Common in the articles about the recent Louisiana flood are situations like water starts coming into the house and there is a frantic rush to safety.
The question which comes to mind is whether or not there were weather forecasts about this so people had ample time to leave? Did people just ignore the warnings? Or were the forecasts wrong: for example 5 inches of rain instead of 20 inches?
My understanding, based on reading various news stories, is that very heavy rain was predicted at least a couple of days in advance, and warnings of flooding potential were issued. But, in some areas, the amount of rainfall was simply far more intense than even the meteorological models had indicated (nearing or surpassing all-time records).
It looks like the issue was a combination of (a) floodwaters rising extremely rapidly, and (b) areas that had never previously had issues with flooding (and, thus, residents may not have been initially worried about having to evacuate).
A couple of links to stories about the situation:
Not only what kenobi 65 wrote, but the weather system that came through stalled over the Baton Rouge and Lafayette metro areas. The system started at the Florida Panhandle and was slowly working its way westward before it parked over Central Louisiana. One aspect that was not forecast in advance was the exact length of the stall. People won’t evacuate if merely anticipating “hard rain overnight” – especially not people in homes well over sea level that have never flooded in recent memory.
Keep in mind that the recently-flooded areas are places that well withstand the worst effects of hurricanes that have whipped the Louisiana coast over the years. The recent flooding was a rainfall/river-cresting event affecting people simply not accustomed to natural disaster threats the way people are in and around New Orleans and the coastal communities.
The WU Wonderblog had a couple of posts on this event days in advance. One warning was posted on Aug 5th, and a more detailed one on Aug 8th.
It was known that it was going to a lot of heavy rain, but as with all forecasts the exact amount was not predictable that far in advance, as well as the difficulty of forecasting the effects of such an unusual amount of rain. Events like this can cause havoc in unexpected ways just because they haven’t happened in a long while, if ever.