Archive for October, 2020

Beautiful Sunny Mild Days and chilly nights on tap through the Weekend…..Forecast models continue to hang on to the ENE flow a bit longer…..So Smoke to remain west for another day….MJO on the Move…..

10:40AM Saturday; All Hallows Eve

Mother Nature is giving us a nice day today as winds at 10,000ft (500MB) increased out of the ENE to 25MPH after 5:00AM this morning. Those ENE winds will continue today. This will give us a steller day with clear skys and warm temps by early afternoon. Winds will continue from the the east Sunday but will be much lighter and may give way to more terrain driven breezes. This may allow some haze to move back into the Mammoth area.  These are very subtle changes and may or may not allow any haze to return. By Monday and Tuesday, the upper high as depected by this mornings GFS is centered over the top of us. However, it is a flat ridge that will give way to increasing westerly flow by Friday.  Can’t rule out some haze next week depending upon the fires behavor.   As far as temperatures are concerned, sensibly, there is not expected to be any notable changes expected through Thursday, with highs in Mammoth in the low to mid 60s and lows at night in the 25 to 30 degree range. It is a dry 4 to 6 day outlook.

Windy weather will develop Friday morning as a vigorious cold front approaches. The Dweebs expect mainly light precipitation from this system Friday afternoon into Saturday with strong winds and colder temperatures. This is not expected to be a major precip producer, however, with another system Sunday, amounts may add up. More later on this….

MJO:

The Madden Julian Oscillation is expected to weaken substantually as it moves over the colder waters of the LA Nina Base state next week. So although it does proppagate through the Western Hemisphere, then out over the Indian Ocean, it is very questionable how strong the pattern change for the weekend will be as the MJO will lend little support.  More time is needed to see how it all develops. and how much snow we will get.  One thing is for sure, its convective envelope is likley to light up the Caribbean again and so Huirracane Zeta that hit New Orleans Wednesday, is not likley to be the last Hurracanne to affect The Caribbean in November!

 

Dr Howard and the Dweebs………………………..:-)

 

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4:30PM

Looking out at Mammoth Mountain late this afternoon. it is evident that something is going on over the higher flight levels. That is smoke folks. However it is at Flight levels of 250MB or about 36,000 feet.   Looking at the 250mb flight level charts, the winds are south westerly…While the winds at 700mb (10,000 ft) are East North Easterly. That is why we continue to be smoke free!  Tomorrows winds at 700MB are forecasted to really lighten up during the day. So do not be surprised when the smoke or haze rolls in again.  Sorry for the news, but we have had some great air quality. However, most likely, it will worsen during the day Friday.

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This mornings models runs seem to keep enough ENE flow at 700mb to keep the majority of the smoke to the west of the Crest today and “Possibly Friday” Now…..There seems to be variable periods of NE flow into Sunday. In between are the diurnal terrain driven breezes that can creep the smoke back over the crest into Mammoth.  So it may be that if we do get some haze or smoke,  it may not be a major problem, or like all the time over the weekend….Forecast indices light winds the next 7 days with above normal temps. Highs in Mammoth will be in the mid to upper 60s with lows between 33 and 25 degrees. The colder temps will be over the lowest elevations of town, just below the inversion.

MJO:

  1. Equatorial Rossby wave activity over the West Pacific, and increasing destructive interference with the La Niña base state may be playing a role in the slower evolution of the signal.
  2. Despite the recent slowdown of the intra-seasonal signal,  dynamical models continue to favor robust propagation of the MJO across the Pacific over the next two weeks. The GEFS brings the index to the Western Hemisphere by Week-2.
  3. Due to the ongoing destructive interference, confidence in robust MJO activity over the next two weeks is low; however, should the signal reach the Western Hemisphere, it could help bring about a pattern change from our currently dry pattern to at least some precipitation for California, between the 6th of November and the 12th. The GFS and ECMWF are just picking up on the pattern change for the week 2 period. However, with that said, there is no significant confidence at this time. The MJO will have to make it through the Central Pacific, in this case, the (DEAD ZONE) 160 East then hold together strong enough to modulate the Westerlies. Its forecast remains a moderate Phase 8 into 1, In Early to Mid-November.  There is a decent signal for precipitation in phase 8/1 (undercutting of the westerlies)  In January, this phase when strong can bring us those magnificent Pineapple Expresses. However, phases 2 and 3 (Indian Ocean) are by far the best phases to be in For Central CA this time of the year.  This is probably 3 weeks away.  See the teleconnections for the MJO precip to phase in November.
  4. SEE: https://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/Composites/Precipitation/

The Dweeber…….:-)

North East Wind Subsiding over the Crest Today….Might be a bit of haze Thursday….Friday into the Weekend looks a bit unhealthy Air Quality Wise….MJO Presenting some interesting possibilities….

As highlighted….Our NE winds are subsiding as high pressure from the west spreads into CA. At the sametime, the upper low over the Desert SW is moving east.  So the NE gredient weakens and terrain driven wind systems can allow the smoke and or haze to move back into the south county, as early as Thursday, but a better chance Friday and Saturday.  It is diffacult to say how much haze or smoke will return to Mammoth as lot will depend upon fire behavor. At the moment, the was still quite a bit of smoke moving WSW over the San Joaquin valley this morning.

Over all the forecast shows warming today with highs in the low to mid 60s at resort levels and 20s and 30s at night through the weekend. The weather pattern is dry through the 5th of November.

Although both the 6 to 10 and 8 to 14 day outlooks are dry for Mono County, there are some interesting developments in the MJO that “may have an affect on our dry weather pattern.  The MJO is an air sea coupled system that creates upper divergence and upper convergence as it travels eastward, Just north of the equator. The MJO can modulate the westerlies if strong enough. In November and through the Borial Spring, the MJO can contribute to some very benifical storminess for CA if in the right areas geographically. During the LA Nina base state, colder than normal SSTAs exist between 160E east to Central America. This base state of colder than normal sea surface temps inhibits convection. (lack of thunderstorms) This La Nina is regarded as moderate and possibly strong by the time we get to December.

The La Nina Base state can distructivly interfear with the MJO and can rapidly weaken it. This is important because of the signifacant precipitation events that the MJO usually contributes to each winter in California. A winter without a few MJO induced patterns can end up drier than normal to some extent.   That is why La Nina has a bias I think, for being drier than normal.  Since 1950, Moderate to Strong La Ninas accounted for 7 out of 11 years with normal to below normal precip for our region.  And the stronger the La Nina beyond moderate, the greater the odds of dryness in some studies.

Getting back to the MJO, the Phase Space, RMM 1 and 2 is showing a progression of an envelope of convection, from phase space 5 to 8, over the next two weeks. There is some some suggestion of a Phase Space 1 which is back over the Indian ocean, according to the GFS model. The ECMWF has a spurious signeture. IE there is something wrong with it. I need both to get confirmation; Otherwise,  I think we will have a pattern change from out of the west by mid month, (Nov) or a little sooner. This means that an envelope of tropical convection will move through the LA Nina region and eventually re-emerge over the indian ocean……”Possibly”   Why is that imp[ortant? The MJO over the Indian Ocean often teleconnects to a -PNA. (Trof in the mean over the far west or over the extream eastern pacific)

 

Stay Tuned!!

 

Dr Howard amnd the Dweebs………………………:-)

Mono Wind Event Set for the West Side of the Sierra Sunday Night…..Smoke to Begin Clearing Sunday Morning…However, Models are slower with NE flow developing…Now not untill this evening……Colder Weather Ahead…

Sunday 11:40AM

12Z WRF is slower to back the flow out of the NNE today.  The latest guidence pushes it back to between 5:00PM and 8PM Sunday tonight.   Good news is that once the NE flow sets in, It should be around through Wednesday Evening…

 

Looking at a cold night tonight with lows in town between 10 and 15 degrees.  For the most part, the Dweebs do not think it will be much colder, except for the lowest elevations in town, where the coldest air usually is.

 

Outlook is Dry Dry Dry!!!

The Dweeber…

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Saturday 1:00PM

Still Smoky in Mammoth with Hazardous Air Quality.   Air Quality expected to be greatly improved by Mid to Late Morning Sunday.

La Nina now expected to be Moderate to Strong this winter. Atmosphere over the Tropical Pacific has coupled to the cold phase. A Full Basin La Nina is forecasted to last all Winter.   Cold SSTAs now stretch from the Central American Coast to 160 East.   This will most likely confine The MJO’s strength to the Western Pacific,  as once it moves over the anomalously colder waters of Central Pacific, tropical forcing will tend to weaken rapidly, due to the cold La Nina base state with Destructive Phasing the most likely outcome. This pretty much keeps any significant modulating effect of the MJO of the westerlies, well short of where it needs to be to benefit California. So the MJO will be working against us this winter.  Although there are other teleconnections that can bring California Precip, the biggest events by far are usually MJO related.  As a result, many storms will be fighting a ridge resulting in Split Flow Blues for CA.   More Later…..

 

Dr Howard and the Dweebs…………………….:-)

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Mono Wind Event is a Katabatic, Down-Sloping winds much like a Santana Wind for Southern CA.   It does not have much effect on Mammoth Lakes other than to bring colder temps and in this case, to clean up our dirty air. Expect improving Air Quality late afternoon Saturday and into Saturday night with good air quality by 1200pm Sunday.   High temps that have been in the 60s will cool to the 50s on Sunday and upper 30s by Monday, low temperatures will be in the upper teens Monday AM.  This will be followed by a warm up Mid Week into the 60s again.

 

Long Range: No significant precip expected for the next two weeks…..

 

MONO Wind Event: (West Side)  From the NWS

What are Mono Winds? Mono Winds are a localized wind that blows across the western slopes of the central Sierra Nevada and into the foothills below from the northeast. The name Mono Winds was given to these winds because they blew into the central Sierra Nevada from the direction of Mono Lake. The word “Mono” was derived from a Native American tribe who once resided in the area. Mono Winds are strong winds that blow downhill across the western slopes of the Central Sierra Nevada from the northeast. In an ideal atmospheric pattern, air moving from the northeast and flows up and over the high peaks of the Sierra Nevada. As this air rushes several thousand feet downhill, it increases in speed and also dries out. The rugged topography of the Sierra Nevada also causes the air to be funneled through tight spaces which further increases its speed. This results in winds that can reach speeds of 50 mph or more. Mono Winds form when an area of high pressure sets up over the Great Basin. Air flows in a clockwise direction around high pressure. In some situations, the air is “squeezed” better than others because of the differences in pressure in the atmosphere. The more air is squeezed, the faster it blows.

In a typical Mono Wind event, winds reach speeds of at least 50 mph while stronger events can see winds exceed 100 mph! A common set-up in the atmosphere for a Mono Wind event shows a high pressure system over the Great Basin and the direction in which air flows around it. The strength of Mono Winds is also determined by the jetstream, which is the band of winds several thousand feet above the surface of the earth. When the winds in the jetstream are in the same direction as the winds closer to the surface of the earth they can “mix down” or more easily and be transported towards the ground. This enables the very strong and powerful winds that typically blow well above the surface of the earth towards the ground. Jetstream winds are often in excess of 80 to 100 mph at over 20,000 feet in the atmosphere. In ideal situations, these winds speeds will be felt by you (or anything else) on the ground.

Mono Winds are part of a family of winds that known in technical meteorological terms as katabatic winds. The term katabatic winds originates from the Greek Word katabatikos which means “going downhill”. In the case of Mono Winds, air is blowing down the mountains of the Sierra Nevada. Many people who have heard of Santa Ana winds are familiar with how these winds also blow downhill. However, while Santa Ana winds can reach speeds of 50 mph or greater easily, they differ from Mono Winds in that they are winds that rapidly heat up as air descends downhill. Mono Winds conversely are cold wind. They typically form just after a cold front has passed through the region and temperatures have dropped off significantly. Santa Ana winds, owing to their warm, dry state are part of a family of winds known as foehn winds. Foehn winds are winds that are forced down a hill and warm as they do so.

In California, the Santa Ana is the most well-known type, and is the name given to a foehn wind in Southern California. However, other parts of California can experience foehn winds. In the Santa Barbara area, foehn winds are known as sundowner while in the Bay Area, they are known as Diablo winds. Foehn winds are known for bringing a high fire danger with them because of their hot, dry nature. In the case of Mono Winds, the cooler state of the air mass helps to allow for “higher” humidity values. However, because of the speed of the winds, they can still help to spread fires. With the exception of a sundowner, Mono Winds as well as Santa Ana winds and Diablo winds typically occur in the cool season months from October through April due to the seasonal variations in weather patterns.