May 20, 2020 – NASA-NOAA Satellite Catches Post-Tropical Storm Arthur’s End
NASA-NOAA’s Suomi NPP satellite passed over the western North Atlantic Ocean and provided forecasters with a visible image of Post Tropical Storm Arthur.
NASA-NOAA’s Suomi NPP satellite found post tropical storm Arthur out in the Western Atlantic Ocean far from the U.S. and parallel to the Virginia/North Carolina border. Credit: NASA Worldview, Earth Observing System Data and Information System (EOSDIS)
During the afternoon (Eastern Daylight Time/U.S.) of May 19, the Visible Infrared Imaging Radiometer Suite (VIIRS) instrument aboard Suomi NPP provided a visible image of Arthur and showed a weak circulation with the bulk of clouds northeast and east of the center. Arthur is located out in the Western Atlantic Ocean far from the U.S. coast and parallel to the Virginia/North Carolina border.
The NOAA National Hurricane Center’s Tropical Weather Discussion on May 20 at 8:05 a.m. EDT noted, “Post-Tropical Cyclone Arthur is north of the area near latitude 35 degrees north and longitude 65 degrees west. Arthur will move southeast to south through Thursday [May 21], and weaken. Large northeastern [ocean] swell from Arthur will affect the waters that are to the NE of the Bahamas, through Friday [May 22], and then subside on Friday night and Saturday.“
Tropical cyclones/hurricanes are the most powerful weather events on Earth. NASA’s expertise in space and scientific exploration contributes to essential services provided to the American people by other federal agencies, such as hurricane weather forecasting.
May 19, 2020 – NASA Examines Tropical Storm Arthur’s Rainfall as it Transitions
When the Global Precipitation Measurement mission or GPM core satellite passed over the western North Atlantic Ocean, it captured rainfall data on Tropical Storm Arthur as the storm was transitioning into an extra-tropical storm.
The GPM core satellite passed over Tropical Storm Arthur in the western North Atlantic Ocean on May 19 at 2:51 a.m. EDT (0651 UTC) and found the heaviest rainfall (red) on the northeastern side of the storm falling at a rate of over 25mm (over 1 inch) per hour. Credit: NASA/JAXA/NRL
The GPM’s core satellite passed over Arthur on May 19 at 2:51 a.m. EDT (0651 UTC) and found the heaviest rainfall on the northeastern side of the storm falling at a rate of over 25mm (over 1 inch) per hour. Lighter rainfall rates were measured throughout the rest of the storm. Forecasters at NOAA’s National Hurricane Center or NHC incorporate the rainfall data into their forecasts.
NHC forecasters noted at 5 a.m. EDT (0900 UTC) on May 19, “Arthur’s cloud pattern has continued to take on a generally post-tropical appearance, though a recent convective burst near its center suggests that it isn’t quite post-tropical yet. Satellite imagery and earlier scatterometer data also indicate the presence of a developing warm front near the cyclone’s center, and this could be contributing the development of the aforementioned convective burst.”
NHC said the center of Tropical Storm Arthur was located near latitude 37.0 north, longitude 70.6 west, about 300 miles (485 km) east-northeast of Cape Hatteras, North Carolina. Arthur was moving toward the east-northeast near 15 mph (24 kph). Maximum sustained winds are near 60 mph (95 kph) with higher gusts. The estimated minimum central pressure is 991 millibars.
The NHC cautions that swells generated by Arthur are expected to affect portions of the mid-Atlantic and southeast U.S. coasts during the next day or two. These swells could cause life-threatening surf and rip current conditions.
Arthur is forecast to become post-tropical later today and is forecast to slow down and turn toward the south in another day or so. Arthur is expected to dissipate by the end of the week.
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 extratropical, subtropical, or remnant lows are all 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 produce high winds.
Hurricanes/tropical cyclones are the most powerful weather events on Earth. NASA’s expertise in space and scientific exploration contributes to essential services provided to the American people by other federal agencies, such as hurricane weather forecasting.
GPM is a joint mission between NASA and the Japan Aerospace Exploration Agency, JAXA.
May 18, 2020 – NASA Finds a Disorganized Tropical Storm Arthur Near North Carolina Coast
Infrared imagery from NASA’s Aqua satellite and radar imagery revealed that Tropical Storm Arthur remains poorly organized. Strongest storms, according to the Aqua data, appeared along and off the southeastern coast of North Carolina.
On May 18 at 2:35 a.m. EDT (0635 UTC), the MODIS instrument that flies aboard NASA’s Aqua satellite showed strongest storms in Tropical Storm Arthur were along the southeastern coast of North Carolina. Those strong storms contained cloud top temperatures were as cold as minus 63 degrees Fahrenheit (minus 52.7 Celsius). Credit: NASA/NRL
Warnings and Watches
On May 18, a Tropical Storm Warning is in effect from Surf City to Duck, North Carolina, and for the Pamlico and Albemarle Sounds.
Satellite Imagery
NASA’s Aqua satellite used infrared light to analyze the strength of storms and found the center of circulation was displaced from the bulk of them. Infrared data provides temperature information, and the strongest thunderstorms that reach high into the atmosphere have the coldest cloud top temperatures.
On May 18 at 2:35 a.m. EDT (0635 UTC), the MODIS instrument that flies aboard NASA’s Aqua satellite showed strongest storms in Tropical Storm Arthur were along the southeastern coast of North Carolina and just off-shore. Those strong storms contained cloud top temperatures were as cold as minus 63 degrees Fahrenheit (minus 52.7 Celsius). Cloud top temperatures that cold indicate strong storms with the potential to generate heavy rainfall.
MODIS imagery showed the low-level center located near the southwestern edge of a complex of ragged convective bands.
Status on May 18, 2020
At 8 a.m. EDT (1200 UTC), the National Hurricane Center (NHC) reported the center of Tropical Storm Arthur was located near latitude 34.5 north, longitude 75.9 west. Arthur was moving toward the north-northeast near 15 mph (24 kph). A turn toward the northeast with an increase in forward speed is expected later today, followed by a turn toward the east on Tuesday.
Maximum sustained winds are near 45 mph (75 kph) with higher gusts. While some strengthening is forecast during the next 48 hours, Arthur is likely to lose its tropical characteristics on Tuesday. Tropical-storm-force winds extend outward up to 90 miles (150 km) mainly to the east of the center.
The estimated minimum central pressure reported from an Air Force Reserve Hurricane Hunter aircraft is 1001 millibars.
Rip Currents and Life-Threatening Surf Along Coastal Areas
Swells generated by Arthur are affecting portions of the southeast U.S. coast and are expected to spread northward along the U.S. mid-Atlantic coast during the next day or two. NHC cautioned, “These swells could cause life-threatening surf and rip current conditions.”
Arthur’s Forecast Path
At 5 a.m. EDT on May 18, 2020, NOAA’s National Hurricane Center noted that Arthur’s movement is going to be affected by two factors: “A baroclinic trough (elongated area of low pressure) and associated surface front approaching from the west should cause Arthur to turn northeastward during the next several hours. The forecast track shows the center passing near or just offshore of the North Carolina Outer Banks. By Tuesday and Tuesday night, Arthur will be entering the strong mid-latitude Westerlies, which will steer cyclone eastward in a day or two.”
May 17, 2020 – NASA Sees Development of Atlantic’s First Tropical Storm
Tropical Storm Arthur formed off the east coast of Florida from a low-pressure system (90L) that developed days before in the Straits of Florida. NASA-NOAA’s Suomi NPP satellite provided forecasters with an image of the new storm.
On May 16, NASA-NOAA’s Suomi NPP satellite provided forecasters with a visible image of Tropical Depression Arthur off the east coast of Florida. Arthur strengthened into a tropical storm soon after Suomi NPP passed overhead. Credit: NASA Worldview, Earth Observing System Data and Information System (EOSDIS)
On Saturday, forecasters at the National Hurricane Center were closely watching System 90L, an area of low pressure that was located just offshore of the southeast coast of Florida. It continued to produce shower activity and gusty winds from portions of southeast and east-central Florida eastward across the northwestern Bahamas and the adjacent Atlantic waters.
Overnight and early on May 17, that low-pressure system became better defined and organized and it became a tropical storm over the Atlantic waters east of Florida.
Visible imagery from NASA satellites help forecasters understand if a storm is organizing or weakening. The Visible Infrared Imaging Radiometer Suite (VIIRS) instrument aboard Suomi NPP provided a visible image of Arthur late on May 16 when it had been classified as Tropical Depression 1. The shape of a tropical cyclone provides forecasters with an idea of its organization and strength, and NASA-NOAA’s Suomi NPP satellite provided a visible image of Arthur and it appeared more circular in nature.
At 5 p.m. EDT (2100 UTC) on May 16, the center of Tropical Depression 1 was located near latitude 28.4 north, longitude 78.6 west, about 505 miles or 810 kilometers south-southwest of Cape Hatteras, North Carolina. By 11 p.m. EDT, Tropical Depression 1 strengthened into a tropical storm and was renamed Arthur.
On May 17, a Tropical Storm Warning was in effect from Surf City to Duck, NC and for the Pamlico and Albemarle Sounds.
NOAA’s National Hurricane Center said, at 8 a.m. EDT (1200 UTC) on May 17), the center of Tropical Storm Arthur was located near latitude 30.3 north, longitude 77.4 west. Arthur is moving toward the north-northeast near 9 mph (15 kph). Maximum sustained winds are near 40 mph (65 kph) with higher gusts. Tropical-storm-force winds extend outward up to 80 miles (130 km) from the center. The estimated minimum central pressure is 1002 millibars.
Some strengthening is forecast during the next 48 hours. Arthur is likely to lose its tropical characteristics on Tuesday.
A turn toward the northeast with an increase in forward speed is expected during the next 24 to 48 hours. On the forecast track, Arthur will remain well offshore the east coast of Florida, Georgia, and South Carolina today, and then move near or just east of the coast of North Carolina on Monday.
Tropical cyclones/hurricanes are the most powerful weather events on Earth. NASA’s expertise in space and scientific exploration contributes to essential services provided to the American people by other federal agencies, such as hurricane weather forecasting.
May 15, 2020 – NASA Analyzes Developing System 90L in Straits of Florida
A low-pressure area designated as System 90L appears to be developing in the Straits of Florida, located between Southern Florida and Cuba. NASA’s Aqua satellite measured cloud top temperatures within the developing system and found some stronger storms.
On May 15, 2020 at 3:45 a.m. EDT (0745 UTC), the MODIS instrument that flies aboard NASA’s Aqua satellite gathered infrared data on 90L. Strongest thunderstorms had cloud top temperatures (yellow) as cold as minus 50 degrees Fahrenheit (minus 45.5 Celsius) over the Straits of Florida. Credit: NASA/NRL
At 8:50 a.m. EDT on May 15, NOAA’s National Hurricane Center (NHC) issued a Special Tropical Weather Outlook issued to discuss the potential for tropical or subtropical development near the northwest Bahamas.
The Outlook stated, “A trough (elongated area) of low pressure located over the Straits of Florida continues to produce disorganized shower activity and gusty winds across the Florida Keys, portions of southeast Florida, and the northwestern Bahamas. Gradual development of this system is expected, and it will likely become a tropical or subtropical storm on Saturday [May 16] when it is located near the northwestern Bahamas. Later in the weekend and early next week, the system is expected to move generally northeastward over the western Atlantic (Ocean).”
NASA’s Aqua satellite provided information to NHC forecasters. One kind of data Aqua provides is 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 May 15 at 3:45 a.m., EDT (0745 UTC) the Moderate Resolution Imaging Spectroradiometer or MODIS instrument that flies aboard NASA’s Aqua satellite gathered infrared data on 90L. Strongest thunderstorms had cloud top temperatures as cold as minus 50 degrees Fahrenheit (minus 45.5 Celsius). As cloud tops continue to cool, they stretch higher into the troposphere. NASA research has shown that when cloud top temperatures drop to minus 70 degrees Fahrenheit (minus 56.6 degrees Celsius), storms have the ability to generate heavy rain.
The NHC Outlook stated, “Regardless of development, the disturbance will continue to bring heavy rainfall to portions of the Florida Keys, southeast Florida and the Bahamas through Saturday. Tropical storm-force wind gusts are also possible across portions of the Florida Keys, southeast Florida, and the Bahamas during the next day or so. In addition, hazardous marine conditions are expected along the Florida east coast and in the Bahamas where Gale Warnings are in effect. Dangerous surf conditions and rip currents are possible along portions of the southeast U.S. coast this weekend and early next week.”
The NHC said that the formation chance through 48 hours and out through 5 days is high.
Tropical cyclones and hurricanes are the most powerful weather events on Earth. NASA’s expertise in space and scientific exploration contributes to essential services provided to the American people by other federal agencies, such as hurricane weather forecasting.
