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Harvey’s Flooding Already Catastrophic and Another 2-3 Feet of Rainfall is on the Way

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.

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Last week at this time, meteorologists were tracking a tropical cyclone moving across the Caribbean. 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 producing very severe thunderstorms that generated record rainfall over places like Kansas City, Missouri.

Harvey was very moisture rich. It issued from a tropical convergence zone and monsoon cycle that had hit unusually high intensity — 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 some serious concern that intense tropical moisture in the form of Harvey could combine with a Gulf and Eastern U.S. weather and climate pattern that had already produced unprecedented rains to generate ultimately catastrophic results.

These fears have now been realized.

As of this afternoon,  parts of Houston and Southeast Texas had received more than 30 inches of rainfall — with up to 26 inches falling in just one 24-hour-period. 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 from globally increasing instances of record rainfall, 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.

(Pivotal weather shows up to 32 inches of additional rainfall for the Houston region through Tuesday. The storm, however, may last through Thursday or later. Image source: Pivotal Weather.)

As much as 1-3 feet of additional rain is still expected from the storm. In the worst case, this would bring ultimate rainfall totals to 50-60+ inches. In a litany that we are hearing practically everywhere now — this would be the worst rainfall event Texas has ever seen in our records. It might, ultimately, be the worst flood from rainfall the U.S. has ever seen.

Moreover, weather models now indicate that Harvey may slowly track back toward the Gulf of Mexico. If this happens, a storm that is already pulling severe volumes of moisture in from the Gulf could be somewhat re-invigorated. Such a result would bring a second pulse of intense rains to parts of Southeast Texas and possibly Louisiana.

(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.

(UPDATED 9)

RELATED REPORTS AND STATEMENTS:

Links:

The National Weather Service

The National Hurricane Center

Harvey has Unloaded 9 Trillion Gallons of Water

Catastrophic Flooding Beyond Anything Experienced in Houston

Global Number of Record-Breaking Daily Rainfall Events

Harvey’s Approach Brings Potential Severe 5-Day Rainfall Event for Texas and Louisiana

Pivotal Weather

Earth Nullschool

Hat tip to Greg

Hat tip to eleggua

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March Heatwave — Among Most Extreme in US History — Fuels Potential for Catastrophic Flooding

This afternoon the National Weather Service issued a catastrophic flood warning for the areas of Eastern Oklahoma, Western Arkansas, Western Louisiana, and Southwest Missouri. The NWS predicted that widespread and potentially catastrophic areal and river flooding were possible in the region today. An enormous, slow-moving low pressure system is colliding with the moistest air mass ever recorded for the central US during March.

The NWS in Minneapolis Minnesota measured the highest levels of moisture ever recorded so early in the year flowing northwards into Minnesota along the cold front yesterday. A large trough of low pressure is now lifting this massive volume of moisture aloft and is expected to dump from 4-8 inches of rain with isolated amounts measuring as high as 15 inches in the warning areas.

Image

Fueling this storm is an extreme record heat-wave that has pumped massive volumes of moisture from the Gulf of Mexico over the central US. This heat wave was spurred by a Pacific La Nina weather pattern combined with abnormal heat and moisture fueled by global climate change.

All throughout the Midwest, records have been shattered with many cities showing the warmest March in history. In Illinois, republican climate change deniers vying for primary voters were greeted with seven days straight of 80 degree weather.

Obama, in a recent chat with Oprah today said “It’s warm every place. It gets you a little nervous about what’s happening to global temperatures. But when it’s 75 degrees in Chicago in the beginning of March it gets you thinking…”

Oprah replied: “Something’s wrong.”Image

The March heat wave is producing a huge swatch of extreme temperatures with North Dakota, South Dakota, Nebraska, Kansas, Missouri, Iowa, Minnesota, Michigan, Wisconsin, Illinois, Indiana, and Ohio all seeing temperatures 20-25 degrees or more above average for this time of year.

From Weather Channel meteorologist Stu Ostro: “This remarkable warmth is associated with a bulging ridge of high pressure aloft that is exceptionally strong and long-lasting for March. While natural factors are contributing to this warm spell, given the nature of it and its context with other extreme weather events and patterns in recent years there is a high probability that global warming is having an influence upon its extremity.”

UPDATE: Storm system sparks flash flooding, severe storms, tornadoes across the warning region (more information available at http://www.weather.com/)

UPDATE: According to reports from The Weather Channel, and the National Weather Service, storms last night dumped up to 12 inches of rain over the warning area, with one area reporting 15 inches. The storm is currently advancing, creating the threat of up to 5 inches of rain in eastern Louisiana and western Mississippi today.

UPDATE: The current heat wave has resulted in over 3,000 record high temperatures over the US.

UPDATE: Weather Channel’s Stu Ostro says extreme weather linked to climate change.

Sources:

Wunderground: http://www.wunderground.com/blog/JeffMasters/comment.html?entrynum=2055

NOAA’s Storm Prediction Center: http://www.spc.noaa.gov/

The Weather Channel: http://www.weather.com/

Think Progress: http://thinkprogress.org/green/issue/

 

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