Hurricane Harvey – A Retrospective
September 1, 2017
by Joseph D’Aleo, Certified Consulting Meteorologist
Hurricane Harvey was a major hurricane at landfall on the Texas coast. That put to an end a streak of 4,000-plus days (nearly 12 years) without a major hurricane (CAT3+) landfall on the mainland. The previous record was 8 years back in the 1860s.
The storm surge and strong winds did major damage near the coast, but, even in a weakened form, Harvey did incredible damage inland due to the fact it stalled, keeping the tropical deluge going for many days. Harvey produced catastrophic river, stream and urban flooding. By the time it exited the state late this week (by the time you are reading this) it will have produced rains that might exceed the modern record for tropical rain events in the U.S.
Over 4 feet of rain may fall in some location(s), which would be a record. The previous record was set with what was earlier a weak tropical storm Amelia in 1978 that dumped 48 inches in Medina, Texas, as it stalled for a full week. Six of the top 10 wettest tropical storms since 1950 were in Texas, all 10 were Gulf storms. What made these storms so wet was the fact that they drew on moisture from the very warm Gulf waters and most, like Harvey, stalled over an area for up to a week.
There have been many flood disasters in the Houston area, even dating to the mid-1800s when the population was very low. In December of 1935 a massive flood occurred in the downtown area as the water level height measured at Buffalo Bayou in Houston topped out at 54.4 feet. This Monday morning, the water level in the same location reached near 39 feet (15 feet lower than in 1935) before dropping.
The trend has been down in recent decades. The last major hurricane in Texas was Bret in 1999.
For the U.S., the trend is down too. We have had seven land-falling hurricanes this decade. Unless we add eight more in the next few months and in 2018 and 2019, this decade would be the quietest since 1850.
Ocean temperatures control where in the tropics hurricanes form. The oceans reach their warmest temperatures in late summer and early fall, and, not surprisingly, that is when the peak storm seasons are.
In the United States, of course, we focus on the Atlantic in the late summer and fall. The eastern Pacific also generates hurricanes that sometimes affect Hawaii. Some of those storms bring heavy rains to Arizona and southern California if they turn north and most fast enough before they can dissipate. The central and western Pacific is on average the most active region because the ocean heat content there is the highest in the global tropics.
In El Niño summers, hurricanes are most common in the eastern and central tropical Pacific. In La Niña years, it is the Atlantic and western Pacific where storms threaten more. The Atlantic goes through cycles of warm and cold. A warm Atlantic favors more hurricanes with landfall threats on the East Coast especially when La Niñas occur. The Atlantic is at the latter stages of the warm mode that started in 1995.
This summer after a try at El Niño this spring, the waters cooled and a La Niña pattern is evolving. The warm Atlantic and evolving La Niña conditions raise the concern that Harvey may not be the last storm to affect the mainland this season. We need to stay wary, even here in the Northeast.
So you know, while we were all enjoying the eclipse a week ago Monday, Harvey was more than a day away from regenerating in the western Gulf of Mexico. These storms can develop and be a threat very fast. You and your family should print off and review the one page hurricane safety tips from NOAA here: www.redcross.org/get-help/how-to-prepare-for-emergencies/types-of-emergencies/hurricane#About.
And say a prayer for the good people in Texas.
Joe D’Aleo, a Hudson resident for the last 25 years, co-founded The Weather Channel and served as its first director of meteorology back in 1982. With more than 40 years of experience in professional meteorology, he has served as chief meteorologist for Weatherbell Analytics since 2011. As a fellow of the American Meteorologist Society, he has testified about weather and climate before federal and state legislatures and taken the science lead on legal briefs to the D.C. circuit and U.S. Supreme Courts. Let Joe know what you think at firstname.lastname@example.org.