INTELLIGENT USE OF THE AVN/MRF

Michael Eckert

HYDROMETEOROLOGICAL PREDICTION CENTER

CAMP SPRINGS, MD

E-MAIL ADDRESS: michael.eckert@noaa.gov

COMAP SYMPOSIUM 00-1COMAP SYMPOSIUM 00-1

15 December 199915 December 1999

Understanding the performance of an operational model is critical to being able to forecast the sensible weather

All models have strengths and weaknesses.All models have strengths and weaknesses. All have trouble handling smaller scale features. All have trouble handling smaller scale features. All have problems with convection.All have problems with convection. All do a decent job in handling the short range All do a decent job in handling the short range

(0-36 hr) forecast of synoptic scale features. (0-36 hr) forecast of synoptic scale features.

Why models have forecast problems Initialization and quality control smoothes data fields. Some of the Initialization and quality control smoothes data fields. Some of the

lost detail may be important. lost detail may be important. Lack of data over the oceans and Mexico. Lack of data over the oceans and Mexico. Atmospheric processes are non-linear; small changes in initial conditions Atmospheric processes are non-linear; small changes in initial conditions

can lead to large forecast variations (this is the basis for ensemble can lead to large forecast variations (this is the basis for ensemble forecasting).forecasting).

Terrain may not have sufficient resolutionTerrain may not have sufficient resolution Model physics are approximationsModel physics are approximations

for lower resolution models (OUR CURRENT for lower resolution models (OUR CURRENT OPERATIONAL MODELS) convection is parameterizedOPERATIONAL MODELS) convection is parameterized

for higher resolution models the micro-physical processes are for higher resolution models the micro-physical processes are parameterized parameterized

The T126 version of the Avn does not have sufficient resolution to adequately depict the rain shadow east of the Cascades. A forecaster needs to know

the climatology of precipitation during certain flow regimes.

Prism climatological precipitation data. Note the distinct rain shadow to the east of the Cascades

12-36 AVN V.T. 12Z 23 FEB 1999

PRECIPITATION ANALYSIS AVN V.T. 12Z 23 FEB 1999

The way the physics are approximated can lead to model errors, for example

The Betts parameterization in the eta is The Betts parameterization in the eta is handled differently over land and waterhandled differently over land and water this can cause the eta and meso-eta to this can cause the eta and meso-eta to

erroneously strengthen the coastal front.erroneously strengthen the coastal front. and to forecast too much rain along the Gulf and to forecast too much rain along the Gulf

and Atlantic Coastal regions and Atlantic Coastal regions

AVN/MRF APPROXIMATED PHYSICS

THE AVN/MRF USE A MODIFIED GRELL SCHEME THE AVN/MRF USE A MODIFIED GRELL SCHEME THIS USES THE CHANGE IN STABILITY TO THIS USES THE CHANGE IN STABILITY TO

DETERMINTE WHEN TO RELEASE ENERGY AS DETERMINTE WHEN TO RELEASE ENERGY AS CONVECTION.CONVECTION.

NO DIRECT MIXING BETWEEN THE CLOUDY AIR NO DIRECT MIXING BETWEEN THE CLOUDY AIR AND ENVIRONMENTAL AIR. AND ENVIRONMENTAL AIR. (except at the cloud top and bottom) (except at the cloud top and bottom)

NO CLOUD WATER EXISTS, THEREFORE ALL NO CLOUD WATER EXISTS, THEREFORE ALL WATER IS CONVERTED TO RAIN. WATER IS CONVERTED TO RAIN.

A NUMBER OF AVN/MRF PERFORMANCE CHARACTERISTICS

HAVE CHANGED IN THE PAST YEAR.

SINCE JUNE THE AVN/MRF AGAIN UNDERPREDICTS SINCE JUNE THE AVN/MRF AGAIN UNDERPREDICTS HEAVIER PRECIPITATION THRESHOLDS. HEAVIER PRECIPITATION THRESHOLDS.

THE AVN/MRF NO LONGER “OFTEN THE AVN/MRF NO LONGER “OFTEN UNDERPREDICTS SURFACE LOWS, ESPECIALLY UNDERPREDICTS SURFACE LOWS, ESPECIALLY OVER OCEANS”OVER OCEANS”

ISOLATED PRECIPITATION “BULLSEYES” HAVE ISOLATED PRECIPITATION “BULLSEYES” HAVE BEEN A PROBLEM, ESPECIALLY DURING THE BEEN A PROBLEM, ESPECIALLY DURING THE WARM SEASON.WARM SEASON.

THIS WAS MORE LIKELY WHEN THERE WAS SLOW THIS WAS MORE LIKELY WHEN THERE WAS SLOW SYSTEM MOVEMENTSYSTEM MOVEMENT

LATEST AVN/MRF CHANGES

June 15, 1998: INCREASED June 15, 1998: INCREASED HORIZONTAL RESOLUTION TO 170 HORIZONTAL RESOLUTION TO 170 AND LAYERS TO 42AND LAYERS TO 42

THIS LED TO A WARM BIAS AND THE DEVELOPMENT OF THIS LED TO A WARM BIAS AND THE DEVELOPMENT OF SPURIOUS PRECIPIATION BULLSEYES/TROPICAL SYSTEMSSPURIOUS PRECIPIATION BULLSEYES/TROPICAL SYSTEMS

July 21, 1998: EMERGENCY MODEL July 21, 1998: EMERGENCY MODEL IMPLEMENTATION TO REDUCE IMPLEMENTATION TO REDUCE ERRORS IN THE JUNE 15TH CHANGEERRORS IN THE JUNE 15TH CHANGE

AVN/MRF Still Often Has Problems Handling Upslope Events

Around 75% of the precipitation predicted by the AVN during this event was grid scale, rather than convective, precipitation. In these cases, the model QPF is often too far to the northwest. The maximum rainfall falls farther to the south along the surface front.

12-36 hr AVN QPF V.T. 12Z 27 APR 98 VERIFYING 24H PRECIPITATION V.T. 12Z 27 APR 98

4”3”

4”3”

5”

About 75% of the AVN Rainfall Over the OK Panhandle Was Grid-scale Precipitation (Not Convection).

36-HR AVN/MRF V.T. 12Z 27 APRIL 98 VERIFYING AVN/MRF

V.T. 12Z 27 APRIL 98

The overprediction of grid-scale precipitation may result in latent heat being released at too low a level in the atmosphere. This tends to cause pressures to lower, often resulting in the lows wrapping up too far to the west or northwest.

Another Case: AVN Wraps Low Too Far North And West. Both Surface and 500 mb Lows Are Too Deep.

AVN 36 HR FCST

APR 1998

AVN VERIFYING SURFACE ANALYSIS V.T. 00Z APR 1998

PRECIPITATION FORECAST IS POOR BECAUSE OF BAD SURFACE AND 500 MB FORECASTS OR VICE-VERSA.

Is this another case with some type of latent heating feedback problem?

Aviation Model handling of 500 mb trough

546

552558

564

570

546

570

576

564

558

564

570

576

558

06h V.T. 18Z Apr 18 36h V.T. 00Z Apr 20 Analysis V.T. 00Z Apr 20

The vorticity increases as the system lifts northeastward even though it never taps into or phases with any northern stream energy.

BIAS COMPARISON OF 12-36 HR

MRF AND EARLY ETA FORECASTS

12-36 hr biasValid 2 Apr - 30 Apr 98

4.0

3.0

2.0

1.0

0.02.001.501.00.75.50.25.10.01

THRESHOLD (INCHES)

BIA

S S

CO

RE

MRF GLOBALEARLY ETA

BIA

S S

CO

RE

THRESHOLD (INCHES)

2.001.501.00.75

12-36 hr biasValid 2 Feb - 28 Feb 98

.50.25.10.01

MRF GLOBAL

EARLY ETA

0.0

0.2

0.4

0.6

0.8

1.0

1.2

THE MRF AND AVN OVERPREDICT ALL THRESHOLDS ESPECIALLY THE HEAVIER ONES DURING SPRING AND SUMMER

VERIFIED TO AN 80 KM GRID

The MRF and MRFX spin-up precipitation bombs and tropical systems erroneously at all

time ranges.

10”+ bullseye

36-h MRFX v.t. 00Z 28 May 199824-h MRFX v.t. 12Z 27 May 1998

24-36-h MRFX v.t. 00Z 28 May 1998

SFC ANALYSIS v.t. 00Z 28 May 1998

MRF PRECIPITATIONConvective - dashed

Gridscale - solid green(inches -Vs- time)

BEFORE 7/21 AFTER 7/21

MRF RELATIVE HUMIDITY(pressure -Vs- time)

BEFORE 7/21 AFTER 7/21

>99% RH

>99% RH

MRF THETA-E (pressure -Vs- time)

BEFORE 7/21 AFTER 7/21

<342

>342

<342

>342

<342

>342

After the change

Latent heat induced precipitation bombs are Latent heat induced precipitation bombs are less common. Surface lows are less prone to less common. Surface lows are less prone to spin up. spin up.

The MRF/AVN still has problems The MRF/AVN still has problems initializing tropical wave at low latitudes. initializing tropical wave at low latitudes.

During Oct-Feb 1999, the AVN/MRF now had a bias of About 1.00 for 1.00” or greater amountsAbout 1.00 for 1.00” or greater amounts .47 for 2.00” or greater amounts.47 for 2.00” or greater amounts .27 for 3.00” or greater amounts .27 for 3.00” or greater amounts

The Aviation significantly The Aviation significantly underpredicted heavier rainfall underpredicted heavier rainfall amountsamounts

During OCT-JAN 1999 4 INCH OR GREATER ISOHYETS

WERE ANALYZED 22 TIMESWERE ANALYZED 22 TIMES WERE PREDICTED 2 TIMESWERE PREDICTED 2 TIMES THE AVIATION FORECAST 3” OR THE AVIATION FORECAST 3” OR

GREATER AMOUNTS 6 TIMES. GREATER AMOUNTS 6 TIMES.

SINCE THE CHANGES IN JUNE AND JULY, THE ETA BIAS FOR HEAVY AMOUNTS HAS DECREASED

SIGNIFICANTLY 1.2

1.0

0.8

0 .6

0.4

0.2

0.0.01 .10 .25 .50 2.001.00 1.50.75

THRESHOLD (INCHES)

BIAS

12-36 hr biasValid 2 Apr - 30 Apr 98

4.0

3.0

2.0

1.0

0.02.001.501.00.75.50.25.10.01

THRESHOLD (INCHES)

BIA

S S

CO

RE

MRF GLOBALEARLY ETA

12-36 HR AVN/MRF BIAS VALID 1 AUG - 25 AUG 1998

WILL THE BIAS INCREASE INCREASE IN THE COLD SEASON?

One of the typical errors of the AVN is to predict convective systems too far north

12-36 HR QPF V.T. 1200Z 29 JAN 1999

12-36 HR QPF V.T. 1200Z 30 JAN 1999

ANALYSIS V.T. 1200Z 29 JAN 1999

ANALYSIS V.T. 1200Z 30 JAN 1999

The AVN/MRF may be right on the synoptic scale

features but cannot handle outflow boundaries, etc. 36 HR QPF V.T. 1200Z 29 JAN 1999

36 HR QPF V.T. 1200Z 29 JAN 1999

ANALYSIS V.T. 1200Z 29 JAN 1999

A SLOW MOVING 500 CLOSE LOW AND QUASISTATIONARY FRONT WERE WELL FORECAST BY THE MODEL. HOWEVER, THE EFFECTIVE BOUNDARY REMAINED

SOUTH OF THE MODEL FORECAST

Despite these problems, the AVN model was the best model during the winter

LOWS TO THE LEE OF THE ROCKIES

THE AVN AND NGM USUALLY PREDICT THEM THE AVN AND NGM USUALLY PREDICT THEM TO FORM TOO FAR NORTH. HOWEVER, TO FORM TOO FAR NORTH. HOWEVER, DURING THE PAST WINTER THE AVN WAS DURING THE PAST WINTER THE AVN WAS SIGNIFICANTLY BETTER AT HANDLING SIGNIFICANTLY BETTER AT HANDLING CYCLONES AND THE ASSOCIATED CYCLONES AND THE ASSOCIATED PRECIPITATION THAN THE ETA. PRECIPITATION THAN THE ETA.

USE THE 300 MB UPPER LEVEL JET. THE USE THE 300 MB UPPER LEVEL JET. THE SURFACE LOW IS USUALLY FOUND BENEATH SURFACE LOW IS USUALLY FOUND BENEATH THE LEFT EXIT REGION OF THE JETTHE LEFT EXIT REGION OF THE JET

The AVN broke continuity on this forecast being much faster than previous runs or models from other centers

When systems are digging into the west with no kicker evident upstream, it is usually smart to follow the lead of the slowest model. In this case the AVN was much to fast with the upper low in the west.

If the 500 forecast is poor, the surface forecast will also be corrupted. Note that surface low in the

plains is too deep and far north on the forecast.

When the avn is in error to the lee of the mountains. This is the typical error.

THE NGM AND AVN/MRF HAVE SERIOUS PROBLEMS WITH ARCTIC AIRMASSES

36 HR NGM V.T. 00Z APR 09, 1995

36 HR AVN V.T. 00Z APR 09, 1995

AVN ANALYSIS V.T. 00Z APR 09, 1995

L

TEMPERATURES ACROSS KANSAS WERE IN THE LOW TO MID 50s WITH STRONG NORTH WINDS. SOUTH OF THE FRONT TEMPERATURES WERE IN THE UPPER 70s TO LOW 90s.

Why models have problems with arctic airmasses Terrain is averagedTerrain is averaged Initialization process sometimes robs Initialization process sometimes robs

shallow airmass of its coldnessshallow airmass of its coldness Models have problems handling the strength Models have problems handling the strength

of the inversionof the inversion The leading edge of the ETA LI gradient is The leading edge of the ETA LI gradient is

often the best indicator of the frontal positionoften the best indicator of the frontal position

MRF PERFORMANCE FOR 3-5 DAY FORECASTS SHALLOW COLD AIR IS NOT HANDLED WELL. SHALLOW COLD AIR IS NOT HANDLED WELL.

THE MODEL IS SLOW TO TRANSPORT SHALLOW THE MODEL IS SLOW TO TRANSPORT SHALLOW COLD AIRMASSES, ESPECIALLY ARCTIC COLD AIRMASSES, ESPECIALLY ARCTIC AIRMASSES JUST TO THE EAST OF THE ROCKY AIRMASSES JUST TO THE EAST OF THE ROCKY MOUNTAINS OR APPALACHIAN CHAIN. THIS IS MOUNTAINS OR APPALACHIAN CHAIN. THIS IS DUE TO MODEL TERRAIN ERRORS.DUE TO MODEL TERRAIN ERRORS.

EASTERLY BOUNDARY LAYER WINDS ARE EASTERLY BOUNDARY LAYER WINDS ARE OFTEN OVERPREDICTED ALONG THE FRONT OFTEN OVERPREDICTED ALONG THE FRONT RANGE OF THE ROCKY MOUNTAINS.RANGE OF THE ROCKY MOUNTAINS.

MODEL HAS A SLIGHT COLD BIAS, ESPECIALLY MODEL HAS A SLIGHT COLD BIAS, ESPECIALLY OVER THE EASTERN THIRD OF THE COUNTRY, OVER THE EASTERN THIRD OF THE COUNTRY, DURING THE COLD SEASON.DURING THE COLD SEASON.

MRF PERFORMACE FOR 3-5 DAY FORECASTS (CONT) MODEL TENDS TO PHASE SEPARATE MODEL TENDS TO PHASE SEPARATE

STREAMS TOO MUCH. POSSIBLY DUE TO STREAMS TOO MUCH. POSSIBLY DUE TO RESOLUTIONRESOLUTION

AT HIGH LATITUTES (NORTH OF 50AT HIGH LATITUTES (NORTH OF 50OO), THE ), THE MODEL PREDICTS TOO MUCH MODEL PREDICTS TOO MUCH RETROGRESSIONRETROGRESSION

TENDS TO WEAKEN THE REMAINS OF TENDS TO WEAKEN THE REMAINS OF UPPER LOWS TOO QUICKLY THAT ARE UPPER LOWS TOO QUICKLY THAT ARE COMING OUT OF THE SOUTHWESTCOMING OUT OF THE SOUTHWEST

A VERIFICATION OF THE 500 H FORECASTS FOR DAY 4

-45 -35 -25 -15 -05-40 -30 -20 -1030

80

90

40

50

60

70

DAY (VALID TIME RELATIVE TO TODAY)

AN

OM

AL

Y C

OR

RE

LA

TIO

N

MEAN ECMWF 70.4ECMWF

MRF

MEAN MRF 70.5

UKMET

MEAN UKMET 62.7

DEPICTS MEDIUM RANGE MODEL PERFORMANCE FOR THE PAST 50 DAYS WORTH OF RUNS. NOTE THAT HOW WELL A MODEL PERFORMS APPEARS TO BE REGIME DEPENDENT.

HIGH DAILY VARIABILITY IS WEATHER PATTERN DEPENDENT. THE

ECMWF IS BEST AT 500 MB BUT CAN HAVE SOME BAD MSLP FORECASTS

HPC/MRF/ECMWF MSLP ANOMALY CORRELATIONS HPC/MRF/ECMWF MSLP ANOMALY CORRELATIONS

MEAN SCORES

THE MEDIUM RANGE MODELS AVAILABLE AT HPC MODEL RUN HORIZONAL VERTICAL

MRF (00 UTC) 104 KM 28

MRF [1999] (00 UTC) 80 KM 42

CANADIAN (00/12 UTC) 70 KM 28

ECMWF (12 UTC) 40 KM 31

UKMET (00/12 UTC) 60 KM 30

NOGAPS (00/12 UTC) 70 KM 24

TIMES RESOLUTION LEVELS

*VALUES ARE APPROXIMATED AND UPDATED AS OF DECEMBER 1998

The best ensemble approach is to use various models to The best ensemble approach is to use various models to assess the possible range of solutionsassess the possible range of solutions

You need to know the characteristics of the MRF

MOS guidance. Stations included in MOS

How HPC breaks up regional verification of MOS

MOS verification for Northwest (left) and northern Plains (right)

MOS POPS ARE USUALLY TOO HIGH

Verification of MOS POPS for Great Lakes Region (top) and Northeast (bottom)

Southwest (left), Southern Plains (right), Southeast (bottom left) and Mid Atantic/Oh Valley (lower right)

NUMBER OF DAYS WHEN THE TEMPERATURE ERROR WAS 8 DEGREES OR GREATER ON DAY 4

HPC MANUAL PROGS USUALLY CUT DOWN ON THE ERRORS DURING THESE TYPE CASES

THE PERCENT OF THE NUMBER OF DAYS (JAN-MAR) HPC FORECASTERS REDUCE THE ERROR BELOW 8 DEGREES F

MAXTEMPSREGIONS

1 2 3 4 5 6 7 8% IMPDAY 3 9.4 3.9 10 14 12 11 9.4 17% IMPDAY 4 9.9 10 6.5 13 2.6 2.1 4.5 5.3% IMPDAY 5 30 11 11 11 5.7 2.8 3.2 11

HPC shows improvement for max temperatures through 7 days for all areas

THE AVN HAS PERFORMED MUCH BETTER SINCE GOING BACK TO T126

During winter its threat scores were higher than During winter its threat scores were higher than those from either the NGM or ETAthose from either the NGM or ETA

The 0-48 hr AVN generally had better mass field The 0-48 hr AVN generally had better mass field forecasts, even to the lee of the Rocy mountains. forecasts, even to the lee of the Rocy mountains.

The number of spurious lows has been reduced The number of spurious lows has been reduced significantly. significantly.

The models bias for 2 inch or greater amounts is The models bias for 2 inch or greater amounts is now considerably below 1.00now considerably below 1.00