Five Things We Learned From Hurricane Sandy

1) Hurricane Sandy was truly astounding in its size and power. At its peak size, twenty hours before landfall, Sandy had tropical storm-force winds that covered an area nearly one-fifth the area of the contiguous United States. Sandy's area of ocean with twelve-foot seas peaked at 1.4 million square miles--nearly one-half the area of the contiguous United States, or 1% of Earth's total ocean area. Most incredibly, ten hours before landfall (9:30 am EDT October 29), the total energy of Sandy's winds of tropical storm-force and higher peaked at 329 terajoules--the highest value for any Atlantic hurricane since at least 1969, and equivalent to five Hiroshima-sized atomic bombs. At landfall, Sandy's tropical storm-force winds spanned 943 miles of the the U.S. coast. No hurricane on record has been larger. Sandy's huge size prompted high wind warnings to be posted from Chicago to Eastern Maine, and from Michigan's Upper Peninsula to Florida's Lake Okeechobee--an area home to 120 million people. Sandy's winds simultaneously caused damage to buildings on the shores of Lake Michigan at Indiana Dunes National Lake Shore, and toppled power lines in Nova Scotia, Canada--locations 1200 miles apart. Over 130 fatalities were reported and over 8.5 million customers lost power--the second largest weather-related power outage in U.S. history, behind the 10 million that lost power during the Blizzard of 1993. Damage from Sandy is estimated at $65 billion, making it the second most expensive weather-related disaster in world history, behind Hurricane Katrina of 2005.


Figure 1. Hurricane Sandy at 10:10 am EDT October 28, 2012. Image credit: NASA/GSFC.

2) NHC's procedures for issuing warnings need improvement. There was plenty of confusion on Sandy's storm surge risk. A post-Sandy federal review of the NWS’ performance found that the surge forecasts were remarkably accurate, but were not communicated in ways that made it easy for officials and the public to understand. NOAA has now set a target date of 2015 to implement explicit storm surge watches and warnings, something they have been working toward for several years. Experimental inundation graphics will come in 2014. It's critical that we do a better job with communicating storm surge risk; storm surge is the phenomenon that presents the greatest U.S. weather-related threat for a massive loss of life in a single day, and was responsible for the largest fraction of direct deaths attributed to Sandy.

Sandy was technically not a hurricane at landfall, it was a "post-tropical cyclone," and NHC opted to handle the warnings using "Hurricane-force wind warnings." Such technicalities are often lost on the public, causing concern that the public may have been under-warned--though there's no evidence that fewer people evacuated from Sandy because of this issue, according to Florida State University researcher Dr. Jay Baker. The NWS and NHC now have the option to keep hurricane and tropical storm watches and warnings in place for post-tropical cyclones to avoid such confusion in the future. TWC hurricane specialist Bryan Norcross had this to say in his Sandy 1-year anniversary blog post: The meteorologists don’t want to hear it, and I don’t like it either, but the truth is, the quality of the meteorology is so far ahead of the quality of threat communications in the U.S. that progress in forecasting is becoming less and less relevant. Andrew Freedman at Climate Central has a detailed look at the communication problems with Sandy's forecast.


Figure 2. Hurricane Sandy’s winds on October 28, 2012, when Sandy was a Category 1 hurricane with top winds of 75 mph (this ocean surface wind data is from a radar scatterometer on the Indian Space Research Organization’s (ISRO) Oceansat-2.) Image credit: NASA.

3) The European ECMWF weather forecast model is better than the U.S. GFS model. The superior performance of the European model for long-range forecasts of Sandy led for calls to improve computer model forecasts in the U.S. NOAA's National Center for Environmental Prediction has significantly upgraded the computer power used to make forecasts since Sandy, but it will be difficult for the U.S. to catch up to the Europeans, as wunderground's climate change blogger, Dr. Ricky Rood, explained in an article for the Washington Post.


Figure 3.The Battery Park Underpass during Hurricane Sandy, October 30, 2012 (top) and one year later (bottom, October 16, 2013.) Image credit: Natan Dvir/Polaris. An impressive set of 148 before-and-after Sandy photos taken from identical locations one year apart have been put together by TWC.

4) Arctic sea ice loss due to global warming may have made Sandy's unusual track more likely. Sandy took the most perpendicular track into the Northeast U.S. coast of any tropical cyclone in the historical record (Hall and Sobel, 2013.) Using historical climate data, these scientists estimated that the return period of a Category 1 or stronger storm hitting New Jersey at such an odd angle was 1-in-700-years. The 2012 Arctic sea ice melt season was extreme, with sea ice extent hitting an all-time record low just weeks before Sandy hit. Could sea ice loss have contributed to the blocking ridge that steered Sandy into New Jersey? A paper published in August 2013 in the Proceedings of the National Academy of Sciences by Elizabeth Barnes of Colorado State and co-authors, "Model projections of atmospheric steering of Sandy-like superstorms", argues that our best climate models project we should see a decrease in the type of steering patterns that brought Sandy to the coast at such an unusual angle. However, as I discussed in an April 2013 post, Arctic sea ice loss tied to unusual jet stream patterns, three studies published in the past year have found that the jet stream has been getting stuck in unusually strong blocking patterns in recent years. These studies found that the recent record decline in Arctic sea ice could be responsible, since this heats up the pole, altering the Equator-to-pole temperature difference, forcing the jet stream to slow down, meander, and get stuck in large loops. The author of one of the new studies, Dr. Jennifer Francis of Rutgers, had this say at Andy Revkin's Dot Earth blog: "While it’s impossible to say how this scenario might have unfolded if sea-ice had been as extensive as it was in the 1980s, the situation at hand is completely consistent with what I’d expect to see happen more often as a result of unabated warming and especially the amplification of that warming in the Arctic."


Figure 4. Tracks of all tropical storms and hurricanes to hit Southern New Jersey, 1851 - 2012. Hurricane Sandy had a track unprecedented in the historical record. Image created by TWC's Stu Ostro using data from NOAA/CSC.

5) There may be more storms like Sandy in the future. The Atlantic hurricane season is getting longer, and ocean temperatures are warming. This increases the odds that we will see more hurricanes in October making it far to north near New England, where they can potentially get entangled with extratropical fall storms. Furthermore, dangerous part-hurricane, part extratropical hybrid storms like Hurricane Sandy are expected to be an increasing threat for Western Europe by the end of the century due to global warming, said a team of scientists led by Reindert J. Haarsma of the Royal Netherlands Meteorological Institute. In a paper called "More hurricanes to hit Western Europe due to global warming", published in April 2013 in Geophysical Research Letters, the researchers described the results from runs of a high-resolution (25 km grid spacing) climate model based on the European Centre for Medium Range Weather Forecasts (ECMWF) numerical weather prediction model. The model predicts that the breeding ground for Atlantic hurricanes will shift approximately 700 miles eastwards as the oceans warm this century. Hurricanes which form farther to the east can spend more time over warm tropical waters before turning north and northeast towards Europe, increasing the odds that these storms will have hurricane-force winds upon arrival in Europe. The researchers concluded that "tropical cyclones will increase the probability of present-day extreme events over the North Sea and the Gulf of Biscay with a factor of 5 and 25 respectively, with far reaching consequences especially for coastal safety."

Sandy links
Colorful 2-D and 3-D model animations of Sandy from Bob Henson of UCAR.

Colorful 5-day animation of Sandy's winds from NASA (Scroll down to third video, 850 mb level.) 

Twelve strange weather features of Superstorm Sandy from Seth Borenstein of AP.

Scientific American has an interesting storm surge simulation video of the flooding of Hoboken, NJ, showing a highly detailed look at how the surge entered the city (2nd video on page.) Animations were sone from modeling by Philip Orton and colleagues at the Stevens Institute of Technology.

PBS' NOVA series did an excellent job looking at the aftermath of Sandy in the their 1-hour show, Megastorm Aftermath, which aired on October 8.


Video 1. ‪After Sandy: Changes and Choices‬. Video produced by the Climate.gov team in cooperation with climate and Earth scientists from the National Oceanic and Atmospheric Administration and other agencies and institutions.

Later today, wunderground's weather historian Christopher C. Burt will have the latest figures from the destructive storm named "Christian" that hit Northern Europe, in his blog. According to Dr. Michael Theusner of the German climate museum Klimahaus, a wind gust of 119 mph (191 kph) was recorded on the island of Heligoland, Germany by the weather station of Germany’s biggest private weather company. If verified, this would be the highest wind gust ever recorded at low elevation in Germany. 

I'll have a new post by Thursday.


Jeff Masters