HMT Event Log SR1

Date: Dec 20-22 2005

Note takers: David Jorgensen & JJ Gourley

Time (UTC)	Event
0010	Arrived on site. Skies overcast – no rain – virga to W and NW.
0015	Leveled truck. Reset radar computer time to GPS time
0038	Data collection began using HMT-VCP12 with 90° scan
0050	Extensive stratiform looking echo to West out to 80 km. Max reflectivity around 45 dbZ at 5.1° elev scan. – very light rain on site
0101	Recabled internal internet to use hub. Can’t get Nav computer to respond but laptop talks fine with data computer
0135	Very light misty rain at site maybe R--. Extensive stratiform echo to W out to 100 km. Max dbz to 44 or so.
0145	JJ going back to town for rest. Will return at midnight or so
0204	More extensive bright band now evident on 90° scan
0208	More extensive stratiform echo echo now to N and NE into the upper reaches of the ARB
0219	Finally got telnet and ftp to work from nav computer. Switched internet cables one more time and rebooted and it worked.
0221	Very light rain at site, but 25 dbZ echo to the west 20 km
0253	Very little precip at site, but west of here there are fairly extensive 25 dbZ echoes ~20 km range, and in the ARB fairly extensive 35-40 dbZ echoes between 350° to 045fi at 20-40 km. Apparently rain just missing the site
0318	A little bigger rain drops on the windshield, but still R- rain at site. Near 50 dbZ echo cores ~15 km to the west.
0331	Rain intensity picking up a bit on site now maybe R
0335	Have now completed 35 volume scans and have used 27% of the disc space. So can probably get about 90 volume scans before the disc hits 91% and triggers the watchdog program to start deleting earlier files. At 12 volume scans/hr that gives about 7.5 hours before data must be backed up.
0335	Intensity of echoes to the west have increased. Now cores are near 50 dbZ
0421	Moderate precip (R+) at site. Large area of >50 dbZ echo from about 225° through 330° at between 20 to 40 km. Organize as a north-south line moving east ward.
0426	A > 57 dbZ cell at 315° 30 km on the 3.1° elev.
0436	Very intense echoes >57 dbZ on the 3.1° elev only 15 kn to the west. Only moderate rain on site so far.
0441	Sfc wind is picking up as well as the rain as the area of intense cores is only 5-10 km from the site to the west on the low level elves.
0453	Strong >50 dbZ bright band seen on the upper elves as a concentric ring about 1-2 km in range
0506	Line on top of site. Moderate rain. Pronounced bright band less than 1 km overhead. Definitely colder than any previous IOP. I would guess maybe 40F here at the site.
0519	Rain tapering off at site. Bright band decreasing in intensity too. Evidence of two ring on the upper tilts, probably a bright band and upper deck
0522	Areal extent of echo must be decreasing as file sizes are getting consistently smaller, from a peak of 7.8 mb at 0340 Z to 6.2 mb now.
0524	Bright band definitely decreasing in intensity, now only 25-30 dbZ rather than 50
0600	Power failed in cab
0610	Contacted Jerry Guynes and trying to diagnose problem
0700	Due to heavy rain can’t diagnose power problem further – will return in the morning to work on the issue when the rain has subsided at bit.
1711	Power restored – a small breaker in a power strip in the rear of the computer rack had tripped – probably as a result of being overstressed by the space heater. Had to diagnose problem with the help of Jerry Guynes at Texas A&M
1711	Radar back up and recording data – all raw product files up to 0555 UTC have been archived to laptop
1745	Rain has stopped at the site. Bright band remains about 800 m above
1749	Radial velocity images show a boundary to the NW of the radar at a range near 25 km to the NW extending out to 60 km due N. Boundary is curved and leading edge is situated from 320-360˚. Boundary is best seen at an elevation angle of 2.4-5.1˚. Could be cold front moving in from NW.
1750	Sky is brightening to the west as dryer air has intruded at mid-levels.
1804	Reflectivity is increasing slightly in intensity from previous levels of 30-35 dBZ to 40 dBZ along and just behind boundary. Also, visibility has dropped at the radar site with blowing fog.
1836	Precip starting again at site and echoes becoming more extensive to W through NE
1849	Graupel pellets & sleet falling
1901	More serious graupel showers
1921	Sky to the west lightening up again
2040	Only light and rather isolated cells over the ARB now. Echo mass is decreasing and we will terminate ops at 00Z or when the precip has decreased to being insignificant hydrological.
2128	Impressive graupel falling at radar site. This is the most impressive shower, albeit brief (less than 5 min) we’ve seen thus far. Size of graupel particles is less than pea-sized and particles are mostly solid (not spongy) and oblate.
2152	Small convective looking showers very close to SW, probably another graupel shower
2212	Another burst of graupel occurred at the radar site similar to the previous one. Reflectivity values are as high as 50-55 dBZ in the cores of the strongest echoes. Oblate spheroids noted again.
2229	Some more strong cells >50 dbZ at 320°/38 km
Jan 19/0037	Another graupel shower
0042	Graupel shower moved on by going ssw to nne. Still max dbZ of lower 50s.
0053	Echoes over the ARB finally beginning to dissipate. Only weak stratiform left max dbz of 35 or so, plus the remnant graupel storm that had moved over site
0100	Shutting down radar data collection
0130	Secured antenna and backing up data to laptop & Nav computer
0144	System secured