NCAR Auto-Nowcaster Convective Weather Group NCAR/RAL

Why We Need ANC ?

Detection and extrapolation of surface convergence boundaries …. ….that trigger thunderstorm initiation and impact storm evolution. The Auto-nowcaster System is unique in its ability to provide nowcasts of storm initiation by…..

Example of Auto-Nowcaster Initiation Forecast 1 hour forecastVerification Initiation nowcasts extrapolation nowcasts

Weather Forecast Office Washington DC Sydney Australia Forecast Office U. S. Army White Sands Missile Range Central U. S. for the FAA Where has the Auto-nowcaster been demonstrated ? Process of being transferred to: Bureau Meteorology Beijing China U.S National Weather Service – Dallas Weather Forecast Office AWIPS

AREA WEATHER UPDATE NATIONAL WEATHER SERVICE FORT WORTH TX 310 PM CDT SUN APR > WARNING DECISION UPDATE FOR NORTH TEXAS MESOANALYSIS PROGRAMS SHOW J/KG CAPE ALONG AND JUST AHEAD OF DRYLINE. THUS...CU/DEVELOPING STORMS ALONG/E OF DRYLINE SHOULD CONTINUE TO INTENSIFY. STORM INITIATION TOOL ALSO SUGGESTS HIGH POSSIBILITY OF DEVELOPMENT FARTHER SW...OVER CORYELL/LAMPASAS COUNTY AREA. DEEP-LAYER SHEAR MORE THAN SUFFICIENT FOR ORGANIZED STORMS AND AT LEAST MID-LEVEL MESOS. AS STORMS EVOLVE INTO THE EVENING...A MORE LINEAR MODE IS EXPECTED. Auto-Nowcaster at Ft. Worth WFO

Data Sets Radar WSR-88D Satellite Mesonet Profiler Sounding Numerical Model Lightning Analysis Algorithms Predictor Fields Forecaster Input Fuzzy Logic Algorithm - Membership functions - weights - Combined likelihood field Final Prediction Flow Chart for the Auto-Nowcaster System

Data Sets Radar WSR-88D Satellite Mesonet Profiler Sounding Numerical Model Lightning Analysis Algorithms Predictor Fields Forecaster Input Fuzzy Logic Algorithm - Membership functions - weights - Combined likelihood field Final Prediction Flow Chart for the Auto-Nowcaster System

Convergence line Example of fuzzy logic Predictor Field 1.5 Likelihood Lifting Zone Membership Function Lifting Zone Likelihood Yes No.5 0

Convergence Predictor Field 2 Membership Function Convergence Likelihood Likelihood

Cumulus clouds Predictor Field Likelihood Membership Function Cumulus cloud type Likelihood

Likelihood 1 Likelihood 2 Likelihood 3 Weight 1Weight 2 Weight 3 Σ Final combined likelihood of initiation

Environmental conditions (RUC) –Frontal likelihood –Layered stability –CAPE (max between 900 and 700 mb) –Mean 875 to 725 mb Relative Humidity Boundary-layer –Convergence –LI (based on METARS) –Vertical velocity along boundary (maxW) –Boundary-relative steering flow –New storm development along boundary Clouds –Clear or Cumulus –Vertical develop as observed by drop in IR temps Blue Regions - Little chance of storm development Green Regions - Moderate likelihood Red Regions - Areas of forecast initiation Predictor Fields used for Combined Likelihood of Initiation

60 Minute Initation (rules with satellite data) Wt: 0.17 Range: to 0.17 Wt: 0.20 Range: to 0.02 Wt: 0.17 Range: to 0.17 Wt: 0.10 Range: 0 to 0.10 Wt: 0.08 Range: to 0.08 Wt: 0.16 Range: to 0.16

60 Minute Initation (rules with satellite data)Cont. Wt: 0.20 Range: -0.2 to 0.2 Wt: 0.20 Range: 0 to 0.20 Wt: 0.20 Range: 0 to 0.20 Wt: 0.25 Range: 0 to 0.25 Wt: 0.15 Range: 0 to 0.15

60 Minute Initation (rules with satellite data)Cont. Lake: Wt: 0.10 Range: to 0 Sat_Clear: Wt: 0.40 Range: to 0 Boundary Collision: Wt: 0.12 Range: 0 to 0.12 Initiation Levels: 0.70 => Init => Init => Init 3

60 Minute Initation (rules without satellite data) Wt: 0.19 Range: to 0.19 Wt: 0.20 Range: to 0.02 Wt: 0.19 Range: to 0.19 Wt: 0.10 Range: 0 to 0.10 Wt: 0.08 Range: to 0.08 Wt: 0.18 Range: to 0.18

60 Minute Initation (rules without satellite data)Cont. Wt: 0.21 Range: to 0.21 Wt: 0.21 Range: 0 to 0.21 Wt: 0.30 Range: 0 to 0.30

60 Minute Initation (rules without satellite data)Cont. Lake: Wt: 0.10 Range: to 0 Sat_Clear: Wt: 0.40 Range: to 0 Boundary Collision: Wt: 0.14 Range: 0 to 0.14 Initiation Levels: 0.70 => 25 dBZ 0.90 => 30 dBZ 1.20 => 32 dBZ

60 Minute Growth and Decay Wt: 0.30 Range: -0.3 to 0.3 Lake: Wt: 0.20 Range: to 0 Wt: 0.21 Range: to 0.21 Wt: 0.15 Range: to 0.15 Wt: 0.20 Range: to 0.20 Growth/Decay Levels: decay 6km to => decay 4km to => decay 2km to 0.20 => steady 0.20 to 0.50 => grow 2km 0.50 to 70 => grow 4km >0.70 => grow 6km

Predictor Fields Large-Scale Environment B-L characteristics Satellite Cloud Typing Boundary characteristics Cumulus development Storm motion and trends

Predictor Fields Large-Scale Environment B-L characteristics Satellite Cloud Typing Boundary characteristics Cumulus development Storm motion and trends

Why do we need a forecaster in the loop?? Forecasters see the larger picture –Conceptual Models –Ignore bad data points –Understand limitations of NWP and observations

FAA RCWF Domain June 12, 2003 Forecaster Entered Boundary

Draw Tool

Entering a convergence boundary in real time is as simple as this demonstration!

Forecaster-tools Boundary Entry

Forecaster Entered Polygons

Ft. Worth WFO April 5, 2005 ForecastVerification

Evaluation of Initiation Cases Forecaster on duty Convection within ANC domain that increased (based on area coverage) >20% in an hour. Covered an area of 3,000 km 2 (Valid Time).

Initiation/Growth Cases 34 Case Days (Ranging from 18 to 210 min – not always consecutive) Divided into 3 categories: –Initiation along line (13) –Initiation in a region (6) –Primarily Growth (15) Initiation along line Initiation in region Growth 60 min Time Interval

Bias vs. POD for ALL Initiation/Growth Cases POD Bias PersistenceANC Forecast Growth/Decay Initiation level 2 Initiation level 1 Extrapolation

Different types of initiation PersistenceANC Forecast Growth/Decay Initiation level 2 Initiation level 1 Extrapolation Red : All Cases Yellow : Initiation - line Cyan : Initiation - region Orange : Growth Forecasts for growth show the most skill Initiation of linear storm systems show most improvement over extrapolation Initiation - Line All Growth Initiation- Region POD Bias

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