A Hindcast Test on the Anomaly A Hindcast Test on the Anomaly Analog Prediction SystemAnalog Prediction System

Meteorology 485Meteorology 485

Matt Steinbugl and Lisa MurphyMatt Steinbugl and Lisa Murphy

April 2, 2004April 2, 2004

Project Goal:Project Goal:

To test several aspects of an objective analog forecast using varying To test several aspects of an objective analog forecast using varying lengths of lead time for surface based anomalieslengths of lead time for surface based anomalies

Select difficult cases, mostly noted by a large change in the anomaly fields Select difficult cases, mostly noted by a large change in the anomaly fields from the ‘month before’ to the predicted month.from the ‘month before’ to the predicted month.

Selected months to predict:Selected months to predict:

October, 2002October, 2002 January, 2000January, 2000 March, 1992March, 1992 January, 1990January, 1990 September, 1988September, 1988 January, 1987January, 1987

January, 1982January, 1982 December, 1983December, 1983 January, 1977January, 1977 August, 1977August, 1977 March, 1971March, 1971 June, 1966June, 1966

Also shown are the months before anomalies Also shown are the months before anomalies to assess the role that persistence has in to assess the role that persistence has in analog forecastinganalog forecasting

Test One – A Single Month LeadTest One – A Single Month Lead

Gather the surface temperature and precipitation Gather the surface temperature and precipitation anomalies for the month prior to the one we are predictinganomalies for the month prior to the one we are predicting

Use the analog-mapper page to draw the precipitation and Use the analog-mapper page to draw the precipitation and temperature anomalies of that month with a 50% temperature anomalies of that month with a 50% downgrade of anomalies.downgrade of anomalies.

Capture analog yearsCapture analog years Use only the years that have a threshold value greater than Use only the years that have a threshold value greater than

50% and 50% and occurred prior to the predicted yearoccurred prior to the predicted year Insert the analog years into the CDC climate divisional map Insert the analog years into the CDC climate divisional map

interface to produce monthly temperature and precipitation interface to produce monthly temperature and precipitation anomalies for the next month (predicted one)anomalies for the next month (predicted one)

Compare the CDC “forecast” maps to what actually Compare the CDC “forecast” maps to what actually occurred that month.occurred that month.

Using the analog mapper, 0.5 standard Using the analog mapper, 0.5 standard deviation was used deviation was used

Palmer Drought Index was not incorporated Palmer Drought Index was not incorporated into these resultsinto these results

Test One – A Single Month LeadTest One – A Single Month Lead

Data Source: Analog-mapperData Source: Analog-mapper

http://analog1.met.psu.edu/ross/climdivmap_withlags/analogmapper.hthttp://analog1.met.psu.edu/ross/climdivmap_withlags/analogmapper.htmlml

http://analog1.met.psu.edu/ross/plotclimdata_withlags/plotmeanclimdathttp://analog1.met.psu.edu/ross/plotclimdata_withlags/plotmeanclimdata.htmla.html

Data Source:Data Source: The Climate Diagnostic Center web site was used to The Climate Diagnostic Center web site was used to

retrieve and display temperature and precipitation retrieve and display temperature and precipitation anomalies for the month that was being “predicted”anomalies for the month that was being “predicted”

www.cdc.noaa.govwww.cdc.noaa.gov

Test One – Single Month LeadTest One – Single Month Lead

Jan 1977Jan 1977

Composites:Composites: Verifications:Verifications:

Jan 1983Jan 1983

Month Before:Month Before:

Test One – Single Month LeadTest One – Single Month Lead

Jan 1987Jan 1987

Month Before:Month Before: Composites:Composites: Verifications:Verifications:

Mar 1971Mar 1971

Test One – Single Month LeadTest One – Single Month Lead Month Before:Month Before: Composites:Composites: Verifications:Verifications:

Mar 1992Mar 1992

Dec 1983Dec 1983

Test One – Single Month LeadTest One – Single Month Lead Composites:Composites: Verifications:Verifications:

Jan 2000Jan 2000

Month Before:Month Before:

Aug 1977Aug 1977

Test One – Single Month LeadTest One – Single Month Lead Composites:Composites: Verification:Verification: Month Before:Month Before:

Jan 1990Jan 1990

The ‘flip’ year proved to be the worst in The ‘flip’ year proved to be the worst in being able to predict the following monthbeing able to predict the following month

Test Two MethodTest Two Method

Only selected anomalies that were 1 standard Only selected anomalies that were 1 standard deviation or larger, but assigned it a value of 0.5deviation or larger, but assigned it a value of 0.5

Acquired years that were common to the three Acquired years that were common to the three sets of analog years to inserted them into CDC’s sets of analog years to inserted them into CDC’s climate divisional map to find the next month climate divisional map to find the next month temperature and precipitation anomaliestemperature and precipitation anomalies

Test Two – Multiple Month LeadTest Two – Multiple Month Lead Using Jeremy Ross’ website to access anomalies for up to Using Jeremy Ross’ website to access anomalies for up to

6 months prior to the forecast month, we used a variety of 6 months prior to the forecast month, we used a variety of anomalies to make a new “mixed” predictionanomalies to make a new “mixed” prediction

One MonthOne Month Same as the single month method, however, this time we Same as the single month method, however, this time we

could only choose two anomalies from the temperature and could only choose two anomalies from the temperature and precipitation fields to acquire analog yearsprecipitation fields to acquire analog years

Three MonthThree Month A three month lead included the selection of only A three month lead included the selection of only

two anomalies from the temperature and two anomalies from the temperature and precipitation fields to acquire analog yearsprecipitation fields to acquire analog years

Six MonthSix Month The six month lead chose only one anomaly from The six month lead chose only one anomaly from

either the temperature or precipitation fields to either the temperature or precipitation fields to acquire the analog yearsacquire the analog years

Test Two: Test Two: Multiple Month LeadMultiple Month Lead Composites:Composites: Verifications:Verifications:

Jan 1977Jan 1977

Jan 1987Jan 1987

Month Before:Month Before:

Test Two: Test Two: Multiple Month LeadMultiple Month Lead

Dec 1983Dec 1983

Mar 1992Mar 1992

Month Before:Month Before: Composites:Composites: Verifications:Verifications:

Test Two: Test Two: Multiple Month LeadMultiple Month Lead Composites:Composites: Verifications:Verifications:

Jan 1983Jan 1983

Jan 2000Jan 2000

Month Before:Month Before:

Test Two: Test Two: Multiple Month LeadMultiple Month Lead Composites:Composites: Verifications:Verifications:

Aug 1977Aug 1977

Month Before:Month Before:

Mar 1971Mar 1971

Test Two: Test Two: Multiple Month LeadMultiple Month Lead Composites:Composites: Verifications:Verifications:

Jan 1990Jan 1990

Month Before:Month Before:

The ‘flip month’ proved again to be the The ‘flip month’ proved again to be the most difficult to predictmost difficult to predict

Challenges of Test Two MethodChallenges of Test Two Method

There were too few years that were There were too few years that were common to all 3 sets for the mixed common to all 3 sets for the mixed techniquetechnique

Instead used years that were common in at Instead used years that were common in at least 2 of the setsleast 2 of the sets

Some that worked well for the one month Some that worked well for the one month lead technique did not for the mixed lead lead technique did not for the mixed lead technique and vice versatechnique and vice versa

Assessments:Assessments: Jan 1977 and Jan 1983 did well for both techniques Jan 1977 and Jan 1983 did well for both techniques Mar 1971 did worse in the mixed technique (Mar 1971 Mar 1971 did worse in the mixed technique (Mar 1971

showed too much warming in the NW in the first method showed too much warming in the NW in the first method and too much warming all over in the mixed technique)and too much warming all over in the mixed technique)

Jan 1983 showed too much cooling in the west in both Jan 1983 showed too much cooling in the west in both methodsmethods

Dec 1983 and Jan 2000 did worse in the first test (Jan Dec 1983 and Jan 2000 did worse in the first test (Jan 2000 showed too much cooling in first method and too 2000 showed too much cooling in first method and too much warming on East coast in mixed technique. Dec much warming on East coast in mixed technique. Dec 1983 showed too much warming in the SE)1983 showed too much warming in the SE)

Had serious problems forecasting a flip month: Jan 1990, Had serious problems forecasting a flip month: Jan 1990, Aug 1977, and also Sept 1988 and Jun 1966 did poorlyAug 1977, and also Sept 1988 and Jun 1966 did poorly

Future Work…Future Work…1. Automate and quantify1. Automate and quantify2. Create an moveable ensemble of analogs 2. Create an moveable ensemble of analogs based on flexible anomaly fieldsbased on flexible anomaly fields3. Design an interface that will combine 10 3. Design an interface that will combine 10 day GFS forecasts with creating the best day GFS forecasts with creating the best analoganalog4. Downscale technique to invite the most 4. Downscale technique to invite the most information outinformation out