SPRITES 99 YUCCA RIDGE FIELD STATION
FMA Research
JD 99233 21AUGUST99
PRELIMINARY SPRITE LOG
The following is a very preliminary listing of the times of sprites imaged at the
Yucca Ridge Field Station. These are based solely on real-time visual inspection of
the video monitoring system. There are most likely some additional sprites not listed
and not all those below may in fact be sprites. All times are UTC. Times are likely
to be within ±5 seconds of actual time.
SUMMARY: Successful balloon mission from Ottumwa from 0039 to 1112 UTC. Convection over the
High Plains was relatively muted. A cluster of two small MCS storms were present in
SD/MN during the early evening hours. They resembled weak supercells at first, and
eventually developed forward leading stratiform regions in the strong northwest flow.
The flash rates were modest (several hundred Fl/hr) with percent positive in the 10%
range. The storms were just large enough to produce sprites, and apparently did
produce them, especially as the stratiform region grew after 0400Z. Viewing from
Yucca Ridge was initially hindered due to some debris clouds, but clear views
become possible to the northeast by 0430 Z. Stars at the horizon were noted.
Several very distinct carrot-type sprites were noted. The Kansas system was
unusual, in that it consisted of two long, parallel NW-SE oriented lines of high
reflectivity with very little stratiform area. This system was atypical of
sprite producers. One very large elve was noted. Additional cases beyond those
listed below are likely present on the video tape, which will take careful analysis
to extract all useful information. A half moon caused light scattering problems early on.
Air was quite clear however. Once scattered clouds evaporated after around 0500 Z,
stars could be seen rising from below the horizon at Yucca Ridge.
VLF audio was also recorded through the dawn hours.
Total TLEs This Campaign: 1592
(S) = Sprite; (E) = Elve; (B) = Blue Jet; (CF/CG) = Cloud/Ground flash; (M)=Meteor
JD 99233 - 21 AUGUST 1999
0302. Start LLTV Observations
0500.28 [S]
0541.58.063 [S]
0546.10 [S]
0800.56.972 [E]
0901 End LLTV Observations