As the 2017 hurricane season continues to threaten more damage to the eastern United States, the Caribbean and elsewhere, Dr Tim Hall, Dr Richard Dixon and the InsuranceLinked editorial team will continue to follow developments on this live blog. It takes over from the Harvey and Irma blog and the Monte Carlo blog.
A footnote on ex-Hurricane Ophelia that hit Ireland on Monday. Around 15 hours prior to the centre of the low hitting Ireland, the NHC were still analysing this as a tropical system (at 10pm UK time on Sunday). The chart below shows the frequency of all tropical systems in the HURDAT2 database (http://www.nhc.noaa.gov/data/hurdat) that have been measured at 75 kt or greater. Clearly Ophelia is anomalously far east for hurricane of this strength.
Yes, records are there to be broken – and records will always be broken and this could easily be a one-off anomaly, but also with Irma being anomalously far east for a 160 knot Cat 5 earlier in the season compared to historical records, there is a need in our industry to have a good think (and engage with academia) about hurricane behaviour in the presence of seemingly ever-rising Atlantic basin temperatures. Do storms form further east as the area of warm seas widens? Are we seeing a propensity towards higher intensities as the seas warm? Is there an overlapping between the hurricane and extra-tropical seasons that we need to take care of in risk models? These are just an example of the questions that for me have arisen from this hurricane season.
RMS estimates economic losses from the Californian fires to be between $3 billion and $6 billion. Insurance losses from Nate are likely to be less than $500m.
Moving right along in this impressive season … There’s a significant chance that Hurricane Ophelia will make landfall on Ireland early next week, either as a hurricane or a transitioned extra-tropical storm with hurricane-force winds.
Six foot surge in Pascagoula Mississippi …
Nate’s forward speed got as high as 26 mph. For some perspective I’ve calculated the maximum forward speed from the HURDAT2 database and the attached picture is the maximum historical forward speed in 2×2 degree lat/long boxes. Provided my maths is right here, Nate could be the fastest-moving Gulf hurricane.
With this in mind, Nate may be of interest during and post-event from a model evaluation standpoint:
1) Nate is moving very quickly and it will be very interesting to see how this plays out in terms of damage: specifically, the impact of duration. The two main cat model vendors have very different views on the impact of duration and this could be another useful data point towards our understanding. We also have Harvey at the other end of the scale that approached Texas extremely slowly: so two good data points this year on the wind duration issue.
2) I’ve read discussion about surge loss impacts potentially being greater than wind loss impacts for Nate. If this is the case, it would be interesting to compare the wind vs. surge impacts post-event against the wind vs. surge loss splits in stochastic sets in this part of the Gulf for similar strength/forward speed simulated events.
3) Simply from an event set perspective, the anomalously high forward speed is a useful stress-test of stochastic event set flexibility. Does the event set of your model(s) of choice have events with forward speeds of 25+ mph in the Gulf?
Friday’s Swiss Re Cat Bond Total Return index (SRCATTRR) is 7% down since the end of August.
Here’s a graphic showing 2017 storm counts accumulated to date (red) and comparing them to the long-term historical mean (blue), as well as to forecasts from my stochastic track model (yellow) driven by warm 2017-like sea-surface temperatures (SST). The warm-SST model much more closely matches the high 2017 activity then a long-term mean. The model also forecasts locally-resolved US and Caribbean landfall rates. These are available upon request (firstname.lastname@example.org).
PR rivers are breaking their banks. Check out the USGS flow rate for the Rio Mauna in SE PR below on a logarithmic scale! And the consequences for such river flooding, here in the streets of Guyana on the southern coast.
Parts of SE PR are seeing strong storm surge. Here’s the water-level record at Yabucoa Harbor, peaking near 6ft above forecast tides around 6am local. In addition to driving severe coastal flooding, the surge exacerbates the inland rain-driven flood by inhibiting drainage.
Maria’s eye made landfall on SE PR about 6am today as a high-end Cat4. In addition to the catastrophic wind damage, there will be extreme flooding. Many eastern PR streams are already at major flood level as of 6am (purple symbols) and 12-18 more inches of rain are expected through Friday. In addition, at least several feet of surge will inhibit river drainage. Expect big flood and mud slides.
The last 6-9 hours has shown a very rapid change in the structure owing to an “eyewall replacement cycle” (EWC) – essentially meaning that Maria is making landfall weaker than it was about half a day ago, but still incredibly damaging. However, an EWC also typically widens the area that gets affected by the strongest of the winds. The left plot below roughly highlights the width of the eye and its projected path from earlier this morning before the EWC. The right plot shows the width of the eye and its path post-EWC. In terms of losses, clearly there is likely a wider area that will get eyewall winds: this could also impact the area that will receive the highest surge, too.
From a loss perspective this new eyewall seems to engulf the northern coast around San Juan and suggests a potentially worse outcome than earlier this morning.
Maria’s central pressure has dipped to an astonishing 909mb, ranking right now as the 10th deepest hurricane ever in the HURDAT record (1851-2017). It’s max sustained winds are 175mph, deep into Cat-5 territory. Perfect conditions—very warm water, moist air, and no wind shear—will keep Maria at this level until its devastating landfall on Puerto Rico tomorrow. It’ll be the first PR Cat-5 landfall since 1928.
The 11am NHC update has Maria returned to Cat5 intensity. And it’s likely to retain that intensity, or close to it, by landfall on southern Puerto Rico Wednesday morning. The Dominican Republic and the Turks and Caicos are in or near the forecast path Thursday and Friday, as well. Going forward, however, the Global Forecasting System 10-day ensemble has only one outlier track hitting the US, and the rest veering north an northeast into the mid Atlantic.
The map below shows where Maria’s hurricane force winds have been (orange) and the area where they’re likely with 50% chance (yellow) and also where Irma went (blue). Clearly much of the eastern and central Caribbean has been affected in the past few weeks by one or the other.
The colours within the countries show the population density – the track of Maria, given that it is a narrow storm, is crucial to how much damage is seen on Puerto Rico: subtle shifts from the current track could significantly change the exposure in its path. Another element to watch out for in the next day is an “eyewall replacement cycle” which could weaken the storm slightly, but more crucially widen the storm such that it affects a greater area, which wouldn’t be ideal for Puerto Rico and the US Virgin Islands.
Hurricanes are powered by warm seas. Over the last 30 years Atlantic sea surface temperature have been rising. The chart is from the catinsight blog:
The 2017 season is relentless. Maria is the 4th major hurricane. Last night it make a direct hit on the Caribbean island of Dominica with surface winds of 160mph (Cat5) and central pressure 924mb. Maria is a relatively compact storm, with a 9-mile eye diameter and 40-mile hurricane-force wind diameter. Mountainous Dominica weakened the storm slightly, but wind shear is light and waters warm in Maria’s forecast path, and the NHC consensus forecast is for a Cat4-5 landfall on Puerto Rico Wednesday.
Posted: Monday, September 18th, 2017