The Hot Blob in the Northeastern Pacific held its own for quite some time. But it now faces the assault of a barrage of tropical cyclones spat from the maw of a monster El Nino that is now tracking its way toward the strongest such event on record. If this keeps up, the Ridiculously Resilient Ridge warding storms off the US West Coast will be besieged by increasingly powerful cyclonic systems. The Ekman pumping from such storms will cool the ocean surface at its periphery and expanding toward its heart, eventually crushing the ocean impetus for ridge formation. The continuation of such a pattern could then kick Bjerknes feedback into higher gear — opening wide the door for powerful storms striking the US West Coast this Fall and Winter.
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A Record-Shattering Barrage of Pacific Cyclones
Late during the evening of August 29th of 2015 something odd happened. For the first time in the history of modern meteorological record keeping, three category four typhoons simultaneously churned their way northward through the Pacific Ocean. These massive and powerful storms, just one category shy of the strongest typhoons we have a measure for, were hurled out of a region of extremely hot sea surface temperatures near the Equator. A zone, that for late August was also hitting record hot levels amidst a building Monster El Nino. And never before in modern memory had so many storms of such high intensity filled Pacific Ocean waters.
(Signs that powerful Fall and Winter storms are coming for the US West Coast? From north to south, strong cyclones are starting to put the squeeze on the Ridiculously Resilient Ridge. The Central and Eastern Pacific between 10 and 30 North, in particular, shows an eye-widening number of tropical cyclones. As of Tuesday, September 1, a whopping four tropical systems were churning northward out of an extremely hot El Nino zone. Image source: Earth Nullschool.)
By today, the furthest northward cyclones had vented their fury and dropped in intensity. Meanwhile, a fourth storm — tropical depression 14-E — was in the process of exploding over the very hot waters of the Eastern Pacific. It’s an unprecedented number of storms flowing out of what may become the strongest El Nino on record as part of a powerful ocean-atmospheric feedback.
Strong Bjerknes Feedback to Crush RRR?
Now, this strong storm pulse is starting to put the squeeze on the famed Ridiculously Resilient Ridge (RRR). It’s a persistent ridge that for the better part of three years has turned storms away from the US West Coast — deepening already prevalent drought conditions over California and threatening water security across the US West.
But now the RRR is surrounded by storms. A strong frontal trough runs from 30 North across the Central Pacific and on up into the Bering Sea. Another significant late summer low churns off the Pacific Northwest — running south and east toward Seattle and British Columbia. And four tropical cyclones push northward into the ridge’s southern boundary. It’s a full court atmospheric press. One that, through the mechanism of Ekman pumping, will push for the generation of upwelling and related cooling of the Northeastern Pacific waters beneath the RRR.
(Sea surface temperature and atmospheric conditions are beginning to fall more in line with an El Nino related pattern called Bjerknes Feedback. Image source: NOAA.)
If this happens, a good portion of the RRR’s atmospheric inertia will fail — opening wide the door for a powerful west to east storm track development fed by heat rising off a Monster El Nino sprawling over the Equatorial zones. It’s a pattern that’s starting to look like a rather significant Bjerknes-type feedback to a record or near record El Nino. One that may well continue to develop and grow ever-stormier as Fall progresses.
2015 El Nino Still Heating Up, Expected to Heat Up More
Feeding the powerful pulse of storms is a still-heating Equatorial Pacific. As of Monday, NOAA’s Weekly El Nino Report found that the critical Nino 3.4 zone had warmed 2.2 degrees Celsius above average. This warming follows an inexorable three month rise that began in June and has mostly continued unabated. Furthermore, seasonal trends together with the already powerful observed atmospheric feedbacks would tend to continue to push surface warming through October and November. So it’s likely that an El Nino that has already ventured well into monster event range will warm further over the coming 4-10 weeks — setting the stage for a possible excession of 1997’s record setting intensity.
(The 2015 El Nino is starting to look like one of the very intense events some climate models predicted as an upshot of human-forced global warming. It’s only early September and Nino 3.4 is already 2.2 C hotter than average. This Equatorial Pacific region is still heating up as storm-forced up-welling begins to develop cool regions in the RRR supporting zones of the Northeastern Pacific Hot Blob. It will take a boatload of strong storms to crush the RRR, but the still strengthening monster El Nino to the south keeps firing them northward. Image source: Earth Nullschool.)
Model runs still point toward this possibility with CPC/IRI convergent and dynamic 3 month average predictions in the range of 2.3 to 2.5 C above average (which would beat out 1997’s 2.2 C departure). Meanwhile, uncorrected CFSv2 model runs continue to put the October, November, December 3 month average prediction in the range of 2.75 C above baseline. A level that would basically blow the 1997 El Nino out of the water. To this point it’s worth re-iterating that weekly sea surface temperature departures for the Equatorial Pacific are now entering record setting ranges. Many analysts, like Weather Underground’s Steve Gregory, expecting these waters to continue to warm over the coming weeks.
Conditions in Context: Look Out For Rough Weather Coming to US West Coast
Though it’s too early to lock in the death of the RRR, conditions are lining up that will continue to put the squeeze on this persistent weather pattern. As a result, chances for some very intense storms beginning to slam into the US West Coast starting during October, November and December are on the rise. For those looking to a possible end to the droughts, wildfires and water shortages in the Western US, this potential change in conditions may be seen as a relief.
However, such an extreme switch brings with it the distinct possibility that storms associated with a potential strongest El Nino on record will be very disruptive. The droughts and numerous wildfires throughout the West have established soil conditions that will only enhance flood related impacts. Powerful rains associated with El Nino will likely increase erosion and further damage soils in regions already impacted by the severe droughts, mass tree deaths, and wildfires related to human forced climate change and fossil fuel burning.
(As of August 13, 2015, some parts of California were facing a rainfall deficit of 2 years or more. In order to break the drought, 2015’s monster El Nino would have to set off severe flood conditions during Fall and Winter. With the RRR under threat, is California staring down the barrel of a switch to an equally ridiculous barrage of storms? Image source: National Weather Service, Phoenix.)
To this final point, parts of California are now entering a 2 year rainfall deficit. A deficit that, in some places, equals 30-40 inches or more. A monster El Nino crushing the RRR and massively amplifying the Pacific Ocean storm track and pumping immense volumes of moisture into the mid-latitudes raises the risk that this much water or more could be dumped upon parts of California and the US West Coast in little more than a season. A switch from persistent, crushing drought to flash flood that could be extraordinarily disruptive.
Hat Tip to Ray Duray
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