The Critical Turn North
We are now in the critical 72-hour window before Irma’s expected interaction with south Florida. The model runs overnight have been fairly consistent, but for a 72-hour forecast, there still seems to be a considerable amount of spread in the timing of the northward turn. I have been blogging about what is causing this northward turn since last Friday, which is a trough of low pressure now positioned over the eastern half of the U.S. I have also been mentioning that Irma would be breaking all sorts of records, which is certainly the case, as only three other Atlantic hurricanes have logged more time as a Category 5 hurricane than Irma.
What we know about Irma over the next few days
- Irma will be a major Category 4 hurricane, and perhaps even a Category 5, as it approaches south Florida.
- The likelihood of a landfall in south Florida is currently 85%.
- The severity of impacts to Georgia and the Carolinas will ultimately be determined based on whether Irma makes landfall along south Florida or if Irma tracks up Florida’s east coast.
- There is still a 55% chance that Irma will make landfall along the Florida Keys or points along the southwest coast of Florida.
- Several models also turn Irma northward before a south Florida landfall which would result in less damage to Florida.
- Based on my analysis of catastrophic model stochastic events, any Category 4 hurricane making landfall in south Florida will likely create at least a $10 billion insured loss event.
Uncertainty in Irma’s forecast improving
Although there is still a high amount of uncertainty in the short range forecasts, the evening forecast models are converging on the idea that Irma will be extremely close to south Florida by late Saturday night with a possible landfall early Sunday morning. I have seen only a handful of models that do not bring hurricane-force winds to south Florida. Most forecast models at this time suggest that winds in excess of 115 mph are possible across the major metropolitan corridor of south Florida. I expect Irma to grow in size as it approaches south Florida, with hurricane-force winds easily extending 50 miles from the center of the storm. However, if Irma tracks up the east coast of Florida, the strongest winds would stay on the right side of the storm, similar to what occurred with Matthew. Irma looks like it could be larger in size than Matthew at this point in time though, so hurricane-force winds would likely have a greater reach inland than Matthew even if Irma tracks up Florida’s eastern coastline.
— Philippe Papin (@pppapin) September 7, 2017
Depending on whether Irma makes landfall, the impacts beyond Florida could vary. If Irma tracks up the middle of Florida, it would likely be in a much weakened state as it tracks northward. If it stays just off the shores of eastern Florida, the hurricane would be in a much stronger state as it tracks up the coast toward Georgia and the Carolinas due to continuously being able to feed off the warm gulf stream waters, and it would likely be a major hurricane at any landfall points north. Currently, for this model scenario, the border between South Carolina and North Carolina has the highest likelihood of landfall at 60%.
With Irma’s forecast cone of uncertainty shrinking, the BMS iVision Verisk Climate wind swath product is providing its first views of what the expected wind damage across south Florida might look like as Irma makes its turn north. It should be noted, however, that this is just one scenario of many that is still possible.
At this time it is too early to determine storm surge. I expect the NHC to run scenarios based on the NHC official forecast beginning Friday. They have already issued storm surge watches for much of south Florida. Currently, Irma is not a worst case scenario for storm surge. At this point areas along the coastline could expect 5 – 10 feet of storm surge, which is highly dependent on storm movement and location.
At this point it looks like Irma should be relatively progressive, so unlike Harvey, it should not stall out over the Southeast. However, large amounts of rain in excess of 15” could still fall over Florida as Irma tracks northward over the weekend and into early next week. These rainfall forecasts will be revised over the next few days.
Irma’s Insured loss
Irma will likely already go down as one of the newest realistic disaster scenarios for the damage it has caused on the Caribbean islands, so I have little doubt the industry will be talking about its impacts to the area for decades to come. Irma passed 50 miles north of San Juan, Puerto Rico, last night. At that time, the strongest hurricane-force winds were on the north side of the storm and extended out from the center of the storm at an estimated 50 miles. This is important because it appears that the northern coastline of Puerto Rico was spared widespread damage as the strongest winds stayed just offshore, although some local damage is being reported across social media. This serves as a great example of why the storm track in relation to the radius of hurricane-force winds is critical in understanding the impacts we might see as Irma tracks up the East Coast of the U.S. The catastrophe modeling companies are releasing event sets to help determine these impacts, but it is premature at this time to share the details of these losses aside from saying the losses will reach into the billions.
Over the last several days I have tried to finding analog events to match Irma’s intensity and there are very few. Although there is less uncertainty in the forecast track today, there are too many different solutions, and how those solutions unfold could have a large impact on the heavily insured south Florida coastline. Given these sensitivities, a difference of even 20 miles can influence loss amounts by the billions.
The catastrophe modeling companies should start issuing their pre-landfall preliminary set of tracks tomorrow which will give some early estimates, but these estimates will also change. I think even tomorrow there will still be some uncertainty on the track Irma will take northward, either over Florida or off the coast. As I mentioned, in a search for Category 4 events that make landfall in south Florida, it is hard to find an event with under $10 billion in insured loss.
BMS Tropical Update – Hurricane IRMA GoToWebinar
Due to popular demand for today’s webinar on Hurricane IRMA (4p ET/3p CT), we have changed the weblink for the webinar.
Please use the link below to register for the Webinar.
Andy Siffert, VP/Meteorologist will be providing an update on Irma’s forecasted track and intensity.
Additionally, Julie Serakos, EVP and head of Cat Analytics will provide a modeling update and Kris Westall, COO and Urban Friesz, VP will provide an update on claims and accounting services.
Please join us for this important update.