Archive for January, 2011

No Change In The Current +Phase PNA Pattern Across The Western Hemisphere….Small Feature May Give The Sierra Some Snow Showers Weeks End

+Phase PNA all the way….That is about all that I can say…..Today.

Actually;

Not a lot of excitement out over the far west. The little feature coming in Saturday night into Sunday would be regarded as nuisance weather a few weeks ago. Today it is big news, as if it comes in like like last nights 06z GFS and this mornings 12z ….it might bring in some snow showers Sunday afternoon and night……Wow!  However, the ECMWF model has it well east of here. Officially, there is nothing in the forecast from NWS precip wise for this weekend.

High temps in the Town of Mammoth will be the  low to mid 50s through Friday, then mid 40s Saturday and then upper 30s to low 40s Sunday and Monday.  Over night low will remain in the 20s until the end of the week when they will cool to the teens into Monday. Sierra Crest winds will be pretty light after today/Ngt until the weekend.

Unfortunately, the current pattern is really entrenched with a very cold and deep Hudson Bay Low well anchored and effecting the eastern CONUS with the other anchoring upper low south of the Bering Sea. This may end up being one of the coldest eastern winters since the mid  70s!

When will winter come back?  Well….its hard to say when. However, it will come back.  The second half of February is a good guess. A better guess is March when the Sun is higher in the sky which will eventually break up the thermal anchoring  Hudson Bay Upper Low.  

We’ve been here before….

The good news is that the Sierra still has a tremendous snow pack!

Interesting recent note from Jan Null past lead forecaster from WSFO SFO:

“Second, through the end of December, San Francisco had 11.65 inches of rain.  Looking at the long term history for San Francisco, this would be the 36th wettest first 6 months of the rainfall season.  What has happened in the past with these wet starts?” 

There have been 40 years when the July through December rainfall in San Francisco was at least 11.00 inches. Of these only 6 ended up with below the 160-year seasonal average of 21.89 inches.  

The Dweebs Comment:

So there is still a lot of good odds that this winter will come back or…….about a 15% chance that it will be dryer then normal….(for the bay Area)

The Dweeber…………………:-)

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Reference Glossary of Weather Terms
Disclaimer: I have been a hobbyist meteorologist for over 30 years here in the Mammoth area and I do this for my personal enjoyment. The National Weather Service saves lives every day . . . I do not. When making important planning decisions please use information provided by the National Weather Service as they are the most knowledgeable and accurate information source available today.

Hemispheric Pattern To Remain Very Stable 4 Wave….No Significant Change This Week

The Western Hemispheric Weather Pattern will remain stable this week as a 4 wave stationary pattern is locked in. Key anchors are the deep Hudson Bay Low over east central Canada keeping the frigid WX over the Eastern CONUS and another deep stationary trough south of the Bering Sea. Teleconnections favor a continuation of strong west coast upper ridge for another week or two.

Even though this pattern will continue, the below normal precipitation pattern of the past will go through periods of weakness or slight retrogression to allow shots of cooling or even some light snow or snow showers.  By the end of this week a system may move through the west coast ridge and provide some light snow or showers.

In the meantime, daytime highs in Mammoth will continues in the mid to upper 40s with lows in the teens and twenties. Winds will continue to be light in town and gusty over the sierra crest.

For the upcoming week….there will be a couple of weak short wave impulses that will be associated with some convergence aloft moving through the Rockies that will build surface pressures and thus increase the NE surface gradient Tuesday into Wednesday. So a period of East or Northeast wind will kick up over the Sierra Crest later Tuesday through Wednesday. Although this is a dry system, it will bring an increase of wind along with slight cooling for the Mammoth area by mid-week. Thereafter, the upper west coast ridge strengthens Thursday into Friday for warmer WX, then weakens Saturday into Monday as a short wave trof moves into California bringing the chance of some light snow or showers to the Mammoth Sunday/Monday along with cooler WX.

It is important to note that the possibility of some light snow for the Mammoth area the end of the week is not a pattern change. Rather just a weakness in the current ridge-trof set up hemispherically.

The next real change when ever it happens will be associated with a break down of the west coast ridge or retrogression of the same. A portion of the Hudson Bay Low will need to move far enough east for the wave length to become excessive, then amplification and retrogression of the west coast ridge to taking place.  Timing wise…..this is not likely until sometime during the latter part of the first week of February.    Additionally, The MJO is still very active and in the favorable teleconnecting area. (El Nino like)  This may actually have been the stimulis in the creation of our current Ridge-Trof pattern as MJO does build a west coast ridge and favors the cold scenario in the east. (Very El Nino Like) Unfortunately for us, and which for whatever reason, the westerlies have not been strong enough without the necessary amplification for under cutting.


Mammoth Mountain continues to groom the excellent snow pack in the high country.


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

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Reference Glossary of Weather Terms
Disclaimer: I have been a hobbyist meteorologist for over 30 years here in the Mammoth area and I do this for my personal enjoyment. The National Weather Service saves lives every day . . . I do not. When making important planning decisions please use information provided by the National Weather Service as they are the most knowledgeable and accurate information source available today.

One more Great Basin slider before upper ridge moves into California Tuesday for above normal temps and very light winds…..temperature inversions will rule by mid week……MJO is at peak now in the favorable teleconnecting area….models hinting change….

Today Friday will be a warmer day with highs back up into the low 50s…winds will be light. Mammoth Lakes high temperature will be 51 degrees.

The next and last inside slider of the series will drop down from the Pacific Northwest and into the Great Basin and Rockies tightening up the gradients once again and increasing winds along the eastern slopes Saturday afternoon and night…then decreasing Sunday afternoon. Not a lot of cooling with this system…possibly 5 degrees……It will be dry.

The Eastern Pacific ridge will progress into California by Tuesday. With the Upper ridge at 120W, fair and calm conditions will result with upper elevation inversions and decreasing air quality for some areas.  Temps will climb back into the low 50s with over night lows mainly in the 20s at resort levels. Winds next week for the most part should be unusually light for January. Although the intensity and shape of the west coast ridge is handled differently by the  global models, other then for the Eastern CONUS….sensible weather for the State of California will be unaffected the next 5 to 7 days with warmer then normal temps at resort levels and throughout Southern Ca. There will be some cold air trapped in the high elevation valleys early next week. Southern Ca will have periods of off shore flow so…..Beach Bunny wx.

MJO:

At peak now. The Dynamic MJO Model begins to weaken the inter-seasonal oscillation next week. The Dweebs have noticed that some west coast signature has been trying to occur. The 18z Thursday run of the GFS had the classic amplification….cut off anti cyclone over AK,  with a strong belt of westerlies under cutting it with polar jet confluent around the 4th of February with an express out of Hawaii. The following run 00z Friday model flopped back again and then the 06z again showed some effort in undercutting but not all that convincing.

It is obvious to the Dweebs that MJO is trying to modulate the westerlies, however it may be a case of too little too late as the enhanced portion of the MJO will be moving over the cooler waters of the La Nina next week and thus stealing its thunder if you will 😉

So…..if this change is going to happen, it better hurry up! Odds are, that given the intensity of the current La Nina, the system will fall apart before greatness can be achieved. However, that is not to say that some sort of weak,  incipient, maladroitic break through may occur during the first week of February…….


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



————————————————-
Reference Glossary of Weather Terms
Disclaimer: I have been a hobbyist meteorologist for over 30 years here in the Mammoth area and I do this for my personal enjoyment. The National Weather Service saves lives every day . . . I do not. When making important planning decisions please use information provided by the National Weather Service as they are the most knowledgeable and accurate information source available today.