Margin of error very slim now
As tough as this is for me to say, we are now in a window of model error (48 hours at about 50 miles) that suggests we are at the point where south Florida will likely see a catastrophic hurricane landfall. Based on some scenarios, this could be a historic and even game changing event for the Florida insurance industry. However, without yet knowing where Irma’s turn to the north will be, there is still some uncertainty around the exact impacts from the storm. Given how the models are now consistently suggesting a landfall location between Key West and Miami, several catastrophic scenarios are likely depending on the track. The consensus at this time seems to be that the landfall location could in the middle of the Florida Keys by early Sunday morning.
If there is any good news, it’s that as of this morning Irma is now a high-end Category 4 hurricane, likely due to an eye wall replacement cycle overnight. However, I feel this small downward tick in intensity will be short lived because some of the warmest sea surface temperatures in the world are in the southern Bahamas, and Irma is expected to track over this area. In general, I feel that Irma will be a strengthening storm as it heads toward the coastline, rather than weakening like Rita and Katrina did. Also, the overall environment continues to have light wind shear, so at this time it is expected that Irma will be a high-end Category 4 or low-end Category 5 hurricane with winds of around 155 mph as it nears the southern Florida coastline. This is likely near the building code requirements for most residential structures in south Florida. Of course, every building’s construction and the surrounding frictional effects will ultimately determine the damage at any given property.
Florida has some of the best building codes in the U.S. These codes were largely developed from past major hurricanes and will be tested with Irma. Source; IBHS
Summary of Impacts
- Wind impacts will depend on slight east or west movements in track over the next 48 hours, with local building construction type and surrounding frictional effects ultimately determining damage. At this point, it is expected that the Florida peninsula will see damaging winds.
- Storm surge is also dependent on track. The current storm surge forecast suggests that the Florida Keys and southwest coast of Florida could see the highest storm surge values of around 9 feet.
- With Irma being a progressive storm, rainfall is expected to be around 15 inches
As suggested a few days ago, Irma will continue to grow in size. Irma is a much larger storm than many past hurricanes that have impacted Florida. In fact, this is a graphic put together by CIMMS/NASA that shows the comparison in size between Category 5 Andrew 1992 and the much larger Category 5 Irma as of yesterday.
Hurricane-force winds are currently extending outward up to 70 miles from the center, with tropical storm-force winds extending outward up to 185 miles. This means virtually the entire Florida peninsula will likely experience damaging winds regardless of track. The exact track, however, will determine where the core of the highest winds in the eye wall will be, about 30 – 40 miles from the center of the storm. Therefore, Irma’s exact track is still critical to understanding the total insured loss.
If we continue to follow the best performing ECMWF model, it puts a landfall location in the lower Florida Keys. This suggests that the winds will be just away from the urban core of the tri-county Miami area, lowering the expected insured loss, but any shift back east would increase this expected loss.
This is last night’s ECMWF model wind swath from Weatherbell. It only shows one scenario of expected winds across south Florida.
This is the BMS iVision Verisk Climate 3-sec wind swath. It is just one possible scenario at this time, but take note of the detailed frictional effect within the model.
Like the wind impacts, storm surge impacts are also highly dependent on track. Based on the NHC’s very detailed storm surge forecast, the Florida Keys and parts of southwest Florida will likely see the largest storm surge heights. The current surge value predictions in the Miami area are not likely to throw watercraft off their moorings, which would be critical to insured loss estimates given the high concentration of watercraft along the southeastern coast of Florida. However, with a change in track and if the storm moves up the coast, I expect these east coast storm surge values to increase putting watercraft at risk. Also, storm surge needs to be watched carefully in the Jacksonville area as Irma tracks northward.
Since Irma will likely be progressing up the Florida coastline and not stalling out, the rainfall amounts should be more typical of a landfalling hurricane. Quantitative precipitation forecasts are currently suggesting upwards of 15 inches of rain.
Latest NWS rainfall forecast.
We have seen in the past that it does not take much rain in the Miami area to cause flooding, due to poor drainage and the built-up urban environment. Other areas to watch are the local channels and possibly the Lake Okeechobee level, which is currently at a low level. However, dikes that hold water in the lake are a known hazard and have grabbed national attention as critical infrastructure that needs to be shored up.
Current water level of Lake Okeechobee. Real-time information can be found here. http://www.weather.gov/mfl/lakeokeechobee
Longer Range Forecast Irma
Just like the impacts to south Florida are dependent on the track shifts of west or east along the Florida Peninsula, the impacts to points north could vary as well. Currently, it appears that a west track is favored up the western side of Florida, which would keep the center of Irma over the Florida peninsula for much of the track and starve it of its energy as it moves northward. The negative aspect of a Florida track is that the entire east coast of Florida would likely see stronger winds, with a decreasing wind field as Irma tracks into Georgia and tropical storm-force winds across South Carolina early next week.
As mentioned in the last few blog posts, small shifts in Irma’s track will ultimately result in major differences in the outcome of insured losses. This is still the case today. Regardless, it is safe to say that Irma will likely be one of the costliest storms to impact the insurance industry. Irma’s track is very similar to some of the realistic disaster scenarios set up by rating agencies. These scenarios often suggest over hundreds of billions of dollars in insured loss. It is likely that the insured losses from this storm will at least be in the tens of billions of dollars, on top of over tens of billions of dollars in losses already from Irma’s strike in the Caribbean.
We will be able to have a better grasp on the exact magnitude of this event by tomorrow, as we will have a better understanding of the turn northward that will determine not only the south Florida impacts, but also the losses that may occur in other east coast states.
Replay of Special BMS Irma Webinar
Due to the special forecast situation and potential impact on the insurance industry, BMS Catastrophe Analytics held a Webinar on September 7th which provided the latest on Irma, its forecasted track and impacts for the insurance industry.
Quick note on Jose
As we know, catastrophe models are built on the concept of clustering. Hurricane Jose was upgraded yesterday afternoon to a major hurricane, heading for the northern Lesser Antilles and hitting the same areas that Irma hit with a peak intensity of 185 mph on Wednesday of this week. Please keep in mind that because of the widespread devastation seen from Irma, the vast majority of structures in these areas are already unsafe. In the long-range, Jose is expected to stall north of the North Caribbean during the middle of next week, with some models then tracking Jose west towards the Bahamas or eastern seaboard of the U.S. I will be watching this closely next week.