Sep. 08, 2019 – NASA Sees Post-Tropical Cyclone Dorian Over Eastern Canada
NASA’s Aqua satellite provided an infrared look at Post-Tropical Cyclone Dorian lashing parts of eastern Canada.
A tropical cyclone is the general name for a hurricane, tropical storm, depression or typhoon. NASA provides data and research on tropical cyclones to analyze intensification, weakening, structure, and behavior. NOAA’s National Hurricane Center uses that data in their forecasts.
NASA’s Views of Dorian Before and After Landfall
Instruments aboard NASA’s Aqua satellite use visible, microwave and infrared light to analyze various aspects of a tropical cyclone.
On Sept. 7 at 1:30 p.m. EDT (1730 UTC), the MODIS instrument that flies aboard NASA’s Aqua satellite provided a visible image that clearly showed Dorian’s center just south of Nova Scotia, Canada.
Dorian moved north and five hours later, Post-Tropical Dorian made landfall at 6:15 p.m. EDT near Sambro Creek in Nova Scotia, Canada, or about 15 miles (25 km) south of Halifax. The estimated maximum sustained winds at landfall were 100 mph (155 kph) and the estimated central pressure was 958 millibars.
After Dorian had crossed over Nova Scotia, at 2 a.m. EDT on Sept. 8, it was centered about 5 miles (10 km) north of the Magdalen Islands, near latitude 47.5 degrees north and longitude 61.8 degrees west in the Gulf of St. Lawrence.
NASA’s Aqua satellite passed over Dorian again and looked at the storm in infrared light. NASA uses infrared light to analyze the strength of storms by providing temperature information about the system’s clouds. The strongest thunderstorms that reach high into the atmosphere have the coldest cloud top temperatures.
On Sept. 8 at 3:05 a.m. EDT (0705 UTC), the Moderate Imaging Spectroradiometer or MODIS instrument that flies aboard NASA’s Aqua satellite gathered infrared data on Dorian and showed the storm bringing rains and gusty winds to areas of Newfoundland, Labrador, Quebec south, Prince Edward Island and Nova Scotia. MODIS showed thunderstorms had cloud top temperatures as cold as minus 50 degrees Fahrenheit (minus 45.5 Celsius).
What is a Post-Tropical Storm?
A Post-Tropical Storm is a generic term for a former tropical cyclone that no longer possesses sufficient tropical characteristics to be considered a tropical cyclone. Former tropical cyclones that have become fully extratropical, subtropical, or remnant low pressure areas, are three classes of post-tropical cyclones. In any case, they no longer possesses sufficient tropical characteristics to be considered a tropical cyclone. However, post-tropical cyclones can continue carrying heavy rains and high winds.
Warnings and Watches on Sept. 8, 2019
NOAA’s National Hurricane Center (NHC) noted on Sept. 8 that a Hurricane Warning is in effect for eastern Nova Scotia from Ecum Secum to Brule, and western Newfoundland from Indian Harbour to Hawke’s Bay. A Hurricane Watch is in effect for the Magdalen Islands. A Tropical Storm Warning is in effect for Prince Edward Island, Magdalen Islands, from Stone’s Cove to Indian Harbour, from Hawke’s Bay to Fogo Island and from Mutton Bay to Mary’s Harbour.
The Canadian Meteorological Service issued many warnings and watches on Sunday, September 8, 2019 for Newfoundland, Labrador, Quebec south, Prince Edward Island and Nova Scotia.
For the Public Weather Alerts for Newfoundland and Labrador: https://weather.gc.ca/warnings/index_e.html?prov=nl
For the Public Weather Alerts for Quebec – south: https://weather.gc.ca/warnings/index_e.html?prov=sqc
For the Public Weather Alerts for Prince Edward Island:
https://weather.gc.ca/warnings/index_e.html?prov=pei
For the Public Weather Alerts for Nova Scotia: https://weather.gc.ca/warnings/index_e.html?prov=ns
Dorian’s Location on Sunday, September 8, 2019
NHC noted that at 8 a.m. EDT (1200 UTC), the center of Post-Tropical Cyclone Dorian was located near latitude 49.4 degrees north and longitude 60.6 degrees west. Dorian’s center was about 55 miles (90 km) east-northeast of Heath Point, Anticosti Island, Canada, and about 90 miles (145 km) northwest of Cape St. George, Newfoundland, Canada. A sustained wind of 55 mph (89 km/h) with a gust to 73 mph (117 kph) was reported at Heath Point on Anticosti Island.
The post-tropical cyclone is moving toward the north-northeast near 26 mph (43 kph), and this general motion with a turn to the northeast is expected during the next couple of days. Maximum sustained winds are near 80 mph (130 kph) with higher gusts. These winds are occurring mainly over water. The post-tropical cyclone is forecast to drop below hurricane strength after passing Newfoundland later today.
The estimated minimum central pressure is 961 millibars.
What’s Next for Dorian?
Dorian is expected to remain a powerful storm through this afternoon, but the global models show steady weakening after the center moves northeast of Newfoundland tonight. Forecasters at NHC said “Dorian should continue north-northeastward today, then turn east-northeastward over the North Atlantic as it remains embedded within the mid-latitude westerlies.”
The forecast track takes Dorian south of Greenland on its trek across the Northern Atlantic. The post-tropical cyclone should should be absorbed by another extratropical low over the North Atlantic in 2 to 3 days.
For updated forecasts from the NHC, visit: www.nhc.noaa.gov
For updated forecasts from Environment Canada, visit: https://weather.gc.ca/
By Rob Gutro
NASA’s Goddard Space Flight Center