Formerly a typhoon, now an extra-tropical storm, Neoguri has taken on more of a frontal system appearance in imagery from NASA's Aqua satellite. The final warning on the system has been issued.
On Oct. 22, the Moderate Imaging Spectroradiometer or MODIS instrument that flies aboard NASA's Aqua satellite provided a visible image of Neoguri. The MODIS imagery indicated that Neoguri had an elongated and poorly defined low-level circulation center with the bulk of clouds and convection (rising air that forms the thunderstorms that make up a tropical cyclone) pushed to the northeast of the center because of strong southwesterly wind shear.
What is Wind Shear?
In general, wind shear is a measure of how the speed and direction of winds change with altitude. Tropical cyclones are like rotating cylinders of winds. Each level needs to be stacked on top each other vertically in order for the storm to maintain strength or intensify. Wind shear occurs when winds at different levels of the atmosphere push against the rotating cylinder of winds, weakening the rotation by pushing it apart at different levels.
What does Extra-tropical Mean?
When a storm becomes extra-tropical, it means that a tropical cyclone has lost its "tropical" characteristics. The National Hurricane Center defines "extra-tropical" as a transition that implies both poleward displacement (meaning it moves toward the north or south pole) of the cyclone and the conversion of the cyclone's primary energy source from the release of latent heat of condensation to baroclinic (the temperature contrast between warm and cold air masses) processes. It is important to note that cyclones can become extratropical and retain winds of hurricane or tropical storm force.
Neoguri on Oct. 22
On Oct. 22 at 5 a.m. EDT (0900 UTC), the Joint Typhoon Warning Center issued the final warning on Extra-tropical Storm Neoguri. At that time, Neoguri was centered near latitude 34.1 degrees north and longitude 141.4 degrees east. That is about 119 nautical miles south-southeast of Yokosuka, Japan. Neoguri was moving to the east-northeast and had maximum sustained winds near 45 knots (52 mph/83 kph). Neoguri is expected to intensify slightly and continue tracking northeastward.
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