A Glimpse into the Techniques and Interpretation of the CPC

A Glimpse into the techniques and interpretation of
CPC‟s Extended-Range Forecasts (ERF)
TEMPERATURE
PRECIPITATION
Anthony Artusa
NOAA Climate Prediction Center
(301) 763-8000 ext. 7530
[email protected]
WeatherBug Roosevelt Hotel NYC October 7, 2010
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COMPONENTS
FLOW PATTERN
TEMPERATURE
PRECIPITATION
WRITE-UP
Valid: Sep 01 - 05, 2010 (6-10 Day Outlook)
Valid: Sep 03 - 09, 2010 (8-14 Day Outlook)
Issued: Aug 26, 2010
PROGNOSTIC DISCUSSION FOR 6 TO 10
AND 8 TO 14 DAY OUTLOOKS NWS
CLIMATE PREDICTION CENTER CAMP
SPRINGS, MD 300 PM EDT THU AUGUST 26
2010 6-10 DAY OUTLOOK FOR SEP 01 - 05
2010 THE MODEL SOLUTIONS ARE IN FAIR
AGREEMENT TODAY, LESS AGREEMENT
THAN EARLIER IN THE WEEK. THE MODEL
SOLUTIONS FEATURE A WEAK RIDGE
NEAR THE ALEUTIANS, WEAK TROUGHING
ALONG THE WEST COAST OF NORTH
AMERICA, RIDGING ACROSS THE
VERIFICATION
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Difference Between Forecasts
Long-waves
Short-waves
5-day Average Height Field (D+8)
Components of D+8 Height Field
(132 -240 Hour Forecast)
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What is the main difference between the
6-10 and Week 2 forecasts?
6-10 500-hPa Height/Anomalies
May 23-27, 2010
8-14 500-hPa Height/Anomalies
May 25-31, 2010
Averaging period is the only difference between these two forecasts.
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Comparison of Models
5
Background notes:
00z (8:00 PM (EDT))
12z (8:00 AM (EDT))
6-10 day forecast: 5-day mean centered on day 8 (D+8)
8-14 day forecast: 7-day mean centered on day 11 (D+11)
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ENSEMBLES
t+14
t=0
{IC}
ANALYSIS
(data assimilation
provides best
estimate of
initial state of
atmosphere)
M2
M2
M1
CTRL
M1
low-res version of analysis
CTRL
M3
M3
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Comparison of Models – D+8 Heights
Ensemble Means (top) & Operationals (bottom)
0z GFS ENS MEAN
0z CAN ENS MEAN
y-12z EC ENS MEAN
0z GFS
6z GFS
y-12z ECMWF
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Comparison of Models – D+8 Anomalies
Ensemble Means (top) & Operationals (bottom)
0z GFS ENS MEAN
0z CAN ENS MEAN
y-12z EC ENS MEAN
0z GFS
6z GFS
y-12z ECMWF
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D+8 Spaghetti Contours
(00z GFS ENM)
Valid May 23-27, 2010
5520 meters
5760 meters
Ensembles provide a measure of forecast uncertainty
Ridge over eastern US (right panel) is more amplified than normal
(compare with black climatology line)
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Model
6-10 day
8-14 day
00z GFS
Blend Weights:
assigned using a
subjective/objective
mix; consider the
Anomaly Correlation
(AC) scores for the
models over past 60
days.
06z GFS
10%
y12z GFS
y18z GFS
00z GFS ENM
20%
06z GFS ENM
25%
y12z GFS ENM
y18z GFS ENM
GFS SUPER ENM
40%
00z ECMWF
y12z ECMWF
00z ECMWF ENM
35%
50%
10%
10%
y12z ECMWF ENM
00z CAN ENM
y12z CAN ENM
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500-hPa Blend Forecast
made: May 17, 2010
This product is available to the public via the web. AWIPS version has heights and
anomalies as two separate figures.
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30-year historical temperature observations (PDF)
Middle tercile
Coldest tercile
Warmest tercile
N
B
33%
A
67%
Credit: (Copyright) Robert Niles, http://www.robertniles.com/stats/stdev.shtml
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Partitioning of Probabilities
100%
80%
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30
33
33
53
60%
33
39
40%
20%
53
33
33
Above
Near
Below
30
13
0%
CLIM
NOR
B>N>A B<N<A
TERCILE BOUNDARIES
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Interpretation of ERF Surface Outlook
N
Central MN
Below: 31.3%
Normal: 37.3%
Above: 31.3%
N=Near Normal Category
Contours are labeled
with the total
probability for the
indicated category.
N
33 N
40
Southern NV
Below: 45%
Normal: 33%
Above: 22%
33
40
B
A
N
50
Northern GA
Above: 55%
N Normal: 33%
Below: 12%
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Generating temperature and precipitation
outlooks for the 6-10/8-14 day period:
Temperature Tools
Precipitation Tools
Klein Equations
Calibrated Precipitation
NAEFS
NAEFS
Analogs
Analogs
Neural Network
Neural Network
Re-forecasts
Re-forecasts
Automatic Forecast
Automatic Forecast
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Temperature Tool (Kleins)
Klein – 0z GFS ENS
Klein – 0z GFS
Klein – Manual Blend
Klein – 6z GFS
Screening Regression
that derives multiple
linear regression (MLR)
equations which express
5-day mean surface
temperature as a function
of 5-day mean 700-mb
heights centered 2 days
earlier, and local 5-day
mean surface temp for a
period 4 days earlier than
the forecast period.
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Temperature Tool (0z NAEFS)
B
E
L
O
W
N
E
A
R
A
B
O
V
E
Joint Ensemble:
20 Canadian members &
20 GEFS members per
Cycle (00z & 12z)
Equally weighted members
and both ensemble systems
are also equally weighted
Both ensembles are „postprocessed‟ (bias-corrected &
calibrated) before combined
into one NAEFS.
Valid May 25-31, 2010
Bias Correction: www.emc.ncep.noaa.gov/gmb/yzhu/gif/pub/manscript_bocui_bias_correction_20100709.pdf
Calibration: Unger, David A., Huug van den Dool, Edward O‟Lenic, Dan Collins, 2009: Ensemble Regression. 18
Mon.Wea.Rev., 137, 2365-2379 (journals.ametsoc.org/doi/abs/10.1175/2008MWR2605.1)
Precipitation Tool (NAEFS)
Wet Tercile
Dry Tercile
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ANALOGS
A1
A10
A2
A3
A9
Height
prog
Avg
Composite
Analog
A4
A8
A5
A7
A6
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COMPOSITE HEIGHT ANALOG
ANALOG WINDOW: +/- 6 WEEKS
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Temperature & Precipitation Tools (Analogs)
0z GFS ENM
0z GFS
y-12z EC ENM
y-12z EC
y-12z EC ENM
y-12z EC
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Temperature & Precipitation Tools (Neural Net)
0z CAN ENM
0z EC ENSM
Derives statistical
relationships between
500-mb heights and
surface fields; uses
larger domain than Kleins
6z GFS
0z EC
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Temperature & Precipitation Tools (Reforecast)
MRF (T62) model (Jan thru Jun 1998) ; Whitaker
Initial conditions use reanalysis (ncep / ncar)
15-member ensemble (Refcst from 11/78 - 2005)
Calibrated probabilities
TEMP
PRCP
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Temperature & Precipitation Tools (Auto)
TEMP
PRCP
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Sample 06Z GFS model
(12-hr total precipitation; MSLP; 850 mb temperatures)
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Nocturnal Thunderstorm Clusters (MCS) often track along the
southern edge of the westerlies (582-588 “corridor”)
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Teleconnections (Temperature)
Made May 17, 2010
500hPa
500hPa
+
Surface
Temp
-
Surface
Temp
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Teleconnections (Precipitation)
Made May 17, 2010
500-hPa
500-hPa
+
Surface
Prcp
-
Surface
Prcp
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Official CPC Surface Forecasts
TEMP
PRCP
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PROGNOSTIC MAP DISCUSSION
( 6-10 day & 8-14 day )
SYNOPSIS:
Ridges/Troughs
Blend
Weights &
Confidence
Temperature
TEMPERATURE
TOOLS
USED
Tools Used
Precipitation
PRECIPITATION
TOOLS
USED
Tools Used
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500-hPa Heights/Anomalies Verification
(May 23-27, 2010)
OBSERVED
HEIGHTS
OBSERVED
ANOMALIES
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Temperature Verification
(May 23-27, 2010)
FORECAST
OBSERVATIONS
General Heidke Skill Score for 3 equal classes:
(H – E) * 100
---------------------------------(T – E)
H: # of “Hits”
=
E: expected # of hits (=1/3)
+71.4
T: total # of stations
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Precipitation Verification
(May 23-27, 2010)
OBSERVATIONS
FORECAST
General Heidke Skill Score for 3 equal classes:
(H – E) * 100
---------------------------------(T – E)
H: # of “Hits”
=
E: expected # of hits (=1/3)
+17.7
T: total # of stations
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Everglades Heron
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