Observations and Simulations of 2005 Atlantic Hurricane Season by NASA

Atlantic hurricane season typically starts from June 1 and ends in November 30 in the northern Atlantic. There’s a noticeable peak from late August through September. Each season peak activity occurs around September 10th.

During the 2005 Atlantic hurricane season there was an unusually high cyclone activity surpassing any other season. The number of category 5 hurricanes, and the most intense hurricane ever measured (Hurricane Wilma) by atmospheric pressure was recorded during this time period.

The visualization ’27 Storms: Arlene to Zeta’ was produced by NASA’s Scientific Visualization Studio. It shows all 27 named storms that formed in the 2005 Atlantic hurricane season. It also analyzes some of the conditions that promoted hurricane formation. Although the visualization lists 27 storms, a re-analysis of the season revealed that a short-lived subtropical storm developed near the Azores Islands in late September. This increased the official tropical storm count from 27 to 28. This storm was not named and is not shown in this animation.

The animation begins by showing the regions of warm surface water that are needed for storm development. This warm surface water layer expands northward through the peak of hurricane season and then recedes as the waters cool. The thermal energy in these warm waters powers the hurricanes. Strong shearing winds in the troposphere can disrupt developing young storms, but measurements indicate that there was very little shearing wind activity in 2005 to impede storm formation. Sea surface temperatures, clouds, storm tracks, and hurricane category labels are shown as the hurricane season progresses.

The visualization is based on the actual data measured by NASA and NOAA satellites in 2005. Satellite data play a vital role in helping us understand the land, ocean, and atmosphere systems and predict the paths and intensities of hurricanes. The animation was showcased in the SIGGRAPH 2007 Computer Animation Festival. It was also a finalist in the 2006 NSF Science and Engineering Visualization Challenge.

The second unnarrated part of the visualization shows a Goddard Earth Observing System Model, Version 5 (GEOS-5) run of the 2005 Hurricane Season driven by Sea Surface Temperatures (SST). The simulation was seeded at the beginning of the run and then ran on its own to create the 6 months of output visualized here. This seeding part is very important. Those “seeds” are the set of initial conditions at the very beginning of the simulation. The GEOS-5 simulation is focused over the Atlantic. What is not shown is the “birth place” of these storms: Central Africa. The following visualization generated by the same GEOS-5 model shows how cumulonimbus clouds form at the tropical regions of Africa. These clouds can seed Atlantic storms if the move over the warm waters of the Atlantic. Satellites watch these clouds with great detail to forecast upcoming Atlantic storms.

The GEOS-5 model did not perfectly replicate all 27 storms recorded the 2005 hurricane season. However it successfully generated 23 storms during that same period. Considering this was an anomalous year, the model did a good job of simulating the large number of storms. An innovative aspect of this global model is the ability to represent realistic hurricane intensities, including 6 hurricanes in the Atlantic for 2005 reaching major strength (category 3 or higher on the Saffir-Simpson scale). This finding could help shape future climate models in predicting hurricane season intensities.

GEOS-5 incorporates well known features of the ocean landscape such as the “loop current”, and high pressure systems such as the Bermuda High Pressure system that affect the intensity and trajectory of the storms. Ocean colors ranging from blue to orange depict air temperatures 2 meters (T2M) above sea level. Since sea surface temperatures are typically measured at sea level and below, the T2M model output behaves somewhat differently. Nonetheless, it is a reasonable proxy to SST. Land cover information is taken from the Next Generation Blue Marble dataset.

Statistical analyses from hurricane track data back to 1850 indicate that for any particular Atlantic Hurricane season, there is approximately a 40% chance that a major hurricane (category 3 or higher) will make landfall in the continental United States. Until hurricane Hermine in 2016, there was a pause lasting 9 years without any hurricanes making landfall.

These visualizations show hurricane tracks from 1980 through 2014. Green tracks are storms that did not make landfall in the continental US; yellow tracks are storms made landfall but were not category 3 or higher when they made landfall; and, red tracks are storms that made landfall and where category 3 or higher. A corresponding chart on the right accumulates the number and types of storms for each year. Notice the large gap in any red blocks between 2006 and 2014.

high pressure system

 

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