LAPS Technical Overview

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LAPS Technical Overview
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LAPS Mission

• A system designed to
• Exploit all available data sources
• Create analyzed and forecast grids with analysis
  systems and numerical models
• Build products for specific forecast applications
• Provide reliable forecast guidance
• Use advanced display technology
• All within a local weather office, forward site,
  or in fully deployed mode

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• LAPS Basic Structure

Univariate Analysis
Analysis Merging/ Balancing
NWP Model Initialization/ Prediction
Data
Very diverse Force geometric,
Reconcile gridded Generate forecasts data
sets smoothing constraints
fields force and user-specific
to interpolate data to
consistency based products
high resolution grids on
atmospheric scale
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LAPS Components - Stage 1

• Data Acquisition and Quality Control
• Univariate Analysis of the Following Fields
• Temperature
• Winds
• Water Vapor
• Clouds
• Microphysical variables
• Vertical motions

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Data Acquisition and Quality ControlLAPS
supports a wide range of data types
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LAPS data ingest strategy
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Multi-layered Quality Control

• Gross Error Checks
• Rough Climatological Estimates
• Station Blacklist
• Dynamical Models
• Use of background and mesoscale models
• Standard Deviation Check
• Statistical Models
• Buddy Checking

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Standard Deviation Check

• Compute Standard Deviation of observations-backgro
  und
• Remove outliers
• Now adjustable via namelist

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LAPS Radar Ingest
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Remapping Strategy

• Polar to Cartesian
• 2D or 3D result (narrowband / wideband)
• Average Z,V of all gates directly illuminating
  each grid box
• QC checks applied
• Typically produces sparse arrays at this stage

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Radar Mosaic
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Analyzed Reflectivity (800 hPa)
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Surface Precipitation Accumulation

• Algorithm similar to NEXRAD PPS, but runs
• in Cartesian space
• Rain / Liquid Equivalent
• Z 200 R 1.6
• Snow case use rain/snow ratio dependent on
  column maximum temperature
• Reflectivity limit helps reduce bright band
  effect

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Storm-Total Precipitation (wideband mosaic)
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Storm-Total Precipitation
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Storm-Total Precipitation (RCWF narrowband)
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Precip type and snow cover
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The LAPS Analysis
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Three-dimensional Analysis

• Looking for a function that is the best fit of
  weather through backgrounds and observations in
  3D.
• Data assimilation techniques Barnes, 3DVar,
  4DVAR, KF. Differences.Barnes is a point-wise
  fitting 3DVAR, 4DVar. KF are global fitting
  schemes.

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LAPS Analysis Philosophy

• Focus on the mesoscale - here model error
  covariances are poorly known - 3-D var is not an
  optimum approach
• Let data define structure
• Use successive corrections (Barnes) exponential
  weight with collapsing radius of influence
• Blend with model background
• Generate smooth fields that will be reconciled in
  stage 2
• Ensure rapid computation

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LAPS Analysis Process and Data Structure
LAPSPRD Directory
LSX
Surface Fields
LT1
3-D Temp
L1S
Prcp Accum
LQ3
3-DHumid
LAPS Inter. Data Files
LW3
Wind
Cloud
LC3
LCP
Derived Pds
LM1
Soil
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Sfc ToverTaiwan
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CAPE
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3-D Temperature

• First guess from background model
• Insert RAOB, RASS, and ACARS if available
• 3-Dimensional weighting used
• Insert surface temperature and blend upward
• depending on stability and elevation
• Surface temperature analysis depends on
• METARS, Buoys, and Mesonets (LDAD)

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LAPS Wind Analysis
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X-sect T / Wind
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700 hPa Winds and Geopotential - Stage 1
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Products Derived from Wind Analysis
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LAPS 3-D Water Vapor (Specific Humidity) Analysis

• Interpolates background field from synoptic-scale
  model forecast
• QCs against LAPS temperature field (eliminates
  possible supersaturation)
• Assimilates all appropriate LAPS upper air data
• Assimilates boundary layer moisture from LAPS Sfc
  Td analysis

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LAPS 3-D Water Vapor (Specific Humidity)
Analysis continued

• Scales moisture profile (entire profile excluding
  boundary layer) to agree with derived GOES TPW
  (processed at NESDIS)
• Scales moisture profile at two levels to agree
  with GOES sounder radiances (channels 10, 11,
  12). The levels are 700-500 hPa, and above 500
• Saturates where there are analyzed clouds
• Performs final QC against supersaturation

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Total Preciptiable Water Taiwan
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3-D Clouds

• Preliminary analysis from vertical cloud
  soundings derived from METARS, PIREPS, and CO2
  Slicing
• IR used to determine cloud top (using temperature
  field)
• Radar data inserted (3-D if available)
• Visible satellite can be used

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Cloud/Satellite Analysis Data

• 11 micron IR
• 3.9 micron data
• Visible (with terrain albedo)
• CO2-Slicing method (cloud-top pressure)

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CloudSchematic
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Cloud Coverage without/with visible data

No vis data
With vis data
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Cloud cover (fraction) with surface stations only
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Cloud fraction with surface stations and radar
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Cloud fraction with surface stations, radar, and
IR
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Cloud Coverage without/with visible data

No vis data
With vis data
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Cloud Isosurfaces
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Cloud/precip cross section
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Cloud Radar X-sect (wide/narrow band)
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Some dependence on cloud type, Updraft goes to
top of cloud
CS
Strongest updrafts in regions of high reflectivity
CB
Downdrafts in stratiform region
Randomness in broad convective regions
Updated CWB/ FSL scheme (cloud derive subr)
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Case Study Example How LAPS is used in the
National Weather Service

• Utility of LAPS analysis-only for nowcasting
• A Convective Event on 14 May 1999
• Location DEN-BOU WFO

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Case Study Example

• On 14 May, moisture is in place. A line of storms
  develops along the foothills around noon LT (1800
  UTC) and moves east. LAPS used to diagnose
  potential for severe development. A Tornado Watch
  issued by 1900 UTC for portions of eastern CO
  and nearby areas.
• A brief tornado did form in far eastern CO west
  of GLD around 0000 UTC the 15th. Other tornadoes
  occurred later near GLD.

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NOWRAD and METARS with LAPS surface CIN 2100 UTC
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Examine soundings near CAPE max at points B, E
and F 2100 UTC
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Soundings near CAPE max at B, E and F 2100 UTC
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CIN minimum in area of CAPE max 2200 UTC
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Point E, CAPE has increased to 2674 J/kg 2200 UTC
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Radar with METARS and LAPS surface helicity 2100
UTC
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Radar with METARS and LAPS surface helicity 2300
UTC A brief tornado did form in far eastern CO
west of GLD around 0000 UTC on 15 May. Other
tornadoes later near GLD area.
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LAPS winds every 10 km, RUC winds every 80
km 2100 UTC
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Cloud, Wind and Mass Dynamic Adjustment
FH FL
??c

Tgt 0
q qs
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700 Hpa Balanced Winds and Geopotential - Stage 2
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700 Hpa Unbalanced Winds and Geopotential -
Stage 1
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LAPS balanced vertical motion and cloud (a) and
eqn of motion residual (ms-1) (b)
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DA Configuration
Data
Data Ingest
Intermediate data files
Error Covariance
Trans
LAPS
GSI
STMAS3D
Trans
Post proc1
Post proc2
Post proc3
Model prep
WRF-ARW
MM5
WRF-NMM
Probabilistic Post Processing
Ensemble Forecast
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The End