Timeliness of Watches & Warnings Questioned After Historic Louisiana Flooding
Watches and warnings are critical components of community preparedness, and how those statements are worded, and the urgency they express, is critical to public compliance. In the aftermath of the historic flooding in Baton Rouge, questions are being asked as to the timeliness, urgency, and effectiveness of the issued watches and warnings.
Who is responsible for advising the public depends on what type of weather system is threatening an area or region. In the case of the system that caused the historic flooding in Baton Rouge, Louisiana, the job fell to the local National Weather Service Weather Forecast Office, and not the National Hurricane Center.
Tropical Cyclone versus Weather System
The system that impacted Baton Rouge with torrential rains began as a low pressure system situated over the Gulf of Mexico. The National Hurricane Center in Miami began monitoring the system in case it turned into a cyclone or hurricane. However, the system lacked markers that are seen in tropical cyclones, such as high wind speeds, warmer central air, and center circulating winds. Since it did not turn into a tropical storm or hurricane, the National Hurricane Center did not issue any advisories, nor was the storm named.
Instead, monitoring of the system for local impacts fell to the Weather Forecast Office (WFO) in New Orleans/Baton Rouge. The local WFO was monitoring the weather system and realized the potential for heavy rainfall and flooding on August 8, and thus began issuing weather advisories - nearly three full days before the system began impacting the area.
Local emergency managers participated in the first Webinar about the system that was held by the WFO on Tuesday to discuss the system's rainfall potential and its impact on rivers, flooding, and the possibility of flash floods.
Difficulty with Localized Predictions
One issue with the system was predicting the amount of rainfall that may occur and its potential localized impact. Meteorologist Kenneth Graham, noted that it is difficult to know precisely where the rain will fall, and the exact amount that is likely to fall in that particular location.
Also, the potential for rainfall amounts in one area to impact another location and its residents is also difficult to predict. Due to the terrain in Baton Rouge, however, flooding can be widespread because there is nothing to stop the water from spreading out.
— NWS New Orleans (@NWSNewOrleans) August 10, 2016
No Historical Reference for Rainfall Amounts Impacting Area
Another issue in this latest Baton Rouge flooding was the lack of historical reference - such rainfall amounts had never occurred in the area.
Due to growing concern about the unprecedented rainfall amounts occurring, and increasing concern over the devastating impacts, the local WFO made a rare move that is typically only allowed when there is an immediate and significant threat to life and property: It elevated the flash flood warnings to flash flood emergencies.
All time records on many Louisiana rivers. You can't use history or your experience to judge the impacts. Please heed warnings! #lawx
— Ken Graham (@wx4keg) August 13, 2016
Some believe the storm lacking a name impacted the perception of its threat to residents, but meteorologists noted that just because a weather system lacks a name, its impacts can still be severe, causing dangerous conditions that can even be deadly. Still, many residents believe the warnings lacked an urgency, which may have caused some to not take the potential flood warnings seriously enough.
Some residents also blame the lack of media coverage and its slow response, which did not occur locally until August 11, when the National Weather Service was already issuing emergency warnings.
Local Weather Forecast Offices
The National Hurricane Center believes that local WFOs should always be consulted for the best information about local area impacts. Just because a storm does not have a name or is not categorized, do not underestimate its potential, heed watches and warnings, and monitor weather radios for up-to-date weather related information.