Hurricane Dorian, from the Caribbean to Canada (Sept. 2019)

Hurricane Dorian (2019) brought heavy rain to the Caribbean, along the US East Coast, and up to Canada.  NASA satellite-based precipitation estimates tracked the storm throughout its lifetime, as shown by the sequence of images below.

September 3, 2019: Hurricane Dorian over Grand Bahama and Abaco Islands

In the early hours of Tuesday, September 3, Hurricane Dorian had been stationary over the island of Grand Bahama for 18 hours, most of the time as a category 5 hurricane.  Storm-total rain accumulation over parts of Grand Bahama and Abaco islands have exceeded 24 inches according to NASA satellite-based estimates. On early Tuesday morning, Dorian’s central pressure has risen and its wind intensity had dropped to category 4 on the Saffir-Simpson scale.  In addition, Dorian had experienced an eyewall replacement cycle on September 2, so by Tuesday morning, the geographic extent of its tropical-storm-force winds had expanded.

These rain estimates come from the NASA IMERG algorithm, which combines observations from a fleet of satellites, in near-realtime, to provide global estimates of precipitation every 30 minutes. The storm-total rainfall at a particular location varies with the forward speed of the hurricane, with the size of the hurricane’s wind field, and with how vigorous the updrafts are inside of the hurricane’s eyewall.

The graphic also shows the distance that tropical-storm force (39 mph) winds extend from Hurricane Dorian’s low-pressure center, as reported by the National Hurricane Center.  The symbols H and TS represent a hurricane of various Saffir-Simpson categories or a tropical storm, respectively.  Visualization by Owen Kelley (NASA/GMU).

September 6, 2019: Hurricane Dorian Brings Tornadoes and Floods to the US East Coast

By Friday morning, September 6, Hurricane Dorian was located off the coast of North Carolina, having generated tornadoes the previous day as the northern rainband came ashore in North Carolina. NASA’s satellite-based realtime precipitation estimates suggest that, during the past day, most of the areas experiencing over 10 inches of rain accumulation remained offshore, while Dorian did drop heavy rain on South Carolina and North Carolina.

The preliminary reports of tornadoes were obtained from NOAA’s Storm Prediction Center, and are shown on the graphic as red circles. Since storm spotters are land based, these reports rarely capture any water spouts (tornado-like events over water) that might occur. As Hurricane Dorian interacted with the U.S. East Coast, the only tornado reports occurred from 4:50 AM to 5:00 PM EDT on September 5 in North and South Carolina.  Scientists think of a hurricane as a heat engine that converts the warmth of the sun-warmed ocean into the kinetic energy of the hurricane’s strong, horizontal wind. When these strong winds reach land, the increased friction of the land surface vs. the ocean surface can convert some of this kinetic energy into tornadoes within the hurricane.

The near-realtime rain estimates come from the NASA’s IMERG algorithm, which combines observations from a fleet of satellites, in near-realtime, to provide global estimates of precipitation every 30 minutes.  The storm-total rainfall at a particular location varies with the forward speed of the hurricane, with the size of the hurricane’s wind field, and with how vigorous the updrafts are inside the hurricane.  This graphic only shows precipitation that fell starting at 0000UTC on September 1, and therefore does not show the precipitation that fell in late August, prior to Hurricane Dorian’s approach to The Bahamas.

The graphic shows the distance that tropical-storm force (39 mph) winds extend from Hurricane Dorian’s low-pressure center, as estimated by the National Hurricane Center.  The Saffir-Simpson intensity category is the number following the “H” in the label on the image.  Visualization by Owen Kelley (NASA/GMU).

September 9, 2019: Dorian Reaches Canada

On Monday morning, September 9, Hurricane Dorian was a post-tropical storm after a mid-latitude weather front and cold seas had altered its tropical characteristics over the weekend. On Saturday and Sunday, Hurricane Dorian struck eastern Canada, causing wind damage and bringing heavy rainfall.  According to the Associated Press, a peak of 400,000 people were without power in Nova Scotia, Canada, because of Dorian.

This graphic shows precipitation that fell during the almost two-week period from August 27 to the early hours of September 9. The near-realtime rain estimates come from the NASA’s IMERG algorithm, which combines observations from a fleet of satellites, in near-realtime, to provide near-global estimates of precipitation every 30 minutes.

This year, NASA began running a improved version of the IMERG algorithm that does a better job estimating precipitation at high latitudes, specifically north of 60 degrees North latitude. The post-tropical remnant of Hurricane Dorian was approaching this cold region at the end of the period shown in this image. While the IMERG algorithm is still unable to estimate precipitation falling over ice-covered surfaces (such as Greenland), IMERG can now give a more complete picture of the water cycle in places such as Canada, which is, for the most part, free of snow cover at this time of year.

At one-day intervals, the image shows the distance that tropical-storm force (39 mph) winds extended from Hurricane Dorian’s low-pressure center, as estimated by the National Hurricane Center.  The Saffir-Simpson hurricane-intensity category is the number following the “H” in the label on the image. “TS” or “PT” indicate times when the storm was either at tropical storm strength or when the storm was categorized as post-tropical.

Red circles over North Carolina indicate preliminary reports of tornados from 4:50 AM to 5:00 PM EDT on September 5, provided by NOAA’s Storm Prediction Center.  Since storm spotters are land based, these reports rarely capture water spouts (tornado-like events over water) that may occur.  Lines of latitude and longitude are curved on this map projection, as would be seen by an observer in Earth orbit, so that both tropical and arctic regions can be shown on the same map with minimal distortion. By combining NASA precipitation estimates with other data sources, we can gain a greater understanding of major storms that effect our planet. Visualization by O. Kelley.


Alaska’s Wildfires, Precipitation, and Lightning (summer 2019)

NASA’s satellite-based estimate of global precipitation can provide valuable information to officials monitoring the many wildfires in Alaska this summer. Wildfires occur in Alaska each summer, but July 2019 was a particularly active month. Few rain gauges exist in the large tracts of Alaskan wilderness, making satellite-based precipitation estimates potentially more valuable for monitoring wildfire. Many wildfires in the Alaskan wilderness are monitored but allowed to burn themselves out. Monitoring triggers firefighting efforts when a fire threatens life, infrastructure, or locations with critical ecological resources.

The movie shows NASA’s IMERG precipitation estimates for May through September, 2019. The total accumulation since May 1 is shown in millimeters (inches) on the left half, while the accumulation during a 3-hour period is shown on the right half. The locations of likely fires are shown in red, based on thermal anomalies observed by the VIIRS instrument on the Suomi NPP polar-orbiting satellite. The VIIRS “hot spot” data has a resolution of approximately 0.25 square kilometers and is based on infrared brightness temperature. Locations of lightning strikes are shown in yellow, as detected by the network of ground sensors that make up the World Wide Lightning Location Network. A flash is detected when five or more WWLLN stations around the world detect a radio-frequency atmospheric signal from the same lightning flash. A gray circle along the southern coast or center of Alaska represents the cities of Anchorage or Fairbanks, respectively.

The first part of the movie covers May 2019, and it is a period of little precipitation, little lightning, and few wildfires.

June 2019 shows an increasing amount of lightning but still few large fires. During June, the storms that do pass through central Alaska deliver only about half of the climatological normal amount of precipitation according to NOAA’s Climate Prediction Center.

At end of June and into July, things start to heat up. Numerous wildfires are present in Alaska even though regional storms reduced the intensity of some fires or put them out. One such storm passes through Alaska’s west coast on June 27 and another on July 1 near Fairbanks. During the first half of July, many wildfires burn. There is an absence of large storms coupled with significant lightning activity, which together contribute both to a dry fuel supply and lightning to ignite it.

By July 25, the U.S. Bureau of Land Management (BLM) reported that over 2 million acres of Alaska forests had burned so far this year, 98% of which were ignited by lightning rather than man-made fire sources. The area burned is equivalent to a square with sides 58 miles long.

Credits: For IMERG data, visit NASA’s Precipitation Measurement Missions ( The Visible Infrared Imaging Radiometer Suite (VIIRS) hot-spot data was downloaded from NASA’s Fire Information for Resource Management System ( Lightning data provided by University of Washington ( Climatological data provided by NOAA’s Climate Prediction Center ( Fire statistics from the Bureau of Land Management ( Visualization by Owen Kelley at NASA Goddard’s Precipitation Processing System.


Large 7-day Accumulation over Western India (August 2019)

In early August 2019, a depression formed in the Bay of Bengal that moved over India contributing to heavy rainfall on India’s west coast. NASA’s satellite data analysis suggests that for August 5 though 11, two feet of rain fell in some places. This estimate is from the realtime multi-satellite algorithm called IMERG, which is run at NASA Goddard.


NASA Announces Release of 19-year Record of Global Precipitation (August 2019)

Larger image

The Global Precipitation Measurement (GPM) mission has released an improved version of a multi-satellite global precipitation-rate estimate. Using this algorithm, NASA has re-examined observations back to April 2000 to create a long-term archive of these high-quality rainfall and snowfall estimates. The algorithm is called IMERG, which stands for “The Integrated Multi-satelliE Retrievals for GPM.”

The IMERG algorithm stitches together the data an international constellation of satellite-borne sensors including infrared, passive microwave, and radar. The algorithm also uses estimate of tropospheric wind to morph precipitation observed at one time into data-sparse regions in earlier or later hours. The algorithm is the most sophisticated data-driven precipitation-estimation algorithm that NASA has ever developed, tested, and provided to the public. The current version of IMERG is designated Version 6.

The image above shows the earliest North Atlantic hurricane in the IMERG Version 6 2000-to-present archive, which is Hurricane Keith. Hurricane Keith formed in the Gulf of Mexico and reached category on the Saffir-Simpson scale before making landfall in Mexico. Using the QGIS application, this image was created from the Final IMERG Geographic Information System (GIS) daily product, a 24-hour summary of the 30-minute global 0.1 x 0.1 degree IMERG files. Both the original HDF5 files and these GIS TIFF translations together form the most popular data produce of the GPM mission, based on number of files that researchers download from NASA Precipitation Processing System (PPS).

To learn more about this data product, please read the Algorithm Theoretical Basis Document or visit the Global Precipitation Measurement (GPM) website. Since 2014, George Mason University’s Center for Earth Observing and Spatial Research (COESR0 employees working at NASA’s Precipitation Processing System (PPS) contributed to testing this algorithm and to creating the long-term archive of this algorithm’s output.


NASA, 2019: The Integrated Multi-satelliE Retrievals for GPM (IMERG) Algorithm Theoretical Basis Document. 38 pp. Available online at

Kelley, O. 2019: The IMERG multi-satellite precipitation estimates reformatted as 2-byte GeoTIFF files for display in a Geographic Information System(GIS). Available online at


Fire and Ice: Intense Convection Observed at High Latitude by the GPM Satellite Radar and a Ground-based Lightning Network (Dec. 2018)

Books about lightning barely mention the polar regions, and books about polar regions don’t mention lightning.  There are societal impacts to the severe weather that often comes with lightning and with the forest fires that lightning can produce.  In Antarctica, climate and weather dynamics are poorly understood, and lightning studies might help identify the preferential locations for convective precipitation. In the present study, lightning storms located 60° to 67° from the Equator are examined using simultaneous observation of lightning and ice-phase precipitation, both produced by storm updrafts.  Hence, lightning is the “fire” and precipitation is the “ice.”

In December 2018, GMU researcher Owen Kelley and coauthors Jeremy Thomas, Natalia Solorzano, and Robert Holzworth (DigiPen Institute of Technology and University of Washington) presenting their finding about polar-region lightning at the American Geophysical Union’s annual conference.  Their presentation is available as a PDF file.

In thunderstorms 60°- 67° from the Equator, the lightning flash rate and the height that updrafts lift precipitation are seen to vary by hemisphere and by longitude.  At these high latitudes, the observations appear consistent between the GPM Dual-frequency Precipitation Radar (DPR) and the World Wide Lightning Location Network (WWLLN). Individual lightning storms are observed to have lightning that is co-located with areas of high-altitude radar echoes.  Four-year-total lightning flash counts and four-year-average radar-based precipitation characteristics show similar geographic variation.


Kelley, O.A., J. N. Thomas, N. N. Solorzano, and R. Holzworth, 2018 Dec.: Fire and ice: Intense convective precipitation observed at high latitudes by the GPM satellite’s Dual-frequency Precipitation Radar (DPR) and the ground-based World Wide Lightning Location Network (WWLLN). poster presentation, H43F-2487, 2018 AGU annual meeting.

WWLLN data and antenna photograph provided by WWLLN / University of Washington.


A Quarter of a Million People View a Facebook Live Event about Hurricane Matthew (October 2016)

The day that Hurricane Matthew began interacting with the US East Coast, CEOSR research Owen Kelley and colleagues at NASA Goddard participated in a Facebook Live event on the NASArain Facebook page. On October 7, 2016, the discussion covered NASA observations of the hurricane and took live questions from viewers. Over 250,000 people viewed the event either during the live broadcast or afterward. The event is still viewable at

Update September 2021: As of the summer of 2021, posts related to the Global Precipitation Mission are now tweeted on the NASA Atmosphere twitter account rather than the NASA Rain twitter account.


Japan Launches Next-Generation NASA Satellite to Track Rain & Snow


GPM Satellite Sees First Atlantic Hurricane


NASA and the Japanese Aerospace Agency Launch GPM Satellite


Invited Talk: Google, Using Google Earth for Near Real Time Natural Hazard Monitoring