Mammoth Weather

Tuesday PM Update:

Updated CRFC QPF showing a drier scenario for Mammoth Wednesday…so 1 to 4 inches is probably going to be it from top to bottom….. An inch or 2 in town as well……

Let hope for a little more westerly trajectory for the Sunday system…..

The Dweeber…..

The Central Sierra will continue with its cold showery pattern through the rest of the week as NW sliders move through California with little moisture. Precipitation is mostly dynamically driven. The next storm for Wednesday is showing up this morning as dryer then the last.  The Dweeb Reports lst discussion indicated that it would be a coastal slider last week. Now subsequent models runs are taking this splitting system pretty much over the top of the Central Sierra with little “over-water” trajectory of a 110knot upper jet. So expect light amounts again aprox (3 to 6 in) possible on Mammoth Mtn mainly Wednesday. Short wave ridging builds in Thursday for some sunshine! But it will continue Breezy over the lip of the sierra, (up-slope wind) especially Thursday morning with good 300mb/700mb coupling. Winds will we much lighter Friday with a milder day as well.

Weekend Outlook:

The weekend looks unsettled as another short wave….this time an inside slider brings wind, cooling and snow showers Saturday afternoon into Washingtons birthday. Again, at this time it appears to be an inside slider according to the EC and GFS…so light amounts of snowfall expected. ( a few inches). Will update Friday

Longer Range:

The Dweebs can not ignore the fact that the long range pattern in the means is showing discontinuous retrogression. This means that over the next three weeks the eastern pacific ridge will be workings its way west…west of Hawaii. This may eventually result in a very stormy pattern for the Eastern Sierra with heavy snowfall the beginning of March.  The Air Sea coupled model has been touting this for a week now with the 500mb positive height anomaly well west near Hawaii and the negative 500 heights anomaly over Ca.

The MJO which has just moved into Phase space 1 from 8 is about as far east as it is going to get, just east of the dateline. According to NCEP, the MJO is expected to remain active the next few weeks as it reemerges into the Indian Ocean in Phase spaces 2/3.

As the MJO gets into the Indian Ocean and progresses east, the PNA index will flip from its current positive phase to one of Negative. During the MJO progression toward the Maritime Continent, the upper Upper Jet across the pacific should contract, leading up to the -(PNA).

Thus the the current storms that are splitting south with small shots of energy coming into California should come in stronger from the west, as the negative phase usually rules between 70E and 100E. Coinsidently, the global models do show retrogression the end of this month, “possibly” leading up to a wet March.

PS: Here is the loading pattern for the +(PNA); Just flip it for the negitive phase.

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/pna/pna_loading.html

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.

Mammoth Mt picked up about in inch from yesterdays wimpy system. It split and headed south down the Baja Coast. The 3 day period beginning with today looks dry. However, some signs showing up for some snow showers this weekend as a tweek in the pattern begins to take shape that will bring colder weather with an increasing chance of some light to even possibly moderate snowfall for Mammoth Lakes next week.

Meteorology:

Both the 12z and last nights 00z EC shows a series of NW sliders into the state as the upper block over Ca weakens and allows undercutting of energy into the Ca state. It is certainly not the ideal situation. The mean ridge position is still over the far west. However, there is still strong blocking ridge over the northwest territories and the energy has to go somewhere. Especially since the wave length opens up, as the Hudson Bay low is forcasted to move east. So the Dweebs look at it as a weakness under the block which should allow some northwest sliders to bring some snowfall shots to the Eastern Sierra. The sliders should be able to bring shots of cold air with fairly meager jet energy. Moisture will be limited. However, some of the new guidance is suggesting some decent dynamics…enough for some fast moving shots of light to “possibly moderate” precip next week. So stay tuned>>>>>>>>>>>>

Now for the fun stuff!

MJO! Yes that illusive bugger is quite strong in Phase space 7. That phase space is not favored for precipitation in California. As mentioned in the past, there has been anomalous rainfall late 7 into 8 during times when the AAM changes. Like during the epic 1-1-97 event. However normally phase 7 is El Nino like which actually promotes amplified ridging in the PNA sector, which is what we have been getting. Now the big question is where are we headed?

The MJO is forecasted by several models.

Below are some very useful links…..

First is a snap shot of where the MJO is and how strong it is. SEE:

Current MJO: http://cawcr.gov.au/staff/mwheeler/maproom/RMM/phase.Last40days.html

Now here is yesterdays NCEP ensemble forecast:

Yesterdays NCEP ESM: http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/CLIVAR/ncpe.shtml

Here is todays NCEP ESM: http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/foregfs.shtml

Here is the lastest ECMWF ESM: http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/CLIVAR/ecmf.shtml

The million dollar question is will MJO stay strong and move into and through Phase Space 1 and 2?

Today’s forecast is not showing that but yesterdays did.

Currently the pattern over the pacific ocean is amplified with probably moderate Meridional Rossby Wave Dispersion. Phase spaces 7 and 8.

IF/When the MJO moves into phase spaces 1 and 2, the eastern pacific ridge retrogrades. This usually results in the FLIP of the PNA sign from positive to negative and we get a nice long wave trof off the west coast bringing storms to the state from north to south. The Northwest will probably turn wet first with the jet shifting south thereafter. The beginning of the intensive observational period for California based upon yesterdays forecast is about 19th of Feb.

Here are the current composites for California for February. As you can see, the significance is high for precipitation and below normal temps in phases 1 and 2 of the MJO phase space.

Temperature Composits and Significance for Feb:

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/Composites/Temperature/JFM/combined_image.png

Precipitation Composites and Significance for February:

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/Composites/Precipitation/JFM/combined_image.png

Another supporting model is the “CFSv2 Forecast”

http://www.cpc.ncep.noaa.gov/products/people/sweaver/cfs_fcst/images1/wk3.wk4_20120207.z500.gif

Week 4 (Feb 29th through the 6th of March) Clearly showing the HT 500 height anomaly retrograded west to northwest of Hawaii with below normal 500 heights over the West Coast. This is a flip of the current PNA index.

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.