NASA examines Dorian's rainfall, temperatures along Carolina coast
As Hurricane Dorian continued to lash the coast of the Carolinas NASA's IMERG assessed the rainfall the storm generated and NASA's Aqua satellite provided a look at the temperatures of the cloud tops to assess strength.
NASA's IMERG Analyzes Rainfall
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 real time 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.
IMERG showed largest rainfall amounts of more than 36 inches over the Bahamas and in an area off the coast of northeastern Florida. A large area of rainfall between 16 and 24 inches fell off the coast from South Carolina to the Bahamas and in a small area far off the North Carolina coast.
The National Weather Service in Charleston, South Carolina noted that 3.06" fell yesterday, Sept. 5. In Wilmington, North Carolina, a rainfall record was set when Dorian dropped 8.58 inches. New Bern, North Carolina also set a rainfall record, when Dorian dropped 2.95 inches there.
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 0000 UTC on September 1, and therefore does not show the precipitation that fell in late August, prior to Hurricane Dorian's approach to the Bahamas.
More Rainfall Forecast from NHC
Using data from the GPM and other satellites, forecasters can estimate rainfall that Dorian will generate along its path.
The NHC said Dorian is expected to produce the following rainfall totals through Saturday: In northeastern North Carolina and additional 3 to 8 inches is forecast with isolated storm totals to 15 inches. Far southeast Virginia can expect 3 to 8 inches, extreme southeastern New England...2 to 4 inches, Nova Scotia and Prince Edward Island...3 to 5 inches and Newfoundland...1 to 2 inches.
NHC said a few tornadoes were possible during the morning of Sept. 6 across eastern North Carolina into southeastern Virginia.
As Hurricane Dorian interacted with the U.S. East Coast, the only tornado reports occurred from 4:50 a.m. to 5 p.m. 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.
NASA's Aqua Satellite Double View
Two instruments aboard NASA's Aqua satellite used infrared light to analyze the strength of storms Dorian. Infrared data provides temperature information, and the strongest thunderstorms that reach high into the atmosphere have the coldest cloud top temperatures.
On Sept. 6 at 3:20 a.m. EDT (0720 UTC), NASA's Aqua satellite provided temperature data on Hurricane Dorian to show where strongest storms were located with cloud top temperatures as cold as minus 70 degrees Fahrenheit (minus 56.6 Celsius).
On Sept. 5 at 8:15 a.m. EDT (1215 UTC), the Moderate Imaging Spectroradiometer or MODIS instrument that flies aboard NASA's Aqua satellite found strongest thunderstorms had cloud top temperatures as cold as or colder than minus 70 degrees Fahrenheit (minus 56.6 Celsius). Those temperatures were in cloud tops of storms around the low-level center of circulation and in a thick band of thunderstorms that wrapped around the storm from west to north to east. Cloud top temperatures that cold indicate strong storms with the potential to generate heavy rainfall.
A second instrument aboard NASA's Aqua satellite called the Atmospheric Infrared Sounder or AIRS instrument also provided infrared data. That data was false-colored in an infrared image created at NASA's Jet Propulsion Laboratory in Pasadena, Calif. AIRS gathered that data on Sept. 6 at 3:17 a.m. EDT (0717 UTC). The strongest storms were mostly over the Atlantic Ocean and east of the center.
Warnings and Watches on Sept. 6
The NHC posted many warnings and watches on Sept. 6. A Storm Surge Warning is in effect for Salter Path, NC to Poquoson, VA, for the Pamlico and Albemarle Sounds, the Neuse and Pamlico Rivers and the Hampton Roads area of Virginia. A Hurricane Warning is in effect from Surf City to the North Carolina/Virginia border and for the Pamlico and Albemarle Sounds. A Hurricane Watch is in effect for Nova Scotia, Canada.
A Tropical Storm Warning is in effect for the North Carolina/Virginia border to Fenwick Island, DE, for the Chesapeake Bay from Drum Point southward, for the Tidal Potomac south of Cobb Island, for Woods Hole to Sagamore Beach, MA, and for Nantucket and Martha's Vineyard, MA. A Tropical Storm Watch is in effect for Prince Edward Island, Canada, the Magdalen Island, Fundy National Park to Shediac, and Francois to Boat Harbour.
The Hurricane Warning and the Tropical Storm Warning have been discontinued west of Surf City, North Carolina. The Storm Surge Warning south of Salter Path, North Carolina has been discontinued.
Hurricane Dorian's Eye Near Cape Hatteras on Sept. 6
At 8 a.m. EDT on Sept. 6, the National Hurricane Center said the eye of Dorian was near Cape Hatteras, North Carolina. It was located near latitude 35.2 degrees north and longitude 75.7 degrees west. Dorian is moving toward the northeast near 14 mph (22 km/h) and this general motion with an increase in forward speed is expected through Saturday, Sept. 7.
Maximum sustained winds are near 90 mph (150 kph) with higher gusts. Dorian is forecast to become a post-tropical cyclone with hurricane-force winds by Saturday night as it approaches Nova Scotia, Canada.
The estimated minimum central pressure based on data from the Air Force Hurricane Hunters and surface observations is 956 millibars.
On the NHC forecast track, the center of Dorian should move to the southeast of extreme southeastern New England tonight and Saturday morning, and then across Nova Scotia late Saturday or Saturday night.