Visually Enhanced Composite Charts for Severe Weather Forecasting and Real-time Diagnosis Josh...
-
Upload
quentin-carpenter -
Category
Documents
-
view
220 -
download
1
Transcript of Visually Enhanced Composite Charts for Severe Weather Forecasting and Real-time Diagnosis Josh...
Visually Enhanced Composite Charts for Severe Weather Forecasting and Real-time
Diagnosis
Josh Korotky
NWS Pittsburgh PA
NROW Annual Meeting 2002
Agenda
Composite Chart Approach and Diagnostic Templates
A Case study
LES 4 Panels
Cyclogenesis 4 Panels
GFS
The real atmosphere has great difficulty simulating the model
atmosphere…
…many good forecasts will continue to be ruined by
atmospheric error!
The Forecaster’s Paradox
Motivation Due to the growing volume of available data…
…and the time intensive process of generating / disseminating forecast and warning products…
…it is critical that forecasters extract relevant information quickly before and during severe weather forecast and warning operations
Diagnostic and forecast methods that use visualization to highlight essential physical processes … Promote a better (and quicker) understanding of the real-time
potential Allow forecasters to better anticipate the most probable range
of convective evolutions for a given environment
Composite Chart Approach Effective composite charts:
Highlight important information….not all information Reveal the physical processes that promote severe storm
development, convective organization, and storm mode Lead to quick recognition of the convective potential
Composite chart contents include: Measures of instability and vertical wind shear 3D moisture content, distribution, and availability Synoptic and mesoscale forcing mechanisms
Charts are enhanced visually by managing colors, images, and contours
Evaluating the Convective Potential
Ingredient Diagnostic
Moisture Moisture Flux (role of LLJ)Specific HumidityDew PointPWLayer RHTheta-e / Theta-e advection
Instability CAPE, LI
Large Scale Lift / Forcing Model Omega / -Div Q
Mesoscale Forcing Moisture Flux ConvergenceTopographic forcingFrontal forcing / Frontogenesis
Vertical Wind Shear Storm-relative HelicityLow – level and deep shearsEHI, VGP
Pressure MSLP, Pressure tendency
Composite Chart Model Diagnostic Templates
MSL Pressure
*Best Lifted Index < 0
Surface Dew Points > xxo F
Specific Humidity
PW > x.x inches
*BL Moisture Flux Convergence
1000-850mb Moist Flux Conv
Moisture Flux / Flux Magnitude
Theta-e / Theta-e Advection*2D Frontogenesis
Potential Temperature
Surface Wind
EHI Index
*0-1km / 0-3km AGL CAPE
*0-1km / 0-3km AGL SR-Helicity
Convective Inhibition
0-1km / 0-3km Normalized Shear
0-6km Normalized Shear
Low – level Features
Upper – level Features
850mb Height / Temp
*850mb Isotachs
850mb Wind Barbs
500mb Height / Temperature
*500mb Isotachs
500mb Wind barbs
DivQ
MSLP
*Accumulating Precipitation /
1000-850mb RH
250mb Height / Wind Barbs
250mb Isotachs
850-300mb Mean Wind
300-200mb Mean Divergence
1000-850mb/700-500mb Omega
MSL Pressure and METARS
*Best Lifted Index < 0
Surface Dew Points > xx o
F
PW > x.x inches
*BL Moisture Flux Convergence
1000-850mb Moist Flux Conv
Moisture Flux / Flux Magnitude
K-Index
BL Theta-e / Theta-e Advection*2D Frontogenesis
Potential Temperature
Surface Wind
EHI Index
*0-1km / 1-3km AGL CAPE
*0-1km / 1-3km AGL SR-Helicity
Convective Inhibition
0-1km / 1-3km Normalized Shear
Deep Normalized Shear
RUC Analysis
A Case Study
Highlights a severe convective wind event that effected parts of Ohio, Pennsylvania, West Virginia, New York, and Maryland on 9 March 2002
Composite charts of model forecast fields (Eta) are supplemented with composite charts of hourly RUC surface analysis Eta for evaluating large scale convective potential Hourly RUC provides a critical link to the model
forecasts
850mb Wind (kt) and Normalized Vcomp Wind Anomaly 08/12 UTC Eta: 33hr Forecast Valid
3/9/02 - 21 UTC
4 – 4.5 SD
850mb Wind and Normalized Vcomp Wind Anomaly
27hr Forecast Valid 3/9/02 - 21 UTC
> 4.5 SD
Upper and Low-level Features
33, 21, 9 hr forecasts valid at 21 UTC 9 March
Upper-level Features - 08/12 UTC Eta 33hr Forecast Valid 3/9/02 -
21 UTC
Low-level Features - 08/12 UTC Eta 33hr Forecast Valid 3/9/02 -
21 UTC
Upper-level Features – 09/00 UTC Eta 21hr Forecast
Valid 3/9/02 - 21 UTC
Low-level Features – 09/00 UTC Eta 21hr Forecast
Valid 3/9/02 - 21 UTC
Upper-level Features – 09/12 UTC Eta 9hr Forecast
Valid 3/9/02 - 21 UTC
Low-level Features – 09/12 UTC Eta 9hr Forecast
Valid 3/9/02 - 21 UTC
Summary of the Large Scale Potential
Successive runs of the Eta indicate:
Deep layer of strong flow 65 – 70 kts at 850mb over Ohio Valley
Significant vertical wind shear associated with vigorous low-level jet SRH 400 – 500 m2s2 0-3km normalized shear > .014 s-1
Moderate moisture Warm sector surface dew points 55 – 57oF
Narrow layer of deep moisture Potential for cloud breaks ahead of front Destabilizing potential
Summary of the Large Scale Potential
Considerable low-level forcing Strong moisture flux convergence Strong frontogenesis along a vigorous frontal system
Significant pressure rise/fall couplet indicates deepening/dynamic system 10mb/3hr pressure rises behind front 8mb/3hr pressure falls ahead of front
But….only marginal instability CAPE forecast to remain less than 500 jkg-1 Best Lifted Index (BLI) expected to reduce no further than -2
A Range of Expectations
Expectations Strong linear forcing will promote a narrow low-topped squall
line Isolated/scattered wind damage the primary threat … unless
the real-time environment destabilizes more than indicated
The real time challenge Do observations / RUC / LAPS analysis indicate greater
instability? Greater instability would indicate more widespread severe
potential
Real Time RUC Surface Analysis3/9/02/ 18 UTC – 3/9/02/ 21 UTC
Linking the model forecast to real-time events…
18 UTC RUC Analysis
19 UTC RUC Analysis
20 UTC RUC Analysis
RUC / Observational Summary at 20 UTC
The moisture, forcing, vertical wind shear, pressure pattern, and pressure tendency substantiate initial expectations…
The environment has destabilized more than expected !!
Observations Winds gusting mid 30s kts ahead of front Radar indicated a developing low-topped narrow squall line Reports from CLE and ILN indicated wind gusts > 80 mph and
wind damage associated with convective line
New Expectations With indications of greater instability and real-time reports…
•Damage is going to be widespread rather than scattered/isolated
•Damage will be from winds…low probability of tornadoes
23 UTC Radar and Satellite
Conclusions
A narrow, low-topped squall line produced significant wind damage throughout the NWS PBZ CWA
Forecast (Eta) and diagnostic (RUC) methods that combine science and visualization… Allowed forecasters to better anticipate the most
probable range of convective evolutions before the event
Promoted a better (and quicker) understanding of the changing convective potential during the event
Contributed to more effective warning decisions.
LES 4 Panels
Model Run Snow Accum
Model Run Accum Precip
*1000-850mb/1000-500mb RH
Ptype Likely Icons
850-700mb Lapse Rate
*1000-850 LR / 850-700mb LR
BL Moisture Flux Convergence
1000-850mb Moist Flux Conv
1000-850mb Thickness
*1000-950mb/850-700mb
Fgen
Potential Temperature
MSLP
Surface Wind
1000-850mb Tadv
Sfc Td
Specific Humidity
*Topo Omega / 700-500mb Omega
900mb Wind
900mb Streamlines
Low – level Features
Low-level Features – Valid 00 UTC
Low-level Features – Valid 00 UTC
Low-level Features – Valid 12 UTC
Low-level Features – Valid 12 UTC
Cyclogenesis 4 Panels
Upper-level Features – Valid 21 UTC 16 Oct 2002
Low-level Features – Valid 21 UTC 16 Oct 2002
GFS