So it’s a Land-falling Atmospheric River, Can That Help the Forecaster Make a Better
QPF?
David W. Reynolds Cooperative Institute for Research in Environmental Sciences
Boulder, CO
Brian KawzenukCenter for Western Weather and Water Extremes
August 8, 2016
International Workshop on Atmospheric Rivers
Outline• Review historical CNRFC (California Nevada River Forecast Center)
derived 24-hr Mean Areal Precipitation (MAP) and IVT correlations for Lake Mendocino Watershed– Is IVT a good proxy for 24-hr rainfall?
• Review CNRFC and GEFS forecast to observed MAPs– Are model and model derived QPFs better related to observed rainfall than IVT?
• Review a land-falling AR case from 2016• Looked at some 10 cases but will only show early March 2016
• Summary and Recommendations
Russian River Watershed
Potter Valley Dam
Healdsburg
Guerneville
Hopland
40N 125W
BBY
IVT calculated here
37.5N 125W
Landfalling AR depicted by IWV and IVT00Z 6 March 2016
http://cw3e.ucsd.edu/?page_id=491#IVT
Not an AR
Minimal strength AR
Moderate strength AR
Normal-duration AR landfall (12-24 hours)
Days from 10 AM PT Thursday 3 March 2016
AR summary for Pt Reyes, CA area, including Russian River
Precipitation forecast from NOAA/NWS California/Nevada River Forecast Center
6-9 inches of rain in favored mountain locations over 3 days (4 AM Fri – 4 AM Mon)
1000
600
800
400
200
0
0 2 3 4 5 61
AR
Str
en
gth
(wat
er
vap
or
tran
spo
rt; k
g/m
/s)
Summary by F.M. Ralph 8 AM PT Fri 4 March 2016
AR Plume Diagram by J. Cordeira/Plymouth St.Univ
What is a more reliable predictor of AR impacts?
IVT strength or QPF derived from models?
IVT QPF Methodology
• Utilize Rutz NCEP/NCAR* AR catalog from1949-2015 and NASA MERRA data** from 1980-2012. • Use 1000-200 mb IVT – show max 6-hr IVT 12z-12z as this showed best results
• Correlate to 24-hr Mean Areal Precipitation (MAP) available from 1949-2015 • Recalculate using upslope wind direction, precipitation threshold of >=.1 “/day and for matching sample
years using Rutz catalog.• Lavers et al. (2016) – showed IVT more predictable than rainfall but is IVT well correlated with
subsequent rainfall?
• Correlate 16-yrs of CNRFC 24-hr forecast MAPs issued daily at 12z to observed MAPs
• Compare 1985-2012 11 member GEFS (V9.1 ) Ensemble Mean MAPs utilized by CNRFC for probabilistic inflows to Lake Mendocino• Rutz and Alcott, 2014 did a similar study using 20 yr GEFS data and CPC QPE for CONUS
* http://rda.ucar.edu/datasets/ds090.0/ ** http://disc.sci.gsfc.nasa.gov/mdisc/data-holdings
Case-study Approach
• Focus on Lake Mendocino Watershed• Use MAP
• Utilize 12z model runs to coordinate with CNRFC 5-Day 6-hr QPFs
• Utilize NWS GFE software• Calculate MAPs for each model available
• Using GFS40 analysis compute layer average vapor transport for each case at 40N 125W at 6-hr intervals• 550-700, 700-850, 850-1000, 200-1000 MB
QPF verification using NWS GFE Software
Lake Mendocino Watershed
Derive the Mean Areal Precipitation (MAP)for each model available
Compare to MAP provided by CNRFC
Compare to IVT at landfall
Max 6-hr IVT NCEP/NCAR from 12z-12z at 40n 125W and 12-12z 24-hr QPE Lake Mendocino 1949-2015
0
200
400
600
800
1000
1200
1400
0 1 2 3 4 5 6 7 8
Max
6-h
r IV
T 1
2z-
12
z
24-hr sum
R2 = .24
Max 6-hr IVT MERRA 12z-12z at 40n 125W and 12-12z 24-hr QPE Lake Mendocino 1980-2012
0
200
400
600
800
1000
1200
1400
0 1 2 3 4 5 6
Max
6-h
r IV
T 1
2z-
12
z
24-hr sum
R2 = .24
CNRFC Day 1 24 hr QPF Correlation to Observed Lake Mendocino Watershed (2000-2016)
y = 1.0306x + 0.0168R² = 0.8252
0.00
1.00
2.00
3.00
4.00
5.00
6.00
0.00 1.00 2.00 3.00 4.00 5.00 6.00
Fcst
Day
1 2
4 h
r (i
n)
Obs 24 hr (in)
Day 1 Fcst vs Obs
Fcst vs Obs Linear (Fcst vs Obs)
R2 Values for CNRFC-GEFS Mean and IVT to24 hr MAP Lake Mendocino
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
24 48 72 96 120 144 168 192
Co
effi
cie
nt
of
Det
erm
inat
ion
R2
Forecast Lead Time (Hours)
CNRFC vs GEFS Mean 24 hr QPF
CNRFC 24 hr QPF R2 GEFS Mean 24 hr QPF R2
Range of 6-Hr Max IVTRutz, Merraor match GEFS or CNRFC yearsAlso SW flow only or >.1” day
CNRFC - 2000-2016
GEFS v9.1 11 member mean 1985-2012
R2 values fall in a very narrow range For various correlations listed- .22-.24
NCEP/NCAR 3-Day Time-Average 6-hr IVT vs 3-day MAP Lake Mendocino 40N and 37.5N
0
200
400
600
800
1000
1200
0 2 4 6 8 10 12 14
3d
ay T
ime
Avg
IVT
kg/m
/s
3-Day Precip
Regression of 3day Time Avg Ivt 40N by 3-Day Rainfall (R²=0.297)
Active Model
Conf. interval (Mean 95%) Conf. interval (Obs. 95%)
0
200
400
600
800
1000
1200
0 2 4 6 8 10 12 14
3-D
ay IV
T 3
7.5
N
3 Day precip
Regression of 3-Day Time Avg IVT 37.5N by 3 Day Rainfall (R²=0.364)
Active Model
Conf. interval (Mean 95%) Conf. interval (Obs. 95%)
3 Day CNRFC Total QPF vs Observations 2000-2016
y = 0.9483x + 0.0344R² = 0.8175
0
1
2
3
4
5
6
7
8
9
0 1 2 3 4 5 6 7 8
3-D
ay F
cst
(in
che
s)
Observed 3 day (inches)
3 Day CNRFC ForecastLake Mendocino
y = 0.0426x - 1.0919
-4
-3
-2
-1
0
1
2
2/1
5/2
000
1/2
/20
02
3/1
5/2
003
2/1
8/2
004
2/2
7/2
004
12
/9/2
004
12
/29
/20
04
3/2
/20
05
12
/21
/20
05
12
/31
/20
05
2/2
8/2
006
3/2
/20
06
2/1
1/2
007
1/6
/20
08
1/2
7/2
008
2/3
/20
08
2/1
7/2
011
3/2
1/2
011
3/2
6/2
011
1/2
2/2
012
11
/30
/20
12
12
/3/2
012
12
/24
/20
12
2/1
0/2
014
12
/5/2
014
12
/12
/20
14
2/8
/20
15
12
/23
/20
15
1/7
/20
16
1/1
8/2
016
3/7
/20
16
3/1
4/2
016
Me
an E
rro
r (i
nch
es)
Year
CNRFC Mean Error 3-Day Obs >= 3"
Mean Error Obs >= 3" Linear (Mean Error Obs >= 3")
Trends in 3-Day Forecast Mean Error (Bias)
IVT Plume Diagrams GEFS
00Z 6 March 00Z 11 March
GFS control forecast (black line), the ensemble-mean (green line), and the maximum (red line) and minimum (blue line) ensemble value at each forecast time. White shading represents +/- 1 standard deviation forecast from the ensemble mean
138 hrs > 250 kg/m/s42 hrs > 500 kg/m/s
5-7 Mar 2016 Layer IVT and CNRFC 6-hr Fcst and Obs MAPs
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
0
100
200
300
400
500
600
700
800
900
0 6 12 18 0 6 12 18 0 6
Rai
nfa
ll (i
nch
es)
IVT
pe
r la
yer
kg m
-1s-1
hr in Z day 5-7 Mar
Mar 5-7 2016 Layer IVT (40n 125W) and Lake Mendocino Watershed 6-hr Precip
6-Hr Precip COY Res Day 1 Fcst Day 2 Fcst Day 3 Fcst Day 4 Fcst Day 5 Fcst 550-700 700-850 850-1000 200-1000
00Z 6 March
Mar 5-6, 2016 MAP QPF Verification
0
0.5
1
1.5
2
2.5
3
3.5
0-24 24-48 48-72 72-96 96-120
24
-hr
rain
fall
(in
che
s)
Forecast Lead Time
MAP QPF valid 12z-12z 5-6 Mar 2016Lake Mendocino Watershed
CNRFC
GFS40
WestWrf
NAM12
HiResNmm
OBS
9-11 Mar 2016 Layer IVT and CNRFC 6-hr Fcst and Obs MAPs
0
0.2
0.4
0.6
0.8
1
1.2
0
100
200
300
400
500
600
700
800
900
0 6 12 18 0 6 12 18 0 6 12 18 0
Rai
nfa
ll (i
nch
es)
IVT
per
laye
r kg
m-1
s-1
hr in Z day 9-11 Mar
Mar 9-11 2016 Layer IVT (40n 125W) and Lake Mendocino Watershed 6-hr Precip
6-Hr Precip COY Res Day 1 Fcst Day 2 Fcst Day 3 Fcst Day 4 Fcst
Day 5 Fcst 550-700 700-850 850-1000 200-1000
11 March
Mar 10-11, 2016 MAP QPF Verification
0
0.5
1
1.5
2
2.5
3
0-24 24-48 48-72 72-96 96-120
24
-hr
rain
fall
(in
che
s)
Forecast Lead Time
MAP QPF valid 00z-00z 10-11 Mar 2016Lake Mendocino Watershed
CNRFC
GFS40
WestWrf
NAM12
HIRESNMM
OBS
Based on Correlations QPF better Predictor of Impacts than IVT
Lake Mendocino
CNRFC 6 Day QPF from 1 Mar 2016
GEFS Model Probability of >= 6”March 1-March 12, 2016
Plume Diagrams from GEFS
Conclusions and Recommendations
• IVT (200-1000mb) not as good an indicator of potential rainfall impacts of land-falling ARs as is model or manual QPFs• Supports Rutz-Alcott 2014 study for CONUS• IVT may be more predictable (Lavers) but IVT not well correlated to
subsequent rainfall for this study area over long term
• Utilize model QPFs (3 day totals) to define strength of land-falling ARs?• R-Cats to define AR strengthas defined by Ralph and Dettinger,2012-BAMS
• Forecaster situational awareness better served by focusing on model QPF- especially looking at 3-5-7 day totals given timing and exact locations can be off utilizing 6-12-24 hr model QPFs
EXTRAS
Feb 5-10, 2015 Layer IVTand CNRFC 6-hr Fcst and Obs MAPs
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
0
200
400
600
800
1000
1200
12 18 0 6 12 18 0 6 12 18 0 6 12 18 0 6 12
Rai
nfa
ll (i
nch
es)
IVT
per
laye
r kg
m-1
s-1
hr in Z day 5-10 Feb
Feb 5-10, 2015 Layer IVT and Lake Mendocino Watershed 6-hr Precip
LMAC1 Precip Day 1 Fcst Day 2 Fcst Day 3 Fcst Day 4 Fcst Day 5 Fcst 550-700 700-850 850-1000 200-1000
Feb 6-7, 2015 24-hr MAP QPF Verification
0
1
2
3
4
5
6
0-24 24-48 48-72 72-96 96-120
24
-hr
rain
fall
(in
ches
)
Forecast Lead Time
MAP QPF valid 12z-12z 6-7 Feb 2015Lake Mendocino Watershed
CNRFC
GFS40
WestWrf
NAM12
HIRESNMM
OBS
Dec 10-12, 2014 IVT vs CNRFC MAP 6-hr QPE250* and 500** kg m-1 s-1 IVT annotated with respect to 200-1000 mb IVT
0
0.4
0.8
1.2
1.6
2
2.4
2.8
0
200
400
600
800
1000
1200
0 6 12 18 0 6 12 18 0
Rai
nfa
ll (i
nch
es)
IVT
per
laye
r kg
m-1
s-1
hr in Z day 10-12 Dec
Dec 10-12, 2014 Layer IVT and Lake Mendocino Watershed 6-hr Precip
LMAC1 Precip Day 1 Fcst Day 2 Fcst Day 3 Fcst Day 4 Fcst Day 5 Fcst 550-700 700-850 850-1000 200-1000
* After Rutz et al, 2014 Mon. Wea. Rev. **Cordeira - http://cw3e.ucsd.edu/?page_id=491#LFT
Comparison of MAPs CNRFC and NWP Lake Mendocino Watershed 24 hr Amounts
0
1
2
3
4
5
6
7
0-24 24-48 48-72 72-96 96-120
24
-hr
rain
fall
(in
che
s)
Forecast Lead Time
MAP QPF valid 00z-00z 11-12 Dec 2014Lake Mendocino Watershed
CNRFC
GFS40
WestWrf
NAM12
HIRESNMM
OBS
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
0
100
200
300
400
500
600
700
800
900
0 6 12 18 0 6 12 18 0 6 12 18 0 6
Rai
nfa
ll (i
nch
es)
IVT
pe
r la
yer
kg m
-1s-1
hr in Z day 19-22 Dec
Dec 19-22, 2015 Layer IVT and Lake Mendocino Watershed 6-hr Precip
LAMC1 6-hr Precip Day 1 Fcst Day 3 Fcst Day 4 Fcst Day 5 Fcst 550-700 700-850 850-1000 200-1000
Dec 19-22, 2015 Layer IVT and 6-hr Fcst and Obs CNRFC MAPs
21-22 Dec 2015 MAP QPF Verification
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
0-24 24-48 48-72 72-96 96-120
24
-hr
rain
fall
(in
che
s)
Forecast Lead Time
MAP QPF valid 12z-12z 21-22 Dec 2015Lake Mendocino Watershed
CNRFC
GFS40
WestWrf
NAM12
HIRESNMM
OBS
Lake Mendocino Operations 2015-2016
01
23
45
60
20000
40000
60000
80000
100000
120000
1-O
ct
6-O
ct
11
-Oct
16
-Oct
21
-Oct
26
-Oct
31
-Oct
5-N
ov
10
-No
v
15
-No
v
20
-No
v
25
-No
v
30
-No
v
5-D
ec
10
-Dec
15
-Dec
20
-Dec
25
-Dec
30
-Dec
4-J
an
9-J
an
14
-Jan
19
-Jan
24
-Jan
29
-Jan
3-F
eb
8-F
eb
13
-Fe
b
18
-Fe
b
23
-Fe
b
28
-Fe
b
4-M
ar
9-M
ar
14
-Mar
19
-Mar
24
-Mar
29
-Mar
3-A
pr
8-A
pr
13
-Ap
r
18
-Ap
r
23
-Ap
r
28
-Ap
r
3-M
ay
8-M
ay
13
-May
18
-May
23
-May
28
-May
Lake
Me
nd
oci
no
Wat
ers
he
d R
ain
fall
(in
che
s)
Sto
rage
(ac
re-f
eet
)
Date
Lake Mendocino Guide Curve
COY MAP MAP 2 Baseline 2007-2014 Deviation STO 1 STO 2
Forecasts Flows and Stage at HoplandDay 5 Forecast
Forecasts Flows and Stage at HoplandDay 4 Forecast
Forecasts Flows and Stage at HoplandDay 2 Forecast
Forecasts Flows and Stage at HoplandDay 1 Forecast
