Tag: Gabrielle 2019

Sep. 10, 2019 – GPM Finds Rainfall Waning in Extra-Tropical Storm Gabrielle

The Atlantic Ocean’s Gabrielle has made a second transition and the Global Precipitation Measurement mission or GPM core satellite provided information about the rate in which rain was falling within the now extra-tropical storm.

Gabrielle made its first transition to a post-tropical cyclone on Sept. 6 and regained tropical storm status later that same day. Now, the storm has become extra-tropical.

The GPM or Global Precipitation Measurement mission’s core satellite passed over Tropical Storm Gabrielle in the eastern North Atlantic Ocean on Sept. 9 at 3:01 a.m. EDT (0701 UTC). GPM found the heaviest rainfall north of the center where it was falling at a rate of over 25 mm (about 1 inch) per hour. GPM is a joint mission between NASA and the Japan Aerospace Exploration Agency, JAXA.

NOAA’s National Hurricane Center noted at 11 a.m. EDT (1500 UTC) on Sept. 10, “Gabrielle has now completed its transition to an extra-tropical cyclone this morning based on the latest GOES-16 satellite imagery. The center of the storm has now become exposed with convection displaced to the north of the center, and a well-defined baroclinic zone has become established in association with the low center.”

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 still retain winds of hurricane or tropical storm force.

The center of Post-Tropical Cyclone Gabrielle was located near latitude 43.9 degrees north and longitude 37.8 degrees west. That puts the center about 695 miles (1,114 km) northwest of the Azores islands. The post-tropical cyclone is moving toward the northeast at near 29 mph (46 kph), and this general motion with an increase in forward speed is expected over the next couple of days. Maximum sustained winds are near 50 mph (85 kph) with higher gusts. The estimated minimum central pressure is 998 millibars.

Gabrielle is expected to weaken over the next two days and dissipate over the far North Atlantic west of the British Isles on Thursday, Sept. 12.

By Rob Gutro
NASA’s Goddard Space Flight Center

Sep. 09, 2019 – NASA Finds Gabrielle’s Strength on its Northern Side

NASA’s Aqua satellite passed over the Central Atlantic Ocean and provided a visible view of Tropical Storm Gabrielle that helped pinpoint its strongest side.

On Sept. 8, 2019 at 2:35 p.m. EDT (1635 UTC), the Moderate Resolution Imaging Spectroradiometer or MODIS instrument aboard NASA’s Aqua satellite provided a visible image of Gabrielle that showed strongest thunderstorms northeast of the center.

The MODIS image also showed that there were also fragmented bands of strong thunderstorms south and southwest of the center.

On Sept. 9, NOAA’s National Hurricane Center or NHC said, “Deep convection associated with Gabrielle has become somewhat less organized overnight with the center located near the northeastern portion of the coldest cloud tops.”

NASA satellites provide research data on structure, rainfall, winds and temperature of tropical cyclones. Those data are shared with forecasters at NHC to incorporate in their forecasts.

NHC noted at 5 a.m. EDT (0900 UTC), on Sept. 9 that the center of Tropical Storm Gabrielle was located near latitude 37.7 degrees north and longitude 48.5 degrees west. Gabrielle’s center is about 1,170 miles (1.885 km) west of the Azores Islands.

Gabrielle is moving toward the north-northeast near 16 mph (26 kph).  A turn toward the northeast with an increase in forward speed is expected today, Sept. 9 and a northeastward motion at an even faster forward speed is expected on Tuesday and Wednesday. Maximum sustained winds are near 60 mph (95 kph) with higher gusts. The estimated minimum central pressure is 997 millibars.

NHC said, “Little change in strength is expected today, but a weakening trend is likely to begin tonight.” Weakening is expected because Gabrielle will be moving into an area of outside winds (vertical wind shear) and cooler sea surface temperatures.

Gabrielle is expected to become an extratropical low pressure area by Tuesday night, Sept. 10 and the extratropical low is predicted to slowly weaken and be absorbed by a larger low pressure system over the northeastern Atlantic in a little more than 3 days

For updated forecasts, visit: www.nhc.noaa.gov

By Rob Gutro
NASA’s Goddard Space Flight Center

Sep. 06, 2019 – NASA Sees Gabrielle Go “Post-Tropical…” for Now

The Global Precipitation Measurement mission or GPM core satellite passed over the Eastern Atlantic Ocean and observed that Tropical Storm Gabrielle had become post-tropical. GPM also gathered data on rainfall rates occurring in transformed and elongated storm.

NOAA’s National Hurricane Center (NHC) said at 5 a.m. EDT on Sept. 6 that Gabrielle has become a post-tropical cyclone over the eastern Atlantic, because “Poorly defined Gabrielle has not produced any organized deep convection (strong thunderstorms) since Thursday morning.” However, regeneration into a tropical storm is expected to occur over the weekend.

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, are 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.

The GPM satellite passed over Gabrielle on Sept. 6 at 3:30 a.m. EDT (0730 UTC). GPM found the heaviest rainfall in nearly 200 miles north of the elongated center, where it was falling at a rate of over 36 mm (about 1.4 inch) per hour. Areas of rainfall of about 25 mm (1 inch per hour) surrounded those stronger storms. GPM is a joint mission between NASA and the Japan Aerospace Exploration Agency, JAXA.

At 5 a.m. EDT (0900 UTC), NHC reported the center of Post-Tropical Cyclone Gabrielle was located near latitude 25.5 degrees north and longitude 37.6 degrees west. That is about 1,095 miles (1,760 km) northwest of the Cabo Verde Islands. The post-tropical cyclone is moving toward the northwest near 12 mph (19 kph).  A turn to the west-northwest with a slight increase in forward speed is expected over the next couple of days.  A decrease in forward speed and a turn to the north are forecast to occur by Sunday morning. Maximum sustained winds are near 40 mph (65 kph) with higher gusts.

Gabrielle is expected to weaken into a post-tropical remnant low by tonight. Thereafter, slow strengthening is expected to occur over the weekend, and the remnants of Gabrielle is forecast to regenerate into a tropical cyclone at that time.

For updated forecasts, visit: www.nhc.noaa.gov

By Rob Gutro
NASA’s Goddard Space Flight Center

Sep. 05, 2019 – NASA-NOAA Satellite Finds Wind Shear Pushing on Tropical Storm Gabrielle

NASA-NOAA’s Suomi NPP satellite passed over the eastern Atlantic Ocean and infrared data revealed that the storm was being adversely affected by wind shear, pushing its strongest storms northeast of its center.

NASA-NOAA’s Suomi NPP satellite used infrared light to analyze the strength of storms in the remnants of Tropical Storm Gabrielle. Infrared data provides temperature information, and the strongest thunderstorms that reach high into the atmosphere have the coldest cloud top temperatures.

On Sept. 5 at 12:18 a.m. EDT (0418 UTC), the Visible Infrared Imaging Radiometer Suite (VIIRS) instrument aboard Suomi NPP found strongest thunderstorms northeast of the center had cloud top temperatures as cold as minus 70 degrees Fahrenheit (minus 56.6 Celsius). Cloud top temperatures that cold indicate strong storms with the potential to generate heavy rainfall. The southern quadrant of the storm appeared to be almost devoid of clouds because of outside winds blowing from the southwest, or southwesterly vertical 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.

NOAA’s National Hurricane Center (NHC) noted in the discussion on Sept. 5, “Although Gabrielle could experience some intensity fluctuations during the next 24 hours, the cyclone should remain in a rather harsh environment during the next 36 to 48 hours, due to south to southwesterly vertical [wind] shear, some dry air in the middle portions of the atmosphere, and oceanic sea surface temperatures on the order of 25 to 26 Celsius.”  Afterward, gradual strengthening is forecast as Gabrielle moves into a more favorable environment.

At 5 a.m. EDT (0900 UTC) NOAA’s National Hurricane Center (NHC) said the center of Tropical Storm Gabrielle was located near latitude 21.9 degrees north and longitude 35.0 degrees west. That’s about 825 miles (1,330 km) west-northwest of the Cabo Verde Islands. Gabrielle is moving toward the northwest near 8 mph (13 kph), and this motion is expected to continue for the next few days with an increase in forward speed. Maximum sustained winds remain near 50 mph (85 kph) with higher gusts.  The estimated minimum central pressure is 1002 mb (29.59 inches).

The NHC said, “Little change in strength is forecast during the next couple of days.  Afterward, some slow strengthening is expected to begin by this weekend.”

For updated forecasts, visit: www.nhc.noaa.gov

By Rob Gutro 
NASA’s Goddard Space Flight Center

Sep. 04, 2019 – GPM Finds a Band of Heavy Rainfall in Tropical Storm Gabrielle

The Global Precipitation Measurement mission or GPM core satellite provided information about the rate in which rain was falling within the Eastern Atlantic Ocean’s latest tropical storm, Gabrielle.

Tropical Depression 8 formed around 5 p.m. EDT on Tuesday, Sept. 3. Twelve hours later at 5 a.m. EDT on Sept. 4, the storm intensified into a tropical storm and was renamed Gabrielle.

The GPM or Global Precipitation Measurement mission’s core satellite passed over Tropical Storm Gabrielle in the eastern North Atlantic Ocean on Sept. 4 at 3:56 a.m. EDT (0756 UTC). GPM found the heaviest rainfall north and east of the center where it was falling at a rate of over 40 mm (about 1.6 inch) per hour. The National Hurricane Center said of that area, “A large curved band of thunderstorms has become better defined in the northern semicircle.” Lighter rainfall rates were measured around that area.

GPM is a joint mission between NASA and the Japan Aerospace Exploration Agency, JAXA.

NOAA’s National Hurricane Center noted at 11 a.m. EDT (1500 UTC), the center of Tropical Storm Gabrielle was located near latitude 20.5 degrees north and longitude 33.8 degrees west. That’s about 715 miles (1,150 km) west-northwest of the Cabo Verde Islands. Gabrielle is moving toward the northwest near 9 mph (15 kph), and this motion is expected to continue through Saturday, with an increase in forward speed expected late in the week. Maximum sustained winds have increased to near 50 mph (85 kph) with higher gusts. Little change in strength is forecast during the next few days. The estimated minimum central pressure is 1003 millibars.

For updated forecasts, visit: www.nhc.noaa.gov

By Rob Gutro
NASA’s Goddard Space Flight Center