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Hurricane Season 2009: Tropical Storm Olaf (Eastern Pacific)
October 5, 2009

AIRS image of Olaf> Click for larger image
The Aqua satellite flew over Olaf on October 3 at 5:05 a.m. EDT captured infrared imagery of his clouds streaming into northwestern Mexico. The images showed some high, cold, thunderstorm cloud tops (purple) as cold as -63F near Olaf's center indicating some moderate rainfall. Credit: NASA JPL, Ed Olsen
NASA Satellite Sees Olaf Stretch Out and Fizzle Over Northwestern Mainland Mexico

Tropical Storm Olaf wasn't given much of a chance when he was born, and he never did make it to hurricane strength before fizzling out late Saturday night. NASA's Aqua satellite captured infrared imagery that clearly showed Olaf's clouds stretched eastward out over mainland Mexico, away from it's center of circulation near Baja California.

At 11 p.m. EDT on Saturday, October 3, the National Hurricane Center issued its last advisory on Olaf. By that time, he was just classified as a remnant low pressure area.

Olaf was basically reduced to a tight swirl of low clouds approaching the west coast of southern Baja California. When precipitation and clouds separate from the center of the wind circulation and that's a tell-tale sign of a storm's demise. That's what happened with Olaf late Saturday. Olaf's clouds and rains moved northeast of his center and were located over mainland Mexico. Northwestern Mexico received Olaf's rains and gusty winds as he faded away.

Quikscat image of Olaf> Click for larger image
NASA's QuikScat captured the eastern half of Olaf's winds using microwaves to see through his clouds on Oct. 2. The purple area in the center revealed the strongest winds. At this time, maximum sustained winds were near 45 mph. Wind direction is indicated by small barbs. White barbs point to areas of heavy rain. Credit: NASA JPL, Peter Falcon
NASA's Quick Scatterometer satellite (QuikScat) passed over Olaf when he was a tropical storm on Olaf captured Oct 2, at 01:42 UTC (9:42 p.m. ET on October 1) and confirmed tropical storm force winds. QuikScat uses microwaves to peer into a storm's clouds and determine the speed of the rotating winds at the surface. At that time, maximum sustained winds were 45 mph, but adverse environmental conditions such as upper level winds and cooler sea surface temperatures weakened Olaf quickly afterward.

NASA's Aqua satellite got a great image of Olaf's clouds stretching away from his center of circulation on October 3. The Atmospheric Infrared Sounder (AIRS) instrument that is used to measure cloud top temperature and atmospheric pressure among other environmental factors clearly showed Olaf's center west of Baja California, but his clouds stretching over the Baja and into northwestern mainland Mexico. Those cloud top temperatures were around -63F indicating that there were still some strong thunderstorms in the storm as it was breaking apart, so Olaf was leaving behind some moderate rainfall and gusty winds as he began to dissipate. As of Monday, October 5, Olaf has dissipated.

Text credit: Rob Gutro, NASA/Goddard Space Flight Center

October 2, 2009

Tropical Storm Olaf's clouds reaching over the southern tip of Baja California in the Eastern Pacific Ocean. > View larger image
The GOES-11 satellite captured an infrared image of Tropical Storm Olaf's (bottom left) clouds reaching over the southern tip of Baja California at 9 a.m. EDT, October 2, 2009 in the Eastern Pacific Ocean.
Credit: NASA/NOAA GOES Project
Tropical Storm Olaf Born, Headed to Baja California

In less than 24 hours, the eighteenth tropical depression in the Eastern Pacific strengthened into Tropical Storm Olaf.

The latest satellite imagery from GOES-11, the Geostationary Operational Environmental Satellite at 9 a.m. EDT, October 2, 2009, shows Olaf's clouds reaching over the southern tip of Baja California. That's just a hint of what he's going to do this weekend, according to forecasters. Olaf is expected to turn toward the northeast over the weekend and make landfall in the central region of Baja California.

GOES-11 is operated by the National Oceanic and Atmospheric Administration, and images are created by NASA's GOES Project, located at NASA's Goddard Space Flight Center, Greenbelt, Md.

At 5 a.m. EDT on October 2, however, Tropical Storm Olaf was about 490 miles west of the southern tip of Baja California, near latitude 22.0 North and longitude 117.5 West. Olaf's maximum sustained winds were near 45 mph, and they are not expected to change much until Olaf makes landfall early Sunday, October 4. At present, Olaf is moving north near 12 mph, but is expected to turn northeast in the next day or two.

Olaf is a good-sized storm, as tropical storm-force winds extend up to 115 miles out from the center. His minimum central pressure is 1000 millibars.

Some good news for residents of Baja California about Olaf's winds, is that there's only a small window of opportunity for the storm to strengthen further. Wind shear is going to increase over the next day, and they can tear a storm apart. In addition, Olaf is working his way into cooler sea surface temperatures (waters need to be at least 80°F to sustain a tropical cyclone's strength), which will also help weaken Olaf in the next two days as he heads for a landfall.

Residents of Baja California should be preparing for Olaf this weekend, and be on the watch for heavy rainfall and gusty winds.

Text credit: Rob Gutro, NASA/Goddard Space Flight Center

October 1, 2009

NASA's Aqua satellite data was used to create this microwave image of TD18E on October 1 at 5:23 a.m. EDT (9:23 UTC). > View larger image
NASA's Aqua satellite data was used to create this microwave image of TD18E on October 1 at 5:23 a.m. EDT (9:23 UTC). Cold areas (yellow-green) indicate precipitation or ice in the cloud tops. The purple area near the center has the coldest cloud temperatures near -63F.
Credit: NASA/JPL, Ed Olsen
It's a Boy? Tropical Depression 18-E Forms in the Eastern North Pacific

At 11 a.m. EDT on October first, the eighteenth tropical depression of the Eastern Pacific hurricane season was born. He's a little guy, but is likely going to grow up to be a tropical storm and get the name Olaf later today or tomorrow. He's not, however, expected to reach hurricane strength.

At the time of his birth, Tropical Depression 18-E (TD18E) had maximum sustained winds near 35 mph. He was located 580 miles west-southwest of the southern tip of Baja California, near 19.0 North and 117.9 West. TD18-E was moving west-northwest at 8 mph and is expected to turn toward the northwest later today or tonight. His estimated minimum central pressure is 1004 millibars.

Forecasters at the National Hurricane Center confirmed TD18E's birth using data from NASA's Atmospheric Infrared Sounder (AIRS) instrument combined with data from the Advanced Microwave Sounding Unit (AMSU) data to create a microwave of the storm. Both AIRS and AMSU are instruments that fly on NASA's Aqua satellite.

NASA's Aqua satellite flew Tropical Depression 18E five and a half hours before it was born. Aqua's instruments were used to create a microwave image from 5:23 a.m. EDT on October 1 that showed high thunderstorms, a sign that the storm was intensifying. The imagery revealed cold areas in the storm that indicate ice in cloud tops, and light to moderate precipitation. The National Hurricane Center reported " overnight microwave (and scatterometer data from NASA's QuikScat satellite) data indicate that the circulation associated with the broad low pressure area southwest of the southern tip of Baja California has become better defined.

The Hurricane Center also said that "The depression does not appear to have much of an opportunity to strengthen. Southerly to southwesterly vertical shear is forecast to increase later today and become stronger thereafter." In addition, TD18E is going to start moving into cooler waters on its northward track.

Text credit: Rob Gutro, NASA/Goddard Space Flight Center