Harvey and Heat

Tuesday, August 29, 2017 at 11:38 am

A truly astounding week it has been in southeast Texas where Hurricane Harvey rapidly strengthened to a category 4 before hitting the coast just north of Corpus Christi.  Of course, the winds were devastating down in that area, but the real story has been the tremendous rainfall that has fallen in the Houston area.  The main cause for this has been an almost complete stagnation of Harvey since landfall Friday night.  The storm moved only about 100 miles inland before completely stalling, then slowly meandering back out to the coast and slowly up toward Houston.  This has allowed an almost continuous onshore flow to bring tremendous amounts of moisture off the Gulf of Mexico and drop it squarely on the Houston metro area for days on end.

Most locations in the Houston area have now seen 3-4 FEET of rainfall! That’s about as much liquid as is contained in 400-500″ of Utah powder.  Remarkable!  In fact, this is now the wettest tropical cyclone in U.S. history, with >49″ reported in one location.

NWS Houston

…and it’s still raining in the Houston area, especially east of the metro area which could see several more inches of rain today.

As a weather nerd and someone who is fascinated by statistical anomalies, this is just about as anomalous as it gets.  For perspective, prior to this week, the wettest 40-day period in Houston’s history was 24.2″ of rain in 40 days in the summer of 1946.  We’ve more than doubled that amount in a 4 day period.  It’s like having the rainiest 40 days you’ve ever seen, back-to-back, then condensing that down into 5% of the timeframe.  Incredible!

Obviously, thoughts and prayers are with the people of Houston!

I’ve seen a number of posts about whether this was caused by climate change.  It is impossible to correlate any one event to climate change, so saying this is a product of climate change is not necessarily accurate.  The main reason for the heavy rains was the slow movement of system due to lack of a steering mechanism in the upper atmosphere.  It is very tenuous to try to tie this to climate change.  It may not be quite as tenuous to say the rapid strengthening and copious moisture transport was facilitated by warmer water temperatures in the Gulf of Mexico as a result of climate change.  So it is possible to say that climate change could have exacerbated the situation, sure, but it’s hard to say this is a direct result of climate change.  The counter-argument would be that this is the first major hurricane to hit the U.S. mainland since 2005 (12 years).  That’s an extremely long time statistically speaking, in a time when we would expect to see more frequent and stronger tropical cyclones.

There will, obviously, be plenty of time for reflection and research on this storm in the years to come.  Right now, our focus should be on helping those in need.  You can donate by visiting the Red Cross website.

As for Utah, we in the midst of yet another heat wave.  The worst of it is to our west, but we well above average too.  This should continue through Labor Day and will likely give us an outside shot of officially seeing our hottest summer ever at SLC.  Wildfires throughout the west will contribute to hazy skies.  I’ve been checking models daily and I am starting to see hints at opportunities for more fall-like weather patterns to develop during the second week of September.  No consensus on anything yet, but I think we will see cooler conditions arriving in the next couple weeks.  I’ll continue to watch and fill you in as soon as I see something tangible.

WSF





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