As a retired National Weather Service meteorologist, I was surprised by a quote on Hurricane Laura’s forecasts in Tuesday’s lead article. Louisiana Department of Children and Family Services spokesperson Catherine Heitman was quoted as saying, “But the shifting path of the storm forced DCFS officials to scramble to get hotels in areas they weren’t expecting. We originally thought the storm was going to hit in southeast Louisiana.”
Though the surge from this storm was over-forecast, the official track forecast was highly accurate, singling out Southwest Louisiana starting with the 5 a.m. forecast Sunday. That’s almost four days before Thursday morning’s 1 a.m. landfall.
There was little variation in the track since that time with New Orleans staying outside the cone of uncertainty from 11 a.m. Sunday onward. Only by going back to the time when Laura was a modest tropical storm Friday did the track point to a position offshore from Southeast Louisiana.
You can’t take a five-day track forecast to the bank. The forecast is only valuable for some preliminary contingency planning. If you looked at the size and shape of the uncertainty cone that Friday, a landfall was likely anywhere from Southwest Louisiana to Panama City.
Many residents fall into this trap. They want to make decisions based on a track as soon as the storm is named, even if it is five days or more from landfall. Early forecasts are often poor because weak storms experience center jumps and don’t have the wealth of hurricane hunter observations that the prediction models thrive on.
Hurricane track forecasts tend to crystallize about three days before landfall as the cones shrink. The challenge is knowing what preliminary actions to take early but waiting until later to finalize decisions.