La Niña is here

By: Dr. Jeff Masters , 1:16 PM GMT on July 15, 2010

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The equatorial Eastern Pacific Ocean continues to cool, and we have now crossed the threshold into La Niña conditions. 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", fell to 0.8°C below average by July 12, according to NOAA.. The Australian Bureau of Meteorology put this number at 0.7°C below average (as of July 11.) Since La Niña conditions are defined as occurring when this number reaches 0.5°C below average, we are well into the territory of a weak La Niña event. La Niña conditions must be present for several months before this will be officially classified as a La Niña event, but it is highly likely that a full-fledged La Niña event lasting at least eight months has arrived. We started out the year with a strong El Niño, so it may seem surprising that we have transitioned La Niña so quickly, However, historically, about 35 - 40% of El Niño events are followed by a La Niña within the same year. Given current trends, I expect the current La Niña to cross the threshold needed to be defined as "moderate" strength--temperatures at least 1.0°C below average in the equatorial Eastern Pacific--by September.


Figure 1. Progression of El Niño to La Niña over the past year, as measured by SSTs in the the tropical Eastern Pacific in the area 5°N - 5°S, 120°W - 170°W, also called the "Niña 3.4 region". Image credit: NOAA Climate Prediction Center.

The implications
It is well-known that both the number and intensity of hurricanes in the Atlantic tend to increase during La Niña events. However, as I discussed in a post last month, since 1995, neutral years (when neither an El Niño or La Niña are present) have had Atlantic hurricane activity equal to La Niña years. The last time we had a strong El Niño event followed by a La Niña event in the same year, in 1998, we had a Atlantic hurricane season 40% above average in activity, with 14 named storms, 10 hurricanes, and 3 intense hurricanes. The season was relatively late-starting, with only one named storm occurring before August 20. I'm thinking this year's season may be similar, though four or more intense hurricanes are a good bet due to the record warm SSTs.

Both El Niño and La Niña events have major impacts on regional and global weather patterns. For the remainder of July and August, we can expect La Niña to bring cloudier and wetter than average conditions to the Caribbean, but weather patterns over North America should not see much impact (Figure 2.) Globally, La Niña conditions tend to cause a net cooling of surface temperatures. Thus, while the past twelve month period has been the warmest globally since record keeping began in 1880, it is unlikely that the calendar year of 2010 will set the record for warmest year ever.



Figure 2. Typical regional weather anomalies observed during June - August when La Niña conditions are present. The Caribbean tends to be cloudier and wetter than average, but there is typically little change to temperature and precipitation patterns over North America. Image credit: NOAA Climate Prediction Center.

The tropics are quiet
There are no threat areas to discuss in the Tropical Atlantic today, and none of the reliable computer models is calling for tropical cyclone development over the next seven days.

Next post
I'll have a new post on Friday.

Jeff Masters

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Quoting Baltimorebirds:
This year it's when things want to develop they either move into land or an envierment thats not sutible for development.

The season has ONLY just begun.
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247. BDAwx
1950 atlantic hurricane season was interesting. :O
just taking a look back at it... :)
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Quoting 954FtLCane:

Hi btwntx08, do yu know if they're still having problems at the border crossing? The reason I ask is that we have freight that is delayed coming from San Luis Potosi MX due to this flooding and haven't heard anything from our vendors.


954, I'm in Reynosa, MX. Our trucks are crossing, but the commercial traffic is terrible. I think a lot of trucks that normally cross to the west have been diverted east. I have to say, I've never seen the Rio Grande so far out of its banks.Good luck with your freight.
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Quoting Baltimorebirds:
could be like a ida type situation.

There is an upper level ridge of High pressure hanging over the Western Gulf of Mexico.

IF anything develops near Honduras it will move inland fairly quick.
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Ida-like genesis yes, Alex and TD2 like track.
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Quoting AussieStorm:

It's dying down as is

Yeah, I'm worried about that.
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Quoting StormGoddess:
Do we know how much longer the SAL is going to hold?

It's dying down as is
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Quoting StormW:


From what I saw in analysis the past 2 days, there could be 2-3 more shots, but I feel it would be limited to above 15N.

I'm hoping the SAL holds as long as possible. That's pretty much where I'm at for the moment. :)
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Do we know how much longer the SAL is going to hold?
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.."I've got a feeling"..
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Quoting StormW:
Try this:

TROPICAL WEATHER SYNOPSIS JULY 15, 2010 ISSUED 12:00 NOON


Thank you, StormW. The lull is nearing its end. I wonder if any of the active Atl waves will present problems down the road.
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Quoting NewBdoBdo:
Morning Storm...I have a question. In late May/early June you posted a picture of the temp of the water in the Gulf of Mexico as being cooled off significantly by the end of Aug/Sept time frame...do you know if that is prediction is still true? Thanks in advance.
what would cause the cooling of GOM by then?? perhaps storms passing thru that area??
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Quoting StormW:


Have to wait for the updated ECMWF Seasonal update to come out...but, I would imagine, as it has been pretty consistent with that forecast.
Thanks..BB later.
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Quoting CybrTeddy:


Look at the post directly above your post. :-)

Definitely an AOI there, not sure of more than that, though.
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Quoting StormGoddess:
Morning, everybody. :) Well, I must say, I'm starting to get the feeling that something is brewing out there. Startin' to feel it in me bones. Not sure where yet.


Look at the post directly above your post. :-)
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Quoting StormW:


Morning!

Morning, Storm! :)
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Morning Storm...I have a question. In late May/early June you posted a picture of the temp of the water in the Gulf of Mexico as being cooled off significantly by the end of Aug/Sept time frame...do you know if that is prediction is still true? Thanks in advance.
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Morning, everybody. :) Well, I must say, I'm starting to get the feeling that something is brewing out there. Startin' to feel it in me bones. Not sure where yet.
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This is the area the GFS parallel, NAM, CMC, NOGAPS, ECMWF, and UKMET develop a low pressure center..
this is our main AOI today, needs to be watched closely.
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12z NAM...84 hours...


Scary stuff...
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Good Morning everyone...I am glad we are in a lull with the tropics, though I feel like this is the eye of a storm...kinda unsettling
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Morn'n everyone...
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Kind of interesting to compare 2010 to other years before the AMO became warm. This map is comparing 1984's SSTs to 2010's SSTs. As you can tell, there is not much comparison in the anomalies...

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Quoting AussieStorm:

China March 2010

Awesome pic of their earlier dust storms.
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Quoting Patrap:
The BOP Internal pressure is almost 3000 psi as the integrity test continues to roll along.




Live feeds from the Gulf of Mexico ROVs
hope they don't blow a gasket
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The Daily Downpour and Portlight Thursday at 3 p.m. ET, 12 noon PT. Listen here!

Posted by: shauntanner, 1:43 PM CDT on July 13, 2010
Listen to the Weather Underground Broadcast Network here!

Join Weather Underground Meteorologists Shaun and Tim for The Daily Downpour today, Tuesday, at 3 p.m. ET, 12 noon PT!


Weather Underground Meteorologists Shaun and Tim will talk about any new updates on the oil spill in the Gulf, the hurricane season, and any weather related topics that are going on around the world.

Dr. Jeff Masters' show Hurricane Haven will be on the air 4 p.m. ET, 1 p.m. PT to discuss the latest on the tropical activity in the Atlantic.

Both shows will be taking your phone calls at 415-983-2634.
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Quoting CybrTeddy:


A Storm in the Bahamas would really suck this year, look at those SSTs!


Indeed. A Katrina/Rita track would really, really suck.

Edit: Might as well add Andrew to that list as well.
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Quoting MississippiWx:
2005:



2010:





A Storm in the Bahamas would really suck this year, look at those SSTs!
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Quoting Bordonaro:

The last thing Southern China needs is more rain. I saw on TV that they were actually blowing holes in dams to let water out of communities, or to keep the water form topping the dams.

They went from extreme nation-wide drought last year, to major flooding.

China March 2010
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The BOP Internal pressure is almost 3000 psi as the integrity test continues to roll along.




Live feeds from the Gulf of Mexico ROVs
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Quoting btwntx08:

Hi btwntx08, do yu know if they're still having problems at the border crossing? The reason I ask is that we have freight that is delayed coming from San Luis Potosi MX due to this flooding and haven't heard anything from our vendors.
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2005:



2010:



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Quoting Patrap:
Gulf of Mexico (Updated every ~10-15 mins)


Bookmarked. Thanks!
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Tropical Storm Coson a couple days ago. It really got its act together!
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Quoting Patrap:


WAVE trak




ESL by LSU site is a good one to save.



Thanks, I bookmarked that page :o)
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Quoting StormW:


Because of being so thick, and contain lots of moisture, they have a tendency to block out the sun.


"Our arrows will blot out the sun!"

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Quoting stormhank:
12Z 84 hour NAM....Link

According to that, a possible TC is located north of Honduras and the precursor to another one north of Hispaniola. Very interesting.
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About JeffMasters

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