Tue Sep 15 2015 07:20 PM
Re: 2015 vs 2014: Tropical Implications for Entire U.S.

It is now certain that we are in the midst of a strong and record-setting El Niño. Also, as noted above in this thread, nearly the entire NEPAC is awash in highly anomalously warm waters, a stubborn feature that has been named The Blob.

While early on it was very clear that the dice were loaded for an El Niño, what was far less certain was should one develop, how strong it would become.

Other critical questions for answering the strength and frequency (or lack thereof) of systems which would form in both the Pacific & Atlantic were even less certain. Two of these were: How many seedlings/disturbances would there be for these exceptionally warm waters to cook, and: How might the massive Blob of very above average SSTs in the East Pac Subtropics affect things, if at all.

Now all three of these questions have largely been answered. 1) We are witnessing a historic El Niño 2) There have been a high number of seedlings in both ocean basins, and 3) The Blob has effectively helped amp up synoptic scale Trofs and Ridges around the country, and in part thereby increasing the likelihood of Trofs along the west coast being able to sweep up tropical cyclones, or at least their remnants and moisture, and tossing them across (anomalously warm waters) and into the desert southwest.

This pattern looks to stay in place throughout the remainder of this year, and likely into at least next spring, as well - alternating at least several more times between deflecting Ridges, and grabbing Trofs, as the atmosphere is highly amplified.

While a deflecting/redirecting Ridge might be welcomed by those from Oregon to Alaska, which would also like to see a hearty winter for a change, this looks less likely, as generally speaking, a strong El Niño ramps up the southern branch of the jet, and sends rounds of juiced-up extra-tropical/sub-tropical cyclones blazing across the southwest, extreme south, and southeast, sometimes producing record precipitation, that owing to its warm water connections, tends to fall mostly as rain, that just runs off - with often deadly repercussions.

It has been so long since much of the southwest has seen significant rain, that many who live there, and those who are visiting, may have almost no idea how quickly these torrents can become flash floods. Sadly, we saw this play out today in the Utah-Arizona border towns of Colorado City and Hildale, where at least a dozen people lost their lives - reportedly at least some of whom that had moved in closer to the flash flood to watch it, and then the second wave, twice as large and exponentially more powerful, came crashing down upon their location.

The realities of a "Godzilla" El Niño are already upon us, but unfortunately, the last time we experienced one was way back in 1997, meaning many people have already forgotten, and some were never there at all to begin with.

That year I chased a tropical cyclone up the Arizona/California border that maintained at Tropical Storm intensity well inland. Fortunately for many, most of its strong winds and heaviest rains ended up occurring over very sparsely populated areas of the desert. The next time such a rarity happens, larger communities may not be so lucky.

But as shown today in the tragedy along the Utah and Arizona borders, you do not need an intact tropical cyclone to create disastrous flooding in the desert southwest - which, unfortunately, has effectively been expanding over the past few years. Just the remnant moisture from El Niño & Blob fueled tropical depressions, storms and hurricanes can prove devastating.

The big takeaway, I think, is that residents and visitors to parts of the U.S. not typically accustomed to having to deal with the effects of severe tropical weather - Hawaii, California, Arizona, Nevada, Utah, and others - would be wise to learn about and prepare for the risks in their areas.

A great place to start is with The National Weather Service Flood Safety Homepage

More on East Pac U.S. Tropical Cyclone landfall possibilities coming up in the next entry.

Stay safe.

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