The first significant rains have moved into Houston this afternoon and early evening as 1 to 3 inches have generally fallen across the area during the last six hours.
Rain accumulations from 12:30 p.m. to 6:30 p.m. Saturday. (HCOEM)
Houston’s bayous have thus far handled the inflow of rain, no doubt aided by the fact that the region’s parched soils have sucked up some of the water and rainfall rates generally have been less than 1 inch an hour.
If the rains hold steady like this there will be few problems. But will they hold steady or increase in intensity? The answer is that, for some areas, tonight will bring mostly steady rains. But for other areas things will get much more intense.
As expected, Houston today has so far only seen scattered light to moderate rain showers. However during the next few hours heavier storms are going to begin rotating into the region.
This won’t be the main event, but it’s going to soften up our soils for what should be considerably stronger storms later tonight.
Some of the latest forecast modeling continues to suggest the onset of this heavier rain, with rainfall rates of perhaps 3 inches an hour or higher, around 8 or 9 p.m. this evening. Such storms will have the potential to flood streets quickly.
Much of the latest modeling also indicates the very heaviest rains — locations where 10 or more inches might fall tonight — will come along the coast, from Matagorda to Galveston to Chambers and Jefferson counties. That doesn’t rule out inland counties, including Harris County, from such extremes, but that seems to be the way models are trending.
During the last few hours we have also seen favorable conditions for funnel cloud development, and most of the southern half of the Houston metro area is under a tornado watch until 10 p.m. tonight.
I’ll have a comprehensive update on the storms at 7 p.m. tonight.
Patricia has weakened into a tropical depression over central Mexico this afternoon, and it’s continuing to move north-northeast toward Texas. Although its circulation has diminished dramatically, its remnants will combine with an upper-level disturbance moving into Texas from the northwest, and also draw moisture from the Gulf of Mexico.
It looks something like this on the surface wind map:
Surface winds at noon. (earth.nullschool.net)
This will lead to a substantial rain event for Texas, including the upper Texas coast. The principal threat remains heavy rain, and more specifically very intense hourly rain rates that exceed the capability of roads and bayous to carry the water away.
The mountainous terrain of Mexico has shredded the once incredibly powerful Hurricane Patricia, and the system is now a tropical storm as it races northeast toward its soggy destiny with Texas. Patricia will combine with a slow moving cool front and ample Gulf moisture to create a potentially dangerous situation tonight in the greater Houston area.
RAIN ACCUMULATION
Forecast models continue to predict an extreme rainfall event for the Lone Star State, and it appears increasingly likely the heaviest precipitation today and Sunday will come along the upper Texas coast. To start with, here’s the latest precipitation forecast from NOAA’s Weather Prediction Center, essentially the best estimates from their meteorologists assessing all of the models for rain between this morning and the end of the event on Sunday night:
(Weather Bell)
The first thing you’ll probably notice is a staggering 11-inch bullseye over Galveston County and Galveston Bay. This indicates the kind of very, very heavy rain this system and its associated tropical air mass are capable of.
