WMOD00176

• Project Name: Annual Report
• Title: Seeding Operations & Atmospheric Research, 2005 Annual Report
• Prepared By: Duncan Axisia
• Date: 12/31/2005
• Weather Modification - Doc Type: Report

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moist airmass. Coupled with an upper level
shortwaye flow out of the southwest, the
Southern Ogallala target had good conditions
for shower activity. The instability in the upper
atmosphere and higher surface dewpoints
made conditions favorable for our first doud
seeding operation of 2005.

The upper level shortw"ave thai provided our
first opportunity for doud seeding moved east
and later developed in to an impressive storm
for the Great Lakes and the northeast. In its
wake came a much weaker low pressure
system. On April 1t~ a strong southeast
850mb jet advected moist air from the Gulf of
Mexico. coupled with southwesterly 300mb
flow. The atmosphere destabilized enough for
thunderstorm development along a surface
dryline established in eastern New Mexico.

The strong low pressure system that moved in
to the northeast shifted the polar front further
north than its usual springtime configuration.
Because of that shift north much of the
southwest was in more stable zonal upper
level flow. A series of surface lows from April
20lt"r through April 25t~ ejected out of the
Rockies beneath the stable zonal flow. Due to
the lack of instability and dry air. the Southern
Ogallala target area was left with no rainfall.

On April 26lt"r, afternoon temperatures in the low
80's aQ'"OSS the area and a southwesterly
surface wind seemed 10 hint at an uneventful
day. However, a dryline in east central New
Mexico developed from a low in the southern
Rockies. With higher dewpoinls to the north
and an area of weak convergence over west
Texas. showers develop moving southeast out
of the northwest portion of the Southern
Ogallala target area.

After the showers on April 26lt"r. a high pressure
from the north settled in to the area. This
synoptic situation led to high cirrus clouds and
windy conditions through the end of the month
in to the beginning of May.

May 2005

A cool high pressure dome was the story at the
beginning of the month with overnight low
temperatures dropping into the upper 30's in

some areas of west Texas. On May 5'-" a weak
upper level shortwave briefly interrupted the
cooler pattem. This provided the Southern
Ogallala target area with light showers, and the
first seeding operation for the month of May.

West Texas quickly dried out again but
temperatures did rebound from the much
cooler than normal values observed in the first
week into the mid 80's for daytime highs. The
synoptic system that provided the Southern
Ogallala area with its first rainfall for May
quickly moved east and west Texas was back
under high pressure until May 121". A vigorous
upper level trough extending south from the
Rockies and a developing thermal low over the
Big Bend/Pecos area in southwest Texas was
responsible for some unsettled weather
between May 12lt"r and May 15m, May 14m was
the second and last operation of the month
within the Southern Ogallala target area. The
drytine accompanied by several weak upper
level shortwaves were responsible for showers
and some isolated thunderstorms across the
southern Texas panhandle culminating in a
Mesoscale Convective System (MCS) that
passed through the area overnight on May
15tt1.

By May 161" a persistent northwest upper level
flow through was established over the
southwest region of the United States and
never relinquished its grip on the region. From
May 17tr1 through May 24tr1 west Texas daytime
highs were above 90 and on May 22"" and 23~
100 was reached. On May 25m a series of
weak upper level disturbances began to sweep
through the area helping to break the heat
wave and push a surface cold front through
west Texas. An MCS formed that passed
through the Southern Ogallala target area
overnight into the morning of the 2Stt1 and this
cell dropped dose to 1 S of rain during the
overnight period. On May 26!~ a stalled frontal
boundary draped across the northem Texas
panhandle and a cold front moving east out of
New Mexico provided isolated thunderstorms
in the region

From May 27lt"r through May 31$1 west Texas
and eastern New Mexico were active with
convective storms firing almost everyday along
the mountains in eastern New Mexico and a
series shortwaves exiting out of the Rockies
ignited thunderstorms along the Texas
panhandle. On May 281"' into May 291'" a line of

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