * UNTIL 915 AM CST... * AT 842 AM CST...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A SEVERE THUNDERSTORM CAPABLE OF PRODUCING A TORNADO. THIS DANGEROUS STORM WAS LOCATED NEAR POST...MOVING EAST AT 70 MPH. HAIL TO GOLF BALL SIZE HAIL IS ALSO POSSIBLE. * THIS TORNADIC STORM WILL ALSO IMPACT... LEITCHFIELD... CLARKSON AND GRAYSON SPRINGS... SAINT PAUL AND TAR HILL... LACON... NATIONAL WEATHER SERVICE LOUISVILLE KY 940 AM EST WED FEB 29 2012 THE NATIONAL WEATHER SERVICE IN LOUISVILLE HAS ISSUED A * TORNADO WARNING FOR... SOUTHERN HARDIN COUNTY IN NORTH CENTRAL KENTUCKY... NORTHERN LARUE COUNTY IN NORTH CENTRAL KENTUCKY... * UNTIL 1000 AM EST... * AT 937 AM EST...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A SEVERE THUNDERSTORM CAPABLE OF PRODUCING A TORNADO. THIS DANGEROUS STORM WAS LOCATED NEAR SUMMIT...MOVING NORTHEAST AT 75 MPH. * THIS TORNADIC STORM WILL ALSO IMPACT... ELIZABETHTOWN... STAR MILLS AND GLENDALE... INDIAN HILLS AND TONIEVILLE... ROANOKE AND COLESBURG... Member Since: June 1, 2010 Posts: 0 Comments: 111

757. Ameister12 2:50 PM GMT on February 29, 2012
This outbreak has turned out to be deadly. One person is dead in Branson, MO and at least three are dead in Harrisburg, IL. Other tornadoes have caused major damage in several other towns and cities and today is looking to be as bad, if not worse then last night. Be safe everyone! Member Since: August 9, 2009 Posts: 9 Comments: 3628

758. jamesrainier 2:51 PM GMT on February 29, 2012
NATIONAL WEATHER SERVICE PADUCAH KY 850 AM CST WED FEB 29 2012 THE NATIONAL WEATHER SERVICE IN PADUCAH HAS ISSUED A * TORNADO WARNING FOR... CENTRAL MUHLENBERG COUNTY IN SOUTH CENTRAL KENTUCKY... * UNTIL 915 AM CST. * AT 847 AM CST...NATIONAL WEATHER SERVICE DOPPLER RADAR WAS TRACKING A CONFIRMED TORNADO NEAR GREENVILLE. DOPPLER RADAR SHOWED THIS TORNADO MOVING EAST AT 60 MPH. * LOCATIONS IN THE WARNED AREA INCLUDE... CENTRAL CITY AND DRAKESBORO. Member Since: June 1, 2010 Posts: 0 Comments: 111

759. TampaSpin 2:53 PM GMT on February 29, 2012
OMG....LOOK at this Tornado forming near Clarkson...TAKE COVER NOW Member Since: September 2, 2007 Posts: 176 Comments: 19767

760. Ameister12 2:54 PM GMT on February 29, 2012
Quoting GeorgiaStormz: a little clearing over the moderate risk area: There is going to be a new round of severe storms this afternoon. The storms that will occur this afternoon are the reason why there's a moderate risk. There will be strong tornadoes, destructive straight line winds, and hail. Member Since: August 9, 2009 Posts: 9 Comments: 3628

761. WDEmobmet 2:54 PM GMT on February 29, 2012
wowwwwww for what ever reason my images arent coming in right, and unfortunately I am not at home so this is the best I can do.... Member Since: February 3, 2010 Posts: 0 Comments: 649

762. WDEmobmet 2:57 PM GMT on February 29, 2012
Quoting TampaSpin: OMG....LOOK at this Tornado forming near Clarkson...TAKE COVER NOW Definetely the beginnings of a solid rotation there. Member Since: February 3, 2010 Posts: 0 Comments: 649

763. SPLbeater 2:58 PM GMT on February 29, 2012
mornin all. what a treat this morning. wake up, and dad is still home not at work. reason? water heater went out:/ Member Since: August 4, 2011 Posts: 43 Comments: 3961

764. jamesrainier 2:58 PM GMT on February 29, 2012
NATIONAL WEATHER SERVICE LOUISVILLE KY 955 AM EST WED FEB 29 2012 THE NATIONAL WEATHER SERVICE IN LOUISVILLE HAS ISSUED A * TORNADO WARNING FOR... SOUTHERN HARDIN COUNTY IN NORTH CENTRAL KENTUCKY... LARUE COUNTY IN NORTH CENTRAL KENTUCKY... EASTERN GRAYSON COUNTY IN SOUTH CENTRAL KENTUCKY... * UNTIL 1030 AM EST/930 AM CST/... * AT 851 AM CST...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A SEVERE THUNDERSTORM CAPABLE OF PRODUCING A TORNADO. THIS DANGEROUS STORM WAS LOCATED NEAR LACON...MOVING EAST AT 65 MPH. GOLF BALL SIZE HAIL IS ALSO POSSIBLE WITH THIS STORM. * THIS TORNADIC STORM WILL ALSO IMPACT... HODGENVILLE... FLINT HILL AND SPURRIER... NOLIN AND UPTON... SONORA AND MAXINE... MATHERS MILL AND BOUNDARY OAK... Member Since: June 1, 2010 Posts: 0 Comments: 111

765. WDEmobmet 2:59 PM GMT on February 29, 2012
Look to the east north east of letchfield. good rotation Member Since: February 3, 2010 Posts: 0 Comments: 649

766. jamesrainier 3:01 PM GMT on February 29, 2012
NATIONAL WEATHER SERVICE LOUISVILLE KY 959 AM EST WED FEB 29 2012 THE NATIONAL WEATHER SERVICE IN LOUISVILLE HAS ISSUED A * TORNADO WARNING FOR... EASTERN HARDIN COUNTY IN NORTH CENTRAL KENTUCKY... NORTHERN LARUE COUNTY IN NORTH CENTRAL KENTUCKY... WESTERN NELSON COUNTY IN NORTH CENTRAL KENTUCKY... * UNTIL 1030 AM EST... * AT 956 AM EST...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A SEVERE THUNDERSTORM CAPABLE OF PRODUCING A TORNADO. THIS DANGEROUS STORM WAS LOCATED NEAR ELIZABETHTOWN...MOVING NORTHEAST AT 45 MPH. * THIS TORNADIC STORM WILL ALSO IMPACT... ELIZABETHTOWN... ROANOKE AND YOUNGER CREEK... NELSONVILLE AND BOSTON... CULVERTOWN... BALLTOWN... NATIONAL WEATHER SERVICE PADUCAH KY 859 AM CST WED FEB 29 2012 THE NATIONAL WEATHER SERVICE IN PADUCAH HAS ISSUED A * TORNADO WARNING FOR... NORTHERN CALLOWAY COUNTY IN WESTERN KENTUCKY... SOUTHEASTERN MARSHALL COUNTY IN WESTERN KENTUCKY... CENTRAL TRIGG COUNTY IN WESTERN KENTUCKY... * UNTIL 930 AM CST. * AT 857 AM CST...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A SEVERE THUNDERSTORM CAPABLE OF PRODUCING A TORNADO. THIS DANGEROUS STORM WAS LOCATED 7 MILES WEST OF MURRAY...AND MOVING EAST AT 65 MPH. * LOCATIONS IN THE WARNED AREA INCLUDE... LAND BETWEEN THE LAKES AREA...ENERGY...CANTON...HARDIN...AURORA AND LINTON. Member Since: June 1, 2010 Posts: 0 Comments: 111

767. AussieStorm 3:01 PM GMT on February 29, 2012
Quoting WDEmobmet: Definetely the beginnings of a solid rotation there. Click for larger image. Member Since: September 30, 2007 Posts: 5 Comments: 13788

768. WDEmobmet 3:03 PM GMT on February 29, 2012
Quoting AussieStorm: Click for larger image. Good capture Aussie... I am at work and without my softwares so being able to see GRLEVEL3 is comforting to see. Thanks man What is the hail core with that cell? Member Since: February 3, 2010 Posts: 0 Comments: 649

769. AussieStorm 3:04 PM GMT on February 29, 2012
Quoting WDEmobmet: Good capture Aussie... I am at work and without my softwares so being able to see GRLEVEL3 is comforting to see. Thanks man No worries mate! Where you working? 2.00" hail, cell is moving at 54kts. Member Since: September 30, 2007 Posts: 5 Comments: 13788

771. WDEmobmet 3:07 PM GMT on February 29, 2012
Quoting AussieStorm: No worries mate! Where you working? I work for Dept. of Defense. Not supposed to be on this site during work but hey, sometimes you just have to break the rules Member Since: February 3, 2010 Posts: 0 Comments: 649

772. AussieStorm 3:09 PM GMT on February 29, 2012
Quoting WDEmobmet: I work for Dept. of Defense. Not supposed to be on this site during work but hey, sometimes you just have to break the rules DoD. nice, don't get caught or you could get court marshaled. lol Member Since: September 30, 2007 Posts: 5 Comments: 13788

773. WDEmobmet 3:09 PM GMT on February 29, 2012
2.00" hail, cell is moving at 54kts. I imagine with a dBZ of 71+, itll prob get bigger Member Since: February 3, 2010 Posts: 0 Comments: 649

774. TampaSpin 3:10 PM GMT on February 29, 2012
Member Since: September 2, 2007 Posts: 176 Comments: 19767

775. ChillinInTheKeys 3:11 PM GMT on February 29, 2012
New Blog!!! Member Since: August 18, 2008 Posts: 0 Comments: 462

776. WDEmobmet 3:11 PM GMT on February 29, 2012
Quoting AussieStorm: DoD. nice, don't get caught or you could get court marshaled. lol Haaha luckily I am just a civilian so cant do that. Member Since: February 3, 2010 Posts: 0 Comments: 649

777. KEEPEROFTHEGATE (Mod) 4:49 PM GMT on February 29, 2012
Member Since: July 15, 2006 Posts: 147 Comments: 41332

778. sunlinepr 4:51 AM GMT on March 01, 2012
Member Since: August 2, 2010 Posts: 19 Comments: 8466

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