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Hurricane Season 2008: Polo (Eastern Pacific)
Nov. 5, 2008

Polo Petered Out in Eastern Pacific

Satellite image of Polo Credit: NASA/SSAI, Hal Pierce
> Larger image
Tropical Storm Polo became a tropical depression late Tuesday night, Nov. 4 and by Nov. 5, Polo was a remnant low pressure area in the open waters of the eastern Pacific Ocean.

At 10 a.m. PST (1 p.m. EST) on Wed. Nov. 5, the remnants of Tropical Depression Polo were fizzling out about 1,200 miles southwest of the southern tip of Baja California. The National Hurricane Center said that "Upper-level westerly winds are not favorable for re-development."

Things started looking bad for Polo on Tuesday, Nov. 4th at 7 p.m. PST when the center of Polo's circulation was degenerating into an open trough (an elongated area of low pressure). Based on the lack of a well-defined circulation center, the National Hurricane Center ceased advisories on Polo. The remnants then continued on a westerly track around 12 mph. It will continue in that general direction until it has completely dissipated.

The image above was made from data captured by the Tropical Rainfall Measuring Mission (TRMM) satellite on Nov. 4 at 7:12 Zulu Time (2:12 a.m. EST). This TRMM image shows the horizontal pattern of rain intensity within Polo while it was still a tropical storm. The center is located near the yellow, green areas, which indicate rainfall around 20 millimeters per hour (.78 inches/hour). Red areas, of which there are none, normally represent moderate rainfall, about 40 millimeters (around 1.5 inches) per hour. The lack of red areas indicate a weakening storm.

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

Nov. 04, 2008

Forecasts for 'Polo' on the Mark

AIRS image of Polo on Nov. 4, 2008> Larger image
Credit: NASA JPL
The National Hurricane Center's forecast for Tropical Storm Polo is on the Mark – he's headed west-northwest and continues headed further out into open waters of the eastern Pacific.

At 7:00 a.m. PST (10 a.m. EST), on Tuesday, Nov. 4, Tropical Storm Polo was packing sustained winds near 40 mph with higher gusts. Some slow strengthening is forecast to happen in the next day or two. Meanwhile, Polo is located about 1,030 miles south-southwest of the southern tip of Baja California. That's near latitude 9.9 degrees north and 117.6 degrees west.

Polo has expanded over a larger area, with tropical storm force winds now extending outward to 70 miles from the center, up from 30 miles out a day before. Estimated minimum central pressure is 1005 millibars.

The National Hurricane Center noted that Polo will be moving over cooler sea surface temperatures in the next couple of days, so weakening is forecast by day 3 (Friday, Nov. 7) and beyond.

Aqua Satellite Sees Cold 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 Nov. 3 at (8:59 UTC) 3:59 a.m. EST.

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 lowest temperatures (in purple) are associated with high, cold cloud tops that make up the top of the storm. 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.

Polo looks like an upside-down comma in blue and purple in this false-color satellite image. The storm at this point in time was not very well developed, but has since become more organized.

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)/Goddard Space Flight Center

Nov. 3, 2008

Water "Polo" in the Eastern Pacific

GOES image of Polo far southwest of Mexico Credit: NOAA/NASA GOES Project
> Larger image
Polo is in the waters of the eastern Pacific Ocean, no, not water polo, a tropical storm named "Polo." Polo is the eighteenth tropical cyclone of the eastern Pacific hurricane season. It was "born" on Sunday, Nov. 2 around 1 p.m. PST (4 p.m. EST) far south of Cabo San Lucas, Mexico in the eastern Pacific's waters.

By 7 p.m. PST (10 p.m. EST) Tropical Depression 18-E strengthened into Tropical Storm Polo. Twelve hours later at 7 a.m. PST on Monday, Nov. 3, Tropical Storm Polo continues its westward trek into open waters of the eastern Pacific Ocean.

Polo had maximum sustained winds near 40 mph and was moving west near 12 mph. Polo will likely strengthen in the next 48 hours according to the National Hurricane Center (NHC).

NHC's discussion said that "Polo is over warm sea surface temperatures and in a light vertical wind shear (winds that if strong enough, can tear a storm apart) environment. Except for the current convective trends...conditions appear favorable for strengthening as indicated by all of the intensity guidance. None of the guidance currently shows Polo becoming a hurricane...so the intensity forecast calls for a peak intensity of 60 knots in 48-72 hours."

At 7 a.m. PST, Polo's center was 1,000 miles south-southwest of the southern tip of Baja California, near latitude 8.8 north and longitude 113.2 west. Polo is a small storm with tropical storm force winds only extending outward from the center to 30 miles. Polo's estimated minimum central pressure is 1005 millibars.

This satellite image was captured on November 3 at 11:45 UTC (8:45 a.m. EST) from the Geostationary Operational Environmental Satellite (GOES-12). In the image, Tropical Storm Polo is the circular area of clouds on the far left in the open waters of the eastern Pacific Ocean.

GOES is operated by the National Oceanic and Atmospheric Administration. It 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