March 1, 2021

Weather News – Road Conditions – weather forecast

Hurricane Delta Slowly Weakens prior to landfall on the Louisiana Coast – Hurricane Research Division

3 min read

AOML scientists observed the slow weakening of Hurricane Delta during the last NOAA P-3 Hurricane Hunter mission, tasked by the Environmental Modeling Center (EMC) on the morning of October 9.  Delta’s minimum central pressure gradually rose and surface wind speeds measured by the Stepped-Frequency Microwave Radiometer (SFMR) steadily lowered throughout the mission.

Time series of (top) SFMR wind speed (blue), SFMR rain rate (red) and flight-level wind speed (green) and (bottom) extrapolated surface pressure (teal) and geopotential altitude (black) from NOAA42 on October 9.

Tail Doppler Radar (TDR) data indicated that Hurricane Delta was being impacted by moderate wind shear.  The hurricane has an asymmetric wind field with stronger winds extending further out from the center of the circulation on the northeast side of the storm.  The precipitation is also much heavier on the north side of the hurricane with very little precipitation on the south side.

TDR derived reflectivity (shading, left) and wind speed (shading, right) at 2 km altitude. Streamlines on the right represent winds at both 2 km and 5 km height, showing a slightly tilted circulation in the vertical.

In addition to collecting data for forecasters and numerical models to use in real-time, AOML scientists also coordinated with several research teams setting up instruments on the ground along the Louisiana coast.  Extra dropsondes were released off the coast of Louisiana near research radars and instrumented towers and will be used to verify observations and gain a better understanding of how the winds change as they come ashore.

As Hurricane Delta moves across Louisiana, storm surge, strong winds, and heavy rainfall are expected to impact many of the same communities that are still recovering from Hurricane Laura.  Risks for flash flooding from Delta’s heavy rainfall exist for almost the entire state of Louisiana, as well as many other regions within the southeastern U.S.

Greatest flash flood risk graphic issued by NOAA/NWS/NCEP/WPC at 11 am CDT on October 9.

>> Scientist H. Holbach
>> Edits by R. Kravetz

For details about reconnaissance aircraft missions, please see NOAA’s official Plan of the Day.

For the latest information about tropical cyclones and other weather systems, please visit the NOAA/NWS/National Hurricane Center.

For information on numerical prediction of tropical cyclones, please visit NOAA/NCEP/Environmental Modeling Center.

To access updates on the Intensity Forecasting EXperiment (IFEX) and other activities via Facebook, Twitter, or RSS feed, check out the NOAA/AOML/HRD page.

To directly access updates on IFEX HFP Operations via our WordPress blog on the web, check the site:

DISCLAIMER: The above discussion is intended to provide a brief summary of recent and future HRD Hurricane Field Program Operations. Any use of this material beyond its original intent is prohibited without permission of the HRD Director, Frank Marks ( Media inquiries should be directed to AOML Communications (, Monica Allen (301-734-1123) or

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