It’s been a busy week for El Niño updates and information. On Monday, NOAA’s Climate Prediction Center (CPC) issued their weekly presentation (pdf). On Tuesday, the Australian Bureau of Meteorology issued their bi-weekly update. On Thursday, the CPC published their monthly discussion. And Saturday, Dr. Michael Ventrice wrote a guest post on Wunderblog.*
In short, an El Niño event is slightly more likely this summer (70% chance vs. 65%) or fall/winter (80% chance). The models currently predict a moderate strength event (+1.0°C to +1.4°C), but Dr. Ventrice is expecting the higher end at +1.5°C. For comparison, the lower limit of an El Niño event is +0.5°C and the “Super” El Niño of 1997-8 was +2.5°C. But, everyone put lots of caveats on these modeled results as estimating the strength of an event is much more difficult than the likelihood of one.
Regardless, Dr. Ventrice emphasizes, “Regardless of what amplitude the ENSO 3.4 Index [ed. El Niño strength] achieves, it only matters if the atmosphere responds.” (Emphasis in original.) His point is that while the Pacific Ocean is highly likely show El Niño-like temperatures, the impact on North America and the Atlantic hurricane season may not appear until August or later. That means there could be heat waves in the central and eastern continental US, continued drought in California, or regular Atlantic hurricanes until the atmosphere “feels” the effects.
* I recommend the Australian website as the easiest to read and understand. CPC’s updates are also good, but can take a few weeks or months to get the hang of the lingo. Dr. Ventrice’s posts are probably the most technical, but also provide excellent coverage into how an El Niño develops and what to watch for in the data.
Jeff Master’s has a post regarding a recent paper connecting the polar vortex and the California drought to climate change. The discussion itself isn’t all that interesting, but it does have an extensive list of past blog posts and research papers regarding weather circulation patterns. Jeff got me interested in the the North Atlantic Oscillation (NAO) several years ago when Greenland was warmer than Florida. Also, the NAO is oldest known climate oscillations, described several centuries ago by (as Jeff calls them) “seafaring Scandinavians,” which is probably a polite way of saying Vikings. I would like to find more about this history, but have not found much info yet.
Also of note, the strong dipole (high pressure/low pressure pair over North America) discussed in the paper naturally occurs prior to an El Niño event. This ties in to several of my previous posts. This isn’t a cause-and-effect matter, but probably coincident expression of conditions that lead to an El Niño season.
Jeff Master’s has an update post from Dr. Michael Ventrice on the El Niño forecast. As Master’s said, it’s highly technical (and above my pay grade), but still interesting none-the-less. Short story, the models are in greater agreement of El Niño conditions and increased strength. To quote, “the latest climate model forecasts are now more aggressive with the amplitude of the potential emerging El Niño.”
The paired wind bursts around the equator (i.e., the washing machine wringers mentioned last week) have faded, but there appears to be potential activity in the Indian Ocean that could move east. This may form the southern half of a new pair of wringers.
The NOAA Climate Prediction Center April monthly expert assessment is due in a week or so and I’ll post more if that has interesting goodies.
Earlier today, I mentioned Jeff Master’s WunderBlog guest post from Dr. Michael Ventrice with a detailed explanation on the signs indicating a significant El Niño event for late 2014. What I found interesting was the pulse of westerly winds that can lead to the El Niño.
The trade winds near the equator typically blow from the east to the west (due to earth’s rotation). This pushes warm surface water where it pools near Indonesia and Australia. Cool deep water then upwells near Chile providing good fishing grounds. To counteract the easterlies, a westerly burst of winds weakens the trade winds. The warm surface waters then stay near Chile and the cool water stays in the ocean’s depths, i.e., an El Niño.
What can cause that westerly pulse? Basically, a pair of cyclones. North of the equator cyclones (or hurricanes in the Atlantic Ocean) rotate counter-clockwise; south of the equator, clockwise. If you have a near simultaneous occurrence of two cyclones bracketing the equator, the rotation will squeeze a burst of wind from west to east. It reminds me of the antique washing machine wringers used to dry clothes.
In late February, Dr. Jeff Master’s blog on Weather Underground published a guest post from Dr. Michael Ventrice of Weather Services International (WSI). The post provided detailed explanation on the signs indicating a significant El Niño event for late 2014. Early in March, National Oceanic and Atmospheric Administration’s Climate Prediction Center issued an El Niño alert. They estimate a 50% chance for an El Niño event in 2014. Following that, Dr. Master’s provided an explanation of the El Niño warning. Finally, Kim Cobb of Georgia Institute of Technology provided another explainer of the warning.
All this background is to note that the last major El Niño event was in 1997-98, prior to the high temperature year of 1998. Any time you hear someone discuss a “slow down” in global warming, they always reference 1998, even though that temperature has been met or exceeded four times since then (source, Goddard Institute for Space Studies). A prediction of an El Niño event is no guarantee of a future heat wave, but it does not bode well, either.