Jay Grymes WAFB Chief Meteorologist LSU AgCenter Climatologist
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Transcript of Jay Grymes WAFB Chief Meteorologist LSU AgCenter Climatologist
Jay GrymesJay GrymesWAFB Chief MeteorologistWAFB Chief Meteorologist
LSU AgCenter ClimatologistLSU AgCenter Climatologist
Flooding in the Amite Basin:Flooding in the Amite Basin: IIncreased Threat in the Coming Months?ncreased Threat in the Coming Months?
Strengthening El Niño?
Flooding in the Amite Basin:Flooding in the Amite Basin: IIncreased Threat in the Coming Months?ncreased Threat in the Coming Months?
-- reviewed daily mean stage for -- reviewed daily mean stage for ‘Amite nr Denham Springs’‘Amite nr Denham Springs’for the period Oct 1974 – present . . .for the period Oct 1974 – present . . .
data courtesy of USGS, Louisianadata courtesy of USGS, Louisiana
-- “flood events” defined as at least one day with -- “flood events” defined as at least one day with daily mean stage ≥ 29.0 ftdaily mean stage ≥ 29.0 ft
-- “moderate flood” defined as at least one day with-- “moderate flood” defined as at least one day withdaily mean stage ≥ 35.0 ftdaily mean stage ≥ 35.0 ft
-- “major flood” defined as -- “major flood” defined as instantaneousinstantaneous stage ≥ 39.0 ft stage ≥ 39.0 ft
Nov-to-Mar Rainfall: Departure from NormalEl Nino Winter/Springs: 1950 - 1995
Rainfall Below Normal Rainfall Above Normal
El Niño El Niño ‘Signature’ along the G‘Signature’ along the Gulf Coast: ulf Coast: ‘‘Active’ Active’ Sub-Tropical JetSub-Tropical Jet
El Niño El Niño ‘Signature’ along the G‘Signature’ along the Gulf Coast: ulf Coast: ‘‘Active’ Active’ Sub-Tropical JetSub-Tropical Jet
Sub-Tropical Jet
““Warm” SSTsWarm” SSTs
More FrequentMore FrequentGulf LowsGulf Lows
El Niño
La Niña
La Nada“Neutral”
December-thru-May Rainfall:Louisiana EC Climate Division
1974-75 thru 2009-10
6-mo. Rainfall (in.)
Rainfall Data: NOAA/National Climatic Data CenterENSO Ranks: NOAA/NWS Climate Prediction Center
El N
iño/
Sout
hern
Osc
illati
on(E
NSO
) Ran
king
Series Median
Seasonal rainfallSeasonal rainfalltends to be greatertends to be greater
during El Niño eventsduring El Niño events
Amite River near Denham SpringsFlood Events: Oct 1974 – Present
by Month
‘Juan’(1985)
‘Allison’(2001)
‘Babe’(1977)
‘Gustav’(2008)
51 Events
River Stage Data: USGS, Louisiana
-- 4 as ‘tropical’-- 3 in summer/fall
Amite River near Denham SpringsFlood Events: Oct 1974 – Present
by Month
19901990
‘Major’ Floods: > 39 ft
1983198319771977
Apr 1977 & Apr 1983Apr 1977 & Apr 1983 . . . ‘major’ floods . . . . . . ‘major’ floods . . .
both during El Niñosboth during El Niños
51 Events
River Stage Data: USGS, Louisiana
Amite River near Denham SpringsFlood Events by Year: 1974 – Present
(All Months)
River Stage Data: USGS, Louisiana
Amite River near Denham SpringsFlood Events by Year: 1974 – Present
(December thru May)
River Stage Data: USGS, Louisiana‘Major’ Floods:
> 39 ft
El NiñoEl Niño
La NiñaLa Niña
ONI Index: NWS Climate Prediction Center
NWS/CPC ENSO ONI Index:Jan-Feb-Mar Index Score
35 Seasons: 9 El Niños & 9 La Niñas
NWS/CPC ENSO ONI Index:Jan-Feb-Mar Index Score
& Occurrences of Winter/Spring Floods
El NiñoEl Niño
La NiñaLa Niña
ONI Index: NWS Climate Prediction Center
11
55
22
22
11
33
11
1100
11
0000
22
1111
00 00
00
El Niños:El Niños:16 floods16 floods
in 9 in 9 seasonsseasons
La Niñas:La Niñas:5 floods5 floods
in 9 in 9 seasonsseasons
La Nadas:La Nadas: 23 floods in 17 seasons23 floods in 17 seasons
No ‘moderate’ to ‘major’ floodsNo ‘moderate’ to ‘major’ floods
ClimaticClimaticRegimeRegime
RatioRatioFloods : SeasonsFloods : Seasons
El NiñoEl Niño 1.8 : 11.8 : 1
La NadaLa Nada 1.4 : 11.4 : 1
La NiñaLa Niña 0.6 : 10.6 : 1
TropicalTropical 0.1 : 10.1 : 1
Flooding in the Amite Basin:Flooding in the Amite Basin: IIncreased Threat in the Coming Months?ncreased Threat in the Coming Months?
ClimaticClimaticRegimeRegime
RatioRatioFloods : SeasonsFloods : Seasons
El NiñoEl Niño 1.8 : 11.8 : 1
La NadaLa Nada 1.4 : 11.4 : 1
La NiñaLa Niña 0.6 : 10.6 : 1
TropicalTropical 0.1 : 10.1 : 1
While flooding in the coming months is not a certainty, climatic signalsWhile flooding in the coming months is not a certainty, climatic signals(El Niño) point to an elevated threat of ‘high water’ along the Amite(El Niño) point to an elevated threat of ‘high water’ along the Amitenear Denham Springs . . . and therefore much of the greater Amite Basin.near Denham Springs . . . and therefore much of the greater Amite Basin.