Tuesday, July 28, 2015

Comparison of the Great Appalachian Storm (1950) and Post-tropical Hurricane Sandy (2012) Surface Analyses

Previously on the blog (from the November 2014 issue of the Wood Duck) we looked at a historical birding event and how the weather likely played an integral part in bringing a number of remarkable birds to the Hamilton Study Area (Holden, 2014) – check out the citation list if you missed it! 


The star of the show was some remarkable observations of the Thick-billed Murre Uria lomvia and the producer was the Great Appalachian storm of 1950. This storm was one of the strongest extratropical cyclones to be recorded in our region for this time of year, and also had an unusual track that brought it ashore and retrograding westwards over the southern Great Lakes. Reproduced below is a surface analysis map of the system on 26 November 1950. 

Figure 1. The Great Appalachian storm near peak intensity (978-980mb) on 26 November 1950 (Wikipedia 2015). 

Sometime after the publication of the November 2014 Wood Duck I was continuing my study of powerful cyclones and their implications to birding when I noticed some remarkable similarities between this storm and the infamous Hurricane Sandy of 2012. Ken Burrell and I had previously completed a summary of events and noteworthy bird observations on the Hurricane Sandy event which helped me to identify some of the commonalities (Holden and Burrell, 2014). Hamilton birders who were present at Van Wagner’s Beach during the morning of 30 October 2012 will not soon forget the swirling flocks of Black-legged Kittiwakes, Jaegers and remarkable Storm-Petrels that passed by that morning. Presented here is a surface analysis map from that very morning from the National Oceanic and Atmospheric Association (NOAA).

Figure 2. Post-tropical Hurricane Sandy on 30 October 2012 (NOAA 2015). 

Interestingly both maps show very large and powerful storms, both have large occluded* fronts passing over the Hamilton area, and both have recently moved from westward (inland) from the Atlantic coastline! Given that our prevailing winds are southwesterly, perhaps the most significant feature here is that both cyclones have gone east to west – a highly unusual direction for a storm to travel in our part of the world. Combined that with the fact that they’re both remarkably strong, we have a one-two punch that was undoubtedly the cause of some great birds gracing our shores.

While both of these cyclones were directed westwards by a blocking ridge of high pressure to the north, among other complicated factors, it should also mention that there are numerous differences between them. Major Hurricane Sandy was a fully tropical cyclone for most of its life, only transitioning to a Post-Tropical cyclone shortly before impacting our area. This is in contrast to the fully extratropical nature of the Great Appalachian Storm. In meteorological terms this is the equivalent of applies to oranges, if not greater (perhaps the fine details would be better suited for a different article). Nonetheless I have found the similarities to be another exciting little discovery in my look at the meteorological world and how it relates to the birds we see. Stealing from my last article; if I ever see anything like this occurring in the future, I will be one “sick day” away from some great birding!

* An Occluded front occurs where a “cold front” overtakes a “warm front” at the earth’s surface

Literature cited:

Holden, B.R. 2014. Reverse Engineering an Historical Birding Event. The Wood Duck 68(3):7-8. Available online at http://hamiltonnature.org/wp-content/uploads/pdfs/wood-duck/wood-duck-2014-11.pdf

Holden, B.R. and K.G.D. Burrell. 2014. A birding perspective and analysis of Hurricane Sandy in Ontario, Autumn 2012. Ontario Birds. 32(1):12-22. Available online at http://peregrineprints.com/zzzz_BRH_KGB_Hurricane_Sandy.pdf

NOAA. 2015. National Oceanic and Atmospheric Association – Weather prediction Center. WPC Surface Analysis Archive for the United States (CONUS) 1500z 30 October 2012. Retrieved from http://www.wpc.ncep.noaa.gov/archives/web_pages/sfc/sfc_archive.php. Accessed by Brandon Holden on 6 February 2015.

Wikipedia. 2015. Great Appalachian Storm of November 1950. retrieved from http://en.wikipedia.org/wiki/Great_Appalachian_Storm_of_November_1950. Wikimedia Foundation, accessed by Brandon Holden on 6 February 2015.

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