For Houston, a city that hosts a massive oil industry, it’s the climate change related flood version of the Fort McMurray fire. And we may well be witnessing, at this time, a tragedy that we could have at least in part prevented, but didn’t.
Last week at this time, . 5-7 day models indicated that the system would enter the Gulf of Mexico by late week. This Gulf was hotter than normal. And for the past three months it had been dumping an over-abundance of moisture into an unusually deep summer trough over the Eastern U.S. This interaction between two features related to human-forced climate change was already .
Harvey was very moisture rich. It issued from a — due, at least in part, to abnormally warm ocean surface waters injecting much higher than normal moisture loads into the tropical atmosphere. And early last week there was .
These fears have now been realized.
As of this afternoon, parts of — with up to . Hourly rainfall rates at times have hit an equally unprecedented rate of up to six inches per hour. For context, one inch per hour rainfall rates in the past have been considered extreme. Six inches per hour is just off the charts. In many places, the most rain ever to fall over a one day time-frame was breached.
As we have seen so often around the world , roads flooded, cars were abandoned, and people were forced to climb onto their rooftops to flee the rising waters. In a Houston that is increasingly looking like post-Katrina New Orleans, more than 1,000 emergency calls for water rescues had been received by this morning. And with rivers hitting never-before-seen heights in a flood-prone city that is also facing the effect of rising sea levels, the rains were showing little sign of abating.
(September 1 GFS model shows remnants of Harvey interacting with a tropical cyclone south of Baja to continue to pull rains over Texas and Louisiana. Image source: Earth Nullschool.)
An additional concern is the fact that later this week Harvey shows a possible interaction with another stationary tropical cyclone forming near the southern tip of Baja in the Pacific. The two storms appear to interact to draw still more moisture from the abnormally warm Gulf over Southeast Texas later this week. Of course, this GFS-based forecast is still longer range — and therefore less certain. But the models do seem to continue to indicate a persistent heavy rainfall potential for an already catastrophically flooded region over an unprecedented long time frame.
This is exactly the kind of extreme rainfall event that some of us have feared coming from a warmer, more moisture-rich atmosphere in which weather systems have tended, more and more often, to persist and produce long-lasting effects. For the sake of all involved, we are now reduced to prayers and hopes that the worst case does not continue to be realized.
Hat tip to Greg
Hat tip to eleggua