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5th International Conference of Mesoscale Meteor. And Typhoons, Boulder, CO 31 October 2006
National Scale Probabilistic Storm Forecasting for Aviation Planning
Talk Focus - Storm Coverage
Presenter: Dr James O. Pinto, NCAR/RALCollaborators: Rasmussen, Steiner, Megenhardt, Rehak, Dixon, Phillips
Acknowledgements : FAA AWRP
5th International Conference of Mesoscale Meteor. And Typhoons, Boulder, CO 31 October 2006
Playbook at 1200 UTC
Need for Reliable Storm Nowcasts of 8+ hrs for Strategic Planning
Fcst valid : 2040 – 0240 UTC
6 hr Probability Forecast
Playbook: Revised at 2000 UTC
Verification
5th International Conference of Mesoscale Meteor. And Typhoons, Boulder, CO 31 October 2006
Storm Characteristics Determine Impact of Air Traffic
5th International Conference of Mesoscale Meteor. And Typhoons, Boulder, CO 31 October 2006
Outline
• Motivation– Need for probability of storm orientation, organization and
coverage (e.g., storm permeability)
• Current Probabilistic Storm Forecast Systems
• Current Research – Storm Coverage Forecasts– Assess explicit model prediction of storm coverage and echo
top heights– Use model and obs climatologies to determine relationship
between storm coverage and forecast valid time, environmental conditions, location.
5th International Conference of Mesoscale Meteor. And Typhoons, Boulder, CO 31 October 2006
Outline
• Motivation– Need for probability of storm orientation, organization and
coverage (IOW: storm permeability)
• Current Probabilistic Storm Forecast Systems
• Current Research – Storm Coverage Forecasts– Assess explicit model prediction of storm coverage and echo
top heights– Use model and obs climatologies to determine relationship
between storm coverage and forecast valid time, environmental conditions, location.
Extrapolation
Deterministic Forecasts of Precipitation - Extrap
12 13 14 15 16 17 18 UTC
1 hrfcst
3 hrfcst
6 hrfcst
Successive fcsts valid at same time.
Verification
1 h
P
2 h
P
Probabilistic Forecast of Convective Hazard
Probabilities may be interpreted as:
-likelihood of storms exceeding 35 dbz at a given time and location
-the coverage of storms exceeding 35 dbz (if reliable).
Probabilities determined via spatial filter and a VIL threshold.
Spatial filter increases with fcst lead time (after Germann and Zawadzki 2004)
Probabilities also influenced by observed trends, environmental conditions and climo.
NCWF2 Hazard Detection with Probabilistic Fcsts
5th International Conference of Mesoscale Meteor. And Typhoons, Boulder, CO 31 October 2006
Probabilistic Forecasts Systems
Probabilities based on:
– Spatial coverage of convective precip predicted by the RUC-20 model
– 3-member time-lagged ensemble
– Square filter of 180 km
– Precipitation rate threshold for convection (1-2 mm/hr)
– Tuned using 40 km truth data set
P.
RUC Convective Prob. Forecast
12 13 14 15 16 17 18 19 20 21 UTC9 hrfcst
7 hrfcst
Successive fcsts valid at same time.
8 hrfcst } 3-member ensemble valid at 21 UTC
7 hr fcst Valid: 21 UTC
Verification
Comparison with Operational 2 hour TSTM Fcst Products
From Seseke et al. 2006 QA ReportNOAA/Earth System Research Lab
5th International Conference of Mesoscale Meteor. And Typhoons, Boulder, CO 31 October 2006
Outline
• Motivation– Need for probability of storm orientation, organization and
coverage (IOW: storm permeability)
• Current Probabilistic Storm Forecast Systems
• Current Research – Storm Coverage Forecasts– Assess explicit model prediction of storm coverage and echo
top heights– Use model and obs climatologies to determine relationship
between storm coverage and forecast valid time, environmental conditions, location.
5th International Conference of Mesoscale Meteor. And Typhoons, Boulder, CO 31 October 2006
Methodology for Improving Storm Coverage Fcsts
• Storm-resolving forecasts using WRF• Compare model and obs distribution of storm
coverages (regionally dependent)– Focus on Southeastern US where scattered storms common– Assess predictability of storm coverage for each region as a
function of environmental conditions, time of day, etc.
• Verification – standard skill scores to assess reliability – Need for more descriptive skill scores such as those available
in MODE (object-based verification).• E.g. storm spacing
WRF Model Reflectivity
Deterministic Forecasts of Convection
Verification – WSI Mosaic
Successive fcsts valid at same time.– Storm-resolving realtime fcsts run in
collab. with Wang and Weismann
– WSM Microphysics, MYJ PBL, Noah LSM
– BCs: NAM – 40 km grid 212
– No Data Assimilation
– Run Jun/Jul 2005 (0Z) & 2006 (00,12 Z)
REPLACE – July 19th
00 ……12 13 14 15 16 17 18 19 20 UTC
8 hrfcst
20 hrfcst
Case Study- 2006 July 19
WRF-ARW (4km) – 20hr fcstWRF-ARW (4km) – 08hr fcst
WRF-ARW (4km) – 20hr fcstWRF-ARW (4km) – 08hr fcst
WRF vs WSI Coverages
Deterministic Forecasts of Storm Coverage
Verification – WSI Mosaic
00 ……12 13 14 15 16 17 18 19 20 UTC
8 hrfcst
20 hrfcst
Successive fcsts valid at same time. – Threshold = 35 dBZ
– Impressive accuracy of timing and location of max coverage areas
– Coverage forecast improves as fcst length decreases
Case Study- 2006 July 19
model
obs
WSI Refl - 2000 UTC
Titan Storm Detections – WSI Reflectivity
– WSI reflectivity mosaic from WSR-88D radar
– Degraded to 4 km using spatial filter
– 35 dBZ and 75 km2 thresholds
r =100 km
Storm Spacing – WRF Reflectivity (20 hr fcst)
– WRF reflectivity – max in column from 00 UTC run
– 35 dBZ and 75 km2 thresholds
100 km
Update with WRF imager =100 km
5th International Conference of Mesoscale Meteor. And Typhoons, Boulder, CO 31 October 2006
Conclusions
•User needs (e.g., aviation planning) drive the system requirements
•Likelihood of storm at a given location not enough info for users in decision making
•Need for PDF expressing likelihood of coverages and joint PDFs of coverage / echo top likelihood.
•Current technology in predicting storm coverages have limited reliability.
•Convection resolving simulations may offer hope in predicting storm coverages and spacing.
5th International Conference of Mesoscale Meteor. And Typhoons, Boulder, CO 31 October 2006
-END-
NRC Report on Weather Forecasting Accuracy for FAA Traffic Flow Management
“Because accurate deterministic 2- to 6-hour forecasts are not available, it is necessary to develop probabilistic forecasts that can readily be used by both humans and automated air traffic management decision support tools.”
NRC Report, 2003
NCWF2 Convective Hazard Detection (NCWD)
Unisys VIL Vaisala CG Ltg
Unisys Echo Tops
Data Feeds
Unisys VILVIL (Stratiform areas blue) VIL (Stratiform Removed)VIL (Echo Tops > 15 kft contoured)VIL (Echo > 15 kft removed)Hazard Detection (filtered VIL + Ltg)
Convective Hazard Detection (NCWD)
Inputs: Unisys VIL & Echo Tops, NLDN C-to-G Ltg
Steps to produce NCWD
1) Stratiform Filter (Steiner et al. 1995)
2) Echo tops Filter (remove echo < 15 Kft)
3) Combine with Lightning
5th International Conference of Mesoscale Meteor. And Typhoons, Boulder, CO 31 October 2006
0 1 2 3 4 5 6 Forecast Length, hours
.2
.4
.6
.8
1.0
Accuracy of Rainfall Nowcasts
>2 mm/h
Extrapolation
Goal - idealized
NWP(CSI)
Current Skill of Nowcasting Technologies
Forecast Skill
5th International Conference of Mesoscale Meteor. And Typhoons, Boulder, CO 31 October 2006
Algorithm for Blending Probabilistic Forecasts (e.g., 4 hr forecast)
ProbabilisticExtrapolation
Fcsts
RUC Probabilistic ConvectionForecasts
Frontal Interest
Climato-logical Interest
Thermo-dynamic
Mask
Merged Forecast ** Amenable to Forecaster Modification
StatisticalPerformance
Weights
Preprocessing
Blending