25 November, 2014

Coachella Valley: The Next Black Sea?

I was once skeptical of the possibility of a major hurricane directly impacting Southern California. After all, the waters off the coast are indeed simply too cold to sustain hurricanes... and the only ones that manage to veer north usually move too slowly over those cold waters and fizzle... with a few rare exceptions, of course, and by the time those rare exceptions manage to reach SoCal, they're only tropical storms to category 1 hurricanes at best. Likewise, if they manage to take the trek up the Gulf of California/Sea of Cortez, which is indeed some of the warmest water in the entire Eastern Pacific basin, with summertime SSTs reaching as high as 90°F on a regular basis, they'd still make landfall in northern Mexico, and have to cross a lot of land to reach SoCal. Or so I thought.

The first clue that I managed to dig up suggesting that the Gulf could pose a hurricane threat, at least to the Inland Empire, came from looking up the elevation of the surface of the Salton Sea. The reading? 237 feet below sea level. That alone raises a bright red flag: Even New Orleans was only about 10 feet below sea level when Katrina hit. What's more, the entire Coachella Valley, more or less, is a bowl, and it's the site of an ancient lake bed that once filled the entire region... the ancient lake, if I'm not mistaken, stretched from what is now Mexicali all the way to what is now Palm Springs. That's one massive lake... and the fact that its floor is now the site of a major population center should be enough to freak out anyone.

Then, I managed to Google " 'sea level rise' 'Coachella Valley' " (inside quotes included, as double quotes). I noticed a KCET article that was rather disturbing, depicting what would happen if climate change raised the level of the Gulf by only a few feet. Then, I switched over to the images tab. That's when I noticed something very disturbing, in regards to the Coachella Valley's only lifeline:

As you can see, the only high ground between the Salton Sea and the Gulf of California is, at most, only about 7 or 8 feet above sea level. What's more, the 20-foot line ― the height of a typical major hurricane storm surge, especially in a warm, shallow environment like the Gulf of California ― is almost the entire width of the Gulf itself. A storm surge of that size eroding a path into a depression like the Salton Sink? Yeah, it's almost impossible to fathom such a catastrophe. You're looking at a region from Mexicali all the way to Palm Springs being completely submerged.

What's more, as previously mentioned, SSTs in the upper-80's to near 90 degrees are well within rapid deepening territory. When Odile managed to traverse the northern Gulf as a tropical storm back in September 2014, guess what happened? The storm grew from a weak to a strong one, with, at their peak, about 60mph winds, before making a second landfall on the northeastern shore of the Gulf. Thankfully, however, Odile had weakened to a tropical storm from, at the first landfall, a Category 4 hurricane, prior to even entering the Gulf... and what's more, this storm could have been much worse.

Remember, what was steering Odile away was an area of high pressure, whose western edge (and clockwise rotation) was already at its easternmost point and began to move westward, keeping Odile over Baja. Had Odile gotten sucked into that high only a day... or two... or three earlier, so that Odile made its first clipper landfall in Puerto Vallarta before moving up the Gulf, I guarantee you Hurricane Odile would have been a 5 by the time it reached the northern Gulf... and then, as the high began to build again, it would have pushed Odile northwestward, resulting in Odile hooking to the west instead of the east. That makes Odile our closest call so far to this.

In fact, those warm Gulf of Mexico waters in the notorious Loop Current that intensified Katrina were also around the same temperature: near 90°F. The difference, however, is that those extreme SSTs, while incredibly anomalous in the Gulf of Mexico, are commonplace in the Gulf of California. So then why haven't there been rapidly intensifying hurricanes in the Gulf of California before? There's a simple explanation for that: it's got a lot more land in the way. Most of the storms that have managed to go up the Gulf have first run into either the Baja Peninsula (mountainous terrain) or mainland Mexico (more mountainous terrain). You need the steering patterns to be near-perfect for this to happen: a strong, blocking high over the western Gulf of Mexico to the east, and, most importantly, a clockwise flow around the high that pushes moisture directly over the Mojave Desert, where the thermal low then grabs it, intensifies due to convection, and rotates, locking that blocking high in place. Then, you need a hurricane that takes a near-perfect path, so that it could get caught up in that, clipping the headland near Puerto Vallarta, entering the Gulf of California, rapidly intensifying, and making its second landfall just to the west of the Colorado River Delta. Yeah, it's not a question of if, it's a question of when... and when it does happen, the results would be disastrous indeed.

Not only would such a storm be disastrous for the Coachella Valley, but, if it is caught by that thermal low and takes that left turn as an intense hurricane, it could also remain a category 3 or higher monster even as it exits the region, provided it misses the San Jacinto and/or San Bernardino mountains, and enters the Los Angeles Basin. The resulting wind (and even tornado) damage, not to mention torrential rainfall, could pose even more problems. Remember, if that basin fills, that water is going to come in contact with not only the hot Salton Sea but also the hot ground. That will in turn add more heat to the incoming storm surge water, moving over a region that is, mind you, 237 feet below sea level, and that heat could then continue to sustain the hurricane as it passes through that inland sea that it creates. So, it would end up continuing to rapidly intensify as it makes that westward hook. Yeah, you can see where this is going: a recipe for disaster indeed.