Archive for September, 2017

Fall Pattern shaping up as we say goodbye to the Summer Ridge….Upper Low ejects out Wednesday as the arrivel of the first Fall trof comes through Thursday into Friday……Next stronger Trof may give first dusting over Sierra next week….

Yesterdays thunderstorms brought some nice rains during the afternoon. The two reporting stations in Mammoth indicated between .14 and .19 of an inch. There was small hail as well. The upper level low is getting the boot inland today as the first Fall Trof makes its way through Central CA at 18Z Thursday. Through the process, we’ll have another day of convection today and the chance of some thunderstorms, but today does not look as active as yesterday for Southern Mono County. In fact the Rapid Refresh Model keeps the bulk of the precip from about Mono Lake northward, for today Wednesday.

Longer Range:

Again…the transition from Summer weather to Fall will occur Thursday. Winds over the higher elevation may gust to 50mph at 10,000-11,000 feet over the passes. Much cooler temperatures are expected Friday with highs in the low 60s in Mammoth and low 50s at elevations above 10,000 feet. Overnight lows will trop to the 20s in the back country Friday AM, then the chilly air settles into the lower elevations over the weekend. Weekend Lows will be in the upper 20s and low 30s at elevations between 6500 and 8000 ft with highs in Mammoth in the low 60s.

By Monday some moderation in temps is expected of about 3 to 4 degrees. The warming will be short lived though, as an anomalous cold Trof for late Summer is forecasted to dig into CA Tuesday and Wednesday. Some of the quick details suggest 500MB temps of -19C and 1000-500MB thicknesses in the low 550s by Wednesday. No doubt it will be rather chilly as Summer makes its exit. These parameters suggest highs in the 40s on Wednesday with lows well down into the 20s. Say goodbye to your tomatos?

With this trof, will come the possibility of the first significant dusting of a few inches over the higher elevations. Climo looks good for this with the equinox storm. However, no matter what we expect, weather is always what you will get, so more time is needed to fine tune the details about the weather for the middle of next week.

Dr Howard and the Dweebs…………………..:-)

Old Closed low is drifting north now and will shift east Tuesday through Wednesday Night….Expect an increase of showers and thunderstorms Tuesday afternoon into Wednesday night….Current pattern to transition toward Fall….

A closed low that has been off shore now for over a week is currently making its way northward toward the Central CA coast. A pattern shift with a fall like trof dropping out of BC, Canada is drawing it northward. This closed low will have plenty of upper divergence and surface deformation for showers and Thunderstorm’s anytime between Tuesday and Wednesday night. The showers that developed this afternoon was the first wave coming through. It has pretty much come and gone. However, there is some convection reforming to our south and so can not rule out some showers later this evening.

The closed low off to our south will be moving north the next 24 to 36 hours. Mono county will becoming under the influence of the NE quad with upper divergence and deformation at the surface. No doubt that there will be thunderstorms over the sierra and that some areas will get some pretty heavy rains within the deformation zone, but at the moment, it is unknown where that will set up for Tuesday afternoon and especially Wednesday.

This weather pattern appears to be part of a significant pattern change. A shift from Summer to Fall like weather. What the Dweebs are looking at on a larger scale is a pattern change that will switch the mean upper ridge currently over the Great Basin to Long Wave Troughing over the northern portion of that region. The Transition will not happen over night through but soon enough.

The first trough coming in this Thursday is part the process that is ejecting the cut off through California Wednesday. That trof will spread breezy conditions and cooler air over our region Friday into Saturday. That trof will be followed by an even stronger Trof the following week if the Euro model is correct. So far any showers directly associated with both systems will remain well to our north. However, the nights will really be cooling down this weekend with low 30s in some areas. Further cooling may occur by the middle of next week. Daytime highs in the low to mid 60s Friday.

Tuesday12:00 PM update shows GFS is coming in deeper and so confidence is increasing for the first dusting of snow next week with the “Equinox Storm”

The first blast of Fall Weather is always exciting here in Mammoth. However, it usually is followed by warmer weather into October.

Dr Howard and the Dweebs………………….:-)

First day of meteorological fall will continue with the trend of above normal temperature’s…..High Humidity to our south will work northward for better chance of warm rains next week….Winter of 2018 looks likely to be very different than 2017

Sky conditions cleared out nicely over night and as a result, lows dropped down into the 40s this morning.  Upper level winds have become easterly as an egg shaped upper high is currently progressing east over Northern CA.  This upper high will become northwest-southeast orientated and allow moisture that is currently over Baja from TS Lidia, to move up through Southern CA. Eventually making its way into the Southern Sierra and north.  Both the southern and central sierra may benefit from wetting rains early next week. The Dweebs expect an out break of thunderstorms at some point. The call for wet storms will be tied into the timing of impulses of upper divergence that would move up from the SSE.  More on that later….

Temperatures will remain both above normal and will be dependent upon cloud cover into next week. Highs this weekend are likely to be in the low 80s with lows in the 40s then low 50s as the moisture increases. Longer range charts for Tuesday and Wednesday show a strong easterly wave over AZ that may pivot into CA then north into the Southern Sierra by Mid-week.  Of note, with the increase of thunderstorms, will bring the increase of lightning and possibly fire starts in the forest.  Lets hope the rains are wet enough to prevent that next week.

Climate:

The Dweebs are starting to look at some of the teleconnections that can effect the weather on a climate scale of time. This is the time frame of 30 days and beyond.  September will likely remain above normal in temperature. However., I do see the possibility of that elusive equinox cool down or trough followed by warming.

The key teleconnections are quite a bit different as compared with last winter.  There is cooler than normal water in the Bering Sea, VS last years warmer them normal SSTA.  The QBO has become East to West arguing for a deeper Hudson bay Low and the Pacific Decadal Oscillation is now neutral trending Cold for the west coast.   This all argues for more meridian flow for the eastern pacific and across the CONUS vs zonal flow from the pacific last winter.  It appears that from a temperature point of view, the Fall will become quite cold (November) with periods of Continental Air backing into the Great Basin at times this Winter. As far as precip, it is still too early for a call, but at the least, not nearly as wet as last winter.  Colder storms will higher snow to water ratios seem more likely. AR events, although still quite possible in an ENSO neutral trending Cold, will be far fewer in numbers. Last winter we has some 15 AR events. Normal is about 5.

 

Dr Howard and the Dweebs…………….:-)