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Hurricane Season 2011: Hurricane Greg (Eastern Pacific Ocean)
08.19.11
 
NASA's Aqua satellite passed over Greg on August 18 at 20:23 UTC (4:23 a.m. EDT), when he was still a hurricane. › View larger image
NASA's Aqua satellite passed over Greg on August 18 at 20:23 UTC (4:23 a.m. EDT), when he was still a hurricane. The infrared image revealed a large area of powerful, high thunderstorms with cold cloud tops (purple) surrounding the center where cloud temperatures were colder than -63 Fahrenheit (-52 Celsius). Just 12 hours later, those cloud tops cooled and Greg weakened to a tropical storm.
Credit: NASA/JPL, Ed Olsen
NASA's Infrared Eye Sees a Warmer, Weaker Tropical Storm Greg

Greg has weakened to a tropical storm in the Eastern Pacific Ocean, and NASA's infrared satellite data confirmed that the storm's cloud tops warmed.

Infrared satellite data reads temperatures of cloud tops and ocean surfaces, to provide forecasters with valuable information about how a tropical cyclone is behaving or may behave. When NASA's Aqua satellite passed over Greg on August 19, the Atmospheric Infrared Sounder (AIRS) instrument, an "infrared eye" read Greg's cloud top temperatures and found them to be warmer than they were from midnight. That means that the cloud tops, especially near Greg's center are not as high in the troposphere (the higher you go in the troposphere, the colder the temperature), which means that there's not as much strength in the storm pushing the air skyward.

At of 11 a.m. EDT on August 19, Greg weakened to a tropical storm with maximum sustained winds near 65 mph and he'll continue to weaken. Greg was located 455 miles southwest of the southern tip of Baja California, near 19.1 North and 115.7 West. It was moving to the west near 9 mph, and will continue on that track. Greg had a minimum central pressure of 991 millibars.

The National Hurricane Center expects rapid weakening over the weekend because Greg will be going into waters cooler than 80F (26.6C), which is the minimum warm temperature needed to maintain a tropical cyclone. Greg is expected to weaken to a remnant low by Sunday, August 21.

Text Credit: Rob Gutro, NASA Goddard Space Flight Center, Greenbelt, Md.



August 18, 2011

GOES-11 caught Tropical Storm Fernanda (left) and Hurricane Greg (right) on August 18 at 1200 UTC. › View larger image
The GOES-11 satellite caught an image of eastern Pacific on August 18 at 1200 UTC (8 a.m. EDT) saw Tropical Storm Fernanda (left) approaching the central Pacific Ocean and Hurricane Greg (right) behind her in the eastern Pacific Ocean.
Credit: NASA/NOAA GOES Project
TRMM saw intense convective thunderstorms within Tropical Storm Greg's rainfall on August 17, 2011 at 0534 UTC. › View larger image
TRMM satellite saw Tropical Storm Greg's rainfall on August 17, 2011 at 0534 UTC (1:34 a.m. EDT). TRMM's Microwave Imager (TMI) showed that intense convective thunderstorms within the developing storm were dropping rainfall at rates greater than 30mm/hr (1.2 inches) in an area near the center of the storm.
Credit: SSAI/NASA, Hal Pierce
NASA Satellite Data Confirms Greg a Hurricane, Fernanda a Tropical Storm

Big sisters don't like being overshadowed by their younger brothers and that's what has happened in the eastern Pacific Ocean with Tropical Storm Fernanda and now Hurricane Greg. Despite the difference in strength, NASA satellite imagery shows some strong convection happening in both tropical cyclones and that they're now matched in size.

Greg grew into a hurricane today is it continues moving near the western coast of Mexico, while Fernanda has maintained tropical storm strength.

The Geostationary Operational Environmental Satellite called GOES-11 caught an image of eastern Pacific on August 18 at 1200 UTC (8 a.m. EDT) saw Tropical Storm Fernanda approaching the central Pacific Ocean and Hurricane Greg behind her in the eastern Pacific Ocean. The image was created at NASA's GOES Project, located at NASA Goddard Space Flight Center in Greenbelt, Md. NOAA manages the GOES-11 satellite and NASA uses its data to create images and animations.

At 11 a.m. EDT (5 a.m. Hawaii Standard Time) Fernanda's maximum sustained winds were near 65 mph, just 9 mph shy of hurricane status. She was located about 1040 miles east-southeast of South Point, Hawaii near latitude 13.7 North and longitude 141.0 West. Fernanda is moving toward the west-northwest near 13 mph and is expected to take a more westerly track in the next 48 hours after which she's expected to weaken because of adverse atmospheric conditions.

Infrared imagery from the AIRS instrument on NASA's Aqua satellite today shows that deep convection (rapidly rising air that creates the thunderstorms that power the cyclone) is still occurring within 60 nautical miles of Fernanda's center, and a small area southwest of the center with cloud tops as cold as -112 Fahrenheit (-80 Celsius)! Cloud tops that high indicate very strong thunderstorms and heavy rainfall, exceeding 2 inches (50 mm) per hour.

That strength isn't expected to hold for the next 48 hours, though. The National Hurricane Center noted "by the time Fernanda passes south of the main Hawaiian Islands it is expected to have weakened to a remnant low."

Fernanda and Greg are now about the same size. Fernanda's tropical storm-force winds extend outward up to 80 miles from the center. Greg's tropical storm-force winds extend to about 85 miles from the center, while his hurricane-force winds extend 25 miles out.

At 11 a.m. EDT (8 a.m. PDT) Greg's maximum sustained winds were near 85 mph, making him a category one hurricane on the Saffir-Simpson Scale. He was moving to the west-northwest near 18 mph and is forecast to move in a more westerly direction in the next couple of days.

Greg was centered about 320 miles south-southwest of the southern tip of Baja California near 18.5 North and 111.5 West and was passing Mexico's Socorro Island. The automated weather station on the island reported sustained winds of 38 mph and a wind gust of 53 mph.

NASA's Tropical Rainfall Measuring Mission (TRMM) satellite saw Greg as a tropical storm on August 17 at 0534 UTC. At that time, TRMM's Microwave Imager showed that intense convective thunderstorms within the developing storm were dropping rainfall at rates greater than 30mm/hr (1.2 inches) in an area near the center of the storm. Greg's rainfall rates have increased as he strengthened into a hurricane. Greg is forecast to move into cooler waters in three days, at which time he will begin to weaken. In the meantime, he continues to chase Fernanda through the Eastern Pacific Ocean.

Text Credit: Rob Gutro, NASA Goddard Space Flight Center, Greenbelt, Md.



August 17, 2011

On August 17 at 1200 UTC (8a.m. EDT), GOES-11 caught Fernanda (left) and Greg (right). › View larger image
GOES-11 caught an image of the eastern Pacific on August 17 at 1200 UTC (8 a.m. EDT) and showed Fernanda (left) moving into the Central Pacific Ocean while Greg (right) is in the far Eastern Pacific.
Credit: NASA/NOAA GOES Project
GOES-11 Satellite Sees Tropical Storms Fernanda and "Little Brother" Greg Chasing Each Other

The Eastern Pacific Ocean is fired up with two tropical storms today, Fernanda and Greg, and both were caught in one image from the GOES-11 satellite. Both appear to be chasing each other to the west, and Fernanda appears a little more organized in satellite imagery and stronger than her "little brother."

The newest tropical storm, Greg, formed this morning, August 17 off the west coast of Mexico from a low previously known as System 99E. Greg is about 135 miles (220 km) south-southwest of Zihuatanejo, Mexico. Because Greg is close to the western coast of Mexico, the National Hurricane Center noted that heavy rainfall is possible in the next day or two along the coasts of two Mexican states: Guerrero and Michoacan.

The Geostationary Operational Environmental Satellite called GOES-11 caught an image of eastern Pacific on August 17 at 1200 UTC (8 a.m. EDT) and showed Fernanda moving into the Central Pacific Ocean while Greg is in the far Eastern Pacific. The image was created at NASA's GOES Project, located at NASA Goddard Space Flight Center in Greenbelt, Md. NOAA manages the GOES-11 satellite and NASA uses its data to create images and animations.

In the image, Fernanda far west of Greg, has a signature shape of a mature tropical storm, while Greg shows high clouds and powerful convection and thunderstorms in the center of circulation, but had not yet fully developed the signature comma shape. The eastern quadrant of Greg's clouds extended over the southwestern Mexico coastline, and his thunderstorms were dropping moderate to heavy rainfall.

On August 17 at 5 a.m. EDT (0900 UTC), Tropical Storm Greg's maximum sustained winds were near 40 mph. Those tropical storm-force winds extend outward up to 45 miles, making the storm 90 miles in diameter. Estimated minimum central pressure is 1004 millibars. Greg was centered near 15.8 North and 102.2 West and moving to the west-northwest near 16 mph (26 kmh). Greg's center is expected to remain well offshore from the southwestern Mexico coastline.

Greg is located in a decent environment for strengthening: moist air, moderate wind shear from the northeast and warm sea surface temperatures near 86 Fahrenheit (30 Celsius). It takes sea surface temperatures of at least 80F (26.6C) to support a tropical cyclone

Tropical Storm Fernanda is stronger than her "little brother" Greg, with maximum sustained winds near 50 mph (85 kmh) and some slight strengthening is still possible, according to the National Hurricane Center. Greg is not only Fernanda's "little" brother in terms of winds but also in terms of extent of tropical storm-force winds. Fernanda's tropical storm-force winds extend out 70 miles from the center making her 50 miles wider in diameter than Greg.

On August 17 at 5 a.m. EDT, Fernanda was still very far from Hawaii. In fact, she was centered about 1,350 miles (2, 715 km) east-southeast of South Point, Hawaii near 11.6 North and 136.9 West. She's moving to the west near 7 mph (11 kmh) and is expected to turn to the west-northwest over the next couple of days. Fernanda is not expected to reach hurricane status as she continues to move west and Greg continues to chase her.

Text Credit: Rob Gutro, NASA Goddard Space Flight Center, Greenbelt, Md.