I summed the heavy rain events (Liberty + Brenham + Davevang) for each day since 1951 and then totaled the events over three year periods. For Houston, that amount in a day typically causes street flooding and motorist inconvenience but poses no risk to life or property. OK, what about heavy rain events? For this review I defined a “heavy rain” as 4 inches or more in a day. The data shows variation but no trend for the last 120 years. This lack of a trend is confirmed by rain data for the “Upper Texas Coast” from NOAA’s Climate at a Glance website. Totals generally rose after the dry 1950s but have trended downwards since the 1980s. Of interest is that there’s no clear trend in annual rainfall. The plot of annual rainfall below shows considerable interannual variability. The three sites (combined) average about 46 inches a year, fairly typical for the eastern US. Liberty, roughly 100 miles east of the other sites, receives on average about 30% more rain than do Brenham or Danevang. Southeast Texas has an east/west gradient in annual rainfall, with eastern areas getting more rain on average. Below is a plot of annual rainfall at the three sites (combined) since 1951. This covers the time when atmospheric CO2 strongly increased.įirst, for background, let’s look at annual rainfall at the three sites. I looked at daily rainfall data for the three sites for the period 1951 thru 2014, a 64-year period. Here are the mapped sites, with Houston visible as the lighter-colored region in the middle:
Unfortunately, there are no USHCN sites in Houston but there are three climate sites nearby: Liberty, Danevang (love that town’s name) and Brenham, located east, west and northwest of Houston, respectively. The US Historical Climatology Network (USHCN) provides convenient online data from climate monitoring stations scattered across the US. Was this a random weather event or was it part of a trend toward more-frequent heavy rain, possibly driven by global warming? Several people drowned and property damage was substantial in a small part of the city. Very heavy rain occurred in the Houston, Texas urban area on Memorial Day 2015.
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