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BMS Tropical Update 9/2/2016 12 PM CDT

Hermine made landfall near St. Marks, Florida, around 1:30 am EDT with winds of 80 mph, making it a strong category 1 hurricane at landfall. As predicted, flooding rains, storm surge and tree fall have been the biggest insured impacts and overall should result in a minimal loss for the insurance industry. The storm has now weakened to a tropical storm near Savannah, Georgia. However, as mentioned in previous posts, Hermine will continue to track overland for the next 24 hours and exit the U.S. coastline near the outer banks of North Carolina. Unfortunately however, as we have seen over the last 16 days, the overall energy of this system is persistent. It now appears that Hermine won’t go away any time soon. After Hermine exits the East Coast, it will become a “post tropical” storm. This means that the storm will actually grow in size, and given that the water is as warm as it can possibly get off the East Coast of the U.S., it will continue to fuel Hermine’s circulation.

Below is a look at the warm sea surface temperatures off the East Coast.

Aug31_SST

Rule of thumb: 26C can maintain a tropical system. 28C can easily intensify it.

After Hermine moves off the East Coast, it will likely merge with a large-scale mid-latitude trough which will slow Hermine’s overall movement. Therefore, all but a few of the forecast models suggest that Hermine will stall over a 3-to-4-day period.

ECMWF_Sept2_Ens00z_Hermine

ECMWF ensembles: Most members “Stall” Hermine, some members hook inland, others out to sea. Still some uncertainty watch closely.

Hermine_Sept2_12z_HuModelsjpg

Where Hermine takes turn to North and stalls will be an important factor for Mid-Atlantic impacts. The farther east, the better

 

This is bad new for the barrier islands and beach communities along the Mid Atlantic. Historically high amounts beach erosion will occur with a very constant wind direction for several days. Keep in mind that this constant flow of water will continue to push water into the back bays, and this water will have no outlet. This will result in major coastal flooding, and perhaps even record flooding, along the New Jersey coastline.  The latest extra-tropical storm surge map forecast can be be found here:

njcapemay_Stormsurge

Major to record flooding forecast Sunday night for many stations along NJ coastline. Record at Cape May is 9.0 feet from January Nor’easter. These forecasts will change several times a day and will depend on the track of Hermine.

 

The winds over this 3-to-4-day period will be very similar to a strong nor’easter, and regardless of how the system is classified and where it might wobbles off the East Coast, tropical storm force winds could blow in many areas of the coastline. There is even a chance that Hermine could regain hurricane status. I have already made my point this week that the NHC seems to be treating the hurricane classification as a classroom lecture. Right now, the storm’s classification is far less important than its ultimate impacts.

NHC_WindProb
There are very few storms of this size that have stalled off the East Coast. One of those storms was the Ash Wednesday Storm (1962) and Hurricane Esther (1961), both of which produced significant insured impacts along the East Coast.

 

Esther_1961_track

Hurricane Esther was the first large tropical cyclone to be discovered by satellite imagery. https://en.wikipedia.org/wiki/Hurricane_Esther#New_England

Great video talking about the storm of 1962 and the lessons that have been learned and why one might not see the same type of damage today.

BMS Tropical Update 9/1/2016 12 PM CDT

Historically, Labor Day weekend is no stranger to hurricane impacts to the U.S. Coastline, and this year is no exception. After all, the peak of the season is just ten days away. With winds of 65 mph, Tropical Storm Hermine is less than 10 mph from being classified as a hurricane. And located 170 miles southwest of Apalachicola, Florida and 220 miles west southwest of Tampa, Hermine threatens insured losses. Several models are now coming around to the idea that the long-standing Florida hurricane drought of 3,966 days will soon end. As a reminder, the last Florida landfalling hurricane was Wilma that struck on Oct 24, 2005, near Cape Romano. (You may also recall category 2 Hurricane Arthur, but despite its landfall in 2014, it failed to cause significant insured losses.)

So will Hermine cause large insured losses? Unfortunately, we cannot depend on historical data to help predict since there is little hurricane history in Hermine’s expected path. The three best analog events for the forecasted landfall location are Hurricane Alma (1966), Tropical Storm Allison (1995), and Storm #5 (1941). Storm #5 and Alma were category 2 hurricanes at landfall, so finding a good benchmark historical hurricane to estimated insured loss is difficult in this case, but given these historical events and the hazards outlined below, a multi-million dollar insurance industry loss cannot be ruled out.

The factors that will lead to insured loss at this point will be multifaceted.

Flooding Rains and Storm Surge

Many areas along the Florida Gulf Coast have already seen significant rainfall. Here is what has fallen so far.

RainfallSofar_Hermine
Many areas of northern Florida will see between 3” – 12” more of rainfall through Saturday. And although the forecasted area of landfall is mostly made up of large tidal marshlands resulting in a coastline that is not as densely populated, it is very prone to storm surge.

Storm surge could top several feet in some areas, despite the fact that Hermine will be a minimal hurricane at landfall.  In fact, data suggest Hermine has the kenetic energy of a category 1 hurricane already.

Wind

Using Verisk Climate forecasted wind swath, BMS clients can now better understand wind impacts to specific risks. This high-resolution model wind field shows hurricane force winds rapidly weaken inland due to frictional effect.

iVision_Hermine_VC_WindsSept1

But this does not mean the winds won’t be strong enough knock down some trees, especially given the moist soil conditions in the area. In fact, this section of Florida is not just beach. There are quite a few trees in the north, especially around the Apalachee Bay. When you combine the foliage with the lack of a hurricane activity over the last 10 years, a natural culling of weak and damaged trees and branches can be expected. And, of course, even tropical-storm force winds can cause minor damage to structures.   One also can’t rule out a tornado or twoSoutheast_biomass

 

 

After Florida Landfall
Even though modeling over the last 14 days has not been the best for Hermine, it is starting to come around. Much depends on the track Hermine takes once inland over Florida. If Hermiane tracks back out over the warm waters of the gulf stream, expect Hermine to re-strengthen into a powerful coastal storm. There is some model disagreement about whether Hermine will become a hurricane again, or a post-tropical storm, but regardless, high surf and strong winds will result. Some models even stall Hermine for a few days off the New Jersey coastline near Labor day. The strength really depends upon whether Hermine stays overland along the east coast of the U.S. or just off shore.

Lastly we are still watching Invest 92L  in the Atlantic.  It is fighting dry air and weak so there is no threat at this point in time of development.

Interesting Point
The first Tweet was sent on March 21, 2006, months after Wilma in 2005. Hermine is likely Florida’s first hurricane in the Twitter era.