Archive for September, 2011

Another Day of Scattered Thunderstorms for Mono County……Although Main Shower activity was north of Mammoth Monday…..Focus will shift further south today for a better chance for southern Mono County……1st plunge of Arctic Air headed for Midwest…..

Yesterday was a bust for Southern Mono County rainfall wise….so much for mesoscale forecasting. Lassen County up in Northern Ca got the brunt.  However, many areas north of Mammoth in Mono County got plenty of rain. Like The Topaz Lake area. Today’s forecast is similar with a flash flood watch issued by NWS for Mono County beginning at 1:00pm to 10:00pm tonight. PWAT is a little less this morning. However, still in the range of heavy rain where the main focus is. There is still good divergence over the Sierra as well as light winds aloft…. (less then 10knots)

Today main focus is between Southern Mono County and Tahoe…..more south of where it was yesterday.

Outlook……

Upper low off Southern Ca coast kicks inland late this afternoon into Southern Ca. The dynamic effects of the upper low is gone by Thursday. Drier air moves into Mono Beginning late Wednesday…..however lots of lingering moisture still around for more garden verity showers Thursday through Saturday. There is a migratory short wave coming through this weekend for cooler WX. Then upper ridge builds next week for warmer weather while the Midwest gets its first Arctic blast from the north about Tuesday/Wednesday.

Long Range Talk:

OK…were headed for another La Nina Winter. Lets say that it is going to be at least a moderate one by January.  And….although it is coming on strong as far as how fast it is developing…..odds are, this may not be an early winter. Early winter as defined by enough natural snow to open Mammoth MT in early to Mid October.

Why?

History:

1. Second year La Ninas usually favor early season arctic outbreaks over the Midwest and Mississippi River areas. The one that is coming next week is about a week early I am told.

2. It this is true, then we must have upstream amplification for that to happen. IE Strong ridging over the far west. Strong ridging over the far west is highlighted by Warmer then normal temps over the Great basin and California.

3. Last year at this time, we were already in a full fledged La Nina. This one is still considered incipient.

4. Although the SSTA’s have warmed in areas of the extreme Eastern Pacific since August, the Dweebs are noting that the warming has stopped and that colder SSTAs have expanded both north and west rapidly since the 28th of August.  This cooling is apparently continuing…..  Colder then normal SSTA’s over the eastern pacific favors storminess with above normal precipitation for most of California. However, the further north you go, the wetter it is with La Nina winters.



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.

More Thunder and Heavy Rain Potential Today and Tomarrow……Flash Flood Watch for Mono County This afternoon….

Some nice rains fell throughout Mono County yesterday.  21 hundreds in the bucket for a weekend total of .45.  Not bad for September.


Today may be the day for heavy rain!!!! Flash flood Watch for Mono County this PM.


A day of heavy rainfall for areas from about Mammoth Lakes to the Alpine County line and on both sides of the crest especially west of the Sierra Crest, west of Bridgeport. 


All the right ingredients:


1. Clear skies this morning.


2. Deeper moisture than yesterday from the surface to 550MB


3. PWATS up to an inch


4. Strong *BRN numbers on the west side of the crest (up to 50)…West of Bridgeport, displaying strong buoyancy relative to wind shear.


    a. May not be applicable over the Sierra


5. Very light winds for slow moving storms that will track about east to west.


6. Again…..Light Vertical shear and strong buoyancy look prime in this area over the elevated heat source of the sierra.


* Bulk Richardson Number
The BRN is meant to estimate the balance between vertical shear and buoyancy, with low BRN values suggestive of vertical shear that is too strong relative to the buoyancy, and large BRN values are suggestive of multicell clusters. Intermediate BRN values favor sustained supercells. BRN values in the range of 10-45 (dimesionless) have been associated with supercells via numerical simulations.


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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.


Upper Low Spins Near Kern County……More Rain and Thunder Expected

Looks like a repeat of yesterday, except more moisture today and an earlier start to rain expected. The intensity of the rainfall will be determained by the amount of sunshine we have. At the moment, its pretty cloudy but there are some breaks. Mammoth picked up .24 inches of rain last evening and night. There was thunder as well.

As per KHNX discussion this AM at 9:00am:

“UPPER LOW IS NOW CENTERED ALONG THE BORDER BETWEEN KERN AND TULARE COUNTIES NEAR 35N/118W. A FAIRLY STRONG VORT MAX AHEAD OF THE LOW HAS PUSHED INTO SOUTHERN NV AND HAS TAKEN MOST OF THE SIGNIFICANT CONVECTIVE ACTIVITY ALONG WITH IT. SOME MID LEVEL MOISTURE IS BEING PULLED BACK FROM THIS FEATURE AND WRAPPED AROUND INTO CENTRAL CA WHICH HAS PROVIDED AREAS NORTH OF KERN COUNTY WITH SCATTERED LIGHT SHOWERS THIS MORNING”.

Only interesting addition is the *MUCAPE:  J/kg

Only about 750 J/kg at 9:00am over head;  However, just a short distance to the west it is as high as 3000 J/kg and just to the east across the NV/CA border 2000 J/KG probably associated with the VT center near the NV/Ca *

Also Retired….WSFO forecaster Doug Armstrong pointed out this AM that there may be some snow over the highest elevations below some of those rain shafts.  (Freezing level is above 12K)

MUCAPE (Most Unstable Convective Available Potential Energy) is a measure of instability in the troposphere. This value represents the total amount of potential energy available to the most unstable parcel of air found within the lowest 300-mb of the atmosphere while being lifted to its level of free convection (LFC). No parcel entrainment is considered. The CAPE and CIN calculations use the virtual temperature correction.

The LPL (Lifted Parcel Level) allows for the determination of the height of the most unstable parcel. This makes it easy to identify areas where the largest CAPE is “elevated.”




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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.