Tracking the rain

WeatherMap Imelda update: The storm went easy on us last night, but we are only at halftime

Stephen Uzick
Sep 18, 2019, 11:08 am
College of DuPage

Good morning everyone. By and large the Houston metro area made it through last night unscathed. While I know people are already starting to label this storm a bust, we are really only at halftime here. Last night the storm progressed further inland than originally expected which is what raised my concern for heavy rain last night. Thankfully that did not develop over the city and most spots ended the day yesterday with very manageable rainfall totals in the 2-4 inch range. Further south though coastal areas of Brazoria and Matagorda counties got absolutely hammered. Spots near Freeport for example picked up 15-20 inches of rain yesterday. So with the first half in the books lets take a look at where things go from here.

From the time concern really began to rise regarding this storm back on Monday the Wednesday afternoon through Thursday morning period was really the period we were most worried about. This morning the center of the storm has broadened as it "unwinds" now that it is over land, however this does not mean the rainfall potential decreases. On radar we can see that the center is near The Woodlands and strong bands of storms extend well to the south along the coast and curve back up into the Beaumont area.


10 AM radarCollege of DuPage

Over the course of the day today and into tonight I expect coverage of heavy rain to move further inland as the center continues pulling off to the north. Two of the high resolution short range models we use have continued to show an intense band of storms developing along the I-10 corridor between Houston and Beaumont late this afternoon and into tonight. We will have to watch how this develops as the afternoon commute could be impacted.

One model's simulated radar Wednesday morning thru Thursday lunch time.Weathermodels.com


Another model's simulated radar for Wednesday morning thru Thursday evening.


Foretasted accumulations through Thursday evening from the model in the image above


If this band does indeed develop and parks itself over the wrong place flooding will be a concern. With these models try not to focus on pinpoint locations, rather look at the general idea that another round of heavy rain is still in the cards. While it does appear that the most likely location for for bombs of very high accumulations has shifted a bit to the east, say east of HWY 59, it is not time to let or guard down yet.

I know people are itching to say this storm amounted to nothing but hype, but it would be unwise to declare it dead yet. This area has a history of storms that bring a light first punch only to return with a knockout blow a day or two later. While I am in no way comparing the impacts of this storm to Harvey or Allison it is important to remember that both of those storms had people declaring them busts halfway through before the second round came. If by Thursday night all is well, I will personally declare Imelda a bust, but we are not there yet.


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WeatherMap: Severe storms Friday Night

National Weather Service

It has been a long while since we have had any significant weather to deal with in our part of Texas - really since Imelda back in September. However the atmosphere will become less benign in the next 24 hours giving us our first taste of severe weather (not including flooding) since last May. I won't get into the nitty-gritty of why storms are going to happen, however it is worth noting that the type of dynamic atmospheric set up being foretasted would be noteworthy even in "severe weather season" (ie the spring), no less in January. Will this be the apocalypse? No. However, it has been a long time since we have seen storms as strong as the ones being forecasted, and the timing (Friday night) makes it significant as it will be dark and people are more likely to be out and about. So lets get to it:

What: A strong storm system will be making its way across Texas on Friday with the atmosphere being primed out ahead of it with strong winds off the Gulf pumping ample warmth and moisture into the area. As this storm system approaches storms there will likely be two phases of storms we need to watch out for.

Phase 1 will be individual storms that manage to form during the late afternoon or early evening on Friday. While the odds of this happening are less than the storms in Phase 2, impacts could be just as, if not more, severe *if* it happens. These Phase 1 storms would be what are called discreet supercells. These are storms that exist on their own, not part of a larger line or blob. It is with these storms that large hail and a strong tornado is *possible*. Again, while there is good certainty that if they can develop they could be significant, there is a high level of uncertainty that they will develop. It is the storms in Phase 2 that will likely affect everyone. So lets move on to those:

Phase 2 storms will come in the form of an intense squall line moving from west to east across the area. The hail potential in these storms will be limited, however there is a rather significant risk of high winds (70-80 MPH+) and isolated tornadoes (weaker than what you would see from Phase 1 storms, but a tornado none the less). Also, the lightning will probably be spectacular. Let me speak to the Phase 2 tornado threat for a moment. Often with an intense line of storms small "kinks" can develop in the line causing rotation and a tornado. Usually the resulting tornado is very short lived (sometimes so fast it appears and disappear before the radar can spot it) and "relatively" weak, meaning weaker than its great plains cousins. However these types of tornadoes still pose a danger particularly to those caught outside or in a car. Make sure you have a way to receive warnings (ie. your phone), especially if you plan to be out Friday night.



Model simulated radar for Midnight Friday nightWeathermodels.com


When: Phase 1 storms, if they develop, would be some time during the late afternoon or early evening, but would be widely scattered. Phase 2 should push into the area as an intense line of storms somewhere between 11 PM and 2 AM

Where: Phase 1 would likely affect those further north and east. Phase 2 storms will get everyone. Again, it is not guaranteed that the part of the line that moves over your exact location will have damaging winds or a tornado, but no one is completely safe from that either.

While rain may be hard enough to cause very isolated spots of high water, the storms will be moving far to quickly to cause any real flood issues. After the storms move through this weekend looks great.

If anything changes I will be back with an update - and as always you can find me on Twitter @stephenuzick

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