When NASA's Aqua satellite passed over the eastern Atlantic Ocean it looked at the weakening Tropical Depression Fiona and a developing tropical low pressure area named System 99L. Fiona became a post-tropical depression today, Aug. 23.
The Atmospheric Infrared Sounder or AIRS instrument aboard Aqua, provided temperature data on the systems as it analyzed them in infrared light. On Aug. 23 at 0841 UTC (4:41 a.m. EDT) infrared data showed both Fiona and the low pressure area designated 99L showed some powerful thunderstorms with high cold cloud tops (as cold as -63F/-53C) in each system. AIRS imagery is created at NASA's Jet Propulsion Laboratory in Pasadena, California.
NOAA's GOES-East satellite saw a tiny, elongated post-tropical depression Fiona and a larger developing System 99L in the Eastern Atlantic at 1145 UTC (7:45 a.m. EDT). The image was created by the NASA/NOAA GOES Project at NASA's Goddard Space Flight Center in Greenbelt, Maryland using data from NOAA's GOES-East satellite.
Fiona appeared elongated as a result of battling vertical wind shear and had a small area of strong convection at the time of the Aqua image. But that area diminished by 11 a.m. EDT.
National Hurricane Center (NHC) forecaster Blake noted in the 11 a.m. EDT discussion "Satellite images indicate that Fiona has lost even more organization this morning with only a weak, elongated circulation and no organized deep convection. Thus, Fiona no longer meets the requirements of a tropical cyclone and this is the last advisory."
Infrared data on System 99L showed a larger area of powerful thunderstorms, although fragmented around its center.
At 11 a.m. EDT (1500 UTC) on Aug. 23 the center of Post-Tropical Cyclone Fiona was located near 26.1 degrees north latitude and 64.5 degrees west longitude. That's about 430 miles (690 km) south of Bermuda.
The post-tropical cyclone is moving toward the west-northwest near 12 mph (19 kph), and a gradual turn toward the northwest with a decrease in forward speed is expected over the next 48 hours. The estimated minimum central pressure is 1014 millibars.
Maximum sustained winds have decreased to near 30 mph (45 kph) with higher gusts. The low should gradually weaken over the next couple of days.
Regeneration is not expected at this time. The NHC forecast noted that the low pressure area should move northwestward into a break in the subtropical ridge (elongated area) of high pressure, then westward as the ridge re-strengthens.