Program Status for 9 February 2001 : IOP 07

T (C)     Z (m MSL)     p (mb)
  0         1282         864
 -3         1763         813.5
 -8         2630         728.8
-13         3314         666.3

winds: 209deg, 27kt
air temp: -15.4degC, dewpt temp: -26.1degC

Will drop a sonde at pt 20.

winds: 233deg, 21kt
air temp: 6.9degC, dewpt temp: 4.8degC

Will do the CZD racetrack pattern. After reaching pt 13, will proceed to pt 14 and run the box counterclockwise. Will wait to see if microphysics stacks are worthwhile.

Likely will leave the Cape Mendocino area for IOP-7 and will try to sample near CZD. Monterey radar images suggest some precip enhancement N of SFO Bay. Will go to investigate.

Currently running a triangle between points 3, 4, and 5.

Features on LF match up well with Eureka 1201 Z radar image.

winds: 234deg, 19kt
air temp: -7.6degC, dewpt temp: -10.6degC

No strong echo activity in current location.

winds: 205deg, 17 kt
air temp: 5.2degC ,dewpt temp: 5.1degC

winds: 212deg, 30kt
air temp: -11.6degC, dewpt temp: -13.4degC

Bright bolt of triggered lightning on front of P-3.

winds: 205deg, 27kt
air temp: 2.2degC, dewpt temp: 2.2degC

Getting pelted with graupel (3-4mm diam) at 3000 ft. Copious radar echoes 45-50 dbz (some greater than 50). NCFR immediately to our west. Great data. Winds showed direction of 153-160 deg below 1000 ft, max winds of 37 kt within blocked flow.

winds: 244deg, 15.5kt
air temp: 2.5degC, dewpt temp: 0.8degC

At 39deg36minN, 125deg3minW, 908mb

winds: 230deg, 21.6kt
air temp: 2.2degC, dewpt temp: 1.3degC

At 39deg5minN, 124deg52minW, 913mb
winds: 232deg, 26.3kt
air temp: 3.2degC, dewpt temp: 2.4degC

Intense rainband (probable Narrow Cold Frontal Rainband):
orient: 30-210deg
echo top: 8km , echo max: 40-45 dbz

T (C)       Z (m MSL)        p (mb)

  0            1220            875
 -3            1732            821
 -8            2726            723
-13            3693            637

Discussion...
No lightning indicated.

Moderate rain was measured across the northern SF bay area between 14z and 15z. Hourly rainfall reports were mainly between .10 and .25 in. Maximum recorded amount for the hour was .40 in. at Yorkville in the Russian River Basin.

At 1542Z the intensity of most showers off the coast were between 25 and 35 dbz. However, an embedded echo of 51 dbz was indicated by radar at 36 deg 38minN 122 51minW.

DW

PACJET IOP#07 Short Term Forecast Discussion
NWS/PACJET Operations Center, Monterey, CA
1440 UTC February 9, 2001

Discussion...
A single lightning strike was detected offshore from Monterey at 1420Z. The location was 36N 124.4W.

Showers continue to track across Northern California, but at this time the strongest radar echoes are noted across the San Francisco Bay Region into the Sacramento Valley.

Santa Rosa reported a wind shift from 150 at 05kt to 260 at 03kt at 1420z. Between 13z and 14z Santa Rosa reported 0.17 in. while Hawkeye reported 0.19, Farallon Island with 0.20, Calistoga 2W with 0.24, and Ross and St. Helena 4WSW each with 0.16. Further South rainfall was just beginning to intensify at 14z with hourly amounts of less than 0.10.

Maximum radar reflectivities at 1444Z are noted over the Santa Cruz mountains with a return of 51 dbz 4 mi SW of the McQueen ridge radar site. Radar generated cell movement was from 197 deg. at 36 kts.

DW

1345 UTC February 9, 2001

Discussion...
No lightning indicated.

Moderate rain is being reported at Santa Rosa with 0.09 in. between 13z and 1328Z. Between 12z and 13z rainfall reported included 0.28 in. at Bridgeville in the Van Duzen Basin, 0.16 at Ft. Seward, and another 0.12 at Honeydew.

Besides the showers moving into Northwest California, there is also an area of enhanced precipitation across the Northern San Francisco Bay Area extending into Lake County. 12z-13z amounts included 0.12 in. at Venado and Upper Lake.

Gauges in the Santa Cruz Mtns. all reported totals of 0.04 in. between 12 and 13z except 0.12 at Scotts Valley.

1230 UTC February 9, 2001

Discussion...
No lightning indicated.
The 1224Z Radar image shows a line of showers with return of 20 to 30 dbz extending SSW to NNE through 40.0N 125W. Strongest returns of 35dbz are indicated of Eastern Humboldt county and about 10 mi offshore from Arcata.

The cold front has reached Pt. Reyes with moderate rain indicated for the past hour in the vicinity of Cazadero.

Rainfall reports from 11Z to 12Z include 0.24 in at Miranda, 0.20 at Orick, 0.16 at Ft. Seward, 0.12 at Honeydew, and 0.08 across much of the Russian and Napa River basins.

DW

Discussion...
The 1124Z Radar image shows the furthest eastward progression of the cold frontal rain band at 40.4N 123.5W. A region of 20 to 30 dbz echoes extends from Crescent City down to Point Arena. There are a few cells of 35 dbz over Cape Mendocino.

IR imagery shows enhanced cloud tops associated with the cold front extend as far south as Point Arena where the front is currently making landfall. Cloud top temperatures are -35 to -45C.

Honeydew reported 0.12 inches of rain between 10Z and 11Z...the same amount it received between 09Z and 10Z. 0.12 also at Miranda in the Eel River Valley and 0.08 at Orick.

DW

Discussion...
First lightning strike detected at 1025Z at 39.8N 124.1W. Cell is moving to the NE with return of 40dbz.

1035Z Radar image shows a maximum return of 50 dbz at 40.52N 124.24W. Echoes of 30 dbz or greater continue to be confined to the vicinity of Cape Mendocino.

DW

0950 UTC February 9, 2001

Discussion...
No lightning strikes detected in the past 3 hours.

0930 Radar image shows a box of mainly 35 to 40 dbz echoes bounded at 40.8N 124.8W to 40.2N 124.8W and extending to the coast. A small maximum of 50 dbz is located at 40.41N 124.62W

0950 Radar indicates this band has of echoes has weakened with echoes as strong as 35 dbz mainly only within 10 mi of Cape Mendocino.

06Z run of the mesoeta depicts negative LI through 15Z only in the region north of Pt. Reyes. At 12Z forecast Maximum CAPE values of 850 J/Kg and LI of -3 are forecast for 38.6N 128W. Nearly as impressive values are forecast for the region from 38.1 129.0 to 39.0 125.6

DW

Discussion...
No lightning strikes detected in the past 3 hours. NCFR is oriented N to S from Southern Oregon Coast to about Cape Mendocino 35 mi offshore, before beginning to trail off to the southwest. frontal position is approx. 85 mi W of Pt. Arena

The front is moving E at approximately 25 Kts. Current maximum radar return 45 dbz 28mi due W of Cape Mendocino.

1710 UTC, February 8, 2001

Short Term (Thu - Sat) Discussion

Model 5H initialized okay with the next Gulf of AK vortex that will slide into the western US this period. The base of the vortex looks a little sharper than what the model height analysis is showing. Vort vertification is good.

Model verification over the eastern Pacific for the past several runs shows the models, especially the AVN, have been moving previous vortexes too far east into the western US. 5H verification shows a clear positive bias over the eastern Pacific. Threrefore, although both the Eta & AVN are not too different, we need to dig these systems farther south. Verification of RH & PWs also shows the models too dry over the eastern Pacific.

Will follow the lead of the Eta which brings more energy into central CA this period. The AVN is strong, but farther north with the main 5H vort that pushes into central CA.

Sensible weather features associated with this next vortex should bring frontal precipitation into northern CA later tonight with the front reaching the SFO region around 12 UTC. Post frontal/orographic precipitation will quickly follow the front as onshore flow increases, while mid/upper level dynamics remain strong. The models are depicting strong left exit region upper jet dynamics over central CA. This should support heavy precipitation in the favored orographic regions of the central/northern CA coastal areas and sierra.

Long Term (Sat - Thu) A second strong Gulf of AK vortex is expected to dig into the eastern Pacific very quickly on the heels of Friday's system. The vortex is expected to move to just off the Pacific northwest coast by Sat evening with strong mid/upper level dynamics digging into northern CA. This should bring another round of mod/heavy precipitation into northern CA Sat afternoon/evening and central CA by Sat night. Beyond this time frame, the models are having some difficulty with mid/upper level heights. Yesterday's models brought shortwave energy through the eastern Pacific ridge axis and into CA by late in the week, but today's medium range models are showing very little energy cutting through the base of the eastern Pacific ridge. This latest solution is very similar to what happened last week, which led to several days of dry/warm weather.

Eckert/PACJET Forecaster