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Hurricane Season 2008: Sub-Tropical Storm Laura (Atlantic Ocean)
Oct. 02, 2008

An Extra-Tropical Laura in North Atlantic Headed to the United Kingdom

Former Tropical Storm Laura lost her tropical characteristics on Oct. 1st over the cold waters of the North Atlantic Ocean, and is headed to the United Kingdom by the weekend.

Around mid-day on Oct. 1, the National Hurricane Center issued its final advisory on Laura. At 11:00 a.m. EDT she was located about 315 miles east of Cape Race, Newfoundland, and south of the southern tip of Greenland. The center was near 46.5 north and 46.5 west. Laura was still packing sustained winds near 45 mph and should maintain that strength into Saturday, Oct. 4 as an extra-tropical low. Laura's minimum central pressure was 995 millibars.

The last National Hurricane Center forecast track has Laura's remnants affecting the United Kingdom sometime on Saturday, October 4. Text credit: Rob Gutro/Goddard Space Flight Center

Oct. 01, 2008

Laura Now In the Open Cold North Atlantic Waters, Becoming Extra-Tropical

AIRS image of Laura on Oct. 1, 2008
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Credit: NASA JPL
Tropical Storm Laura is now moving over the cold waters of the North Atlantic Ocean, and is also running through cold air. Because it takes 80 degree F warmth to maintain a tropical cyclone, Laura is going to undergo changes in her structure and become extra-tropical.

Forecasters at the National Hurricane Center expect Laura to become extra-tropical later today, Wednesday, October 1. Despite the changeover, she's still expected to maintain her strength.

What's the Difference in Tropical and Extra-Tropical?

Becoming extra-tropical in Laura's case means going from a warm core or center (that is, the air around the center is warmer than the surrounding air) to a cold core center where the air in the core is colder than the surrounding air, like a typical low pressure system. Secondly, the strongest winds in a counter-clockwise spinning extratropical cyclone are found in the upper atmosphere (over 20,000 feet high), whereas a tropical storm's strongest winds are at the surface.

At 5:00 a.m. EDT on Wednesday, Oct. 1, Laura was packing maximum sustained winds near 45 mph, and was moving toward the north-northeast near 16 mph. Laura was located 295 miles east-southeast of Cape Race, Newfoundland, Canada, or near 44.8 north and 47.6 west. Minimum central pressure was 1001 millibars.

QuikSCAT Watching the Storm's Winds from Space

NASA's Quick Scatterometer satellite (QuikScat) has been watching Laura's winds by using microwaves to peer into the clouds. QuikScat can determine the speed of the rotating winds. This image from QuikScat shows Laura's wind speeds in different colors and wind direction are indicated by small barbs. White barbs point to areas of heavy rain. The highest wind speeds are normally shown in purple, which indicate winds over 40 knots (46 mph). The strongest winds are represented in the center of circulation. This image was captured on Sept. 30 at 8:25 UTC (4:25 a.m. EDT). Text credit: Rob Gutro/Goddard Space Flight Center

Sept. 30, 2008

Sub-Tropical Storm Laura Northbound into Cold Atlantic Waters

Satellite image of Laura Credit: NASA/NOAA GOES Project
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Sub-tropical Storm Laura is keeping to the open waters of the central Atlantic Ocean, and is on a journey northward.

At 5:00 a.m. EDT on Sept. 30, Laura was still maintaining a northern track at 13 mph, although she is expected to turn to the north-northeast in the next 24-48 hours. Her maximum sustained winds were near 60 mph although once she gets into the cooler waters of the North Atlantic Ocean, they should sap some of Laura's strength. In fact, Laura may lose her tropical characteristics in a few days, according to the National Hurricane Center.

Laura was located about 485 miles south-southeast of Cape Race, Newfoundland, near latitude 40.3 degrees north and longitude 49.0 degrees west. Minimum central pressure was 996 millibars.

This visible image was created on Sept. 30 at 8:49 a.m. EDT from the Geostationary Operational Environmental Satellites (GOES-11 and GOES-12). In the image, Sub-Tropical Storm Laura is located on the right side of the image, while Kyle's remnants are pushing off eastern Canada, in the upper center of the image.

GOES-11 and 12 are operated by the National Oceanic and Atmospheric Administration. This image was created by NASA's GOES Project, located at NASA's Goddard Space Flight Center, Greenbelt, Md.

Text credit: Rob Gutro, NASA's Goddard Space Flight Center

Sept. 29, 2008

Sub-Tropical Storm Laura Forms in Central Atlantic, Headed North

Satellite image of Laura Credit: NASA/JPL
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On Monday, Sept. 29, with Tropical Storm Kyle's remnants were working their way through eastern Canada, another cyclone in the Atlantic Ocean was keeping forecasters busy: Laura.

Laura formed as a sub-tropical storm, that is, outside of the tropics, during the early morning hours on Sept. 29. The tropics range from the equator to 30 degrees north latitude. Specifically, Laura formed at Latitude 37.2 north and longitude 47.3 west.

At 11:00 a.m. EDT, Sept. 29, Tropical Storm Laura's maximum sustained winds were near 60 mph and some strengthening is forecast during the next day or so before Laura moves over colder waters. She was located near latitude 37.4 north and longitude 47.8 west or about 695 miles south-southeast of Cape Race, Newfoundland. Laura is moving toward the west-northwest near 8 mph and she's expected to turn toward the northwest, then north-northwest and swing toward the north-northeast by Tuesday, Sept. 30. Estimated minimum central pressure is 995 millibars.

If you look on a map of the world, Laura is at the same latitude in the Atlantic as the state of Virginia, and at a longitude directly south of Greenland, out in the middle of the Atlantic Ocean. Current computer models predict that Laura will take a right turn by the end of the week and head toward the United Kingdom.

Aqua Satellite Catches Laura's Cloud Temperatures

This infrared image was created by data from the Atmospheric Infrared Sounder (AIRS), an instrument that flies aboard NASA's Aqua satellite. It was taken on Sunday, Sept. 29 at 12:59 p.m. EDT (4:59 UTC). The infrared image shows a huge temperature difference between the tops of the clouds in a tropical cyclone and the warm ocean waters that power it.

The AIRS image shows the temperature of the cloud tops or the surface of the Earth in cloud-free regions. The lowest temperatures (in purple) are associated with high, cold cloud tops that make up the top of the area of low pressure. Those temperatures are as cold as or colder than 220 degrees Kelvin or minus 63 degrees Fahrenheit (F). The blue areas are around 240 degrees Kelvin, or minus 27F.

The infrared signal of the AIRS instrument does not penetrate through clouds. Where there are no clouds the AIRS instrument reads the infrared signal from the ocean and land surfaces, revealing warmer temperatures in orange and red. The orange temperatures are 80F (300 degrees Kelvin) or greater (the darker they are, the warmer they are), and tropical cyclones need sea surface temperatures of 80F to strengthen and maintain their strength.

The data from AIRS is also used to create an accurate 3-D map of atmospheric temperature, water vapor and clouds, all of which are helpful to forecasters.

Text credit: Rob Gutro (from NHC reports), NASA's Goddard Space Flight Center