Tropical Cyclones


Tropical cyclones develop primarily in the summer months in regions with very warm sea surface temperatures, high low-level humidity and resulting instability that favors the development of thunderstorms, low amounts of vertical wind shear, and within the lower latitudes where these environments combine with a Coriolis force sufficient for establishing a surface area of lower pressure.  As they build in intensity, tropical waves and disturbances progress through categories of tropical depressions and named tropical storms, then to hurricanes and major hurricanes, the latter defined as a category three or higher on the Saffir-Simpson hurricane scale.  Tropical cyclones are readily observed in satellite imagery as organized clusters of thunderstorms in the lower tropical latitudes, and are much better known for the distinct, cloud-free eye common to major hurricanes as they move across the open oceans.  These cyclones bring large areas of damaging winds in addition to other threats from prolonged heavy rains and coastal inundation as a result of high storm surge, often requiring large evacuation zones when they threaten to impact populated areas, including the islands of the Pacific, southeastern Asia, and the Gulf Coast or eastern seaboard of the United States.

Tropical cyclones are frequently observed by NASA’s Global Precipitation Measurement (GPM) mission where their structure is made apparent through use of passive microwave brightness temperatures at various frequencies and polarizations.  In addition, their intense rainfall rates are readily mapped by the Integrated Multi-Satellite Retrievals for GPM (IMERG) product, and additional views of their three-dimensional structure made available through active radar scanning by the GPM core satellite.  Mapping of offshore heavy rain rates can provide responders with an expectation of what will occur after landfall, and improved identification of the storm’s center can aid tracking of the system and improved initialization with numerical weather prediction models.  Inland, rainfall estimates can be combined with streamflow and inundation models to understand flood risks resulting from the storm, and combined with topographical models and other information to characterize landslide threats.  Following landfall, flooding can be mapped using optical remote sensing from NASA’s Moderate Resolution Imaging Spectroradiometer (MODIS) instruments aboard the Terra and Aqua missions, the Visible Infrared Imaging Radiometer Suite (VIIRS) aboard the NASA/NOAA Suomi National Polar-orbiting Partnership (S-NPP) mission, or from the higher resolution views of the USGS/NASA Landsat-7 and Landsat-8 missions.  VIIRS also provides a unique opportunity to map power outages from space, which occur frequently as a result of landfalling tropical cyclones, and help to monitor the recovery of power in the days and weeks that follow.  Should post-storm cloudiness obscure a view of the land surface, synthetic aperture radar measurements of water extent from the European Space Agency’s Sentinel-1A and 1B platforms can assist with active scanning of inland surge and flood waters.  Finally, widespread damage to vegetation and treefall can be mapped over time from the aforementioned platforms, with ecosystem recovery monitored in the years that follow through consistent and continued imaging of the affected area

Latest Updates

November 13, 2017
ESA Sentinel-1 Imagery
Acquired Nov. 11. 2017 Acquired Nov, 11 2017 NASA color coded SAR based flood detection maps reveal extensive flooding in areas of Vietnam. The SAR data used in analysis are Copernicus Sentinel data (2017), processed by ESA. In the figures, the blue tones represent flooding due to Typhoon Damrey while the black color represents water covered areas before the...
November 13, 2017
Google map image with Inundation layer.
Inundation Layer from Project Mekong App as of 11/10/2017. Current inundation layer from the Project Mekong App as of 11/10/2017. Red indicates areas with detected flooding. The application uses LANCE MODIS imagery (collected today, 11/10/2017) and applies a dynamic surface water classifier based on statistical training and thresholding of NDVI values. The method is outlined in more detail in Ahamed and Bolten, 2017 (...
November 13, 2017
Total rainfall map using IMERG model
NASA IMERG model generated from October 31 to November 6, 2017 data.  NASA's Integrated Multi-satellitE Retrievals data (IMERG) estimates precipitation from a combination of space-borne passive microwave sensors. This image shows IMERG rainfall estimates over Southeast Asia during the period from October 31 to November 6, 2017. IMERG estimated that more than 500 mm (19.7 inches) of rain was common in this part of south central Vietnam.
November 13, 2017
Topo relief map with flood modelling layer overlay.
Topographic relief map showing estimated flood extent. Darthmouth Flood Observatory of University of Colorado estimated maximum flood extent on November 7th, 2017 using NASA MODIS and Copernicus Sentinel 1 satelite data, operated by the European Space Agency (ESA). In the figure, the light gray denotes all previously-mapped flooding, and red is the active flooding. Blue shows the reference water extent...
October 2, 2017
ARIA Damage Proxy Map of Dominica from Hurricane Maria
The Advanced Rapid Imaging and Analysis (ARIA) team at NASA's Jet Propulsion Laboratory in Pasadena, California, and Caltech, also in Pasadena, created this Damage Proxy Map (DPM) depicting areas including Dominica that are likely damaged (shown by red and yellow pixels) as a result of Hurricane Maria (Category 5 at landfall in Dominica on Sept. 18, 2017). The map is derived from synthetic aperture radar (SAR) images from the Copernicus Sentinel-1 satellites, operated by the European Space Agency (ESA). The images were taken before (Mar. 27, 2017) and after (Sept. 23, 2017) the landfall of...