WMOD00290 ‎(3)‎

• Title: Automated Objective Analysis and Prediction of Mesoscale Convective Systems
• Prepared By: David A. Matthews, Leon Osborne
• Date: 6/6/1983
• Weather Modification - Doc Type: Report

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Reprinted from Preprint Volume ot Extended Abstracts:
Sixth Conference on Numerical Weather Prediction.
June 6-9. 1983. Omaha. Nebr. Published by the
American Meteorological Society. Boston I Mass.

AUTOMATED OBJECTIVE ANALYSIS AND PREDICTION
OF MESOSCALE CONVECTIVE SYSTEMS
by

1.5

David A. Matthe~ws
Bureau of Rec 1 amalt ion
Denver, Colorado

and

Leon Osborne
University of North Dakota
Grand Forks, North Dakota

1. INTRODUCTION

One major source of natural variability in
convective rainfall is the mesoscale triggering
of convection. This triggering has been shown
to initiate deep convection on a scale below the
synopt i c network (Byers and Br ah am, 1949;
Fujita, 1963; Maddox, 1981). Mesoscale triggers
often generate lines of convection and clusters
on the High Plains. Matthews (1980) found that
during 1977, 70% of the cases at the Texas
HIPLEX field site had either lines or clusters
of convective clouds organized on the mesoscale,
as seen in the vi sib 1 e imagery from the GOES
satellite. Analyses by Haragan, Jurica, and
Leary (1980) show that organized convective
systems contribute nearly 70% of the summertime
precipitation at the Texas HIPLEX site.

This paper discusses a technique which per-
mits rapid analysis of the kinematic and thermo-
dynamic structure of mesoscale triggers of
convective precipitation. A brief description
of the techni que and ex amp 1 es of the automated
graphics products are presented for the 1979
Texas HIPLEX mesonet (Riggio, et al., 1983).

Results from a meso-~ band pass filter
analysis of rawinsonde data observed in a seven
station network shown in Fig. 1 are presented.
This fi lter emphasized phenomena with wave
lengths of 200 km. Vertical profiles of the
vertical motion and individual rawinsonde
observations were used to initialize a numerical
cloud model which simulated the effect of
lifting and cloud-environment interaction in the
prediction of convective clouds and their

potential for development. Digital radar
observations provided a means of verifying model
predictions and correlating the mesoscale
kinematic analyses with radar echo structure.

The paper also briefly describes the
objective analysis method, and a numerical
mode 1, and presents resul ts from one case
study.

2. OBJECTIVE ANALYSIS METHOD

The objective analysis method developed by
Barnes (1973) and modified by Maddox (1980) was
i nterf aced wi th the Bureau I s Skywater Envi ron-
mental Data Network to provide real-time analy-
sis of all National Weather Service and Skywater
rawi nsondes. Barnes used a Gaussian wei ght

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A Synoptic: Rowinsollde Site
a Mes~ Rowinsoncle Site

Figure 1: Texas HIPLEX rawinsonde network and
NMC sounding locations with detai led
.2' ~x, ~y meso-~ objective analysis
grid.

function to provide an Objective analysis of
meteorological fields. The method is used here
to provide a basic analysis tool for scale
separation. The method first uses a low pass
filter which smoothes the observation data field
with a known rE!SpOnSe to defi ne a macrosca 1 e
field. Then a band pass fi lter extracts the
mesoscale signal using a modification (Maddox,
1980) of the analysis technique developed by
Doswell (1977). Finally, an objective analysis
of the total fields is recovered by adding the
mesoscale field to the macroscale field analyses.
Shortwave noise is controlled by selecting the
appropriate weight function for the phenomena of
interest.

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