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Intelligent Use of LAPS. By Ed Szoke 20 May 1999. LAPS. A system designed to: Exploit all available data sources Create analyzed and forecast grids Build products for specific forecast applications Use advanced display technology …All within the local weather office.

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Intelligent Use of LAPS

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Intelligent Use of LAPS


Ed Szoke

20 May 1999


A system designed to:

  • Exploit all available data sources

  • Create analyzed and forecast grids

  • Build products for specific forecast applications

  • Use advanced display technology

    …All within the local weather office

Why do analysis in the local office?


-Strategic plan for the modernization and associated restructuring of the National Weather Service

Data Acquisition and Quality Control

Local Data

  • Local Data may be defined as that data not entering into the National Database

  • Sources

    • Highway Departments

      • Many States with full or partial networks

    • Agricultural Networks

      • State run, sometimes private

    • Universities

      • Experimental observations

    • Private Industry

      • Environmental monitoring

Problems with Local Data

  • Poor Maintenance

  • Poor Communications

  • Poor Calibration

    Result ---------------->Inaccurate,



Quality Control Methods

  • Gross Error Checks

    Rough Climatological Estimates

  • Statistical Models

    Buddy Checking

  • Dynamical Models

    Use of meso-beta models

Requirements for QC Scheme

  • Runnable in weather offices on small workstations

  • Adaptable to ongoing model improvement

  • Adaptable to daily variations in model skill

Requirements for QC Scheme (cont.)


  • Adaptable to small workstations

  • Accommodates models of varying complexity

  • Model error is a dynamic quantity within the filter, thus the scheme adjusts as model skill varies

LAPS Overview

  • LAPS Grid

    • Horizontal Resolution = 10 km

    • Vertical Resolution = 50 mb

    • Size: 61 x 61 x 21

LAPS Analysis Software

  • Analysis package has been in each version of WFO-Advanced delivered to PRC and NWS

  • LAPS in current build (AWIPS 4.2) is primitive

  • Awaiting requirements for build 5.0, such as resizeability, relocatability, advanced quality control techniques, etc.

Sources of LAPS Information

  • The LAPS homepage

    provides access to many links including:

  • What is in AWIPS LAPS?

Initially (Version 4.0) NOT MUCH!


4.1 METARS 8bit IR Only None Inactive Network RUC (Can use Eta)

4.2 +LDAD** Same Low-level Inactive Network RUC (Can use Eta)

Z, Level 3


Full All Derived Mulitple RAOBS RASS Other Models

LAPS Soundings Radars Boundary

10bit IR All levels Layer

& VIS Z and V Profilers

** if Available

Quote from the Field

"...for the hourly LAPS soundings, you can go to interactive skew-T, and loop the editable soundings from one hour to the next, and get a more accurate idea of how various parameters are changing on an hourly basis...nice. We continue to find considerable use of the LAPS data (including soundings) for short-term convective forecasting."

The Component of LAPS

There are 3 main components

1) Temperature

2) Moisture

3) Wind

See Steve Albers discussion at

3D Temperature

  • Interpolate from model (RUC)

  • Insert sonde and RASS if available

    • normally radius of influence not used unless more than one sounding

  • Insert surface temperature and blend upward

    • depending on stability and elevation

      • Surface temperature analysis depends on

        • METARS and LDAD

        • Gradients adjusted by IR temperature

3D Moisture

  • Preliminary analysis from vertical “soundings” derived from METARS and PIREPS

  • IR used to determine cloud top (using temperature field)

  • Radar data inserted (3-D if available)

  • Visible satellite used

Products Derived from Wind Analysis

Case Study Example

An example of the use of LAPS in convective event

13-14 May 1999

Location: DEN-BOU WFO

Case Study Example (cont.)

  • Late on the 13th we see moisture returning in far eastern CO on “screaming” southerly flow. A Severe Thunderstorm Watch was issued at 4 PM (2200 UTC) for portions of northeast CO and nearby areas.

  • Note the change in the moisture near LBF

LAPS surface CAPE with CIN and METARS

LAPS sounding near LBF

2300 UTC

LAPS sounding near LBF

0000 UTC

LAPS sounding near LBF

0100 UTC

Case Study Example (cont.)

  • On the next day, 14 May the 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.

NOWRAD and METARS with LAPS surface CAPE

2100 UTC

NOWRAD and METARS with LAPS surface CIN

2100 UTC

Dewpoint max appears near CAPE max, but between METARS

2100 UTC

Examine soundings near CAPE max at points B, E and F

2100 UTC

Soundings near CAPE max at B, E and F

2100 UTC

RUC also has dewpoint max near point E

2100 UTC

LAPS & RUC sounding comparison at point E (CAPE Max)

2100 UTC

CAPE Maximum persists in same area

2200 UTC

CIN minimum in area of CAPE max

2200 UTC

Point E, CAPE has increased to 2674 J/kg

2200 UTC

Divergence and Equivalent Potential Temperature are co-located

2100 UTC

How does LAPS sfc divergence compare to that of the RUC?

Similar over the plains.

2100 UTC

LAPS winds every 10 km, RUC winds every 80 km

2100 UTC

Case Study Example (cont.)

  • The next images show a series of LAPS soundings from near LBF illustrating some dramatic changes in the moisture aloft. Why does this occur?

LAPS sounding near LBF

1600 UTC

LAPS sounding near LBF

1700 UTC

LAPS sounding near LBF

1800 UTC

LAPS sounding near LBF

2100 UTC

Case Study Example (cont.)

  • Now we will examine some LAPS cross-sections to investigate the changes in moisture, interspersed with a sequence of satellite images showing the location of the cross-section, C-C` (from WSW to ENE across DEN)

Visible image with LAPS 700 mb temp and wind and METARS

1500 UTC

Note the strong thermal gradient aloft from NW-S (snowing in southern WY) and the LL moisture gradient across eastern CO.

LAPS Analysis at 1500 UTC, Generated with Volume Browser

Visible image

1600 UTC

Visible image

1700 UTC

LAPS cross-section

1700 UTC

LAPS cross-section

1800 UTC

LAPS cross-section

1900 UTC

Case Study Example (cont.)

  • The cross-sections show some fairly substantial changes in mid-level RH. Some of this is related to LAPS diagnosis of clouds, but the other changes must be caused by the satellite moisture analysis between cloudy areas. It is not clear how believable some of these are in this case.

Case Study Example (cont.)

  • Another field that can be monitored with LAPS is helicity. A description of LAPS helicity is at

  • A storm motion is derived from the mean wind (sfc-300 mb) with an off mean wind motion determined by a vector addition of 0.15 x Shear vector, set to perpendicular to the mean storm motion

  • Next we’ll examine some helicity images for this case. Combining CAPE and minimum CIN with helicity agreed with the path of the supercell storm that produced the CO tornado.

NOWRAD with METARS and LAPS surface helicity

1900 UTC

NOWRAD with METARS and LAPS surface helicity

2000 UTC

NOWRAD with METARS and LAPS surface helicity

2100 UTC

NOWRAD with METARS and LAPS surface helicity

2200 UTC

NOWRAD with METARS and LAPS surface helicity

2300 UTC

Case Study Example (cont.)

  • Now we’ll show some other LAPS fields that might be useful (and some that might not…)

Divergence compares favorably with the RUC

The omega field has considerable detail (which is highly influenced by topography

LAPS Topography

Vorticity is a smooth field in LAPS

Comparison with the Eta does show some differences.

Are they real?

Stay Away from DivQ at 10 km

Why Run Models in the Weather Office?

  • Diagnose local weather features to enhance conceptual models

    • sea/mountain breezes

    • modulation of synoptic scale features

  • Take advantage of high resolution terrain data to downscale national model forecasts

    • orography is a data source!

Why Run Models in the Weather Office? (cont.)

  • Take advantage of unique local data

    • radar

    • surface mesonets

  • Have an NWP tool under local control for scheduled and special support

  • Take advantage of powerful/cheap computers

LAPS Philosophy

  • Much of what LAPS generates makes it ideal for initializing a local scale model- even if some of the products may not be particularly useful in the WFO (like the cloud analysis, etc.)

Modeling Approaches

  • Diagnostic Mode

  • Basic Operational “Downscaling” Mode

  • Data Assimilation and Forecast Mode

SFM forecast showing details of the orographic precipitation, as well as capturing the Longmont anticyclone flow on the plains

LAPS Summary

  • You can see more about our local modeling efforts at

  • What else in the future? (besides hopefully a more complete input data stream to AWIPS LAPS...)

  • Learn more about a different kind of visualization, D3D, at

D3D Example

Example of Powerful Sounding Tool in D3D

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