Strong Cold Windy System on the Way…..Batten down the Hot Tub Covers Soon……Light Snowfall Begins after Midnight tonight with Light Snow Monday through the Night…Fair weather returns Wednesday through Sunday with Another System Worth Watching for the following Sunday………
Sunday October 27, 2013
Posted at 10:48 am by Howard
Regarding the MJO’s support for a pattern change later next week. The MJO is weak and not expected to provide modulation to the westerly’s.
However, both the ECMWF and GFS ensemble runs have a strengthening signal indicated in them. According to the CPC, this is due to other modes of tropical variability.
Longer range GFS week 2 proggs are consistent in a stormy period the 2nd half of next week while little in the way of precipitation is shown for the Sierra by the ECMWF through 360 hours.
5:45AM Tuesday Update:
Upper low over north central NV will begin to exit later today. As it does one last vort center will sweep SSW across Eastern Ca, combining with 700mb RH of 70%+ for some upslope conditions this afternoon on the eastern slopes of the sierra. So expect a few more inches of snow today….
By tonight, the system should be into Utah as 500MB heights rise over California drying us out and warming us up. Longer range models still looking very good for a series of storms with positive tilt systems entraining possibly subtropical moisture later next week. As mentioned before, the MJO is expected to become more active from it currently inactive state. NCEP Global forecast Ensembles has a strong intrusion in the phase 1 region later next week…should it more to phase 2…that would be quite favorable for storminess climo wise. Blocking over AK is still in the cards late next week. PS the ECM is not nearly as bullish….
This was a storm that exceeded everyone’s expectations. Including, The NWS, The Dweebs and all the weather weenies I know!
But who cares! The mountain picked up about a foot. Near the village, 8 to 10 inches fell and even over the lower elevations of town about 6 inches. What happened??? The Dweebs could not follow on a hour by hour bases, but this morning about 9:00am a rather intense band of precipitation developed over the central part of Mono County around Bridgeport. It slowed and it was S to S+ for about three hours. About 6 inches fell in a 6 hour period. Mother Nature can make one quite humble when she decides to. The 00z Monday ECMWF had precipitation over the Mono County Crest only up to a 1/2 inch of QPF.
Where do we go from here?
The current upper low is spinning over Central NV with the low at 700mb over northern NV. The upper jet is still off shore. No doubt more showers will continue to circulate around the upper center… Later Radar from SFO has a band that is up over Reno that will most likely slide down our way in the northerly flow. So a few more inches of snowfall is certainly possibly over night. Actually, until the upper center moves out of NV we will have the chance of showers as a lot of moisture has been brought into this system from the off shore jet that is still doing its thing! A few more inches is possible over night. All models purge the upper low out of the Great Basin by Wednesday. There after, a renewed period of fair weather is expected with a warm up into the 50s. All Hallows Eve still looks fair.
If you read my mornings discussion in the outlook, it still portrays the longer range. IE the period of the second half of next week….It looks stormy!!
Dr Howard and the Dweebs……………………….:-)
Monday Morning Update:
The past few days, the Dweebs believed that the ECMWF was over done on its precipitation for today. As of 9:00AM It looks like it is going to pan out with some 6 to 7+ inches of snow at the Plot at 9,000 ft Temperatures are in the low 20s and so SNOW TO WATER RATIOS ARE HIGH. The heaviest snowfall will be confined to the morning. So showery weather will occur this afternoon and evening with lighter accumulations.
Western Hemispheric Pattern according to the Climatic Prediction Center trends strongly toward a positive NAO and Negative PNA. This coincides with strongest storm to hit British Isles in 10 years. With a Positive NAO, lower pressures is found in the polar regions with polar jet retracting and consolidating northward into north Atlantic. This results in milder temps for east coast and stormy conditions in England.
At the sametime…..the PNA forecast is to become more negative with time with high latitude blocking in North Pacific (Alaska) and deepening troughs over Western US. Surface low deepening in Western Pacific beginning 00z 30th with amplification energy (Hovmoller) reaching west coast around 00z Nov 3rd Sat PM. There is good model consensus among medium range models and ensembles with this trough moving into Western US this weekend. However, at the moment, the deterministic runs of todays ECMWF and GFS make for a low confidence forecast precip wise….IE not enough confidence to mention precipitation for next weekend……just cooling for Sunday. However that my change…….
More importantly…..GFS through 384 hours hemispheric loop shows high latitude blocking in Northern Pacific and digging troughs (negative anomalies) over Western US. This should be reflected in a more negative PNA over the far west Week 2.
UPSHOT…..Odds increasing for a series of central west coast storms as high latitude blocking north of Alaska with time suppresses the polar Jet with a split and strong southern branch effecting mainly central and southern California with time.
MJO Tropical Forcing is expected settle into Phase spaces 1 and 2 later this week. This supports west coast storm track Week two.
Dr Howard and the Dweebs……………………….:-)
Sunday AM Updaters
No changes this morning except to tweak the timing a bit and to highlight a windier system.
The Blended QPF is still about a half-inch in the vicinity of Mammoth Mt. So 1 to 3 inches seems good for the Town of Mammoth and between 3 inches and as much as 5 or 6 inches over the crest and in the bowls. For Mammoth Mt, this is not a system that has a favorable Orographical component to it like other areas both north and south where amounts will be greater.
Snowmaking will benefit greatly from the cold air in the system with 700mb temps down to -5C by 1:00AM Monday then cooling to -8C by 8:00AM Monday. In fact the new 12z Sunday NAM has at least -7C at 700MB (10,000ft) through Tuesday at 8:00am. Clifford, you’ll really be able to spray it on the first half of the new week!! Although temperatures begin to moderate upwards on Wednesday with the 0C line back over us by Wednesday afternoon…..Snowmaking remains favorable throughout most of the day Wednesday, and of course into the night……
Timing of the system appears to be quicker now with the cold front blowing through our area before Sunrise Monday. Most of the precipitation will occur behind the front. However, most of the wind will occur before the front. So it would be very wise to tie down those hot tub covers now!
Daytime highs in Mammoth Monday will be difficult to move above freezing at elevations above 8,000ft. There appears to be a pretty strong band of precip developing behind the front. For the time being it is not expected to stay strong enough this far south to change the QPF for our area.
The outlook looks Dry Wednesday through the end of the week. High temps moving back into the 50s by Friday with flat ridging spreading over our area for All Hallows Eve so keep a candle in Jacko to keep him warm for that night.
The Weekend will be fair with seasonal temps in the 50s for the days and 20s at night.
There is another weather system that will affect our area possible as early as the following Monday/Ngt. The ECMWF has it coming in as a Trough from the west that would bring addition snowfall to our area. However the GFS model has it as an inside slider which is typically dry. Although the Westerly’s are gaining strength now with the jet stronger and pushing further south…….It is too soon to plan on more naturel snow. As always stay tuned…..the Dweebs have you covered………………..
Dr Howard and the Dweebs………………………:-)
The last weekend in October to finish off on a warm note with increasing winds Sunday night leading to snowfall by Mid morning Monday……Forecast Models agreeing on a more westerly trek now with Signifacant Accumulations fo the Sierra Monday into Tuesday night…..
Saturday October 26, 2013
Posted at 8:53 am by Howard
Models have come around to the thinking of the ECMWF (European model) that the system will take a more westerly trek with the upper jet enough off shore, allowing the Front Rt exit region to do its magic by providing lift and vorticity over and near the coastal waters of the far eastern pacific. This bodes well for more significant accumulations now for the Sierra with a good 3 to 6 inches possible beginning Monday morning through Tuesday night. The new 12z NAM shows a slowing of the system over California, which if correct would keep the showers going possibly into Wednesday AM over the Southern Sierra. So the Dweebs are predicting 3 to 6 inches over the upper elevations beginning Monday AM through Tuesday night. The snow level will begin about 8500 but lower rapidly Monday to 5000ft.
It is likely that Tioga and Sonora passes will close early Monday AM…so visitors in the eastern sierra plan accordingly….
Dr Howard and the Dweebs……………………..:-)
Today’s Weather Glossary Term:
ACE Index: Accumulated Cyclone Energy Index. The measure of total seasonal activity used by NOAA. It is a wind energy index that is defined as the squares of the maximum sustained surface wind speed, in knots, measured every 6 hours for all named storms while they are at least tropical storm strength. The ACE index is combined with the seasonal total number of named storms, hurricanes, and major hurricanes to categorize a hurricane season as being above normal, near normal, or below normal. The 1950-2000 seasonal average for ACE in the Atlantic Basin is 96.
October to Turn Colder Next Week as Western Canadian Short Wave Digs into Western Great Basin bringing a few inches of snow over the upper elevations of the Central Sierra…..Between today and the rest of the week enjoy Mammoth’s Excellent Indian Summer Weather!
Thursday October 24, 2013
Posted at 5:18 am by Howard
Models have come around to the thinking of the ECMWF (European model) that the system will take a more westerly trek with the upper jet off shore and allowing the Front Rt exit region to do its magic by providing lift and vorticity over and near the coastal waters of the far eastern pacific. This bodes well for more significant accumulations now for the Sierra with a good 3 to 6 inches possible beginning Monday morning through Tuesday night. The new 12z NAM shows a slowing of the system over California, which if correct would keep the showers going possibly into Wednesday AM over the Southern Sierra. So the Dweebs are predicting 3 to 6 inches over the upper elevations beginning Monday AM through Tuesday night. The snow level will begin about 8500 but lower rapidly Monday to 5000ft.
It is likely that Tioga and Senora passes will close early Monday AM…so visitors in the eastern sierra plan accordingly….
Dr Howard and the Dweebs……………………..:-)
ECMWF has been the most consistent the past 3 runs showing the upper center of the 500mb geopotential heights centered near Susanville 5:00am Monday with the upper jet off the west coast. The GFS is now trending in that direction with the upper jet axis forecasted last night to be along the NV/CA border Monday and with this afternoons run, it is displaced west over the Sacramento valley. This is the compromise that the dweebs believed would happen. However…what may happen if it digs even further west like the ECMWF…..??? The 12z ECMWF puts the bull’s-eye back over Mammoth Lakes….
Update in the AM….
Stay Tuned…….Were almost 48 hours away>>>>>>
Latest guidance once again has gone there separate ways with the 00z run of the GFS centered near the NE Nevada Border and Southern Idaho Tuesday afternoon, while on the ECMWF, the Center swings SE from North of Tahoe Tuesday AM and is near Bishop, Ca by Tuesday at 5:00pm. This is the main reason why the big differences in precipitation for the Central Sierra Eastern Slopes, whereby the GFS model has a few snow showers and the ECMWF has a Solid 6 inches in some areas. In fact in the Tahoe area, it forecasts about an inch of Water EQ on the west side over the crest. That’s about 10 to 12 inches of snow. So here we are Friday morning with still……A low confidence forecast for snowfall for the Monday night/Tuesday period.
What do the Dweebs think? I think that there are enough short term ECMWF ENSEMBLE Runs to argue against the greater odds of the GFS for it being totally Dry.
Thus a compromise between the two……1 to 3 inches for that time frame. If there is much more…the EC was correct. If little or nothing accumulates, the GFS was correct. In that the 12z Friday GFS was not available at the time of this discussion, I will update if necessary.
As another point not mentioned above, I took a quick look at the 200 MB Potential Heights for 00z Tuesday from last nights run of the ECMWF. The Front Right Exit region is clearly off shore. The nose of the upper jet “is off the Central Ca coast”. This is the reason why the EC is so much wetter then the GFS.
Dweebs will update later today.
Remember……………Forecast models are not perfect……Just forgiven……………;-)
Dr Howard and the Dweebs……………………………………..:-)
Both EC and GFS are much closer this afternoon with a closed low over the Great Basin Monday night and Tuesday. So Snow Showers and light accumulation is expected. The EC is still in my estimation over done with well over 6 inches of snow for Mammoth Mt by Tuesday night. The GFS is still skimpy with maybe an inch.
More in the morning………………
Dr Howard and the Dweebs………………..:-)
The Dweebs had a look at the precip forecast from the deterministic 00z Thursday ECMWF for the area around Mammoth. It showed a total of .8 to .9 of an inch of QPF. This is very likely over done. It accomplishes this by a further west set up of the upper low between Mammoth and SFO Monday night. The GFS has only a trace (.01) within the same period of time. Its set up has the upper center over Central Idaho with the upper flow over land. Clearly, with the further westerly track of the deterministic ECMWF, there is more opportunity of the upper flow to get over water Tuesday and this is why it is wetter. However the ECMWF Ensembles is more like the GFS this mornings. So….Chances are that there will be a compromise with the upper center closer to the Sierra but to the east of it….still limiting the QPF. The GFS track is being favored by NWS as they only have a slight chance of snow showers at this time. Lets take a look out over the western pacific to see what is causing the Amplification up-stream…..
There are two tropical storms. One is a super typhoon. Both will become extra tropical and phase with the westerlies. This is what amplifies the down stream trof/ridge combo and drives the downstream short wave out of western Canada Sunday Night into Washington state. To the Dweebs…..The phasing of the TS’s looks constructive; IE ahead of the next upstream short wave coming off Asia. That would argue for more amplification and thus a track more toward the EC. Will Update in the AM.
Although little change in the weather under a ridge of high pressure is expected through weeks end…..Amplification of the eastern pacific ridge near 140West will bring a classic inside slider to the high country Monday through Tuesday night.
Temperatures will drop a good 20 degrees from current temps and along with the cold will come wind as well. Confidence in some light snowfall is increasing as the ECMWF model from last night run is now more or less in line with both the GEM and GFS. Therefore, expect snow showers to develop anytime after Monday afternoon. High temperatures will continue in the low 60s through Sunday then fall to the low 40s by Tuesday, Night time’s lows in the 30s will fall into the teens by Tuesday and into Wednesday AM. Thereafter, upper ridging will build back in for All Hallows Eve and continue into the first few days of November. So a return of fair weather with warmer temps expected for the end of October into early November.
Dr Howard and the Dweebs…………………………:-)