Second warmest March on record; will La Niña be gone by hurricane season?
March 2008 was the 2nd warmest March for the the globe on record, according to statistics released by the National Climatic Data Center. Over the Northern Hemisphere, and over all of the globe's land areas, March 2008 was the warmest March in the 128-year global record. Only the presence of a moderately strong La Niña event that cooled ocean waters in the central and eastern equatorial Pacific prevented March 2008 from surpassing March 2002 as the warmest March on record. March broke a string of three straight months when the globe did not record a top ten warmest month ever. Between February 2006 and November 2007, the globe set top ten monthly warm temperature records for 22 straight months.
Figure 1. Departure of temperature from average (the anomaly) for March of 2008, the second warmest March on record for the globe. While the U.S. recorded slightly below average temperatures, much of Asia and Europe saw remarkably warm temperatures. Image credit: National Climatic Data Center.
How much cooling did La Niña give to the globe in March?
La Niña is a periodic cooling of the Equatorial waters of the Eastern Pacific that occurs every 3-7 years. The cooling is due to a natural cycle of anomalous winds from the east that act to push surface waters away from the coast of South America, allowing cold water from deep in the ocean to rise to the surface to replace the surface waters blown to the west. These cool waters often cause a noticeable drop in global temperatures. Conversely, when the opposite phenomena occurs--an El Niño event, which brings anomalously warm Sea Surface Temperatures (SSTs) to the Equatorial Eastern Pacific, enough heat is added to the atmosphere that global temperatures warm significantly. According to Trenberth et al. (2002), a typical El Niño event increases global temperatures by about 0.1°C. Exceptional El Niño events, such as occurred in 1997-1998 and 1982-1983, increase global temperatures by up to 0.2°C. El Niño events heat the atmosphere by causing changes in cloudiness and atmospheric circulation, and through direct radiation of heat from the ocean to the atmosphere. There is a lag of 3-6 months between the time an El Niño event occurs and the time the atmosphere heats in response. Similarly, when a La Niña event occurs, heat is drawn out of the atmosphere and the oceans are recharged with heat. Global temperatures cool, again with a lag of 3-6 months. The correlation between global temperature anomalies and El Niño/La Niña temperature anomalies can be plainly seen in Figure 2. Note that the correlation is not perfect--there are some El Niño/La Niña events that do not affect the global temperature much. For example, global temperatures did not cool much during the strong 1988-1989 La Niña event. Therefore, it is a good bet--but not certain one--that had we not had a strong La Niña event this winter, March 2008 would have been the warmest March on record, since it missed the record by only 0.04°C.
Figure 2. Comparison of temperature anomalies in the equatorial Pacific Ocean bounded by a box between 5°S, 5°N, 120°W, and 180°W (the Niño 3.4 region) and global temperatures for 1950-1998. Means for 1950-1976 and 1977-1998 (horizontal lines) are shown separately to highlight a climate shift that occurred in 1976/1977. The reasons for this shift are unknown. Note that when an El Niño event occurs, the globe tends to warm by about 0.1°C, and when a La Niña event occurs, the globe tends to cool. Image credit: American Geophysical Union's Journal of Geophysical Research.
Warmest month ever stats
It is interesting to compare what the phase of El Niño/La Niña was during each of the 12 record warmest months the globe has recorded. If we adjust for the 3-6 month lag between an El Niño/La Niña event and the monthly global temperature records, it turns out that nine of the twelve monthly records were set when an El Niño event occurred during the 3-6 month period prior to the record. Considering that climatologically El Niño conditions are present only about 25% of the time, El Niño has a major impact on when record global warmth will occur. The warmest year on record, 1998, occurred during the strongest El Niño of the past century. The table below compares the 12 monthly global temperature records with the temperature in the Niño 3.4 region (a 3-month average centered four months before the record was set). El Niño events, which occur when the Niño 3.4 index is greater than 0.4°C, are marked with an "E".
Record......Niño 3.4 index
-----------------------------
Jan 2007 +0.7 E
Feb 1998 +1.7 E
Mar 2002 -0.1
Apr 1998 +2.5 E
May 1998 +2.3 E
Jun 2005 +0.5 E
Jul 1998 +1.4 E
Aug 1998 +1.1 E
Sep 2005 +0.5 E
Oct 2003 +0.0
Nov 2004 +0.7 E
Dec 2003 +0.4
Figure 3. A La Niña event exists when ocean surface temperatures in the equatorial Pacific Ocean bounded by a box between 5°S, 5°N, 120°W, and 180°W (the Niño 3.4 region) are cooler than 0.4°C below average (based on means from 1971-2000). La Niña events between 0.5°C and 0.9°C are referred to as weak, 1.0°C and 1.4°C are moderate, and 1.5°C or cooler, strong. The winter of 2007-2008 saw strong La Niña conditions, but this has weakened to a moderate event in March. Image credit: NOAA Climate Prediction Center.
An El Niño by hurricane season?
Presence of El Niño conditions usually causes enhanced levels of wind shear over the Atlantic, reducing hurricane activity, so it would be nice to see an El Niño this Fall. The strong La Niña event we had over the past winter has weakened considerably in the past two months, and is now classified as a moderate event, according to the latest El Niño discussion issued by NOAA's Climate Prediction Center. There is some hope that an El Niño will develop by hurricane season. Two of the long-range computer models are now calling for an El Niño to develop by hurricane season (Figure 4), and none of them were calling for El Niño last month. However, there is probably not time for a full-fledged El Niño event to develop, and it is expected that we will have weak La Niña or neutral conditions this hurricane season. Since reliable El Niño records began in 1950, there has never been a switch over to El Niño by hurricane season from a La Niña as strong as the one we have now. Columbia University's International Research Institute is predicting that neutral El Niño conditions are most likely for the coming hurricane season (57% chance), with a 20% chance of an El Niño, and 23% chance of a La Niña. This is pretty much what climatology says--on average, we experience El Niño conditions 25% of the time and La Niña conditions 25% of the time.
Figure 4. Computer model forecasts of El Niño/La Niña made in April. 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. Image credit: Columbia University's IRI.
References
Trenberth, K. E., J. M. Caron, D. P. Stepaniak, and S. Worley, >Evolution of El Niño, Southern Oscillation and global atmospheric surface temperatures", J. Geophys. Res., 107(D8), 4065, doi:10.1029/2000JD000298, 2002.
I'll be in Orlando next week for the American Meteorological Society's bi-annual hurricane conference, and plan to make some quick posts during the week to update everyone on the latest hurricane research. I may make one more post before then.
Jeff Masters
Reader Comments
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Ivan max sustained 125, pressure 931 from 939
Katrina max sustained 125, pressure 925 from 913
Those 2 were about even but Ivan was strengthening, Katrina was weakening. Katrina was larger than Ivan, that was never in question. Katrina's larger size made made it's massive surge sustainable which was nightmare for MS/AL coastal towns. Katrina's surge went inland for miles. The Panhandle of Florida is less surge prone so was somewhat protected from similar surge from Ivan.
This whole conversation goes back to my original point, that the 1 in 100 year event is the one that hits you. There have been many worse than Ivan and Katrina (like Hugo or Camille) in past but the big one is the one you get.
Just before it made landfall in the United States, Ivan's eyewall weakened considerably, and its southwestern portion almost disappeared. Around 2 a.m. CDT September 16 (0700 UTC), Ivan made landfall on the U.S. mainland in Orange Beach, Alabama as a Category 3 hurricane with 120 mph (190 km/h) winds. Ivan then continued inland, maintaining hurricane strength until it was over central Alabama. Ivan weakened rapidly that evening and became a tropical depression the same day, still over Alabama. Ivan lost tropical characteristics on September 18 while crossing Virginia.
But I guess you would know. :~)
Shortly after emerging over the southern Gulf of Mexico early on 14 September, Ivan turned north-northwestward and then northward. A steady weakening trend also ensued as moderate southwesterly flow on the east side of a large mid- to upper-level trough over the central United States and northeastern Mexico gradually caused the vertical shear to increase across the hurricane. As Ivan neared the northern U.S. Gulf coast, the upper-level wind flow ahead of the trough became more westerly and strengthened to more than 30 kt, which helped to increase the shear even more and advect dry air into the inner core region. Despite the unfavorable environmental conditions, the presence of cooler shelf water just offshore and eyewall replacement cycles, Ivan weakened only slowly and made landfall as a 105 kt hurricane (category 3 on the SSHS; see Figure 2c and Figure 3b.) at approximately 0650 UTC 16 September, just west of Gulf Shores, Alabama. By this time, the eye diameter had increased to 40-50 n mi (Figure 4c), which resulted in some of the strongest winds occurring over a narrow area near the southern Alabama-western Florida panhandle border.
The weakening of major hurricanes as they approach the northern Gulf coast has occurred on several occasions in the past when one 3
or more of these factors have been in place. Indeed, an unpublished study by the National Hurricane Center (NHC) reveals that, during the past 20 years, all 11 hurricanes having a central pressure less than 973 mb 12 h before landfall in the northern Gulf of Mexico weakened during these last 12 h.
Tropical Cyclones Outlook (0600z 26APR)
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A low pressure area has formed over southeast Bay of Bengal. In association with the LPA convective clouds are seen over southeast Bay of Bengal and Andaman Sea.
Convective clouds are also seen over southeast Arabian Sea.
Marine Bulletin (0900z 26APR)
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A low pressure area persists over southeast Bay of Bengal and surrounding neighborhood.
I'm out on bail, but I've got this thing 'round my ankle! ;P I apologize to WU, Doc and the good bloggers here for the interruption yesterday evening. I let something bother me that I shouldn't have and I let it get out-of-hand. Hopefully, that'll not happen again. Nonetheless, it was a mistake and I regret it. I appreciate the kind, supportive comments sincerely. Thank you - you're a great group!
Now, since there was some talk of eddys, check this out! Appears to be a rather large loop about to spin-off the current! By the time it spins off and the current propagates itself again, it could leave some really warm, potentially explosive waters in the GOM in a few months.
I'm out on bail, but I've got this thing 'round my ankle! ;P I apologize to WU, Doc and the good bloggers here for the interruption yesterday evening.
I let something bother me that I shouldn't have and I let it get out-of-hand. Hopefully, that'll not happen again. Nonetheless, it was a mistake and I regret it.
I appreciate the kind, supportive comments sincerely. Thank you - you're a great group!
Now, since there was some talk of eddys, check this out! Appears to be a rather large loop about to spin-off the current! By the time it spins off and the current propagates itself again, it could leave some really warm, potentially explosive waters in the GOM in a few months.
That warm loop would certainly need to be taken into consideration as we approach June.
Yeah, seems like the serious variables are beginning to stack up! ugh!
I'm not sure if anyone else noticed, but the warm SSTs anomalies of the African coast, seem to be spreading westward (into the MDR; not good news).
BRACE BRACE BRACE !!
Sheri
Yes MLC... We now have to see how fast the MDR, warms up...
We could call it the DOOMLIST LOL
- Pottery, "doom list" - ugh! It's the end of April, not too much further, now, and it's here.
Link
El Nino? Naw
This year:
I'll check back later, when the beer is cold.
April 13 SST forecast
April 22 SST forecast
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