Dr. Jeff Masters ·

Above: Wind turbines in Naguabo, Puerto Rico, had their blades sheared off by the ferocious winds of Hurricane Maria’s northern eyewall on September 20, 2017. Image credit: NWS San Juan.

Two months after Category 4 Hurricane Maria pounded Puerto Rico and the Virgin Islands, the Thanksgiving holiday on the islands will be a difficult one. Approximately half of Puerto Rico’s 1.5 million customers still do not have power, 10% do not have water service, and a third of the island’s cell phone towers are not working. In the U.S. Virgin Islands, 73% of the 103,000 residents still had no power two weeks ago. Last week, Puerto Rico Governor Ricardo Rossello asked the federal government for $94.4 billion in disaster recovery aid; $5 billion in aid has been approved for Puerto Rico thus far by Congress. In mid-November, U.S. Virgin Islands Governor Kenneth Mapp asked Congress for $7.5 billion in Hurricane Maria and Hurricane Irma disaster assistance; Congress has thus far only approved $0.5 billion in loans to the Virgin Islands. The combined $102 billion in damage aid requests for Maria from the two governors would put Maria in second place behind Hurricane Katrina of 2005 ($161 billion in damage) on the list of costliest weather disasters in world recorded history, if we assume the damage aid requested is a measure of the actual damage incurred. An early estimate of insured damages from Maria from insurance broker AIR Worldwide was $40 - $85 billion; since total damage is typically about double insured damage, Maria's pricetag may end up being well in excess of $100 billion.

Figure 1. Total damage estimates (not just insured) of all U.S. weather-related disasters that have cost at least $30 billion since 1980. Statistics from 1980 – 2016 are taken from NOAA/NCEI; damage estimates from Hurricane Harvey and Hurricane Irma (2017) are from insurance broker Aon Benfield; damage estimates for Hurricane Maria (2017) are from the Puerto Rico and U.S. Virgin Islands governments. These figures are for the U.S. only; Hurricane Irma did an additional $15 billion in damage to the non-U.S. Caribbean islands, and Hurricane Maria did additional heavy damage in excess of $1 billion to Dominica and other Caribbean islands. Note that there are a wide range of preliminary damage estimates for Hurricane Harvey, from $58 - $198 billion, and it is possible that the final damages from that storm will top Maria's. The top five events listed here are also the five most expensive weather-related disasters in world history; according to EM-DAT, the most expensive non-U.S. weather-related disaster in world history was the 1998 flood in China, which cost $46 billion.

An official death toll of 58, but indirect deaths may be closer to 500

The official death toll from Maria is 26 direct deaths (due to drowning or wind-related effects) and 29 indirect deaths in Puerto Rico; 2 direct deaths and 1 indirect death occurred in the U.S. Virgin Islands. However, the indirect deaths are likely greatly underestimated. A CNN analysis based on data from 112 funeral homes in Puerto Rico identified 499 storm-related deaths in the month following the hurricane. The article argued that this is likely an underestimate, since there are always a significant number of bodies that do not get processed through funeral homes. A more accurate way to estimate the storm’s indirect deaths might be to look at the total number of deaths this year compared to last year, and 472 more people died in September 2017 than September 2016, according to Puerto Rico's Demographic Registry.

Figure 2. Indirect deaths from 59 tropical cyclones (which include hurricanes, tropical storms, and tropical depressions) affecting the U.S. from 1963 – 2012. Image credit: Bulletin of the American Meteorological Society, “Fatalities in the United States Indirectly Associated with Atlantic Tropical Cyclones” (2016), by NHC’s Ed Rappaport and FEMA’s Wayne Blanchard.

According to a 2016 article authored by NHC’s Ed Rappaport and FEMA’s Wayne Blanchard, “Fatalities in the United States Indirectly Associated with Atlantic Tropical Cyclones”, 59 tropical cyclones that hit the U.S. between 1963 – 2012 had 1,803 direct deaths and 1,418 indirect deaths. By far the largest number of indirect deaths were the more than 500 associated with Hurricane Katrina of 2005. Heart attacks were the dominant cause of indirect deaths, accounting for 31% of the total. The authors noted that while improvements in forecasts have led to a reduction in the number of direct deaths in recent years, the lengthening of the forecast period from two to five days has likely led to an increase in some indirect deaths. The longer preparation period gives more time for people to fall off roofs or have heart attacks during the strenuous labor to get ready for the storm, for example.

Figure 3. Total rainfall from Hurricane Maria in Puerto Rico. Image credit: NWS San Juan (@NWSSanJuan)

Maria’s rains: 2nd highest on record for a Puerto Rico tropical cyclone

The National Weather Service in San Juan issued their preliminary Hurricane Maria report last week. The report documented that Hurricane Maria’s torrential rains triggered massive flash flooding and landslides, with over 80% of the island receiving at least ten inches of rain in 48 hours. Maria’s peak rainfall of 37.90” was measured at Caguas at an elevation of 1475 meters, in a mountainous area about 15 miles inland from where the eye made landfall. According to NOAA, the only wetter storm to affect Puerto Rico since 1956 was Tropical Depression Fifteen of 1970, which dumped 41.68” at Jayuya.

As we reported the day of the storm, much higher rainfall amounts than the 37.90” in Caguas were measured in a mountainous area that received the fierce winds of Maria’s northern eyewall, including two stations that measured over 30” of rain in a single hour. These rainfall measurements were rejected as being invalid by the NWS in San Juan in their post-storm report. The rain gauges in question were elevated on poles (see photo here), and it is likely that the intense vibration of these poles during the eyewall winds caused the tipping-bucket mechanism in the rain gauges to register large numbers of false clicks that were erroneously assumed to be due to the weight of the falling rain.

Figure 4. Landslides from Hurricane Maria in Puerto Rico. Image credit: NWS San Juan.

Widespread near-record and record river flooding was observed across the island, and streamflow data from the U.S. Geological Survey showed that 53 out of 65 river gauges in Puerto Rico met or exceeded flood stage. Among these rivers, 30 exceeded major flood stage, while 13 reached or exceeded their all-time record level. The highest density of landslides was in west central Puerto Rico, where more than 25 landslides per square mile occurred.

Video 1. This video taken at Yabucoa, Puerto Rico, near Hurricane Maria’s landfall point shows an extraordinary reversal of Maria’s eyewall winds multiple times. The first huge gust happens around 0:50, throwing cars around. The reversal of the winds multiple times could be due to tornado-scale mesovortices embedded in the eyewall, in combination with the funneling effect of the high rise building across the street. Interestingly, a video shot by storm chaser Josh Morgerman of iCyclone just a few miles away shows a flow that is smoother and steadier, without wild directional shifts. He writes: “This makes sense, because I was right at the coast, where the wind was coming off the open ocean with very little friction.” (The weird reversing wind video was shot a couple of miles inland, where there was lots of friction.) Maria made landfall in Yabucoa, Puerto Rico as a strong category 4 hurricane with maximum sustained winds of 155 mph.

How to help victims of Hurricane Maria

As you give thanks this Thanksgiving weekend for all your blessings, please keep in your prayers the people of Puerto Rico and the Virgin Islands affected by Hurricane Maria. If you are interested in volunteering your time to the Red Cross or other relief organizations, see this link: How To Volunteer: Puerto Rico Needs Your Help.

If you want to give a donation, the Portlight.org disaster relief charity, founded and staffed by members of the wunderground community, is responding to Hurricane Maria in Puerto Rico and the U.S. Virgin Islands, and is also continuing its efforts for victims of Hurricane Harvey and Hurricane Irma. Also consider a donation to hurriup.org, founded by wunderground member Patrap, which has been sending portable generators to Puerto Rico (I’ve contributed to both charities).

USVI Recover is the official site for recovery efforts in the U.S. Virgin Islands from Hurricane Irma and Hurricane Maria. The nonprofit Community Foundation of the Virgin Islands (CFVI) has established the Fund for the Virgin Islands, with 100% of donations benefiting those in crisis. The New York Times has a list of local, national, and global charities providing relief for those affected by Hurricane Maria. Another comprehensive list can be found at weather.com, which notes: “Giving money to vetted and established relief agencies [as opposed to donating goods] is ‘always the best way to help,’ according to the U.S. Agency for International Development.”

Video 2. Drone footage of Hurricane Maria’s damage in Puerto Rico was released by the National Weather Service (NWS) in San Juan. The damage to the Puerto Rico Doppler radar in Cayey at minute 6:00 is striking, as well as the snapped blades on the wind turbines (seen at minute 2:00) in Naguabo, which experienced the strong right-front quadrant of the hurricane’s eyewall.

Have a wunderful Thanksgiving holiday, everyone! I am personally giving thanks this Thanksgiving that I can enjoy the company of my family under a roof with electrical power and water--and that I don’t have to write about a major hurricane in the Atlantic. That’s what I was doing last year on Thanksgiving Day, when Category 3 Hurricane Otto hit Central America!