Dorian – Atlantic Ocean

Aug. 30, 2019 – Update #3 -NASA Satellites On-Hand As Dorian Becomes a Category 3 Hurricane

As Hurricane Dorian was upgraded to a Category 3 hurricane on the Saffir-Simpson Hurricane Wind Scale, NASA’s fleet of satellites were gathering data during the day to assist weather forecasters and scientists.  At 2:oo pm EDT the National Hurricane Center (NHC) posted a supplemental advisory. NHC reports that “extremely dangerous  Hurricane Dorian poses a significant threat to Florida and the northwestern Bahamas.  The Hurricane Hunter plane finds Dorian is now a major hurricane.”

IMERG estimates Hurricane Dorian's rain
As of early on August 30, Hurricane Dorian has been producing 2 to 6 inches of rain along the path of its inner core for several days. This estimate 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 in the hurricane’s eyewall. The graphic also shows the distance that tropical-storm force (39 mph) winds extend from the Hurricane Dorians low-pressure center, as reported by the National Hurricane Center. The symbols H2, H1, and TS represent category 2 hurricane, category 1 hurricane, and tropical storm, respectively. Visualization by NASA Goddard.

NASA’s Global Precipitation Measurement mission satellite uses its IMERG algorithm with data from a fleet of satellites to provide global estimates of the precipitation within the storm every 30 minutes.  This map displays the estimated rainfall accumulation for the region from August 27th – August 30th, prior to Dorian becoming a Category 3 storm.

NOAA-NASA’s Suomi NPP satellite uses its complement of instruments onboard to dissect storms and provide information on many different aspects of the hurricane including storm strength, cloudtop temperature, circulation, and rainfall, among others, within the structure of the storm.  The next three images are all from the Suomi NPP satellite and its instruments which help scientists figure out the intensity of the storm and help predict where it will ultimately end up.

Suomi NPP image of Dorian
NASA/NOAA’s Suomi NPP satellite was in an ideal position for observing Dorian at 0617 UTC (2:17 am EDT) at an almost nadir view (right over the storm). The infrared imagery showed a somewhat circular storm, though a bit lopsided. However, the convection was strong enough to result in several overshooting tops and tropospheric gravity waves are atmospheric waves (in this observation from the troposphere) that are produced by strong thunderstorms near the eye and radiate outward in expanding spirals giving forecasters and scientists a good indicator of the strength of the storm. This top-down view of Dorian allowed the microwave sounder to observe the inner structure of the storm. Credit: NASA/NOAA/UWM-SSEC-CIMSS/William Straka III

Hurricane Dorian is currently at latitude 24.8N and longitude 70.3W which is about 445 miles (715 km) east of the northwestern Bahamas and about 625 miles (1005 km) east of West Palm Beach, FL.   The NHC forecast is: “A slower west-northwestward to westward motion should begin tonight and continue into early next week. On this track, the core of Dorian should move over the Atlantic well north of the southeastern and central Bahamas today and tomorrow, be near or over the northwestern Bahamas on Sunday, and be near the Florida peninsula late Monday.”

Suomi NPP ATMS instrument shows the circulation of Dorian.
From the 88.2GHz BT, the circulation of the storm is easily seen with the convection showing colder temperatures. Credit: NASA/NOAA/UWM-SSEC-CIMSS/William Straka III

Currently the storm’s maximum sustained winds are 115 mph (185 km/h) with higher gusts, and is moving northwest at 10 mph (17 km/h).  Hurricane-force winds extend outward up to 25 miles (35 km) from the center and tropical-storm-force winds extend outward up to 105 miles (165 km). The minimum central pressure is 970 mb.

Suomi NPP MISR instrument showing rainfall in Dorian
Suomi NPP’s MiRS instrument provided the rain rate and also showed the rain wrapping into the circulation center. Credit: NASA/NOAA/UWM-SSEC-CIMSS/William Straka III

The summary of watches and warnings in effect have not changed since the last NHC update at 11:00 am EDT.

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By Lynn Jenner
NASA’s Goddard Space Flight Center