Pattern Change initiates Dry SW flow aloft for drying trend into Friday…..Although little change in temps are expected for Mammoth Lakes…..Subtropical Moisture returns at weeks end…

RECAP:   Yes its been been very warm to hot across the State.  Down in Southern California, the protracted heat wave has caused misery for many. At resort levels at Mammoth Lakes, we actually had some very pleasant weather over the weekend with highs in the 70s.  That was because when we really moisten up, we loose a lot of in coming solar radiation and thus there was a lack of surface heating.  Mammoth did have some light showers, mainly in the late afternoon and early evening hours along with some thunder. Southwest flow was initiated yesterday. With more sunshine during the day, we got up to 84 degrees on Tuesday.  Nights in the 50s

Current Pattern:

The subtropical high at 500MB was centered over SW Utah this morning,  (597DM) and is progged to weaken through Friday over AZ to 591DM. So a 60 decameter drop.  This is in response to a trof of low pressure moving into Washington state today.  For Mammoth, although heights will fall the next few days, there will be more sunshine, as our airmass continues to dry from west to east. So the effects of airmass cooling will be negligible, with only a few degrees of cooling by Friday.  At night it will be a different story as the dry airmass  allows lows at night to pull back into the 40s.  Also, expect a resumption of  the Mono Zephyr, beginning today into Friday.   Another point to make is that there are a lot of fires burning to our west.  With the upper flow becoming more WSW. Expect smoke from the west to arrive later today or tonight….

For you folks in Southern Ca, there will be some 5 to 10 degrees of cooling which will begin today. By weeks end, coastal sections may be in the 70s, Coastal Plain in the 80s and Valleys in the 90s by the weekend.

Owens Valley:

Upper flow was still SSE this morning but becomes SW later today.  So today is the last of the Thunderstorms for a while. Drying continues in the Owens Valley through Friday..

Dew-points will come down a bit as well.

Outlook:

Hurricane Genevieve is nearing Cabo San Lucas. This tropical storm will move along the Baja Coast and weaken over time over the colder water.  Moisture will be released northeastward as the systems becomes a depression, with its remains exiting possibly over central or northern CA Monday Afternoon or night.  Although there may be some showers or thunderstorms from this system, main effect will be an increase of moisture for California, beginning Saturday over Southern Ca and Sunday and Monday for the rest of California.\

There is some suggestion from this mornings 12z GFS run that another Subtropical low will spin up, this time in the “COL”, and track toward CA mid week next week. That may be a good precip producer for the fires burning throughout Northern CA. This is a long shot at this point but worth watching…

We are getting close to the time when California may benefit from a dying Hurricane that could bring beneficial rains to the state. A Window is opening over the next few weeks….

Anyway…..It is worth noting that Meteorological Fall arrives on the first of September, so the days will become notably shorter in the next few weeks along with much cooler night

Dr Howard and the Dweebs……Covering the Eastern Sierra Weather for 40 years……:-)

 

 

 

 

After an overall mild Summer, Southern CA will experience its first long term heat and humidly wave this weekend into next week….

Saturday AM update:

The hottest dome of air of the Summer is expected to continue building today through Tuesday. A 600+DM at 500MB subtropical high builds into South Eastern Nevada with 600DM iso heights extending to the CA NV boarder Monday and Tuesday.  This is quite the heat pump. Upper Flow will be mainly SSE over Southern CA, so dew points will make it feel even warmer as compared to earlier in the Summer. And…the Circulation around the periphery of the anticyclone has the impulses well off shore, so no real trigger mechanism for any rain coming up from the south. in the medium range.

This is likely to be the peak of the Summer heat associated with the subtropical high. Later in the Summer and Fall Katabatic type systems with winds moving off shore could rival temps in the Fall, but with much less humidly. The Upper High peaks Monday and Tuesday so heat will build through then. Highs 105 to 110 in the Valleys of So-Cal are possible with an easing of the heat not expected until later next week.

In the high country of the Sierra and Mammoth Lakes, this particular pattern is associated with not only above normal temps, but in this case, atmospheric modification,  Moisture, now already in place, was aided by the remains from tropical storm Elida this past week. Recent afternoon convention has modified our air mass further with recent afternoon and evening thunderstorms. The high elevated heat source of the Sierra is notorious for this.  Often times, this is the Sierra’s natural cooler, as cloud cover will help keep those high temps confined to the low to mid 80s here. If this were early to mid July, we would be looking at low 90s.  However, without much of an afternoon Zephyr, lows at night will be mostly in the 70s through 9:00pm to 10:00pm, and may remain in the 60s through 1:00AM the following morning. . These mild temps are contingent upon no significant rain early in the evening.  As the Old Farmers Almanac says, these are the “Cat Nights” of the Summer!   😉

 

Dr Howard and the Dweebs……………………

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The weather has been mostly copacetic this Summer with only short term heat waves and little in the way of humid weather.  That looks to change in the short term as a strengthening subtropical high works in tandum with a low pressure circulation off shore, This is expect to channel subtropical moisture from the remains of tropical storm Elida some 1400 miles south of the Channel Islands, late Wednesday afternoon. Subtropical cloudiness like altocumulus castellanus, was observed Wednesday, a sign of subtropical moisture aloft moving into Southern CA. Dew points were in the low 60s west of the Coast Range, 40s in the east San Gabriel valley and 30s in the high deserts. That will change over the next few days…

Dewpoints will be increasing the next few days….

For Mono and Inyo counties, 500mb heights are expected to rise to the mid to upper 590s DM.  This will challenge some high temperatures records early next week. The upper flow for the most part is southerly but at times southeasterly. This may tap monsoonal flow and initiate precipitation if there is some triggering mechanism. Too soon to tell, so the forecast called for mainly isolated TSRWs,.  Stay tuned if the models indicate some kind of upper jet or wave rounding the periphery of the upper high that will build north into southern Utah, next week.

 

Although moderate zephyr winds will blow during the afternoon and evening hours for a few day, they will weaken as the Thermal trof jumps the sierra to the west this weekend….

 

High in Mammoth in upper 70s Friday then low to mid 80s this weekend…..possibly mid to upper 80s early next week….

 

Stay Tuned…………………

 

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

Late July Heat wave on tap as subtropical high sets up over Southern California today….Pattern is Dry through the weekend….Isolated thunderstorms return the following week….

TGIF Everyone….

As we come to the end of July, The Dweebs have come to the realization that its been an A-Typical Summer. The June Gloom season has lasted much longer than usual along the southern coasts of California. LA has not had any significant heat waves so far. The waters off the Southern CA coast are much cooler than normal. The Sierra and Southern Deserts has yet to experience deep SE flow. The AZ Monsoon season has been anemic at best.

Weather Type:

The large scale weather pattern over the West and Southwest has been highlighted by a stronger than normal, persistent upper trough off the coast of the Pacific Northwest. This trough has in the “long range means”, displaced the Subtropical High to the east. It has warped its configuration to where the upper flow along the west coast has been vigorous WSW. In the wintertime, that may be normal. But in the Summer?  By this time of the summer we usually experience much lighter flow aloft or southerly flow.

The results of the enhanced WSW flow over Southern CA has been steeper pressure gradients between the deserts and the coast.  Stronger onshore flow leeds to more persistent June Gloom along the coast. Stronger westerly winds over coastal waters creates up-welling, resulting in colder SSTs and then feeds back to even stronger differences in air pressure and intensifies and deepens the marine layer further.

A positive result that is beneficial from the strong up welling, is that more nutrients are lifted upwards in the seas which can be beneficial to fish population.

Short, Medium and Longer Range:

No sensible change is expected in Sierra Weather through next Tuesday.  Expect an enhanced afternoon and early evening Zephyr in Mammoth. This will suppress high temps by as much as 5 degrees from what we would expect from the current 500mb height structure this time of the year. High temps will range in the very low 80s with night time lows dependent upon the micro climates of Mammoth as they relate to breezes during the night.  Lows may range up to 10 degrees cooler in areas like the Mammoth RV Park verses Snowcreek where it may remain somewhat breezy all night. As an example, In the meadow last night, it was breezy enough to keeps lows limited to 62 degrees, whereby in the more eastern sections of the city limits, lows were in the low 50s.  These spreads are likely to continue the next few days. Our air-mass is bone dry now. So be especially careful with fire. No campfires are allowed in the forest now. Only in approved campsites.

Longer Range:

An extension of the Eastern Pacific Trof develops while the upper ridge weakens over the SW. As the cap comes off and heights fall….instability develops with a pattern similar to what we had some 10 days ago with isolated to scattered thunderstorms. High Temperatures will cool to the 70s later next week. Lows in the 40s and 50s.

Still no sign of the AZ monsoon….

 

Dr Howard and the Dweebs……………………..:-)

 

 

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Tuesday July 28th:

This looks like the Summer without the Monsoon

Latest guidance continues the trend of dry weather in the high country with little if any convection expected this week. A strong subtropical high develops over Southern California today that is east-west oriented. This system builds the heat over the state without any import of SE moisture. In addition, strong subsidence will put a lid on any convection as the freezing level hikes to 17,000 feet, both Wednesday through Friday. High temperature records will be in jeopardy toward the weekend in the high country and over the weekend for the Owens Valley.  Additionally, the Trof over the pacific NW will weaken temporarily, then strengthen again, increasing the gradient for a bit stronger Mono Zephyr during the afternoon and evening hours. Thus you will be able to opened the windows in the evening and let the west wind blow some of the heat out, a little later in the week. This Ridge shifts more east with time into AZ, as the Eastern Pacific Trof strengthens. This allows some cooling next week. However, the trof in the Pacific Northwest keeps the SW flow going, so not much more than isolated TSRWs expected when the heat breaks. Eventually, we get a weak closed low set up again, off the Central CA coast like this past weekend, for the return of high based thunderstorms. However, this is not the AZ monsoon!

 

Dr Howard and the Dweebs………………………:-)