Tag: Imelda 2019

Sep. 20, 2019 – NASA Estimates Imelda’s Extreme Rainfall

NASA estimated extreme rainfall over eastern Texas from the remnants of Tropical Depression Imelda using a NASA satellite rainfall product that incorporates data from satellites and observations.

NASA’s Integrated Multi-satellitE Retrievals for GPM or IMERG, which is a NASA satellite rainfall product, estimated that by Friday morning, September 20, Tropical Storm Imelda had dropped over 24 inches of rain between Beaumont and Houston, Texas. Estimates of between 16 and 24 inches have fallen between Freeport and Beaumont, and 6 inches and more over a large area between southwestern Louisiana and Palacios, Texas. An image showing these rainfall totals was created at NASA’s Goddard Space Flight Center in Greenbelt, Md.

This near-real time rain estimate comes from the NASA’s IMERG, which combines observations from a fleet of satellites, in near-real time, to provide near-global estimates of precipitation every 30 minutes. By combining NASA precipitation estimates with other data sources, we can gain a greater understanding of major storms that affect our planet.

If one compares the IMERG satellite-based rain estimate to that from a National Weather Service ground radar, one sees that IMERG correctly identified the large region of heavy rainfall near Beaumont, but IMERG failed to resolve an extremely narrow band of heavy rainfall along Galveston Island. Such good detection of large rain features in real-time would be impossible if the IMERG merely reported the precipitation observed by the periodic overflights of various agencies’ satellites.

Instead, what the IMERG does is “morph” high-quality satellite observations along the direction of the steering winds to deliver information about rain at times and places where such satellite overflights did not occur. Information morphing is particularly important over the majority of the world’s surface that lacks ground-radar coverage. Basically, IMERG fills in the blanks between weather observation stations.

The NASA image also identified where the rainfall from the remnant of Imelda caused a U.S. Geological Survey river gauge to swell to “major flood” stage. “Major” flood generally means that nearby homes and roads were flooded.  In addition, there were several preliminary reports of Imelda-spawned tornadoes on Wednesday and Thursday, September 18 and 19.

NOAA’s National Weather Service noted on Sept. 20, “Intense tropical rainfall continues in portions of Southeast Texas and Southwest Louisiana from the remnants of Imelda. These additional rains will only compound ongoing issues with flooding. The heavy rain focus will gradually shift to the Arkansas-Louisiana-Texas region on Friday, Sept. 20.”

Hurricanes are the most powerful weather event on Earth. NASA’s expertise in space and scientific exploration contributes to essential services provided to the American people by other federal agencies, such as hurricane weather forecasting.

For more information about NASA’s IMERG, visit: https://pmm.nasa.gov/gpm/imerg-global-image

For local forecasts, visit: www.weather.gov

By Owen Kelley / Rob Gutro
NASA’s Goddard Space Flight Center

Sep. 19, 2019 – NASA Estimates Tropical Depression Imelda’s Huge Texas Rainfall

Northeastern Texas has borne the brunt of Tropical Depression Imelda’s heavy rainfall and NASA estimated that rainfall with an algorithm that incorporates data from satellites and observations.

By Thursday morning, September 19, Tropical Storm Imelda had dropped over 10 inches of rain over a large area between Houston and Beaumont, Texas. At NASA’s Goddard Space Flight Center in Greenbelt, Maryland, a graphic was produced that shows precipitation that fell starting on Tuesday, September 17, the day that Imelda formed as a tropical depression in the Gulf of Mexico, intensified into a tropical storm, and made landfall in Texas, all within a few hours.

The near-realtime rain estimate comes from the NASA’s Integrated Multi-satellitE Retrievals for GPM (IMERG) algorithm, which combines observations from a fleet of satellites, in near-realtime, to provide near-global estimates of precipitation every 30 minutes.  This satellite-based rain estimate is somewhat coarse in resolution and can miss short-lived, intense storm-cells, but the IMERG algorithm often does captures the large-scale features of storms wherever they form in the world.  While the United States is fortunate to have a network of ground radars that can provide higher-resolution precipitation estimates, in other parts of the world, notably over most of the world’s oceans, the IMERG rain estimate is an important reference point.

By combining NASA precipitation estimates with other data sources, we can gain a greater understanding of major storms that affect our planet.

NOAA’s Storm Prediction Center also reported several preliminary reports of tornadoes on Wednesday evening, September 18.

On September 19 at 5 a.m. EDT, NOAA’s National Weather Service Weather Prediction Center (NWS NPC) in College Park, Md. forecast indicated that Imelda’s heavy rainfall is expected to continue. Flash flood watches are in effect for parts of eastern Texas and western Louisiana.

The NWS forecasts that Imelda is expected to produce the following rainfall amounts through Friday: Across the Upper Texas Coast into far southeast Texas… an additional 5 to 10 inches with isolated storm totals of 25 to 35 inches are possible. Across portions of southwest Louisiana…an additional 3 to 5 inches with isolated totals of 10 inches are expected. For the rest of east Texas…2 to 4 inches with isolated totals around 8 inches are forecast. These rainfall totals may produce significant to life threatening flash floods.

At 5 a.m. EDT (0900 UTC), the center of Tropical Depression Imelda was located near latitude 31.3 North, longitude 95.5 West. That puts the center of Imelda’s circulation about 110 miles (180 km) north of Houston, Texas and about 70 miles (115 km) northeast of College Station, Texas.  The depression is moving toward the north-northwest near 5 mph (7 kph) and this motion is expected to continue through today. Maximum sustained winds are near 30 mph (45 kph) with higher gusts. The estimated minimum central pressure is 1009 millibars. A gradual weakening is forecast during the next 24 hours.

Hurricanes are the most powerful weather event on Earth. NASA’s expertise in space and scientific exploration contributes to essential services provided to the American people by other federal agencies, such as hurricane weather forecasting.

For more information about NASA’s IMERG, visit: https://pmm.nasa.gov/gpm/imerg-global-image

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

By Owen Kelley / Rob Gutro
NASA’s Goddard Space Flight Center

Sep. 18, 2019 – NASA Infrared Data Shows Heavy Rain Potential Along Gulf from Imelda

One of the ways NASA researches tropical cyclones is using infrared data that provides temperature information. The AIRS instrument aboard NASA’s Aqua satellite captured a look at those temperatures in Tropical Depression Imelda and gave insight into the storm’s rainfall potential over eastern Texas.

Cloud top temperatures provide information to forecasters about where the strongest storms are located within a tropical cyclone. Tropical cyclones do not always have uniform strength, and some sides are stronger than others. The stronger the storms, the higher they extend into the troposphere, and  the colder the cloud temperatures in those storms.

NASA provides data to forecasters at NOAA’s National Hurricane Center or NHC so they can incorporate it in their forecasting.

On Sept. 17 at 3:41 p.m. EDT (1541 UTC) NASA’s Aqua satellite analyzed the storm using the Atmospheric Infrared Sounder or AIRS instrument. AIRS found coldest cloud top temperatures as cold as or colder than minus 63 degrees Fahrenheit (minus 53 degrees Celsius) north and east of Imelda’s center. NASA research has shown that cloud top temperatures that cold indicate strong storms that have the capability to create heavy rain. Some of the heaviest rain at the time of the image was over the Texas coastline.

Forecasters incorporated the insight into rainfall potential into their forecasts. On Sept. 18, as Imelda moved slowly to the north, heavy rains and significant flash flooding were spreading inland over eastern Texas and are expected during the next couple of days.

NOAA’s National Weather Service (NWS) Weather Prediction Center (WPC) in College Park, Md. posted, “Flash flood watches were in effect for southeast Texas and extreme southwest Louisiana.”

That heavy rainfall potential is in the forecast from the NWS WPC: Imelda is expected to produce the following rainfall amounts through Friday [Sept. 20]: Across the Upper Texas Coast into eastern Texas, including the Houston and Galveston areas…additional 5 to 10 inches.  Isolated storm totals of 20 to 25 inches. Across portions of southwest Louisiana…4 to 8 inches with isolated totals of 10 inches. These rainfall totals may produce significant to life threatening flash floods.

At 11 a.m. EDT (1500 UTC), NWS said the center of Tropical Depression Imelda was located near latitude 30.6 degrees north and longitude 95.6 degrees west. The depression is moving toward the north at near 5 mph (7 km/h) and this motion is expected to continue through tonight. Maximum sustained winds are near 30 mph (45 kph) with higher gusts. Little change in strength is forecast during the next 48 hours. The estimated minimum central pressure is 1009 millibars.

Hurricanes are the most powerful weather event on Earth. NASA’s expertise in space and scientific exploration contributes to essential services provided to the American people by other federal agencies, such as hurricane weather forecasting.

The AIRS instrument is one of six instruments flying on board NASA’s Aqua satellite, launched on May 4, 2002.

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

For updated NWS rainfall potential maps, visit: https://www.wpc.ncep.noaa.gov/tropical/qpf/tcqpf.php?sname=AL112019

By Rob Gutro
NASA’s Goddard Space Flight Center  

Sep. 17, 2019 – NASA’s Terra Satellite Sees the Birth of Tropical Storm Imelda

NASA’s Terra satellite passed over the western Gulf of Mexico during the early afternoon of Sept. 17 and captured a visible image of the newly formed Tropical Depression 11.

The eleventh tropical depression developed during the late morning of Sept. 17. Soon afterward it briefly strengthened into a tropical storm and was re-named Imelda. Then Imelda made landfall near Freeport, Texas. A Tropical Storm Warning was in effect from Sargent to Port Bolivar, Texas.

On Sept. 17 at 1:30 p.m. EDT (17:30 UTC), the Moderate Imaging Spectroradiometer or MODIS instrument that flies aboard NASA’s Terra satellite provided a visible picture of the storm shortly after it made landfall on the southeastern Texas coastline. The storm appeared to be slightly elongated, and when Terra passed overhead the western quadrant of the storm was already over land while the eastern half was over the western Gulf of Mexico.

At 1 p.m. EDT (1700 UTC), the center of Tropical Storm Imelda was located near latitude 28.7 North, longitude 95.4 West. The storm is moving toward the north near 7 mph (11 kph), and this general motion is expected to continue through early Wednesday. Maximum sustained winds are near 35 mph (55 kph), tropical storm strength, with higher gusts. Some slight strengthening is possible before the center moves onshore. The estimated minimum central pressure is 1009 millibars.

For local Houston area radar, visit: https://www.weather.gov/hgx/

A north-northwestward motion is expected Wednesday night and Thursday. On the forecast track, the center of the depression will move inland over the Upper Texas coast later today, and move farther inland tonight and Wednesday.

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

By Rob Gutro
NASA’s Goddard Space Flight Center