Hurricane Sally to bring “historic flooding” to Gulf Coast region

While hurricane Sally’s wind speeds have remained relatively static throughout today as a Category 1 hurricane, the expectations for rainfall from the storm have increased, with the NHC warning of a “historic flooding” event for the northern Gulf Coast region.

Update, September 16th, 07:30 BST: Hurricane Sally intensified to category 2 strength with winds of 105 mph at the last-minute prior to landfall, raising the prospects of more wind and perhaps surge related damage than last nights forecast suggested. The rain threat persist, with storm totals of as high as 16 inches already recorded. More in our latest update here.

Original article: Hurricane Sally continues to meander slowly towards the Gulf Coast, with maximum sustained winds currently pegged at 85 mph and higher gusts, while minimum central pressure is down to 983 mb.

Sally’s winds had made it to 100 mph last night, but the storm has since weakened a little as it interacts with the coastal region.

So now, the expectations for the wind and surge intensity and height of hurricane Sally has lessened somewhat, but the expectations for the rainfall totals from the storm continue to increase.

Hurricane Sally current position and forecast path:

The NHC says that little change in strength is expected as hurricane Sally moves towards landfall, but notes that it remains a dangerous hurricane.

You can see a modelled intensity forecast for hurricane Sally below (from TropicalTidbits.com):

Sally is sluggishly moving at just 2 mph and with outer rainbands already raking the coastal region, rainfall totals will add up over a particularly prolonged period with hurricane Sally.

Storm surge totals are now expected to be 3 foot to 7 foot across a wide area of coastline around the Mississippi, Alabama, Florida coastline, but the earlier concerns about overtopped levees in the New Orleans area have lessened, as Sally moved further east.

A peak storm surge forecast map for hurricane Sally from NOAA can be seen below:

The rainfall situation and the potential for significant inland flooding though has become particularly concerning.

The NHC said, “Sally is forecast to produce 10 to 20 inches of rainfall with isolated amounts of 30 inches along and just inland of the central Gulf Coast from the western Florida Panhandle to far southeastern Mississippi. Historic flooding is likely with extreme life-threatening flash flooding likely through Wednesday. In addition, this rainfall will lead to widespread moderate to major flooding on area rivers.

“Sally is forecast to move inland Wednesday and track across the Southeast producing rainfall of 4 to 8 inches, with isolated maximum amounts of 12 inches, across portions of southeastern Mississippi, southern and central Alabama, northern Georgia, and the western Carolinas. Significant flash and urban flooding is likely, as well as widespread minor to moderate flooding on some rivers.”

These rainfall totals are akin to other slow moving hurricanes of recent years, such as Harvey and Florence, which both caused significant flooding.

As ever, flood losses tend to see a lesser percent flowing to private reinsurance capital, than wind or surge related damages, though the economic and also NFIP hit could be more significant it now seems.

It would take a particularly significant flood event for the NFIP’s reinsurance program to come into play. But with forecast storm totals of up to 30 inches that cannot be ruled out.

It’s also worth noting that insured values and concentrations of insured risks are said to be higher with hurricane Sally, than they were with recent hurricane Laura.

Whether that means a more meaningful insurance and reinsurance market impact remains to be seen over the next couple of days, as the initial storm impacts and the prolonged rainfall situation plays out as Sally moves slowly ashore.