GPM Eyes Hurricane Ida Shortly Before Landfall
Hurricane Ida struck southeast Louisiana as a powerful Category 4 storm on Sunday, Aug. 29, 2021 - the 16th anniversary of Hurricane Katrina’s landfall in 2005. Ida brought destructive storm surge, high winds, and heavy rainfall to the region, and left over 1 million homes and businesses without power, including the entire city of New Orleans.
The NASA / JAXA GPM Core Observatory satellite flew over the eye of Ida shortly before landfall at 10:13 a.m. CDT (1513 UTC), capturing data on the structure and intensity of precipitation within the storm. This animation shows NASA's IMERG multi-satellite precipitation estimates and NOAA GOES-E satellite cloud data, followed by 3D data from the GPM Core satellite. NASA processed these observations in near real-time and made them available to a wide range of users including weather agencies and researchers.
After Ida passed over Cuba as a Category 1 storm, it intensified rapidly to reach Category 4 strength near its Louisiana landfall. According to the National Hurricane Center (NHC), Ida's central pressure reached a minimum of 929 hPa with a 15 nautical mile (17 statute mile) wide eye. At the time, Ida had its lifetime-maximum wind speed of 130 kt (150 mph) in the eyewall shortly before 10 a.m. CDT on Aug. 29.
The 3D Dual-frequency Precipitation Radar (DPR) data collected by the GPM Core satellite shows a healthy hurricane inner core in Ida. The small 17-mile-diameter eyewall is surrounded by a nearly complete outer ring of precipitation approximately 85 miles in diameter. Beyond this central structure, an arc of precipitation exists another 40 miles further from the eye to the southeast. The eye hosts many clouds extending well above 6 miles (10 km), which indicates that Ida was still actively growing at the time of this overpass.
This animation shows estimated precipitation rates (blue/yellow shading) and accumulations (green/purple shading) at half-hourly intervals from Aug. 26 - 30, 2021, derived from NASA's IMERG algorithm. Below the precipitation rate data, cloud cover is shown in shades of white/gray based on geosynchronous satellite infrared observations. Ida's track is shown as a multi-colored line, based on data from the National Hurricane Center (NHC).
During Ida’s rapid intensification from a Category 1 to a Category 4 hurricane from Aug. 28 - 29, rainfall accumulations over the Gulf of Mexico increased, exceeding 12 inches across a wide swath of ocean. After making landfall around mid-day on Aug. 29 in southeastern Louisiana, Ida moved inland just west of New Orleans, generating heavy rainfall along the way. Preliminary IMERG estimates through 5:30am CDT (1030 UTC) on Monday, Aug. 30 showed accumulations greater than 6 inches across southeastern Louisiana, with isolated locations already exceeding 12 inches.
In addition to estimating total accumulations, IMERG also captures the transition in rainfall structure associated with developing tropical cyclones. Over the Caribbean, most of Ida's rainfall occurred on the eastern or righthand side of the storm track. As the storm strengthened and matured, the rainfall distribution became more symmetric due to rain bands wrapping completely around the circulation, as seen over the Gulf of Mexico after Ida intensified. Finally at landfall, the rainfall structure once again became asymmetric, as the eastern side of the counterclockwise circulation continued to have access to very moist air drawn over warm ocean water and the western side became more detached from this source.
NASA continues to monitor Ida as it moves north over the southeastern U.S., providing Earth-observing satellite data, maps and analysis to stakeholders to aid response and recovery efforts.
GPM overpass animation by Alex Kekesi (NASA GSFC / SSAI) and the NASA Goddard Scientific Visualization Studio
IMERG animation by Jason West (NASA GSFC / ADNET)
Text by Owen Kelley (NASA GSFC / GMU), Jacob Reed (NASA GSFC / Telophase), Jason West (NASA GSFC / ADNET) & Stephen Lang (NASA GSFC / SSAI)