Breezy..Dry SW Flow to Continue Today and Wednesday….Mid Level Moisture on the Way for Thursday with a chance of some light rainfall…..At the Moment a Dry Weekend is Forcasted…..AZ Monsoon Shifts into High Gear with additional chances of rainfall later next week….
Tuesday July 9, 2013
Posted at 9:23 am by Howard
Latest modeling, Radar and Sat Maps show main action today over SE Ca with small meso-scale convective cluster near Needles, CA within PWAT of 2 inches. Not a great day to be water skiing in Parker past FOX’s. PWAT over Bishop about an inch and over Mammoth .75 Although Lot’s of Moisture today in the mid levels….No significant forcing in the Mammoth area as per SPC. Skies over-developed so not much heat to work with. Slight chance of showers remains a good forecast for Mammoth today. (20%pops)
Southerly flow slowly shifting east, so we may get some sunshine yet.
Highs today will struggle to get out of the 60s with lows tonight in the low 50s. Some gusty SW winds possible. Friday looks to be a bit warmer day……Nice weekend shaping up in a drier SW flow. Highs upper 70s Saturday and near 80 Sunday.
Tuesday AM Update:
Over the past week, its been clear that there has been a little stronger Trof (Cool Pool Aloft) in the Pacific NW then climatology. This is making for a bit stronger and persistent Zephyr in the Mammoth Area. The Zephyr is the product of the differential heating of air masses that are separated topographically from one another and become induced thermally by the differential heating of the deserts to the east, on a diurnal time scale. Trofing in the pacific NW only intensifies the differences and creates a diurnal west wind system that is highlighted by lighter winds in the AM hours as compared to the afternoon and evening hours. The warmer seasonal pattern stretches north south throughout most of the Eastern Ca, along the Lee of the Sierra.
Monsoon Moisture and Mid July:
Monsoon Moisture or SSE flow is most common From Mid July Through Early August here in the Eastern Sierra. Moisture from the subtropics is usually benign unless it is associated with some kind of dynamic lift. If there is enough daytime heating, modification of the air mass within the column occurs from elevated heat sources to produce Thunderstorms in the Summer.
However, Mammoth, topographically is situated naturally in a low spot down wind of the Zephyr. The West or SW flow is often strong enough to shift a localized convergence zone more to the east of Mammoth than many areas both North and South of us. This results in an eastward displaced convergence zone usually east of Highway 395, as compared to areas north/south of our immediate location. This often results in rainfall, in areas both north and south of Mammoth while Mammoth remains dry. This was the case during the Fourth of July Holiday Weekend where thunderstorms raged over Grant Lake near June Lake northward while Mammoth remained mostly clear. This is structurally topographically driven.
Although High pressure aloft remains strong over the Great Basin and California, an impressive looking “Easterly Wave” underneath the upper high has quite a bit of subtropical moisture associated with it. A mesoscale convective cluster raged over the Sonoran Deserts last night and is moving WNW. In addition, hurricane Eric near Southern Baja is adding juice to the mix. 700mb/rh and as well as upper level wind trajectories suggest that this moisture may begin to advect into Central Ca from the SSW after midnight Wednesday. Although moisture advection from the SW or SSW is usually benign into our area rainfall wise in the Summer……It will have to be watched for any spokes of vorticity that might create lift and dynamics from an usually stable trajectory. Timing is early Thursday into Early Friday for the Central Sierra. Showers and some isolated thunderstorm’s are a possibility. The key to the brief pattern change is whether or not any areas of dynamics are associated with this moisture. IE Spokes of vorticity.
So the advection of mid level moisture is expected Thursday morning 1st, then possibly airmass modification Thursday PM and any associated instability could ignite some rainfall in our area. Will take another look at it tomorrow and again Thursday AM.
The weekend outlook shows a drier SW flow returning…..keeping the Jazzer’s happy!! However, an influx of moisture is again possible, later next week as we get into the meat of the seasonal wind season.
Dr Howard and the Dweebs………………………….:-)
Its Sierra Weather at its Finest…..The Up-Coming Week will have a few Extra Warm Days Monday and Tuesday…Then Cooler Breezier Days Wednesday through Friday…..Next Heat Wave Brewing beginning about the 15th…..
Saturday July 6, 2013
Posted at 10:16 am by Howard
The Heat Wave is broken….now a typical weather pattern develops over the far west with highs each day in Mammoth upper 70s to low 80s dipping down to the low 50s during the hours prior to Sunrise. The Mono Zephyr (west wind) will insure a dry pattern in Mammoth the next 7 days with isolated thunderstorms in and around the Mono County convergence area. (That is the area where the west wind converges with the south winds that come up from the Owens Valley in the PM)…..well to the east of Mammoths City Limits.
Upper Pattern Highlights for the upcoming week:
Upper Subtropical High will occupy the southern 2/3rd of the country with its extreme western periphery effecting California. For the most part…all of California will be under SW flow insuring a dry air-mass. The high elevated heat sources like the Sierra will produce some isolated Thunderstorms. These will be mainly in the late afternoon and early evening hours. As mentioned above, for the Mono county area, most of these build up’s will be associated within the west wind/south wind convergence areas….well east of Mammoth Lakes. There will be a two day bulge westward with short term strengthening of the continental high Monday into Tuesday. Daytime highs in Mammoth will be in the low 80s then. By Wednesday…the upper high retreats eastward with about 5-6 degrees of cooling and a stronger Zephyr Wednesday through Friday.
Another Pattern Change:
By the Weekend of the 15th, the next Heat Wave will begin to effect California by Sunday. The Subtropical Continental high strengthens over the Four Corner states and a large dome of High Pressure aloft develops near the 4 corners states then spreads west into California the following Monday the 15th for another protracted heat wave.
Again…..this looks to be another major heat wave that will last a week or longer and will eventually be associated with thunderstorms later in its progress. SE flow is also suggested for SE California and at least Southerly Flow for the Sierra.
Dr Howard and the Dweebs………………………………………:-)
First its the heat…then its the humidity!…Bishops Heat has Peaked shattering old record of 105 Monday with 109….Now add humidity….Temperatures to slowly drift downward beginning today……
Tuesday July 2, 2013
Posted at 9:03 am by Howard
Dew points were up this morning with mid 40s widespread. Lots of sunshine this morning will guarantee an active TSRW set up for the high county with POPs north of 40% this afternoon and evening for the Mammoth Area. Mammoth had a high of 88 yesterday at the 7700 foot level.
Latest IR shows lots of mid and high level moisture streaming NW from SE California. Showers and thunderstorms are occurring in the southern most areas of Inyo County at the moment. The moisture is moving our way! Dew points will continue to rise making it feel humid and at the same time making it more difficult to challenge yesterdays high of 109 in Bishop. This is the beginning of the end of the great heat wave of the Central and Southern Great Basin of 2013. One that will go down in the record books as both one of the earliest, strongest and longest heat waves for Eastern California, Western and Southern Nevada.
So expect rain and thunder this afternoon. Heat waves like this usually break with thunderstorms on the back end as the dome of high pressure weakens… it usually does so with a much more unstable air mass. Our air mass is super heated now……add moisture and add the little impulses circulating around the upper high and you get the ingredients for some very good Thunderstorms. At the moment, precipitable water amounts are not excessive, at around in inch…good of some wetting rains. But let’s see what happens tomorrow as the upper high winds down.
Drying is expected to begin Thursday night and by the weekend, a dry SW flow is expected…..Returning our weather to more normal dry conditions with high temps in Mammoth Lakes in the low 80s. and lows in the 40s.