Heavy Rains Flood Southeastern Texas

In general the weather is nice throughout the lower 48 on this Monday April 18.  The major exception is in Southeastern Texas where a slow moving system has dropped nearly 10" of rain in places.  Radar estimates of rainfall are over a foot in places west of Houston

NWS Houston/Galveston radar estimates Saturday PM-now

This is what that much rain in a short amount of time will do

Photo via Reed Timmer/twitter 

On the ground

Via ABC 7/twitter

Off an overpass

Via CNN/Twitter

Unfortunately there are starting to be reports of fatalities.  Floods are the number one killer of Americans in a given year.  So what exactly is causing this?  At the surface a stationary boundary is situated across Central Texas with a upper low to the west in the Rockies and high pressure in the Eastern US

WPC Surface analysis 2 PM EST

The counter clockwise flow around the low and the clockwise flow around the high are allowing for convergence in Southeast Texas.  This is better shown at the mid levels of the atmosphere

12z NAM 500 mb vort 8 am

The upper low in the Atlantic is not moving and neither is the high in the Southeast.  As result of the upper low in the Rockies which dropped 4 feet of snow this weekend we have an "omega" block because the atmospheric pattern looks like the Greek letter Omega.  On Tuesday-Wednesday the jet stream will break this block temporarily (looks like the pattern returns by the end of the week but further east).  It will be slow to get out of Texas but the heaviest rain will shift north of Houston and east of Dallas into Arkansas and Louisiana.

WPC 1-3 day rainfall (begins 8 PM tonight ends 8 PM Thursday)

As Dr. Marshall Shepherd (U of Georgia, Florida State) described on twitter part of the problem with these heavy rain events is the amount of blacktop pavement that this water is able to just run down.  Combine it with outdated storm drain designs and some added warmth to the atmosphere and we have flash flooding problems.  On the other hand global warming isn't responsible for the omega block.  The same people who claim that also claimed our warm March was global warming.  Well in March there was very little blocking and a fast jet across the US.  As usual the truth is in the middle but very few people sit in the middle anymore.

Good luck to everyone suffering in Texas today.