paul schultz noaa forecast systems laboratory local analysis and prediction branch

January 24, 2005

The LAPS “hot start”Initializing mesoscale forecast models

with active cloud and precipitation processes

Paul SchultzNOAA Forecast Systems LaboratoryLocal Analysis and Prediction Branch

January 24, 2005

The LAPS team

• John McGinley, branch chief, variational methods• Paul Schultz, project manager, modeler, your

speaker today• Brent Shaw, most recent lead modeler• Steve Albers, cloud analysis, temp/wind analysis• Dan Birkenheuer, humidity analysis• John Smart, everything

January 24, 2005

Goals

• Address NWP “spin up” problem– Explicit short-range (0-6 h) QPFs and cloud forecasts

• Focus on a “local” modeling capability– Must be computationally inexpensive– Exploit all locally-available meteorological data– High-resolution grids– Robust data ingest, QC, and fusion

• Develop a flexible solution for easy technology transfer– Hardware/OS independence– Choice of mesoscale model

• Demonstrated in WRF, MM5, RAMS• COAMPS, ARPS, NMM?

January 24, 2005

Basis

• Scale analysis of thermodynamic energy equation appropriate for convective-scale motions strongly suggests latent heat release forces the action

• Put saturated updrafts where they belong• Relax 3-D horizontal divergence to support

updrafts

dt

dq

Tc

L

zw c

p

LAPS Three-Dimensional Cloud Analysis

METARMETAR

METAR

Pilot reports

Doppler radar

Satellites

January 24, 2005

001.ze

0005.001.

ze

00005.

ze

T > -10°C ST SC SC -10°C < T < -20°C AS AS AS

T < -20°C CS CS CI

0005.0

ze

001.0005.

ze 005.001.

ze

005.ze

T > -10°C SC CU CU CU/CB (>5km depth) -10°C < T < -20°C AC AC AC AC

T < -20°C CI CC CC CC

Cloud typing

“stable”

“unstable”

January 24, 2005

Example cloud type analysis

January 24, 2005

Cumulus vertical motions

January 24, 2005

LAPS Dynamic Balance Adjustment

( ) b are background quantities; (^) are solution increments from background; ( )’ are observation differences from background

)ˆ(ˆˆ)ˆˆˆˆˆˆ(ˆ vDufvvvvvvvuvuv ybppbbyybbxxbt

2222

22

22'22

ˆˆˆˆ

)ˆˆˆ()ˆ()ˆ(

)ˆ()ˆ()ˆ()ˆ(

BBvBuB

vuvu

OOvvOuuOJ

VV

pyxtt

cVk j i

V

January 24, 2005

LAPS Dynamic Balance Adjustment

FH

FL

0ˆ Tvsv qq

c

January 24, 2005

Results

3D Simulated Clouds

00Hr Fcst, Valid 28 Mar 01/00Z 01Hr Fcst, Valid 28 Mar 01/00Z

January 24, 2005

Example: first forecast hour, 5-min frames

January 24, 2005

MODEL NOISE |dp/dt|

Balanced

Unbalanced

January 24, 2005

Quantitative Assessment

• Comparison of parallel model runs using three kinds of initialization (hot, warm, cold); otherwise identical

• Objective verification of model performance using hot start vs. other initialization methods– Approximately 40 forecast cycles during Jan

2001 – Gridded comparisons using LAPS analysis as

truth– Computed various threat scores, RMSE, etc.

Model Initialization Comparisons

Time-n Time

MM5 Forecast

LAPS Analyses

MM5 Nudging MM5 Forecast

MM5 Forecast

Eta

Eta LBC for all runs

Dynamically balanced,Cloud-consistent LAPS

LAPS II

Cold start

Warm start

Hot start

no LAPS analysis; interpolatefrom larger-scale model

pre-forecast nudging to a series of LAPS analyses; sometimescalled dynamic initialization

diabatic initialization using the balanced LAPS analysis

Results of Initialization Comparisons

ETS for Hourly Snowfall > 0.001 m

0.000

0.050

0.100

0.150

0.200

0.250

0.300

0.350

1 2 3 4 5 6 7 8 9 10 11 12Forecast Hour

ET

S

MM5HOTMM5WARMMM5ETA

Results of Initialization Comparison

ETS for Cloud Cover > 50%

0.000

0.100

0.200

0.300

0.400

0.500

0.600

0.700

0.800

0.900

0 1 2 3 4 5 6 7 8 9 10 11 12Forecast Hour

ET

S

MM5HOT

MM5WARM

MM5ETA

January 24, 2005

Example – 21 June 2001/0600 UTC Run

GOES IR+NOWRAD, Valid 21/0600 UTC MM5 00 hr Forecast, Valid 21/0600 UTC

January 24, 2005



paul schultz noaa forecast systems laboratory local analysis and prediction branch

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