NASA Satellites See Calvin Go from Hurricane to Remnant Low
Hurricane Season 2011: Tropical Storm Calvin (Eastern Pacific Ocean)
NASA satellites have watched Calvin become a hurricane on July 8 and weaken quickly to a remnant low pressure area by July 10. Calvin's remnants are now over cooler waters and are dissipating.
Tropical Storm Calvin strengthened into a hurricane around 5 p.m. EDT on Friday, July 8 with maximum sustained winds near 65 knots (75 mph/120 kmh). At that time it was located about 340 miles south-southwest of Cabo Corrientes, Mexico near 16.3 North and 108.5 West.
On July 8, NASA's Aqua satellite passed over Tropical Storm Calvin and captured visible and infrared images of the storm. The infrared image from the Atmospheric Infrared Sounder (AIRS) instrument was taken at 20:29 UTC (4:29 p.m. EDT), about 6 hours before it briefly became a hurricane. The infrared image showed an area of strong thunderstorms with cloud top temperatures as cold as -63 Fahrenheit (-52 Celsius) around the center of the tropical storm.
The Moderate Resolution Imaging Spectroradiometer (MODIS) instrument on the same satellite took a visible image of Tropical Storm Calvin six minutes later and showed a well-organized and strengthening tropical storm.
July 9, Calvin's winds weakened below hurricane strength to 50 knots (57 mph/93 kmh). By July 10 at 0300 UTC (July 9 at 11 p.m. EDT), Calvin's maximum sustained winds were down to 30 knots (34 mph/55 kmh), so it was down to depression status.
By July 11 at 8 a.m. EDT Calvin had degraded further as the low moved into cooler sea surface temperatures. Sea surface temperatures of at least 80F (26.6C) to maintain the strength of a tropical cyclone, but the water temperatures are cooler than that where Calvin is now located. All signs of deep/strong convection (rapidly rising air that forms the thunderstorms that would power it) are gone on satellite imagery. Its center was just west of Isla Clarion, near 19 North and 116 West. Its maximum sustained winds were between 20 and 25 knots.
Visible imagery from the GOES-11 satellite at 1445 UTC (10:45 a.m. EDT) on July 11 shows the remnants of Calvin as a swirl of clouds in the eastern Pacific Ocean, several hundred miles off the western Mexico coastline. GOES-11 is operated by NOAA, but the NASA GOES Project at the NASA Goddard Space Flight Center in Greenbelt, Md. created the image.
The low is expected to dissipate sometime on Tuesday.
Rob Gutro, NASA Goddard Space Flight Center
, Greenbelt, Md.
July 8, 2011
NASA's TRMM Satellite Sees Powerful T-storms Around Tropical Storm Calvin's Center
Tropical Storm Calvin grew stronger during the day on Friday, July 8, and by early afternoon he was on the verge of hurricane-strength. The TRMM satellite provided a look under the hood of the storm and noticed the heavy rainfall at the center of its heat engine.
The Tropical Rainfall Measuring Mission (TRMM) satellite can measure rainfall from space, and rainfall rates can be a gauge for the strengthening or weakening of a tropical cyclone.
TRMM's Microwave Imager (TMI) data provided good coverage of recently formed tropical storm Calvin as it passed above on July 8, 2011 at 0137 UTC (July 7 at 9:37 p.m. EDT). A TRMM pass showed that Calvin had become very well organized and the TMI rainfall analysis showed that rain was falling at a rate of over 50 mm/hr (~2 inches) in powerful thunderstorms near Calvin's center of circulation. Some heavy thunderstorms were also seen over southwestern Mexico.
At 11 a.m. EDT on July 8, Tropical Storm Calvin's maximum sustained winds had already grown to 70 mph. That's just 4 mph under hurricane strength. The National Hurricane Center said that Calvin could become a hurricane today, but some weakening should begin on Saturday, July 9. The center of Tropical Storm Calvin was located about 290 miles (470 kilometers) southwest of Manzanillo, Mexico near near latitude 16.2 north and longitude 107.6 west. Calvin is moving toward the west near 17 mph (28 km/h).
Calvin is then forecast to weaken as it passes over slightly cooler water and dissipate to a remnant low on Monday, July 11, 2011.
Hal Pierce/Rob Gutro, SSAI/NASA Goddard Space Flight Center
, Greenbelt, Md.
NASA Satellite Sees Strength in Tropical Storm Calvin
Thunderstorms are the heat engine that drive tropical cyclones, and infrared satellite data from NASA showed a large area of powerful thunderstorms around Tropical Storm Calvin's center.
The third tropical depression of the eastern Pacific hurricane season has now become the season's third tropical storm, too. It strengthened into a tropical storm at 11 p.m. EDT on July 7, 2011.
When NASA's Aqua satellite passed over the tropical cyclone on July 7 at 19:47 UTC (3:47 p.m. EDT) it was still a tropical depression but strengthening over the warm waters of the eastern Pacific. The Atmospheric Infrared Sounder (AIRS) measures cloud top temperatures and spotted the heaviest thunderstorms over the ocean at that time. Strongest thunderstorms are suggested in infrared imagery when you have the coldest cloud tops, and AIRS noted cloud top temperatures colder than -63 F/-52C just off-shore. Those storms were dropping rain at 2 inches/50 mm per hour.
By 5 a.m. EDT on July 8, Calvin's winds had picked up more to a sustained level of 50 mph (85 km/h). Tropical-storm-force winds extend outward up to 50 miles (85 km) from the center. Calvin's center was located about 215 miles (345 km) south-southwest of Manzanillo, Mexico near 16.3 North and 105.9 West. It was moving to the west-northwest near 15 mph (24 km/h) and had a minimum central pressure of 1000 millibars.
The National Hurricane Center expects Calvin to strengthen a little more over the next 24 hours as wind shear weakens. However, because Calvin is moving in a northward direction it is moving into cooler waters which will sap some of the storm's strength, so Calvin is expected to weaken back to depression status by Sunday.
Rob Gutro, NASA's Goddard Space Flight Center
, Greenbelt, Md.
July 7, 2011
NASA's TRMM Satellite Sees Third Tropical Depression Form in E. Pacific
The Tropical Rainfall Measuring Mission (TRMM) satellite passed over an area of low pressure in the eastern Pacific Ocean south of Mexico on July 7, 2011 at 0234 UTC (July 6 at 10:34 EDT) and captured rainfall in the newly formed third tropical depression of the hurricane season.
The National Hurricane Center (NHC) in Miami, Florida upgraded this area of low pressure to a tropical depression at 1500 UTC (8:00 a.m. PDT). At that time, maximum sustained winds were near 35 mph (55 km/h) and the center was located near 14.8 North and 101.2 West, which is about 355 miles (570 km) southeast of Manzanillo, Mexico. Tropical Depression 3E is moving to the west-northwest near 13 mph (20 km/h) and has a minimum central pressure of 1005 millibars.
The rainfall analysis from TRMM's Microwave Imager (TMI) and Precipitation Radar (PR) data was overlaid on an infrared image from TRMM's Visible and InfraRed Scanner (VIRS) by Hal Pierce of SSAI at NASA's Goddard Space Flight Center in Greenbelt, Md. The analysis showed that there were only a few areas of moderate to heavy rainfall associated with the developing tropical depression at the time of this TRMM orbit.
The strongest rainfall (about 2 inches/50 mm per hour) appeared in isolated areas south of the center of circulation. The moderate rainfall was falling at a rate between .78 and 1.57 inches (20 and 40 mm) per hour.
Conditions are expected to be favorable for the depression to become a tropical storm within the next couple days, and when it does, it would be renamed "Calvin." The storm is expected to remain over open waters well south of the coast of southwestern Mexico.
Hal Pierce, SSAI/NASA's Goddard Space Flight Center
, Greenbelt, Md.