Project Status

IOP-12 ended early Tuesday morning at about 12 UTC. when only a few lingering weak instability showers remained over the ARB. 36 hour total precip at Blue Canyon from 00 UTC Monday to 12 UTC Tuesday was 5.54 inches. Another rain gage a bit farther up in the ARB (Huysink) got 7.76 inches of liquid equivalent. Another notable feature of IOP-12 was a very vigorous narrow cold frontal rainband (NCFR) that passed through the basin from about 06 UTC to 07 UTC. During its passage through Foresthill at about 06 UTC the estimated surface winds were in excess of 60 mph.

Jorgensen

Posted by Status Editor at 04:20 PM | Permalink

IOP-12 continues to at least tomorrow morning. Precip in the ARB is going through a lull as the first wave pulls out. Another wave will reinvigorate precipitation this afternoon and evening with perhaps another 3 inches possible in the ARB. The supplementary soundings will terminate as planned at 12 UTC Tuesday (OAK) and 15 Z (Slough House). Radars will continue to at least 12 UTC and perhaps a bit longer depending on rain in the ARB. Radar crews will chat about the echoes over the ARB early tomorrow morning and decide on an appropriate termination time.

The Colfax S-band profiler, thought to be fixed, has suffered a problem and the data will be removed from the real-time web page until further notice.

Jorgensen

Posted by Status Editor at 07:56 PM | Permalink

As of 8 AM PST Monday morning (16 UTC) Blue Canyon received 1.99 inches since the rain began at about 00 UTC. In spite of this impressive ~16 hr total, a lot of the wave energy and precip is just north of the ARB as seen by the DAX radar. Precip will continue in the ARB through about 15-18 UTC Tuesday as the trough continues to dig.

Jorgensen

Posted by Status Editor at 05:16 PM | Permalink

At the present time (Sunday night 8 PM PST, Monday 0500 UTC) rain is falling in the ARB. Since 00 UTC Blue Canyon has picked up 0.48 inches of precip equivalent. The scanning radars began operations at 00 UTC. At Foresthill the SMART-R radar has shown several distinct bands of precip move over the site from the west accompanied by heavy surface rain. Some echoes exceeded 55 dbz in intensity. A very strong bright band was noted on the upper tilts.

Jorgensen

Posted by Status Editor at 04:58 AM | Permalink

At the present time (20 UTC), precipitation echoes have moved onshore over the coastal mountains and are creeping into the Sacramento area. The airmass ahead of the precipitation is relatively dry, so virga and/or light sprinkles through the afternoon is probably the most we should expect. However, once we move into the evening hours, enough moistening at low levels should have occurred to allow more intense rain rates at the surface. The present thinking is that precipitation should start accumulating in the American River Basin after 03 UTC 27 Feb. Intensity should pick up overnight and into Monday. Cold frontal passage is expected around 06-08 UTC 28 Feb. Thereafter, post frontal showers should continue through the better part of Tuesday, maybe into Tuesday evening. The next event does not appear to begin until late Wednesday-we will monitor this over the next couple of days.

The current plan for IOP 12 is as follows:

Scanning radar operations--XPOL and SMART-R should be ready to start operations by 00 UTC 27 Feb. If there are no echoes in their scanning domain, they will delay operations accordingly. At present, they should not expect to begin operations any later than 03 UTC.

Oakland (OAK) supplemental soundings--will commence at 03 UTC 27 Feb and end at 09 UTC 28 Feb (a total of 9 3-hourly supplemental launches).

Sloughhouse soundings--will commence at 00 UTC 27 Feb and will continue at 3-hourly intervals through Monday and into Tuesday morning. The time of the last Sloughhouse sounding is not yet known as some staffing issues need to be clarified (stay tuned)

Instrument status issue:

The Colfax (CFC) S-band profiler was repaired on Friday and re-depolyed to its site on Saturday (thanks to Clark King, Jim Jordan, Scott Abbott and especially Dave White). Data from the profiler is back online on the HMT-West 2006 web site.

Kingsmill

Posted by Status Editor at 08:16 PM | Permalink

IOP-12 is on schedule to begin at 00 UTC Monday (4 PM PST Sunday). Latest guidance indicates that the event will go on a bit longer that yesterday's model runs. Another wave comes close on the heels of the Monday system that will give another shot of precip on Tuesday. Rain is expected to taper off sharply after 4 PM PST Tuesday. Radar crews should be prepared to to operate for 48 consecutive hours. Total QPF may exceed 5.5-6 inches in the ARB for IOP-12. Freezing levels are still expected to remain high, 7-8 kft decending to perhaps 5 kft by Tuesday.

Supplementary soundings are scheduled to begin 4 PM PST Sunday and continue to 4 AM Tuesday morning. However, an alert has been given to the OAK sounding site that additional soundings may be requested on Tuesday to 21 UTC. Since the total supplementary NWS sondes are limited to 16, and 9 are proposed for the Sunday-Tuesday morning event, using 3 additional on Tuesday would limit what could be done for the Thursday event to only 4. The Sloughouse soundings will also be extended to 4 PM Tuesday if sufficient student crews can be assembled. A decision on extending the soundings will be made tomorrow.

Once the rain subsides Tuesday evening, there will be a lull until early Thursday when another wave, this time much colder will arrive. The QPF is expected to be modest, 1-2 inches, because of the short duration of the event. Precip tapers off late Thursday evening.

Jorgensen

Posted by Status Editor at 08:38 PM | Permalink

IOP-12 will begin 00 UTC Monday Feb. 27 (4 PM PST Sunday). Light precip is expected to start over the ARB from warm air advection in the warm sector of an advancing cold front/upper wave. Heavier precip is expected from both orographic lift and baroclinic lift processes beginning around 06-09 UTC. Rain will taper off early Tuesday after the frontal passage. Snow levels start out rather high, 7-8 kft, and then descend to perhaps 5 kft as the trough axis passes and the ARB comes under the influence of cold air advection.

The SMART-R and XPOL radars will begin ops at 00 UTC Monday. Soudings from Sloughouse will also begin at 00 UTC. The first OAK supplementary sounding will be 03 UTC. Supplementary soundings will continue to Tuesday 09 UTC (OAK) and Tuesday 12 UTC (Sloughouse). The end of IOP-12 is expected to be around 12 UTC Tuesday, although if the rain tapers off significantly before then the radars could suspend data collection earlier. Total QPF for IOP-12 could be as high as 5.5" at BLU.

There will be a break in the precip as short wave ridging occurs from late Tuesday to early Thursday. Another wave with QPF perhaps 2" will occur on Thursday. Its possible that another IOP will be declared on the Thursday storm. That decision will not be made until perhaps Tuesday.

Jorgensen

Instrument Status Issues:

The faulty transmitter from the Colfax S-band profiler is now back in Boulder and its condition is being evaluated. More might be known by later this afternoon. However, it appears unlikely that the profiler will be back in operation for IOP 12.

The faulty temperature and relative humidity sensors at Blue Canyon have been replaced and the data are now being displayed on the HMT-West 2006 web page. As a result of this repair, snow depth data at Blue Canyon is now also being displayed again.

The untelemetered rain-gauge and associated data logger at Yankee Jim Crossing has been destroyed beyond repair as a result of vandalism (gun-fire). Data acquisition stopped on 27 January.

Kingsmill

Posted by Status Editor at 08:03 PM | Permalink

Dry conditions continue in the American River Basin today and are forecasted to continue into Sunday. Starting midday Sunday a low drops down from the Gulf of Alaska and digs a trough along the west coast and returns the ARB to a favorable flow environment for precipitation. Light precip could start as early as Sunday afternoon, but the strongest moisture advection (and heavy rain) likely will start 06-12 UTC Monday and continue until frontal passage on Tuesday. QPF amounts for this system could be 2-3 inches of liquid equivalent with freezing levels starting fairly high at 7,000 ft and dropping down to perhaps 5,000 ft with frontal passage. The GFS model indicates the rain will lull on Wednesday before another vigorous system comes ashore Thurs-Friday. Total QPF for the entire week could be as high as 8" of precip.

Although no deployment or supplementary sounding decisions were made today, it's highly likely that IOP 12 will be delared starting Sunday afternoon or evening and will run to Tuesday. Radar crews should be prepared to deploy Sunday if this forecast scenario holds up. Decisions on deployment and soundings likely will be made tomorrow.

Jorgensen

Posted by Status Editor at 09:13 PM | Permalink

Dry conditions continue to prevail in the American River Basin and the forecast is for this to continue into the early part of the weekend. Then, we are looking at the possibility of a shift to wetter conditions in the Sunday-Monday time period. However, there are some uncomfortably large spreads in the model ensembles, so confidence in this shift is not yet very high. Partly in response to this issue, a request has been submitted by NWS Western Region to the Winter Storms Recon program to do targeted observations in support of forecasts for this event. The status of the request is unknown at this time.

Instrument status issue: The Colfax (CFC) S-band profiler has a faulty transmitter, which needs to be shipped back to Boulder for repair. This instrument will likely be down until at least the middle to end of next week.

Kingsmill

Posted by Status Editor at 07:48 PM | Permalink

The forecast for this week is for continued dry conditions in the American River Basin. However, next week is starting to look like it might be relatively wet. The longer range models are suggesting a pattern shift to wetter conditions starting on Monday, 27 February. We will keep track of the forecasts as the time for this anticipated pattern change approaches.

Status issue: The SMART-R is scheduled to depart Foresthill on Wednesday 1 March for its return trip to Oklahoma. However, if an IOP is ongoing on that date, the SMART-R will continue operations through the end of the IOP.

Kingsmill

Posted by Status Editor at 07:45 PM | Permalink

Dry conditions are expected in the American River Basin through this week and probably also through next weekend. There is some hint of wetter conditions for the following week, but that is still a long way off.

Kingsmill

Posted by Status Editor at 07:24 PM | Permalink

The HMT-West 2006 web page came back up a few hours ago. It went down on Saturday morning in assocation with power outages in the Boulder area and subsequent start-up problems.

The cold precipitation event of last Friday and Saturday resulted in a little less than 1 inch of liquid at Blue Canyon. Here is the status report that Dave Jorgensen wanted to post after the Sunday coordination call:

***********************************
The precip event ongoing in the ARB is winding down this morning. Only lingering showers remain. Blue Canyon got about 0.75" of precip from this event, so the decision not to deploy was a good one.

Once this system pulls out of Northern California the upper air pattern will flatten out to a flat ridge and not many strong impulses should affect the target area for at least a week. The ensembles point to next weekend as being the first chance for a significant precip event in the ARB.

The SMART-R is scheduled to return to Norman on March 1st, unless there is an ongoing IOP and it will stay a day or two to finish it before departing.
*************************************

Kingsmill

Posted by Status Editor at 05:26 PM | Permalink

Precipitation echoes are currently evident in the American River Basin, but they are small scale and very shallow (based on the profiling radar data). So far, Blue Canyon has picked up about 0.1 inches of liquid---sites downslope from Blue Canyon, such as Foresthill, have not yet recorded any precipitation accumulations. The forecast calls for 0.5 to 0.75 inches of liquid equivalent over the next 24 hours or so.

In the longer range, there are no promising precipitation systems on the horizon yet for next week.

Status issue: There is a communication problem at the Colfax (CFC) field site that is not allowing data to be transmitted back to Boulder for display on the web. It is believed that instrumentation at the site is operating normally. ESRL staff will visit the site next week to troubleshoot.

Kingsmill

Posted by Status Editor at 07:38 PM | Permalink

The forecast from yesterday is still on track: precipitation over the American River Basin during the Friday-Saturday period will likely occur, but it will be on the light and showery side. Precipitation amounts still not likely to exceed 0.5 inches of liquid. We will stick with the decision not to activate an IOP for this event.

In the longer range, the next possible precipitation event for our target area is not forecast to occur until later next week.

Kingsmill

Posted by Status Editor at 07:08 PM | Permalink

Weather conditions in northern California have become cooler and cloudier as advertized during the past couple of days. However, recent forecasts for precipitation have shown a downward trend in accumulations. Yesterday, the models were indicating that the Friday-Saturday event would be in the 1" to 1.5 " range. This morning's solutions are mostly in the 0.25" to 0.5" range. In addition, there is not much in the way of an upslope wind component to effect an orographic enhancement of the precipitation. The system is still forecast to be quite cold (snow levels in the 1500-2000 ft range), but with the relatively low values of QPF (and a decreasing trend), this does not seem like an event worthy of activating an IOP. Therefore, there will not be any crew deployments or sounding operations for this event. The forecast for next week does not look particularly promising for wet weather---hopefully things will change.

Status issue: The temperature and relative humidity sensors at Blue Canyon have developed problems that make their data erroneous. The snow depth sensor requires good temperature data (for speed of sound calculations) to make accurate estimates of snow depth. As a result, these sensors are not currently being displayed on the time-series plots of Blue Canyon data available on the HMT-West 2006 web page. ESRL staff will visit the site early next week to repair the faulty temperature and relative humidity sensors.

Posted by Status Editor at 07:51 PM | Permalink

Weather pattern change for the American River Basin is underway, with cooler air filtering in from the north Forecasts are still calling for a precipitation event to occur during the Friday-Saturday time period. There is confidence in the fact that it will be a pretty cold event (snow levels perhaps below 2,000 ft by event end). However, there is still uncertainty about timing and precipitation amounts. With this sort of cutoff situation, the outcome is very sensitive to the exact trajectory of the low center. This mornings model solutions suggested a trajectory that was somewhat further east than yesterdays solutions, which means that the system would have less time over water to pick up moisture. If the future solutions continue this trend, then the event could possibly fizzle below our interest level. However, if the solutions flip back to a more oceanic trajectory, the event could be more significant, and perhaps delayed somewhat.

We will monitor the next couple forecast cycles and then make some decisions about crew deployments during the Wednesday coordination call

Kingsmill

Posted by Status Editor at 08:13 PM | Permalink

The anticipated more favorable weather pattern for the American River Basin is about to manifest itself. The first disturbance will affect the area during the Wednesday-Thursday time period. As the forecasts have been indicating, this system appears to have limited moisture and will probably produce only showery precipitation that adds up to no more than about 0.1 inches of liquid Although this is not worth initiating an IOP, this event will help moisten the lower levels of the atmosphere, which might limit the duration of virga at the outset of the next more significant event forecast to start affecting the area on Friday. This latter system is now forecast to start Friday afternoon/evening and continue through Saturday into early Sunday. The models are indicating that it will be a relatively cold system, with snow levels in the 3,000-4,000 ft range, perhaps descending to 2,000 ft toward the end of the event. A decision on crew deployments probably will not be made until Wednesday.

Kingsmill

Posted by Status Editor at 08:09 PM | Permalink

The weather pattern change for the American River Basin is still on track to occur during mid-week. However, the first disturbance to go through in the Wednesday-Thursday time frame appears moisture starved, and as a result, likely will not produce much more than 0.1 inches of precipitation. This type of system does not seem worthy of an IOP. A more promising event appears to be in store for next weekend. We will keep tabs on how the models handle this event over the next couple of forecast cycles.

Kingsmill

Posted by Status Editor at 07:42 PM | Permalink

Dry weather will prevail over the American River Basin during the next few days, but there is still antcipation of a pattern change during the middle to later part of next week that will provide a more favorable environment for wet weather. At present, it appears that the highest probability for the next significant precipitation event is in the Friday-Saturday time frame of next week. However, we should be prepared for the possibility of an earlier event, perhaps in the Wednesday-Thursday time frame of next week. The next couple of model simulation cycles should help us resolve these issues.

Kingsmill

Posted by Status Editor at 07:37 PM | Permalink

Although continued dry weather is expected over the American River Basin during this weekend and the early part of next week, there is now some indication that wetter weather may be in the offing for the middle to later part of next week. The new, higher resolution version of the EC model has indicated such a pattern change for the last few days and the GFS is starting to move toward that type of solution. Certainly a situation that warrants close monitoring in the next few days. It's still too early to discuss possible crew deployment scenarios, but stay tuned.

Kingsmill

Posted by Status Editor at 07:43 PM | Permalink

The forecast for the American River Basin continues to indicate dry weather into at least the middle of next week. Therefore, no crew deployments are anticipated for the foreseeable future.

Operations summaries for IOP's 10 and 11 have now been posted to the Operations Summary blog

Status: There is currently a disruption to data collection at Alta due to a scheduled power outage. The site should be back up in the next day or so.

Kingsmill

Posted by Status Editor at 07:45 PM | Permalink

The forecast models continue the outlook for dry weather in northern California at least into the early part of next week. Therefore, no crew deployments are likely in the next few days. Six weeks are left for HMT and only 3 weeks for the SMART-R operations at Foresthill.

CNRFC's web site has an extensive summary of the Christmas-New Year's storms and their impacts, with great information and graphics. Look for it under "Storm Summaries" in the left sidebar at:
http://www.cnrfc.noaa.gov/dec2005storms.php

- Martner

Posted by Status Editor at 07:40 PM | Permalink

Dry weather continues in northern California today and in the forecast for the next several days. No crew deployments are likely for the next few days.

ESRL/GSD is considering changes to their high-resolution model products. See the description below by Chris Anderson. If you have concerns or want to encourage one of the change options, please contact Chris by e-mail (christopher.j.anderson@noaa.gov).

- Martner

--- Proposed changes for ESRL/GSD's high-rez model products ----
First, it appears to us that the 1-km and 3-km grids are redundant. By
removing the 1-km grid, it greatly reduces the strain on our computing
resources. Second, we heard during the forecast discussion that
forecasters may like a longer forecast period. I am running some tests
during the current dry period, and I have found we can keep the same 3-hourly
update cycle and run a 48-hour forecast period.

Here's a list of things we could do if we drop the 1-km grid:
(1) Run the forecasts out to 48 hours
(2) Update the 12-hour forecasts as frequently as hourly rather than the
current 3-hour cycle
(3) Add the NMM

We couldn't do all of these things, but in some cases we could do more
than one of the items listed above.

- Anderson

Posted by Status Editor at 07:40 PM | Permalink

Dry weather is forecast for all of California for the next several days. The next slim chance of precip is seen for the coming weekend (Feb. 11). See "Forecast" for the dry details. No crew deployments are likely in the next few days.

- Martner

Posted by Status Editor at 07:37 PM | Permalink

All the forecast models indicate dry weather should prevail in the ARB for the next several days. Therefore, no crew deployments are expected for the next few days. Daily conference calls and updates will continue as usual, however, in case things take an unexpected turn toward storminess.

- Martner

Posted by Status Editor at 07:39 PM | Permalink

IOP-11 will end at 21 UTC (1 p.m. PST) today with the final Sloughhouse sounding. The research radars collected data from approximately 11 to 20 UTC today. The anticipated cold front reached the ARB a little later than forecast and with less vigor than we had hoped. The HMT guages show rain accumulations of about 0.7" at Blue Canyon (just about what the NWS predicted), 0.8" at Foresthill, 0.5" at Colfax, 0.4" at Auburn. Thre was less than 0.1" in the Central Valley. The best FROPA signature was at Foresthill with a good pressure check, wind shift, and onset of rain around 14 UTC this morning. Overall, this was not a stellar weather case for HMT.

The reserach radar crews are now released and will head for home when they can.

A big ridge is building in behind today's front and the outlook is for dry weather for all of the upcoming week. Nevertheless, the daily conference calls will continue, as usual.

- Martner

Posted by Status Editor at 07:44 PM | Permalink

IOP-11 is underway with soudings form Slough House and the research radars scanning, as a band of rain moves into the ARB. The band, which arrived later than expected, is oriented NE-SW and does not appear to be particularly intense yet. The system may evolve into orographic precip before clearing out this afternoon.

- Martner

Posted by Status Editor at 02:31 PM | Permalink

A vigorous cold front over the eastern Pacific is heading for northern Cailfornia. It is expected to move through the ARB quickly tomorrow. HPC is forecasting just over an inch of precip. The storm also has the possibility of producing a potent narrow cold frontal rainband with strong winds. HMT will conduct IOP-11 on this storm.

The IOP will begin at 03 UTC Saturday (7 pm Friday night) with the first of 7 Slough House soundings, starting ahead of the first rain there. No supplemental soundings are requested from OAK. The X-pol and SMART-R radar crews should be ready to begin collecting data by late tonight - nominally at 1 a.m. PST. However, they can fine-tune a more appropriate start time based on the regional NEXRAD images. The cold front is predicted to reach the ARB around 12 UTC (4 a.m. PST) Saturday. Heaviest precip will be from 12 to 18 UTC. Abrupt clearing should begin around 20 UTC.

Radar crews will return to their home bases on Sunday. Next week promises to be a dry one.

- Martner

Posted by Status Editor at 08:45 PM | Permalink

IOP-10 will end at 20 UTC (noon, PST) today. Blue Canyon received a little over 2 inches of rain, Foresthill had 1.8 inches and Auburn 1.1 inches. Oakalnd supplemental sondes covered 24 hours during the heart of the storm. Slough House soundings only included 00 - 09 UTC today. Both scanning research radars covered the entire event wihout any down time, and all (or neraly all) of the unattended HMT instruments worked fine. This storm caused the largest bump on the hydrographs since New Years. Overall, it was another good case for the project. Forecasters correctly sided with the wetter NAM model, which turned out to be the correct one.

The next storm is expecteed to arrive Friday night and last into Saturday afternoon. The NAM has it looking stronger than we thought yesterday, but again the brunt of the storm will be north of our area. QPF ranges from 3/4 to 1.5 inches. Because the radar crew are already on site, we will keep them there, at least one more day, for the possibility of working that storm, although it is below our deployment threshold for sending crews out to California. A decision on whether the Saturday storm warrants an IOP will be made at tomorrow's conference call. Meanwhile radar crews should be prepared to work a storm from Friday night into Saturday afternoon. Dave White will try to line up students for the possibility of launching sondes over this preiod too. No supplemental soundings will be requested from Oakland, however.

- Martner

Posted by Status Editor at 07:50 PM | Permalink

IOP-10 continues. Orographic echo still clings to the project area, although it is looking ragged this morning. The rain accumulations for the event so far include 1.77 inches (ALERT gauge) and 1.98 inches (HMT gauge) at Blue Canyon, 1.70 inches at Forest Hill, and 1.04 inches at Auburn. Showers are forecast through this morning. Radar crews should continue collecting data at least until the conference call today.

This afternoon and Friday should be dry, but the Saturday storm is looking somewhat stronger now, especially in the Eta model, and will be the main topic of today's call. Radar crews should be prepared for the possibility (although not probable) of staying on for that event.

HMT's Forest Hill (FHL) met station and soil condition station are on-line on the project Web page.
Ground hog saw its shadow in PA this morning.

- Martner

Posted by Status Editor at 01:18 PM | Permalink

IOP-10 is underway. It began at 12 UTC (4 am PST) this morning with both research radars scanning and collecting data. However, the storm is rather tardy getting into the project area. Precipitation began at Blue Canyon around 6 am this morning and has now accumulated only about 1/4 inch there. Nevertheless, forecasters still expect better intensities are forthcoming, with the heaviest precip starting late this afternoon and continuing over night. The radar crews should plan on continuing operations at least to sunrise tomorrow. We will stick with the original schedule for the Oakland supplemental soundings (15 UTC, 1FEB - 09 UTC, 2FEB). Sounidngs by the students at Slough House, unfortunately will only cover the latter part of this period, starting at 00 UTC this afternoon (thanks to many mid-term exams). The wind profiler at Slough House is back in business.

The great disparity between the NAM (formerly Eta) and other models, such as the GFS, which predicted far less precip, is something to ponder as we learn tomorrow which ones got the forecast for this mid-week storm right or wrong. Today, they are finally getting closer to agreement.

The next storm is still scheduled for Saturday and still looks weak.

- Martner

Posted by Status Editor at 07:50 PM | Permalink

IOP-10 began at 12 UTC this morning with the commencement of data collection by both scanning research radars. Precipitation has not yet begun in the ARB, but NEXRAD shows good echoes not far north of I-80. Oakland soundings start their 3-hour sequential series at 12 UTC also.

- Martner

Posted by Status Editor at 01:03 PM | Permalink