NASA sees the formation of early Atlantic Ocean Tropical Depression 1

April 20, 2017
On April 19 at 0746 UTC (3:46 a.m. EDT) the GPM satellite saw moderate to heavy rainfall over the Atlantic's TD01. Rain was falling at a rate of over 30 mm (1.2 inches) per hour east of center. Highest storms reaching altitudes above 11 km (6.8 miles) were just to the west of the low's center. Credit: NASA/JAXA, Hal Pierce

A low pressure area in the Atlantic Ocean, located southwest of the Azores was designated as Subtropical Depression One on April 19 as NASA examined its rainfall. By April 20 it had become the Atlantic's first tropical depression.

Just as the subtropical depression was forming in the North Atlantic Ocean on April 19 at 11 a.m. EDT (1500 UTC) the Global Precipitation Measurement Mission or GPM core observatory satellite flew directly over it and identified areas where rainfall was heaviest in the system.

Data collected by GPM's Microwave Imager (GMI) and Dual-Frequency Precipitation Radar (DPR) instruments April 19, 2017 at 0746 UTC (3:46 a.m. EDT) showed moderate to heavy rainfall within the low area. DPR revealed that rain was falling at a rate of over 30 mm (1.2 inches) per hour in showers located to the east of the low's of circulation. GPM's radar (DPR Ku Band) also showed that a few storms rotating around the low pressure center were dropping rain at a rate of almost 36 mm (1.4 inches) per hour.

At NASA's Goddard Space Flight Center in Greenbelt, Maryland, a 3-D examination was created using GPM's Radar (DPR Ku Band) data. That 3-D analysis showed most of the storms around the low pressure area were fairly shallow. Some of the highest storm tops just to the west of the low's center of circulation were found by DPR to reach altitudes above 11 km (6.8 miles). GPM is a joint satellite mission between NASA and the Japan Aerospace Exploration Agency, JAXA.

On April 19 at 0746 UTC (3:46 a.m. EDT) the GPM satellite saw moderate to heavy rainfall over the Atlantic's TD01. Rain was falling at a rate of over 30 mm (1.2 inches) per hour east of center. Highest storms reaching altitudes above 11 km (6.8 miles) were just to the west of the low's center. This is a 3-D image of the tropical depression. Credit: NASA/JAXA, Hal Pierce

At the time of formation, the National Hurricane Center (NHC) determined that it was a sub-tropical low pressure area. The difference between this and a tropical cyclone is found in the temperature structure. This low had a cold core while tropical cyclones that normally form in the tropics, are warm core. That changed on April 20 at 11 a.m. EST when it was designated a and developed a warm core. At that time NHC's discussion noted "Conventional satellite imagery indicate that the convection, although not very deep, has become more symmetric around the center, suggesting that the subtropical cyclone has transitioned into a tropical depression."

At 11 a.m. EST (1500 UTC), the center of Tropical Depression One was located near 36.1 degrees north latitude and 40.0 degrees west longitude. That's about 730 miles (1,170 km west of the Azores. The Azores are an archipelago in the mid-Atlantic Ocean. The depression was moving toward the northwest near 14 mph (22 kph), and that general motion is expected to continue until dissipation. Maximum sustained winds were near 35 mph (55 kph) with higher gusts. The estimated minimum central pressure is 996 millibars (29.42 inches).

The National Hurricane Center (NHC) predicts that this system will become a remnant low pressure area later today, April 20 and become absorbed by a larger low at night or early Friday, April 21. The is then expected to be absorbed by a larger low pressure area.

On April 19, 2017 at 0746 UTC (3:46 a.m. EDT) NASA/JAXA's GPM satellite showed moderate to heavy rainfall over TD01 in the Atlantic Ocean. In this flyby animation, rain was falling at a rate of over 30 mm (1.2 inches) per hour in showers east of center. Highest storms reaching altitudes above 11 km (6.8 miles) were just to the west of the low's center. Credit: NASA/JAXA, Hal Pierce

Explore further: NASA measures rainfall rates in Tropical Cyclone Maarutha

Related Stories

NASA measures rainfall rates in Tropical Cyclone Maarutha

April 18, 2017

Tropical Storm Maarutha became the first tropical cyclone of 2017 in the Bay of Bengal when it formed on April 15, 2017. Although the tropical cyclone only lived two days, NASA gathered rainfall rate data on it on the day ...

NASA's GPM analyzed rainfall in ex-Tropical Cyclone 11S

March 16, 2017

Ex-tropical cyclone 11S was still generating some heavy rainfall, despite losing its tropical status and becoming a sub-tropical storm when the GPM core satellite passed overhead. The Global Precipitation Measurement mission ...

Forming Atlantic Tropical Depression 8 seen by NASA

August 29, 2016

The Global Precipitation Measurement mission or GPM core satellite passed over Tropical Depression 8 as it formed off the coast of North Carolina in the Atlantic Ocean. GPM measured rainfall rates and analyzed the heights ...

NASA sees heavy rain in Tropical Depression Ma-on

November 10, 2016

Tropical cyclones have been forming frequently in the Western Pacific Ocean since July 2016. Thirty-six named tropical cyclones have formed in the Western Pacific in less than five months with 14 of them becoming typhoons.

Recommended for you

The world needs to rethink the value of water

November 23, 2017

Research led by Oxford University highlights the accelerating pressure on measuring, monitoring and managing water locally and globally. A new four-part framework is proposed to value water for sustainable development to ...

'Lost' 99% of ocean microplastics to be identified with dye?

November 23, 2017

The smallest microplastics in our oceans – which go largely undetected and are potentially harmful – could be more effectively identified using an innovative and inexpensive new method, developed by researchers at the ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.