Both WPO and EPO to remain in negative phase this week providing a nice high latitude block to the Westerlies……Energy and cold air now pooling up over the mid latitudes of the Mid Pacific…..Upper Jet to make a Run for the West Coast later this week…..
Monday February 2, 2015
Posted at 9:49 am by Howard
Spoke with the King WX Dweeb T. Cylke this afternoon. He gave me some kind words of advice. Never trust a warm storm of subtropical origin such as this one, in trying to predict snow levels. Why? Because of Micro Physical processes that can allow snow to fall at unusually low levels. This morning’s WX discussion from WSFO forecaster Wallman mentioned that there is an isothermal between 10K and 6500. ISO thermal layers can allow snow to fall to much lower elevations as the temperature in this case could become trapped near freezing through the layer. This would have the result of allowing wet snowflakes to fall to much lower elevation then expected.
The point is “All bet off on the snow level”…….Just know that it will be rising and falling a lot this weekend….
Additionally, I am “Out Voted” on the term Pineapple Express. Although “I do not agree” that this particular event is the colloquially known pattern of the Pineapple Express, in other words this particular version of an AR. Two noted and respectable Meteorologists disagree…..So I yield……;-)
Wednesday AM Update:
Some positive information coming out from the CRFC this morning. It appears that most of the precipitation over this region will be occurring Friday night into Saturday during a colder period of time. The SL is usually about 500 feet lower at night and the cool sector is in with the first wave Saturday. So we should get a nice shot of snowfall on Mammoth Mt Friday Night into Saturday afternoon. The snow level looks low enough for some 2 to 5 inches of accumulation in town near and above 8000 feet with last night’s guidance. There looks to be a break Saturday night through Sunday afternoon with only light showers in the forecast. That is certainly good news as the Freezing level goes up Saturday night and especially into Sunday to 10,500 feet. But little precipitation is expected. The next wave moves in Sunday evening and between the evening and midnight the freezing level is at or little above 10,000. So rain is likely Sunday night in town until midnight. The snow level is above 8500 to about 9K with rapidly lowering snow levels after midnight and into Monday AM. I expect 3 to 6 inches in town by Monday Noon at the Village by this 2nd wave. Mammoth Mt will have 1 to 2 feet of sierra cement above 9,000ft. by Monday Noon storm total. All in time for the Presidents Holiday weekend!!!!!
We ridge up again later next week as the high latitude block retrogrades and weakens. However, during weeks 3 ands 4 according to the CFSv2 Weekly Climate Anomalies, high latitude blocking returns to both the EPO and WPO region as they turn negative of sign. Thus more undercutting of the East Asian Jet is expected along with its extension to the west coast. At the moment, total precipitation for the month of February is expected to be 125% of normal. This is considering this weekends storm as well as the storms expected during the 2nd half of February. Based upon the same models temperature anomalies, it has been indicated that the last week of February will be below normal in temperature. That below normal temperature anomaly is expected to extend into the first 10 days of March. At the moment, March is expected to be 160% of normal precip wise.
It is interesting to note that during that 1st ten-day period, the emphases in the model as far as precip shows that a higher percentage of normal is expected from the sierra crest to the Nevada border. May the model be suggesting a Tonopah Low during the 1st 10 days of March? The Model continues wet through the 20th with rising temps between the 10th and the 20th. Please keep in mind that this is not a forecast. It is an outlook. There is a difference!
Tuesday AM Update:
The town is buzzing with weather rumors so I’ll give you all the straight scoop! First of all this not a Pineapple Connection or Pineapple Express. Those are specific patterns that combine specific anomalies across the northern pacific. You may very well read or hear about this being a pineapple express. However that term does not apply here. However, this is an “AR” event, or formally an atmospheric river event. Here is the difference, all pineapple expresses are AR events, however, not all AR events are Pineapple Expresses.
I can go into and explain the pattern of a Pineapple Express, but I will save that for another time.
An “AR” event is one in which contains specific criteria of PWAT for its terminology. PWAT or Precipitable Water is simply the depth of water in a column of the atmosphere, if all the water in that column were precipitated as rain. It is a factor in how much precipitation is expected within a time frame of a storm. The “AR” is a stretch of moisture that extends some distance off the west coast, and in this example, that contains at least the criteria of an AR via PWAT.
Tuesday AM Update:
CRFC came out this morning with a whopping 3.37 inches of water between this Friday and Monday AM. Keep in mind that this moisture is still coming through the west coast ridge so it is warm. Nevertheless, it is expected to reach the Sierra and slightly beyond. The Desert areas for the most part will be shadowed out like Nevada and Bishop. But at least it is something that will insure much better ski conditions for Mammoth Mt for the Presidents holiday. Snow levels will be high throughout the storms…But will vary.
In the beginning on Friday, as moisture increases, there will be a cooling effect due to the drier air and low dew point. As the air mass juice’s up, the snow level will rise. And, depending how saturated the air mass becomes locally, and where the freezing level is, will govern the snow level. By the fact that CRFC is painting over 3 inches of water, it appears that the air mass will become very saturated at times. So there maybe times that it will rain all the way to the top and times when it will snow down 7K or 8K. Typically, the snow level in a normal storm is 1,000 to 1500 feet below the freezing level. However, when the air is totally saturated, it can equal the Freezing Level. So variable amounts of moisture, (RH at the 700MB), relative to the freezing level will for the most part determine the snow level. The good news is the on Saturday when the freezing level is really high, the QPF that day is low.
Here are the freezing levels for Yosemite by 6 hour increments expected Friday through Monday AM. Courtesy of CRFC-You make the call! 😉 10.4 = 10,400ft etc
Friday>>> Sat>>> Sun>>>> Mon 10.4/ 10.0/ 9.8/ 9.5/ 10.3/ 11.1/ 11.9/ 11.1/ 10.9/ 10.2/ 9.9/ 8.8 10am 4pm 10pm 4am 10am 4pm 10pm 4am 10am 4pm 10pm 4am
So the best chance of lower elevation snows would be early Saturday AM around 4:00am and again especially (Sunday Night into Monday AM)
We could see between 1 and 2 feet above 10K by Monday AM
As highlighted above, the WPO (Western Pacific Oscillation) and EPO Eastern Pacific Oscillation are now both in the Negative mode, providing a block over the high Latts between the Gulf of AK and Eastern Siberia. This in effect forces Upper Jet energy to “Under Cut” this block. This favors an “AR” event for Northern CA northward. Additionally, this is well supported by the MJO as it moves into phase 8 next weekend. The block is “retrogressive” and so heights will again begin to fall in the EPO area then WPO area leading to the strengthening of the West Coast ridge week 2.
While the eastern pacific/far western ridge continues to reign over the Golden State, there is now hope for heavy precipitation for at least Northern CA; The Wine Country Northward. For the Sierra, the story is the same temperatures wise as this pattern also keeps heights in the mean, very high over most of the state. This spells out for the most part, high elevation snow as 500MB heights in the mean remain well above 570DM over Mammoth Lakes. Considerations for the snow level are; the time of day, IE the timing of the waves either day or night. (SL) +/-500 feet. How saturated the air mass is over Mammoth. A fully saturated air mass can keep the snow level very close to the freezing level barring any mico-physical processes. Where as usually the snow level can range from for 1000ft to 1500 feet below the freezing level. Although it is possible there may be a few waves that lower the snow level + or – of 8000 feet. The freezing level is expected to range up and down of 700MB (10K ft) next weekend. So the snow level will probably average about 9,000 feet next weekend. Latest CRFC shows the freezing level coming down Friday Night about Midnight to 9400. That could drop the snow level to between 8K to 85K. May be a few inches piling up just above the Village by Saturday AM. Beyond that wave that finishes through Saturday, the 12Z ECMWF has another large plume of moisture at 700mb moving in Sunday about 12:00 Noon into Monday. I am not sure what to make of it as the GFS does not show it at all…..
So the ridge is not going away anytime soon, it is just being forced to flatten and shift a bit east as a result of the Strong Upper Jet. At this time, the Southern 3rd of the state looks to stay out of the precipitation. Although it is a bit early to forecast amounts of snowfall, best guesses for this time frame is that Mammoth Mt could pick up a good foot of heavy wet snow next weekend at and above 10K Ft. with 6 inches or so at the Main Lodge Friday/Night. The Dweebs will fine tune later this week. No doubt amounts will range up and down depending upon which model you look at. The following week looks dry up to the 15th but there is still that question about the ECMWF for Sunday afternoon into Monday.
As mentioned in the last discussion, precipitation is expected to come back to the high county along with much cooler temperatures later in the month of February and into March. Although there is no real defined period of time that it will begin with any confidence, the last week of February looks to me to be of best interest…..
Update: 5:10PM Monday:
New 02z run ECMWF EPS Weeklies shows a change beginning “the end” of the 3rd week of February. It shows retrogression of the Eastern Pacific High and a cold pattern setting up over the far-west the last week of February.
Will update later this week………………………….
Dr Howard and the Dweebs…………………………:-)
Mostly Cloudy Skies to give way to Sunshine Saturday…..Gusty North to NE winds are expected over the crest with light breezes else ware……Dry weather is expected through Mid Week……A chance of high elevation snow next weekend…..
Friday January 30, 2015
Posted at 9:23 am by Howard
Some changes are taking place out of the central pacific that over time may affect Northern CA and the Pacific NW. There is a large cyclonic gyre (Long Wave Trof) that has developed north of Hawaiian Islands that is for the time being a part of the REX block associated with the -WPO. For the time being The system is just a large REX. However, by week 2 the GFS model shows the Arctic opening up with cross polar flow into the Central Pacific. The pattern suggest a major “AR” event for the Pacific Northwest south to Northern CA by Next weekend. If the Baroclinic Zone gets into Central CA, we cold get rain and high elevation snow. The chance of that looks around next Saturday the 7th of February. The west coast ridge is still there…however, the jet energy is so strong, it dampens it pretty good. As a side note, the MJO is in phase 8 which lends interseasonal support to this notion. Just as a side note, a shift of just 100 – 150 miles south would make a huge difference in precip amounts for Central and Northern CA next weekend.
The Dweebs have done a researching this morning looking at several climate models for the next three months. The consensus is that it will be wetter then normal for the period February-March-April. Looking at the Multiple Model Ensemble which combines all the Climate models as an average;
See: http://www.cpc.ncep.noaa.gov/products/NMME/current/images/NMME_ensemble_prate_us_season1.png (For precipitation)
See: http://www.cpc.ncep.noaa.gov/products/NMME/prob/images/prob_ensemble_prate_us_season1.png (For probability)
Additionally, it looks like the PDO will remain in the positive phase for some time now. Which usually coincides with warmer than normal SSTA for the California Coast.
And….according to the last Scripps update early this month, EL Nino conditions may make another run for it again next fall.
The Dweebs had a good look at all this mornings guidance and they still are singing the same tune, as the ever resilient ridge keeps its grip upon California. Although there is no formal consensus on, or explanation why the west coast ridge has been so persistent on the time scale as such, our 6 to 10 day outlook continues to show a persistent ridge over the far west.
Water wise, the information from DWP shows that there is “about” the same amount of water in the snow up on Mammoth Pass as there was last year at this time. However, last years data showed that it begin to increase in early February, where our current 6 to 10 day outlook continues to be dry. It should be noted that at this time, the confidence level in yesterdays 6 to 10 outlook was at 80% as compared to the 8 to 14 day outlook the same time which was indicated to be only 40%. This may mean that there is possibly of a transition going to happen around the middle of the month of February which coincidently goes along with the 21 day cycle. So sometime around the 11th or 12th there could be a pattern change. However, remember that we can always go from one dry pattern to the next and that has been happening during that last two transitions. I am referring to the transition of the 1st of January and again about the 21st. The 21 day cycle was brought to my attention by a former Lead forecaster of the NWS over 10 years ago and I think that it may have been related to the Late Meteorologist, Ernest Hovmuller’s time scale work.
Although, the drought producing system continues to be a strong one that has its grip upon CA, I still expect it to break during the 2nd half of February, with a good chance of significant precipitation before month’s end and into March. This is based upon a current consensus among the various climate models.
Dr Howard and the Dweebs………………………..:-)
Subtropical Moisture Associated with a Rex Block Pattern will stream in later today and tonight with a chance of Snow Showers Thursday through Friday…….Expect a Partly Cloudy Weekend into Next Week
Wednesday January 28, 2015
Posted at 9:17 am by Howard
More light showers are possible the next two days as a weak subtropical baggy trof spreads mainly high clouds throughout CA. …..The snow level will range from 6500 to 7,000 Ft. No significant accumulation expected. The weekend outlook for Saturday and Sunday shows Gusty Ridge Top winds as an upper ridge builds in. Winds will initially blow out of the NE, then back from the north Sunday. It will be breezy as well over the Valleys of Mono County where there are north/south orientated valleys. As the upper ridge at 500mb build over CA, temperatures will warm again over the CA State next week.
The REX Block Morphs back to a full latitude ridge over the far west as a Positive PNA pattern strengthens at the same time. Although the Daily Runs of the various longer range models show phantom systems both approaching and moving through the mean ridge position or in inside slider fashion, they should for the most part be discounted, from bringing any meaningful precipitation to CA. The next transition based upon the 21 day cycle will be more toward the middle of February.
Dr Howard and the Dweebs………………………………….:-)
Although the pattern has changed a bit from earlier in January, showing more of a REX Block, IE A coupled Upper High with an Upper Low to its south, the pattern is still a dry one for the Eastern Sierra. The biggest indice that stands out the most is the super strong positive PDO teleconnection which hit a record high of 2.51 last December. I expect that this teleconnection will prove to be very high again for January. One part of the +PDO is warm water along the west coast. Warm water along the west coast is, at the least, supporting other teleconnections in keeping an upper ridge extremely strong over the far west. This indice probably has its greatest effect over the Northern Hemisphere during the darkest months, like Mid Nov, through Mid Feb. I would expect that as the days get longer and the Sun gets higher in the sky, later in February and March that the system of teleconnections that are responsible for the dry pattern over the state will break up as we head toward Spring and Spring itself for at least some badly needed precipitation.
For those that want to read a Paleoclimate study on the Climate of CA, here is a good study and link. This study does offer an insight to past climate here in the eastern sierra. http://www.waterboards.ca.gov/waterrights/water_issues/programs/bay_delta/deltaflow/docs/exhibits/ccwd/spprt_docs/ccwd_malamud_roam_etal_2006.pdf
In reading through the dissertation, it makes reference to the affects of the little ice age and its effects on the Eastern Sierra. It was noted that during the 17th and 18th century that the Eastern Sierra as well as the Great Basin turned especially cooler and wetter. As a side note, the Little Ice Age was associated with the Maunder Minimum, in which was a period of time with either very low or none existent Sunspot Activity. This went on for about 80 years.
Coincidently, we are currently going through a solar hibernation according to David Archibald, a solar scientist. As we come off of the double peak over the past few years, it may be that over the next few years, the eastern sierra actually goes through a period of greater moisture and cooling, if sunspots indeed disappear later in the current cycle 24. The Dweebs will give it another 2 to 3 years to see if we turn extra wet again. This maybe wishful thinking, but it is worth noting! 😉
Expect A chance of showers Thursday thru Friday with little accumulation of new snowfall. Highs in Mammoth will be in the 40s reaching low 50s by this Sunday. Night time lows mostly in the 20s. Will update weather for the next week this weekend.
Dr Howard and the Dweebs…………………..:-)