Start up the hype machine! Again.
SURF:
Not much surf lately except for some NW windswell last weekend and some background SW swells during the work week. Today we've got more background SW swell, but with the cold front moving through, it's pretty junky. Tomorrow cleans up slightly but it's not that impressive.
FORECAST:
The weekend SSW swells backs off by Tuesday and Wednesday is pretty small.
WEATHER:
Is today finally the end of our rainy season? Just when I gave up hope back in April, this month has turned out to be our 2nd wettest May ever in San Diego with over 2.5" of rain. Today we're only expected to get less than a quarter inch from spotty showers (and maybe a stray thunderstorm) and then it cleans up tomorrow. By Sunday we should have nice cool conditions. Nothing exciting is forecasted next week with just seasonal night/morning low clouds/fog and temps in the low 70's at the beaches.
BEST BET:
Sunday with the new fun SSW and cleaner weather or next Thursday with about the same conditions.
NEWS OF THE WEEK:
As you know by now, waters in the equatorial Pacific in the spring of 2014 were warmer than normal and it led to two things: An increase in our hurricane activity (see the full report here) and the hope of a stormy El Nino winter. Well, we got one thing right- the active hurricane season. So what happened to the El Nino? There were a couple explanations like the ‘blob’ and La Nina. But the warm waters of El Nino haven’t gone away in our spring of 2015. In fact, the equatorial Pacific has gotten warmer. So is El Nino going to do an encore this hurricane season AND finally rear it’s ugly head this winter? The National Oceanic and Atmospheric Administration thinks so. And if our 2nd wettest May on record is any indication, I may just believe the hype too. Here’s the latest compelling arguments from NOAA:
There’s a 90% chance that the current El Niño will continue through the summer, and forecasters estimate the chance that it will continue through the end of 2015 at greater than 80%. This is a pretty confident forecast. What are the forecasters looking at that gives them such confidence?
Warm and Getting Warmer
Sea surface temperatures (SST’s) in the equatorial Pacific remained substantially above average during April. Also, there is still a lot of warmer-than-average water below the surface in the upper 300 meters of the ocean, helping to ensure that the above-average sea surface temperatures will continue for at least the next few months.
The atmospheric response to the warmer waters in the equatorial Pacific that we began to see in February strengthened through March and April: the Trade winds are more westerly than average, upper-level winds are weaker than average, and more rain was present in the central equatorial Pacific. These are all signs of the weakened Walker Circulation, present during El Niño events, and act to reinforce El Niño events.
This consistent atmospheric coupling is a change from the pattern we saw throughout 2014, when conditions changed from week-to-week. With a climate phenomenon like the El Niño/Southern Oscillation (ENSO), we expect to see more of a persistent pattern. (This doesn’t mean that the El Niño atmospheric conditions are always present every week, but that they are on average over the season.)
Conditions Look Good, But What’s Behind The Confident Forecast?
Nearly all computer model forecasts predict a continuation of the warmer-than-average SST’s through the end of 2015. There is a lot of agreement among the models that the SSTs will remain warm, and most models are forecasting SSTs more than 0.5°C above average through the October-December period. This agreement in forecasts, in combination with an ongoing consistent atmospheric response, is a large contributor to the high probability that this El Niño will continue through the fall.
As far as how strong this El Niño will ultimately be, it’s difficult to say. There is a fair amount of variation in the forecasts. The statistical models, which predict how current conditions are likely to change by applying statistics to historical conditions, are generally on the lower side of the forecast envelope, around 0.5°C – 1°C, the range of a “weak” event.
Many of the dynamical models, which use physical equations to predict how current conditions will evolve, have forecasts of warmer than 1.5°C, our threshold for “strong” events. Based on past model runs, the bias-corrected NMME dynamical model forecasts made in early May for the October-December period have a typical error of about 0.6°C, meaning, according to this set of models, there’s a 2-in-3 chance that the average temperature will be in the range of 2.2°C +/- 0.6°C—i.e., between 1.6°C and 2.8°C. *
Models – both dynamical and statistical – tend to have a harder time making successful forecasts during the spring as well. Also, El Niño events typically peak in the early winter, which is still six months away. These factors combine to make it difficult to predict the peak strength of this El Niño. It’s likely that we’ll have a clearer picture of the potential strength in the next month or so. For reference, the potential strength of the strong 1997-1998 El Niño didn’t become apparent, and wasn’t formally mentioned by NOAA’s Climate Prediction Center until July of 1997.
A Special Snowflake
Speaking of typical events, though – this is not one of them. It is unusual for sea surface temperatures in the region to start off warm in the winter and then continue to be warm through the spring and summer. In the 60-year record, only one El Niño event, in 1986-1987, had similar behavior. The evolution and strength of this event might be a little easier to predict if it were starting at a more typical time of year.
OK, But What’s Going to Happen???
The most substantial US temperature and rain impacts from El Niño occur during winter. Right now, it’s too early to forecast with much confidence the effect this El Niño may have on the US next winter. (Although the good chance that this El Niño will last into winter does tilt the odds towards the expected temperature and precipitation impacts). The Australian Bureau of Meteorology has just raised their event tracker to “El Niño” status, the equivalent of issuing an El Niño Advisory for us. (They have slightly different thresholds for declaring the onset of El Niño.) El Niño events are linked to increased drought and heat waves in Australia, especially during their winter (our summer), so they monitor its evolution closely.
Also, since it’s very likely that this event will continue through the summer, we may see some effects on the tropical cyclone seasons. The western Pacific tropical cyclone season is off to a roaring start, with seven named storms so far (the average is two!), which is likely linked to the warm Pacific waters.
So there you have it. It’s official: Start up the hype machine!
PIC OF THE WEEK:
The first thing that struck me when I saw this shot is that it looked like a burrito. I doubt it had anything to do with me going to Chipotle last night. Anyone else hungry right now?
Keep Surfing,
Michael W. Glenn
Invaluable
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