“Here I am. Rock you like a hurricane.” - Scorpions, 1984

Overview

2020 has seen a record-breaking number of hurricanes in the North Atlantic, so I was interested in looking at historical hurricane frequencies. The animation above visualizes the global number of tropical cyclones every year from 1980 to today, and where in the world these storms formed.

A tropical cyclone is a rotating storm system of clouds and thunderstorms that originates over warm tropical or subtropical oceans.1 In the North Atlantic and eastern North Pacific oceans, tropical cyclones are called hurricanes. In the western North Pacific they are called typhoons, and in the western South Pacific and Indian oceans they are called cyclones.2 A tropical cyclone is characterized by high winds, heavy rain, and low atmospheric pressure. Factors that support development of tropical cyclones include warm water, thunderstorm activity, and low wind shear.3 When tropical cyclones make landfall, they bring heavy rain, wind, and storm surge, which make them a serious concern for coastal areas in the tropics and subtropics.

The naming of these storms occurs when the cyclone reaches tropical storm strength, or 34 knots (39 mph/63 kph). Naming first began in order to quickly identify storms in warning messages and make reporting easier. The World Meteorological Organization 4 maintains a list of names for all tropical cyclones, and each list of names repeats every few years. Below is a bar plot of the number of named cyclones by ocean basin and by season, from 1980 to today.

Because 2020 is breaking some records in the Atlantic hurricane season, I also wanted to take a look at hurricane frequency in the North Atlantic only. Below is a bar plot of the number of named cyclones by season for the North Atlantic. The Atlantic hurricane season typically occurs from June 1st to November 30th. This season began early, with the first storm, Arthur, forming on May 16. Then, on September 18, the alphabet was exhausted and we had to move on to the Greek alphabet. On November 10, 2020, Hurricane Theta formed, becoming the 29th named storm of the season and breaking the previous record of 28 storms in 2005.5 As of November 20, 2020, the latest tropical cyclone in the Atlantic was Hurricane Iota, the second hurricane in history in the month of November to reach Category 5.6

An above-average season was actually predicted for 2020, largely due to the development of La Nina. La Nina typically brings cooler-than-average sea surface temperatures across the Pacific and weakens the wind shear over the Atlantic, making hurricane formation much more likely in the Atlantic.7

Because it was a well above-average season, and from the above graph it appears that perhaps hurricane frequency may be increasing, we have to wonder if climate change is playing a role. Since 1970, sea surface temperatures have increased by about 0.1 degrees Celsius per decade, particularly in the North Atlantic.8 However–perhaps surprisingly–in general, climate change isn’t expected to have much of an effect on the number of hurricanes that form each year.9 It should be noted that there are conflicting studies and models, with some showing an increase in frequency and and others suggesting that the frequency of storms may even decrease.10 Thus, the connection between climate change and hurricane frequency is not very straightforward; though the most recent studies are showing that climate change will cause fewer storms to form, and they will be much more intense.

So, the greatest anticipated impact of climate change is that hurricanes will be stronger and more destructive. This means that a greater proportion of storms will turn into major hurricanes, and they will become intense more quickly. This project explores hurricane frequency. Next steps to build upon this might include visualizing intensity of these storms to get an even better look at the big picture.

Data Description

Visualized in the animation above is the location of formation of tropical cyclones from 1980 to November 2020 (ending with Iota in the North Atlantic). The data come from the IBTrACS (International Best Track Archive for Climate Stewardship), which is managed by NOAA (National Oceanic and Atmospheric Administration). Here, IBTrACS version 4 was used, specifically tropical cyclone track data since 1980. The dataset is updated twice every week, and it was last downloaded on November 15, 2020.

The dataset, which contains track data for every tropical cyclone in the world from 1980 to November 2020, was downloaded in CSV11 format from IBTrACS.12 The data were read in to a python13 script which turned them into a dataframe using the pandas14 library. Then, the desired variables - storm id, season, basin, name, latitude, and longitude - were filtered for. The first row of the dataset was dropped, as it contained information on units and not actual data. Additionally, python read the “NA” (for North Atlantic) as a null value, so the script fixed this as well by replacing the values back to “NA.” Finally, for each tropical cyclone, the first row of data was selected to get the location of formation of the storm.

The script then created a new CSV file which only contained formation location data. This CSV was visualized in QGIS15 by season (year). Then, image files for each season were saved from QGIS and loaded into GIMP,16 where the images were exported as an animated GIF.17 The GIF was converted to an MPEG-418 video using Ezgif.19

The script also utilized pandas to further process the data to obtain seasonal counts of the number of storms. Then, Matplotlib20 library was used to create the two bar plots: a count of all named tropical cyclones for every ocean basin and season, and a count of all named tropical cyclones in the North Atlantic basin by season. The two plots were saved to the local directory in the PNG21 image format.

Author: Natalie Larsen. Last edited: 2020-11-20.

  1. Tropical Cyclone Climatology. National Hurricane Center. Accessed 2020-11-20. Online: https://www.nhc.noaa.gov/climo/↩︎

  2. Tropical Cyclone. Britannica. Accessed 2020-11-20. Online: https://www.britannica.com/science/tropical-cyclone↩︎

  3. How do hurricanes form?. NOAA. Accessed 2020-11-20. Online: https://oceanservice.noaa.gov/facts/how-hurricanes-form.html↩︎

  4. Tropical Cyclone Naming. World Meterological Organization. Accessed 2020-11-20. Online: https://public.wmo.int/en/our-mandate/focus-areas/natural-hazards-and-disaster-risk-reduction/tropical-cyclones/Naming↩︎

  5. 2020 Atlantic Hurricane Season takes infamous top spot for busiest on record. NOAA. Accessed 2020-11-20. Online: https://www.noaa.gov/news/2020-atlantic-hurricane-season-takes-infamous-top-spot-for-busiest-on-record↩︎

  6. Hurricane Iota explosively intensifies to Category 5 as it bears down on Nicaragua. Washington Post. Accessed 2020-11-20. Online: https://www.washingtonpost.com/weather/2020/11/16/iota-nicaragua-honduras-category-five/↩︎

  7. La Nina develops during peak hurricane season. NOAA. Accessed 2020-11-20. Online: https://www.noaa.gov/news/la-nina-develops-during-peak-hurricane-season.↩︎

  8. Hurricanes and Climate Change. Union of Concerned Scientists. Accessed 2020-11-20. Online: https://www.ucsusa.org/resources/hurricanes-and-climate-change.↩︎

  9. Climate Change May Cause More Storms to Rapidly Intensify as Delta Did. Scientific American. Accessed 2020-11-20. Online: https://www.scientificamerican.com/article/climate-change-may-cause-more-storms-to-rapidly-intensify-as-delta-did/↩︎

  10. Hurricanes and Climate Change. Center for Climate and Energy Solutions. Accessed 2020-11-20. Online: https://www.c2es.org/content/hurricanes-and-climate-change/.↩︎

  11. Spreadsheet File Formats; CSV. FileFormat. Copyright 2001–2020 Aspose Pty Ltd. Accessed 2020-11-20. Online: https://docs.fileformat.com/spreadsheet/csv/↩︎

  12. IBTrACS version 4. World Data Center for Meteorology, Asheville; NOAA. Accessed 2020-11-20. Online: https://www.ncdc.noaa.gov/ibtracs/index.php?name=ib-v4-access↩︎

  13. Python. Copyright (C) 2001–2020. Python Software Foundation. Accessed 2020-11-20. Online: https://www.python.org/↩︎

  14. Pandas. Pandas is a fiscally sponsored project of NumFOCUS. Accessed 2020-11-20. Online: https://pandas.pydata.org/↩︎

  15. QGIS. Software released through CC-BY-SA by the QGIS Development Team. Accessed 2019-10-28. Online: https://www.qgis.org↩︎

  16. GNU Image Manipulation Program (GIMP). Software released through CC-BY-SA by The GIMP Development Team. Accessed 2020-11-20. Online: https://www.gimp.org/↩︎

  17. Image File Formats; GIF. FileFormat. Copyright 2001–2020 Aspose Pty Ltd. Accessed 2020-11-20. Online: https://docs.fileformat.com/image/gif/↩︎

  18. Moving Picture Experts Group Standard 4 (MPEG-4). Standard developed by a working group of the International Organization for Standardization (ISO) and the International Electrotechnical Commission (IEC) joint technical committee. Accessed 2020-11-20. Online: https://mpeg.chiariglione.org/↩︎

  19. EzGIF. Accessed 2020-11-20. Online: https://ezgif.com/↩︎

  20. Matplotlib. Copyright 2002–2012 John Hunter, Darren Dale, Eric Firing, Michael Droettboom and the Matplotlib development team; 2012–2020 The Matplotlib development team. Accessed 2020-11-20. Online: https://matplotlib.org/↩︎

  21. Image File Formats; PNG. FileFormat. Copyright 2001–2020 Aspose Pty Ltd. Accessed 2020-11-20. Online: https://docs.fileformat.com/image/png/↩︎