NASA imagery reveals Paulette became a strong extratropical cyclone 

September 16, 2020

Tropical cyclones can become post-tropical before they dissipate, meaning they can become sub-tropical, extra-tropical or a remnant low-pressure area. As Hurricane Paulette transitioned into an extra-tropical storm, NASA's Terra satellite provided a visible image of the powerful storm, and the National Hurricane Center issued their final advisory on the system.

What is a Post-tropical Storm? 

A Post-Tropical Storm is a generic term for a former tropical cyclone that no longer possesses sufficient tropical characteristics to be considered a tropical cyclone. Former tropical cyclones that have become fully extratropical, subtropical, or remnant lows--all three classes of post-tropical cyclones. In any case, they no longer possesses sufficient tropical characteristics to be considered a tropical cyclone. However, post-tropical cyclones can continue carrying heavy rains and high winds.

What is an Extra-tropical Storm?

Often, a tropical cyclone will transform into an extra-tropical cyclone as it recurves toward the poles (north or south, depending on the hemisphere the storm is located in). An extra-tropical cyclone is a storm system that primarily gets its energy from the horizontal temperature contrasts that exist in the atmosphere.

Tropical cyclones have their strongest winds near the earth's surface, while extra-tropical cyclones have their strongest winds near the tropopause - about 8 miles (12 km) up. Tropical cyclones, in contrast, typically have little to no temperature differences across the storm at the surface and their winds are derived from the release of energy due to cloud/rain formation from the warm moist air of the tropics.

Visible NASA Imagery Shows the Transition

Visible imagery from NASA's Terra satellite revealed Paulette's extra-tropical transition.

On Sept. 16 at 10:16 a.m. EDT (1416), the Moderate Resolution Imaging Spectroradiometer or MODIS instrument aboard NASA's Terra satellite provided a visible image of the storm. The MODIS image showed Paulette had a closed surface wind circulation about a well-defined center, but the storm has become asymmetric with the bulk of the clouds north of the center.

U.S. Navy Hurricane Specialist Dave Roberts at NOAA's National Hurricane Center (NHC) in Miami, Fla. noted, "Conventional GOES-16 [satellite] visible and enhanced BD-curve satellite imagery show that Paulette has merged with the large baroclinic zone extending over the north-central Atlantic. Deep convection just to the north of the surface center that was noted on earlier microwave images has dissipated.  Therefore, the system is now classified as extratropical cyclone and this is the last NHC advisory."

According to NOAA, a Baroclinic Zone is a region in which a temperature gradient exists on a constant pressure surface. Baroclinic zones are favored areas for strengthening and weakening systems; barotropic systems, on the other hand, do not exhibit significant changes in intensity. Also, wind shear is characteristic of a baroclinic zone.

Paulette's Final Advisory

At 11 a.m. EDT (1500 UTC), the center of Post-Tropical Cyclone Paulette was located near latitude 43.3 degrees north and longitude 45.2 degrees west. That is about 450 miles (725 km) east-southeast of Cape Race Newfoundland, Canada. The post-tropical cyclone is moving toward the east-northeast near 35 mph (56 kph), and this general motion is expected through Thursday. Maximum sustained winds have decreased to near 85 mph (140 kph) with higher gusts. The estimated minimum central pressure is 973 millibars.

Paulette's Final Forecast

Further weakening is forecast during the next couple of days. The cyclone is forecast to slow down and turn toward the southeast and south late Thursday and Friday.

Meanwhile, ocean swells generated by Paulette will continue to affect Atlantic Canada, Bermuda, the Bahamas, and portions of the east coast of the United States through tonight. These swells are likely to cause life-threatening surf and rip current conditions.

NASA Researches Earth from Space

For more than five decades, NASA has used the vantage point of space to understand and explore our home planet, improve lives and safeguard our future. NASA brings together technology, science, and unique global Earth observations to provide societal benefits and strengthen our nation. Advancing knowledge of our home planet contributes directly to America's leadership in space and scientific exploration.
-end-
For updated forecasts, visit: http://www.nhc.noaa.gov

By Rob Gutro 
NASA's Goddard Space Flight Center

NASA/Goddard Space Flight Center

Related Tropical Cyclone Articles from Brightsurf:

NASA finds post-Tropical Cyclone Dolly exiting the tropical stage
NASA's Terra satellite provided a night-time look at what is now Post-Tropical Storm Dolly in the Northern Atlantic Ocean.

NASA find Herold a fading ex-tropical cyclone
Former Tropical Cyclone Herold is now a fading area of low-pressure in the Southern Indian Ocean and NASA's Aqua satellite provided forecasters with a visible image.

NASA sees Tropical Cyclone Herold's eye
NASA's Aqua satellite passed over the Southern Indian Ocean and captured an image of a well-developed Tropical Cyclone Herold at hurricane strength, east of Madagascar.

A new method to improve tropical cyclone intensity forecasts
There are many reasons for model errors in numerical weather forecasting of tropical cyclone intensity.

NASA catches the dissipation of Tropical Cyclone Claudia
Tropical Cyclone Claudia was dissipating in the Southern Indian Ocean when NASA's Terra satellite captured a visible image of storm as it flew overhead in its orbit around the Earth.

NASA finds tropical cyclone 02S consolidating
NASA's Aqua satellite captured an image of Tropical cyclone 02S and the visible image showed that the storm was getting better organized.

NASA finds Tropical Cyclone's Vayu getting stretched
When NASA's Aqua satellite passed over the Northern Indian Ocean, it captured an infrared image that revealed Tropical Cyclone Vayu was elongating.

NASA takes Tropical Cyclone's Vayu's temperature
NASA's Aqua satellite passed over the Northern Indian Ocean and took the temperature of Tropical Cyclone Vayu as it moved northward in the Arabian Sea.

NASA catches development of Tropical Cyclone 02A
Visible imagery from NASA's Terra satellite provided confirmation of the development of Tropical Cyclone 02A in the Arabian Sea, Northern Indian Ocean.

NASA goes infrared on powerful Tropical Cyclone Fani
NASA's Aqua satellite focused an infrared eye on a very powerful Tropical Cyclone Fani as it approached landfall in northeastern India.

Read More: Tropical Cyclone News and Tropical Cyclone Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.