How Much Rain Could South Louisiana Receive This Weekend?

Forecasters with the National Hurricane Center are continuing to monitor an area of disturbed weather in the southwestern Gulf of Mexico this morning. The Hurricane Center has given the system a 60% probability of becoming at least a tropical depression by Thursday and a 90% probability of becoming a tropical cyclone at some time during the next five days.

As of now, the greatest threat the system seems to be bringing to any coastal area it impacts is the threat of flooding rainfall. Unfortunately one of those coastal areas the system could impact is the coast of Louisiana.

You often hear weather guessers on TV and Radio speaking of "forecast models". Those models are scientifically fine-tuned speculation based on current and supposed future conditions. Since Nature has its own way, sometimes the model runs can be really accurate, other times they can miss by a lot.

However, the past few decades have seen great improvement in the accuracy of almost all forecast products, including the longer-range models that scientists use to forecast the impacts of tropical systems.

The speculation with the system that is currently in the Gulf of Mexico is that it will drift to the north later today and impact South Louisiana with very heavy rainfall beginning late in the day Friday and lasting through Sunday.

Just how much rainfall a particular area will receive will be highly dependent on the actual track of the center of this disturbance. Forecasters believe that the majority of convection and rainfall associated with the system will be located to the north and east of that center of circulation.

Yesterday, KATC TV's Chief Meteorologist Rob Perillo posted some of the more respected forecast models rainfall potential with this system. And the numbers posted are not really good if you happen to live in an area where high water is a concern.

The GFS or Global Forecast System rainfall projection is suggesting that the heaviest rain will fall across the heart of Acadiana, generally from the Lafayette area eastward across the basin. Yes, that model forecast suggests that the Lafayette area could see in excess of six inches of rainfall.

Now the GFS isn't the only forecast model that is showing high rainfall rates for Acadiana. This is the rainfall potential graphic based on the European Weather Model.

As you can see the Euro Model doesn't call for six inches of rain in Lafayette. It is only suggesting a rainfall total of four and three-quarters of an inch. The difference in totals is that the Euro Model has the system moving faster than the GFS model does.

One major sticking point that Rob Perillo brings out in his blog on the KATC Website is this. It's not as much about the rainfall total as it is about the rainfall rate. Drainage systems around the region can handle a lot of rain over a large time frame. However, a deluge of two to three inches of rain in an hour, which is quite common with a tropical system, would create the most chaos and damage in South Louisiana.

The bottom line is this. We are going to see a lot of rain with this system. Today and Thursday would be your best days to plan ahead and make preparations for a major rain event.

So, it might be a good time to catch up on your television viewing. If you like game shows then you probably already knew about this.