La Niña drawing to a close
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
Reader Comments
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Precip
Which side of the low over the great lakes will produce the bad stuff?
954 AM EST MON FEB 27 2012
.DISCUSSION...
WEAK SHORT WAVES MOVING ONSHORE THE FLORIDA WEST COAST EARLY THIS
MORNING CONTINUES TO SUPPORT A LARGE AREA OF LIGHT RAIN OVER THE
NATURE COAST AND THE NORTHERN FLORIDA PENINSULA...WITH PARTLY
CLOUDY SKIES BEING OBSERVED ACROSS THE REMAINDER OF WEST CENTRAL
AND SOUTHWEST FLORIDA. THE ONGOING RAIN AREA ACROSS THE NATURE
COAST IN ASSOCIATION WITH THE SHORT WAVES WILL GRADUALLY WEAKEN
AND SHIFT EAST WITH THE SHORT WAVES THE REMAINDER OF THE MORNING
WHILE CONVECTIVE SHOWERS WILL BEGIN TO DEVELOP ACROSS THE CENTRAL
AND SOUTHERN ZONES BY LATE MORNING INTO THE AFTERNOON WITHIN A
MOIST AND UNSTABLE AIR MASS. MORNING RAOB AND MODEL SOUNDING DATA
SUGGESTS THE POSSIBILITY OF SOME STRONG TO SEVERE STORMS ACROSS
CENTRAL AND SOUTHERN ZONES WHERE ONGOING CONSIDERABLE BREAKS IN
THE CLOUDS SHOULD ALLOW FOR SOME FAIRLY GOOD DAYTIME HEATING AND
POSSIBLE SEA BREEZE DEVELOPMENT. WITH RATHER COLD TEMPERATURE
ALOFT (-13C AT 500MB) AND LOW WET BULB ZERO LEVELS ANY STORMS
THAT DO DEVELOP WILL BE CAPABLE OF PRODUCING HAIL AND OR DAMAGING
WIND GUSTS...AND WILL ADD THIS WORDING TO THE ZONES IN A MID
MORNING UPDATE. OTHER THAN THIS NO OTHER GRID OR ZONE CHANGES
ARE EXPECTED AT THIS TIME.
Feb 26th, 2012
Feb 26th, 2011
Snow will be on the north and west sides most likely, severe weather to the south. Moist air being pulled up from eastern gulf and a 60-90kt jet over AL, GA, SC, NC, VA maybe a chance for severe weather.
Answer satifying? :D
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Come back to Haunt him......Neutral Conditions is some of the worst conditions for land falling Hurricanes. This if the ESNO conditions of Neutral will be correct, could very well be a rough Cane season for many! BEWARE
Quoting AussieStorm:
Big rains coming to most of Australia.
Flood warning have been issued, Flash flood warning have been issued. This could be a very big event.
Action: Quote | Modify Comment
Member Since: July 15, 2006 Posts: 113 Comments: 28801
do you still not believe
BeijingAir %u200F @BeijingAir
02-28-2012 01:00; PM2.5; 278.0; 328; Hazardous (at 24-hour exposure at this level)
it won't
conditions are what they are
at the moment we watch as always
MDR region is to have a lower storm output
so it will be up to the carb and GOM
for storm formation this season
with a few from MDR
my numbers say at the moment
11 to 14 systems are likly
could be more
but may be less
we shall see
may break 50 today storm a coming
Date: 12:00 PM EST Monday 27 February 2012
Condition: Mainly Sunny
Pressure: 29.98 inches
Tendency: falling
Visibility: 15 miles
Air Quality Health Index: 3
Temperature: 47.8°F
Dewpoint: 28.4°F
Humidity: 47 %
Wind: WSW 25 gust 32 mph
I drive out of West Palm Beach the day before Andrew hit. The thought of that storm still makes me jumpy.
7 of them could make a us landfall
so numbers are just that
numbers nothing more
I remember that well being in Miami at the time....Andrew was forecast to go up towards your parts Broward and Palm Beach), took a bit of a sharp turn between Sat evening and Sunday and took a beeline to extreme South Florida exploding over the Gulf Stream when sheer relaxed considerably. Not much damage North of Miami proper cause it was a very compact buzz saw when it came across Cutler Ridge.
That's another good point. Small does not mean they will be weak.
You post on here regularly and I have several friends who live in the Keys. I hear your points, but, if you know a bad storm is headed your way (towards the Keys), and evacuations are ordered, please do so......... Not a good idea to take your chances (drowning in storm surge is NOT a peaceful way to go) and much less so if you have kids or other family down there with you.........
NATIONAL WEATHER SERVICE MELBOURNE FL
201 PM EST MON FEB 27 2012
FLZ058-059-064-271945-
MARTIN-OKEECHOBEE-ST. LUCIE-
201 PM EST MON FEB 27 2012
...A SIGNIFICANT WEATHER ADVISORY IS IN EFFECT FOR STRONG WIND GUSTS
BETWEEN 45 AND 55 MPH AND SMALL HAIL OVER WESTERN MARTIN COUNTY...
SOUTHEASTERN OKEECHOBEE COUNTY...SOUTHWESTERN ST. LUCIE COUNTY...
* UNTIL 245 PM EST.
AT 200 PM EST...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STORM CAPABLE OF PRODUCING STRONG WINDS AND SMALL HAIL 5 MILES EAST
OF FOUR SEASONS ESTATES...MOVING EAST-SOUTHEAST AT 20 MPH.
THE PRIMARY THREAT WILL BE CLOUD TO GROUND LIGHTNING STRIKES AND
GUSTY WINDS OF 45 TO 55 MPH...WHICH CAN CAUSE UNSECURED OBJECTS TO
BLOW AROUND...SNAP TREE LIMBS OR CAUSE POWER OUTAGES. HEAVY RAINFALL
WILL TEMPORARILY REDUCE VISIBILITY. SEEK SHELTER INDOORS UNTIL THE
STORM PASSES. HAIL UP TO THE SIZE OF COINS IS ALSO POSSIBLE.
LAT...LON 2721 8079 2736 8074 2731 8032 2701 8050
TIME...MOT...LOC 1900Z 287DEG 16KT 2725 8067
$$
52
Stories like this remind us of how important it is to keep improving track and intensity forecasts, up to 3 days out, minimum. If u get told to evacuate, u should be able to feel pretty confident that evacuating is the right action. You should also feel comfortable about staying. S FL in particular, and coastal locations in general, have a serious challenge when it comes to timely and appropriate evacuation. People should only be leaving if staying is lifethreatening, but quite a few in the paths of storms seem to be leaving to avoid the post storm discomfort. All this adds to the problems of conjestion on key roadways. Uncertainty about the forecast creates even more difficulty.
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