The University of South Alabama Mesonet and its performance during the heavy rainfall event of Hurricane Ida (2009) Dr. Sytske Kimball Professor of Meteorology Department of Earth Sciences University of South Alabama Credits: Saphique Albert, David Brown, Sean Huber, Meghan Mee, Ivory Reinert, Russell White

University of South Alabama Mesonet Geographic details 26 fully operational weather stations Average spacing between stations is about 30 km (19 miles) Stations in 13 counties in 3 states: MS (3), AL (8), and FL (2) 325 km (203 miles) in east-west direction 30-100 km (19-62 miles) in north-south direction

10 m (30 ft) 10 m (30 ft)

Data collected Variables: Saved every minute 1.5, 2, 9.5, and 10 m temperature 2 and 10 m relative humidity 2 and 10 m horizontal wind speed and direction 10 m vertical wind speed Photsynthetically active radiation (400 – 700 nm) Total solar radiation (400 – 1100 nm, visible spectrum) Rainfall Atmospheric pressure Surface temperature Saved every minute

Website http://chiliweb.southalabama.edu/ Archived data (csv Excel files) (Near) real-time data Time series Station map Meta-data (station photos etc)

Texas Electronics TE525 90 cm

Hydrological Services TB3 90 cm

Hurricane Ida History Entered the Gulf of Mexico early on 9 November 2009 , encountered strong shear, and weakened to a tropical storm. Regained hurricane strength at 1800Z (12:00 CST) on 9 November while approaching the mouth of the Mississippi River. Weakened 6 hours later to a tropical storm due to cooler water and vertical shear associated with a short-wave trough. Turned northeast and became extra-tropical about 3 hours before making landfall on the Alabama coast (Dauphin Island) at around 10:40Z (05:40 CST) on 10 November 2009.

GOES-12 visible image from 9 Nov 2009 at 1225 UTC (6:25 a.m. CST)

Hurricane Ida (Nov 2009)

KMOB WSR-88D derived rainfall totals (inch) from 23:47Z (17:47 CST) on 8 Nov 2009 to 17:02Z (11:02 CST) on 10 Nov 2009

Flooding along the Fish River in South Baldwin County, AL

Radar 17:45 CST 8 Nov 11:02 CST 10 Nov Gauges: 07:00 CST 09 Nov KMOB Gauges: 07:00 CST 09 Nov 07:00 CST 11 Nov

Rain gauge rainfall totals (mm) from 13:00Z (07:00 CST) on 9 Nov 2009 to 13:00Z (07:00 CST) on 11 Nov 2009

Providers ASOS Various MADIS CoCoRAHS USA Mesonet 2 National Estuary Program (NEP) sites

USA Mesonet Rainfall totals (mm) Weeks Bay Foley Elberta

Flooding at the mouth of Weeks Bay in South Baldwin County, AL

Foley, Baldwin Co., AL

Flash Flood Guidance an indication of the amount of rainfall over a period of time necessary to cause small streams to overflow their natural banks based on an estimate of average soil moisture and stream flow conditions in a given county e.g. if the 3-hour FFG = 2.5“ then flooding should begin on small streams if that amount or more falls in a 3-h period issued twice daily at about 11 am and 9 pm CST

Foley, hourly rainfall on the hour

Foley, 3-hourly rainfall on the hour

Foley, 3-hourly rainfall by the minute

Foley, 6-hourly rainfall on the hour

Foley, 6-hourly rainfall by the minute

Conclusions It can be challenging to issue flood warnings when relying just on ASOS observations ASOS locations are spaced relatively far apart ASOS rainfall totals are not always provided on a regular (e.g. hourly or better) basis ASOS’s often go out in bad weather Mesonet data are helpful because they are available at finer spatial and temporal resolutions Flash flood warnings would improve further if FFG products were available more frequently

Thank You!! http://chiliweb.southalabama.edu/ skimball@usouthal.edu