PACJET Projects
HMT 2004
IOP 1: 20 Jan 2001
IOP 2: 23 Jan 2001
IOP 3: 25 Jan 2001
IOP 4: 31 Jan 2001
IOP 5: 1 Feb 2001
IOP 6: 6 Feb 2001
IOP 7: 9 Feb 2001
IOP 8: 10 Feb 2001
IOP 9: 11 Feb 2001
IOP 10: 12 Feb 2001
IOP 11: 17 Feb 2001
IOP 12: 18 Feb 2001
IOP 13: 21 Feb 2001
IOP 14: 24 Feb 2001
IOP 15: 25 Feb 2001
IOP 16: 1 Mar 2001
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2001 - Monterey, CA
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Program Status for 18 February 2001: IOP 12

Status | Observations | Forecast Discussion | Flight Plan | Soundings Status

Sunday, February 18 Flight in progress. Take off was at 1735 PST.
Monday, February 19 Weather briefing at 1000 PST.
Possible P-3 flight.

Status | Observations | Forecast Discussion | Flight Plan | Soundings Status

0915 UTC
0904 UTC
0843 UTC at 33.80degN, 123.27W, 976mb
heading: 192deg at 1000 ft

winds: 184deg, 42kt
air temp: 12.3degC
dewpt temp: 11.7degC
mix rat: 8.9g/kg

0825 UTC Lower fuselage radar NCFR image: echo max: 55+ dBz, echo top: 8km, convective core reaches to 3km
Tail radar image: convective core reaches to 3 km, just above freezing level.
0807 UTC at 35.47N, 123.04W, 972mb:
heading: 176deg at 1000 ft.

winds: 168deg, 49kt
air temp: 10.8degC
dewpt temp: 9.4degC
mix rat: 7.6g/kg

0742 UTC NCFR becomes much weaker at 36.15N, 123.69W as observed by P3 at 0742 UTC. We will "shoot the gap" from cold side of NCFR to warm side. Echo tops much lower at this location as well (extend only to 3km).

After "shooting gap" just on east side of NCFR, winds are 158deg at 45 kt (compared to 23 kt on cold side) at 1000 ft.

0734 UTC at 35.61N, 123.74W, 975mb:
heading: 359deg at 1000 ft

winds: 230deg, 20kt
air temp: 8.7degC
dewpt temp: 5.1degC
mix rat: 5.7g/kg

All obs data has been taken on cold side of cold front (post- frontal).

0725 UTC
0655 UTC Sounding during P3 spiral (in cold air) at 35.6N, 126.2W

P(mb)  Ht(m)  T(degC)  Td(degC)  ff(kt)  dd(deg)
 925    700     7.1       5.3      35      233
 850   1388     1.8       1.3      29      232
 700   2921    -8.1     -14.3      40      243
0650 UTC Winds on cold side of NCFR at 18000 ft were 200deg at 100kt (at 0650 UTC at 35.6N, 126.1W) when P3 was at the rear of the cold frontal rainband.
0640 UTC Flight level data and information from dropsonde#2 seems to indicate that rainband (NCFR??) is indeed the true NCFR.

Sounding showed:
at 900 mb winds: 235deg, 23m/s, T=4degC on cold side

air temp on warm side at 900mb was 7degC with winds 170deg, 31m/s.

Seeing cold air convective cells at 0645UTC at 35.47N, 126.02W. Back edge of precip appears to be at ~125degW. Width of precip (NCFR + wide cold frontal rainband trailing NCFR) is 100km.

0635 UTC Dropsonde#3 at 35.5N, 125.3W

P(mb)  Ht(m)  T(degC)  Td(degC)  ff(kt)  dd(deg)
1000     63     8.8       6.2       -       -
 925    705     5.8       0.8       -       -
 850   1391     1.6      -1.5      31      240
 700   2936    -6.5     -12.5      57      225
0630 UTC at 35.47N, 125W, 513 mb:
heading: 256deg at 17500 ft

winds: 205deg, 74kt
air temp: -20.1degC
dewpt temp: -21.0degC
mix rat: 1.4g/kg

drop#3 will be at 35.5N 126W in 11 minutes.

0627 UTC Sounding #2 at 35.5N, 124.5W

P(mb)  Ht(m)  T(degC)  Td(degC)  ff(kt)  dd(deg)
1000     76     8.6       5.3       -       -
 925    718     5.6       1.6       -       -
 850   1405     1.4      -0.9      59      245
 700   2951    -5.9      -8.0      41      210
0612 UTC at 36.09N, 124.38W, 512mb:
heading: 187deg at 17500ft

winds: 198deg, 68kt
air temp: -20.3degC
dewpt temp: -22.1degC
mix rat: 1.3g/kg

0547 UTC at 35.61N, 124.60W, 973mb:
heading: 342deg at 1000 ft

winds: 158deg, 50kt
air temp: 10.2degC
dewpt temp: 9.6degC
mix rat: 7.7g/kg

Currently still trying to find way to get to other side of rainband (NCFR??).

0530 UTC At 34.41N, 124.59W, 976mb:
heading: 14deg at 1000 ft

winds: 172deg, 48kt
air temp: 11.7degC
dewpt temp: 10.3degC
mix rat: 8.1g/kg

0521 UTC
Tail radar image of rainband (NCFR??) included. Currently running parallel to band trying to find point to penetrate.
0505 UTC
Radar echos in line show supercell like characteristics.
0500 UTC at 33.44N, 124.20W, 927mb:
heading: 269deg at 2500 ft

winds: 195deg, 44kt
air temp: 9.7degC
dewpt temp: 7.4degC
mix rat: 6.9g/kg

Moving to penetrate NCFR(??).

0454 UTC The P3 is interpreting the second band as trailing stratiform precip. Estimate of primary band movement is eastward at 30kt.

Heading west toward line, hoping to penetrate to clarify picture. Should arrive in 20 minutes.

0442 UTC at 33.43N, 124.13W, 882mb:
heading: 111deg at 3800 ft

winds: 206deg, 43kt
air temp: 6.1degC
dewpt temp: 5.6degC
mix rat: 6.7g/kg

Pilots have spotted lightning as we have been tracking this storm.

0433 UTC at 33.57N, 124.76W, 881 mb:
heading: 191deg at 3800 ft

winds: 203deg, 48kt
air temp: 7.0degC
dewpt temp: 3.7degC
mix rat:5.8g/kg

0418 UTC
0343 UTC At 33.50N, 124.54W, 974 mb:
heading: 112deg at 1000 ft

winds: 176deg, 38kt
air temp: 11.6degC, dewpt temp: 9.2degC, mix rat: 7.5g/kg

Have modified flight plan due to inability to penetrate NCFR (too continuous and convective). Current plan is to make flux stacks east of NCFR. Currently on first leg.

0332 UTC at 33.61N, 125.28W, 974mb:
heading: 114deg, at 1000 ft

winds: 172deg, 46kt
air temp: 11.6degC, dewpt temp: 10.1degC, mix rat: 8.0g/kg

Unable to penetrate NCFR. Convective line was too continuous. Could not find a clear path through NCFR. NCFR image shown at 0322.

0322 UTC
0315 UTC at 33.34N, 125.89W, 959 mb:
winds: 186deg, 56kt
air temp: 12.0degC, dewpt temp: 9.6degC
NOTE: on WARM side of NCF

Punching through NCFR. Mix ratio on warm side: 8.2g/kg

0300 UTC Descending at pt 1. During descent at pt 1, LLJ seen at 920 mb 52kt ,mix rat=7.2g/kg Pt 1 located at 33.05N, 125.71W

Other levels during descent at pt 1:

Press(mb)  Ht(m)  T(degC)  Td(degC)  ff(kt)  dd(deg)
 925        738    10.5      7.8       51      196
 850       1440     5.4      2.7       47.6    220
0254 UTC at 33.03N, 125.76W, 505mb:
heading: 223deg at 18100 ft

winds: 234deg, 68kt
air temp: -20.1degC, dewpt temp: -25.5degC

0243 UTC at 33.53N, 125.26W, 505mb:
heading: 225deg, at 18100 ft

winds: 234deg, 66kt
air temp: -19.1degC, dewpt temp: -29.2degC

LLJ information from drop:
At 0235UTC, at 33.97N, 124.89W
Max winds: 22m/s, 195deg at 800m

Preliminary estimates of eastward movement of possible NCFR is 26 kt toward the east during the evaluation time from 0218-0248 UTC.

0235 UTC Sounding#1 at 33.97N, 124.89W

P(mb) Ht(m) T(degC)  Td(degC)  ff(kt)  dd(deg)
1000    99   12.6      8.5       31      160
 925   748    8.2      5.8       42      190
 850  1442    3.6      1.0       41      210
 700  3001   -3.1     -9.2       44      220

0225 UTC 34.44N, 124.39W, 505mb:
heading: 223deg at 18000 ft (~27 min to pt 1)

winds: 226deg, 58kt
air temp: -21.5degC, dewpt temp: -40.0degC

0214 UTC
0209 UTC 35.3N, 123.55W, 505 mb:
heading: 225deg, at 18000 ft (42 min to pt 1)

winds: 229deg, 50kt
air temp: -20.7degC, dewpt temp: -38.6degC

0146 UTC 36.41N, 122.42, 599 mb:
heading: 220deg at 13000 ft, 1h 8min to pt 1

winds: 206deg, 29kt
air temp: -13.7degC, dewpt temp: -38.9degC

0133 UTC 850mb ob coming out of MRY:

winds: 170deg, 24kt
air temp: 3.5degC, dewpt temp: -12.4degC

Status | Observations | Forecast Discussion | Flight Plan | Soundings Status

Forecast Discussion
Forecast discussion for 18 February 2001

2055 PST
Center of circulation at 0430Z at N38.97/W134.43 and elongated NW-SE. Appears occlusion process occurring southeastward from the low with the triple point at N37.93/W129.66 at 0430Z. Buoy#59 (N38/W130) wind shifted at 03Z to SSW from the SSE at 12KTS. Lightning activity around N35.22/W125.39 continues to decrease slightly over the last 1/2 hour...but still active with 7 strikes in last 15 minutes at 0430Z.

2040 PST
Comment regarding 0322UTC message about NCFR. It is the opinion of PACJET Ground Ops and WFO that you are looking at a possible squall at the previously mentioned NCFR location. In fact there may even be another instability line between you and the trailing edge of the coldfront. The guess is that surface front trailing edge from N36.5/W128.2 south to N34.21/W127.79. Latest lightning at 0430Z N35.51/W125.44 to south at N34.4/W125.48.

1934 PST
Low circulation elongating NW-SE centered at N39.42/W135.49. Back edge of vort lobe at N34.86/W127.54 pushing east at 41 knots at 070 degs. Bottom edge of cold air at N33.57 at 0330Z. Coldest temps at cloud top at -54C at N36.02/W126.39 at 0330Z. At 0415Z lightning strike at N34.8/W125.52.

1930 PST
After coordinating with forecasters, it appears speed of frontal system at 36N 126.5W moving 070 degrees at 41 knots.

1930 PST
Edge of warm front has moved onshore. Front has moved around 65 mi in 1.5 hours. At 03Z, back edge of cold front 39.12N 131.58W cold cloud tops arching to 33.31N 127.32W and front edge at 36.93N 125.67W. At 0315Z 24 + strikes 8 - strikes, coldest cloud still -53C at 36.04N 126.87W. Area of coldest cloud tops is expanding from 01Z to 03Z. AT 03Z buoy 59 38N 130W SSW12 temp 50 sea 53 pressure 996 waves 10 feet 8 sec. Back edge of frontal band appears to be farther west than depicted in the radar image sent. Appears from IR sfc front feature back edge around 1 degree further west.

1845 PST
AT 0230Z 43 + lightning strikes and 3 - strikes in line extending from 36N 126.83W to 34N 126.65W. Coldest cloud tops -53C at 35.4N 127.04W. Coldest cloud tops stretch from 37N 128W to 35.2N 126.75W.

1840 PST
Apprarent embedded TSTMS as cloud top temps at -53C with 15-min 50+ lightning strikes in depicted N-S line as of 1800 PST from N36.93/W127.92 south to N33.81/W127.03. Surface cold front back line still even with upper clouds back line at N35.17.

1815 PST
Speculate that trailing edge of warm front from N39.19N/W127.44 arcing to southeast N33.32/W122.23. Coldfront, per previous message, apparently below upper clouds with trailing edge at N38.77/W132.2 arcing southeast to N35.01/W129.02 and then southwest N30.32/W133.30 (out from under high clouds). Note: At nose of colder air (nose of jet) at N35.0 obvious convective activity noted with lightning strikes at W127.0. These strikes showing N-S line from N36.06 south to N34.08. This feature appears to be moving east and curving NNE at about 32Kts at 1730 PST.

1745 PST
Upper air circulation center at N40.0/W136.5 moving north at 1730 PST and in counter-clockwise curve and apparently tending toward NNW at this time. Circulation supporting negative-tilt difluent flow with apparent driving jet with nose at N35.56/W129.13 at 1730 PST. Southern extent of cold air apparently bottomed out at N32.5. It appears that system beginning to move more north of east with low pulling north and no further south push of supporting jet. Associated vort lobe apparent arcing from N40.0/W133.4 to N34.4/W128.7. High clouds still over the surface frontal position with lowest temps at cloud top at -51.0C.

Again relatively poor initialization by the 12Z NGM and ETA models as the circulation center by satellite WV imagery appears to be near N37/ W138. This location is farther southeast than either the NGM and ETA which depict only a trof axis to the NW of that position. And to the AVN credit, it does show semblance of circulation at 12Z initialization and only slow by about a degree. Satellite WV imagery depicts nice vorticity lobe along W137 between N33-38. This energy is expected to support oncoming frontal system targeted to reach NORCAL Coast pre-dawn on Monday. Cold air in previous system no further south than N39.5 but this system driving colder air down to N32.5. Like the forecast problem of past 48 hours, hemisphere flow pattern still in process to estalish better zonal flow beneath what has been a blocking ridge in the Gulf of Alaska around N55/W140. Per Monterey WFO Staff model performance had been too fast with oncoming systems. Timing for main onshore precipitation adjusted slightly slower than models might otherwise indicate to reflect arrival of precip around 10Z for North Bay. QPF for North Coast close to an inch for system from 10Z-00Z.

AVN model seems to hint at a change toward more energy in the lower latitude split flow and again Monterey WFO indicating some 36-42 hour periodicity for inclement weather through the coming weekend. Weather systems expected to be stronger tonight with continuing shower activity through Monday night along the Central Coast due to instability. Weak and dirty ridge Tuesday leading to a similar system Wednesday Night. Outlook calls for a strong system late Saturday but no means of model consistency or commn solution at that time.

PACJET P3 targeted to depart 1730 PST Sunday Feb 18th for operational data gathering.

Status | Observations | Forecast Discussion | Flight Plan | Soundings Status

Flight Plan

MRY - P1 FL 180 to FL 200
P1 Spiral down to 1,000 ft.
P1-P2 Flux stack and porpoise 1,000 ft to 8,000 ft.
P2-P3-P4 Frontal module.
P4-P5 Porpoise 1,000 ft to 8,000 ft.
P5 Spiral up to 8,000 ft and back down to 1,000 ft.
P5-P6 1,000 ft
P6 Spiral up to 8,000 ft and back down to 1,000 ft.
P6-P5 1,000 ft.
P5-P7 Porpoise 1,000 ft to 8,000 ft.
P7-P8-P7 Frontal module.
P7-P9-P10 Porpoise 1,000 ft to 8,000 ft.
P10-P11-P10 1,000 ft with spirals up and down to 8,000 ft.
P10 Spiral up to 8,000 ft.
P10-P12 8,000 ft.
P12 Spiral up to FL120
P12-P10 FL120
P10-P16 1,000 ft with porpoises to 8,000 ft.
P16-MRY Return flight.

Status | Observations | Forecast Discussion | Soundings Status

Sounding Status
18 February
Bodega BaySoundings as event develops.
CazaderoSoundings as event develops.
OaklandSoundings requested at 3Z.
RenoNo special soundings requested.
19 February
Bodega BaySoundings as event develops.
CazaderoSoundings as event develops.
OaklandSoundings requested at 9, 15, 18 and 21Z.
RenoNo special soundings requested.
20 February
Bodega BaySoundings as event develops.
CazaderoSoundings as event develops.
OaklandSoundings requested at 3 and 6 Z.
RenoNo special soundings requested.