Jay Grymes Jay Grymes WAFB Chief Meteorologist WAFB Chief Meteorologist LSU AgCenter Climatologist LSU AgCenter Climatologist Flooding in the Amite Basin: Flooding in the Amite Basin: I I ncreased Threat in the Coming Months? ncreased Threat in the Coming Months? Strengthening El Niño?
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Jay Grymes WAFB Chief Meteorologist LSU AgCenter Climatologist Flooding in the Amite Basin: I ncreased Threat in the Coming Months? I ncreased Threat in.
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Jay GrymesJay GrymesWAFB Chief MeteorologistWAFB Chief Meteorologist
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
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.