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Archive for September, 2018
First Fall Storm of the wet season making its way to California early next week…..Precipitation is likley but how much….Never trust a storm this time of the year!…..
Friday September 28, 2018
9/29/2018
Fridays Headline is above still applicable for this afternoon Saturday. Models still struggling with pattern along with TS Rosa moisture. New ECMWF is back again from three days ago bringing in a 3rd system that is colder for Midweek. More moisture from Rose is in play as well with the Tuesday and Wednesday time frame. The 3rd system will move in Thursday and it is colder with more wind. European is beefing up QPF as well. So the Yo Yo is in full swing this afternoon. Can’t wait until there are multiple runs for the same scenario. We continue to struggle with a low confidence forecast, even 3 to 4 day away.
The up shot from all this is the same as the Dweebs have been touting. If you going into the backcountry in the upper elevations, especially above 10,000 feet, bring winter gear next week just in case it snows. This afternoons NCEP WPC QPF is back up to an 1.00 of moisture over the Crest next week.
Why is all this change going on in the models. It is Fall and early Fall into October along with Mid march into April are notorious for model flip Flopping. The content is cooling off, and the Pacific Ocean is coming into play.
Just enjoy some of nature’s best!
The Dweeber……….;-)
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9:40AM Friday
GFS has just finished running and the tracking of the second system, takes it to the Bay Area, then South East along the coast line to San Diego. This is much like last nights 00Z and 06Z runs. In this scenario, most of the cold air remains to the west of the sierra crest along with the precip. If by chance the storm swings inland a bit more to the north, then more precip would be expected. At the moment, about .25 to .35 is expected over the Mammoth Sierra Tuesday into Wednesday. A few inches of snowfall is certainly possible. The Southern Sierra should fare better with up to 8 to 10 inches over the higher elevations where there is more vertical motion, more moisture and being closer to the upper low itself, colder aloft. The snow level over the southern part of the Southern Sierra will be possibly 7000 to 8000 feet.
The CRFC has the freezing level above 11,000 ft Tuesday over the Mammoth Crest Tuesday. Typically snow levels with a system like this are about 1500 feet below the freezing level. So about a 9500 foot snow level is certainly possible during the main part of the storm Tuesday. This storm is likely to bring a good dusting as temperatures will cool further by Wednesday AM with the snow level dropping briefly to about Canyon Lodge
I update again Later Saturday.
Dr Howard and the Dweebs……………………:-)
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As headlined, we will be greeted by our first storm of the season Tuesday of next week. Precipitation is likely Tuesday, however, more time is needed to know what part of California will benefit best. Those hiking in the back country need to keep a weary eye on the forecast as there are enough differences in the models to warrant….
Next up date in an hour…..
Enjoy the next few very nice days ahead as major pattern change takes shape…..Undercutting storm track may pick up some badly needed moisture from TS Rosa for good precip producer next week…….
Wednesday September 26, 2018
9/27/2018 AM Update
Forecast models have come in considerably drier this morning with precipitation for the Tuesday and Wednesday time frame. TS Rosa will not, as of this time, be a player in contributing any additional moisture to the system for the Sierra next week. That closed low approaches the coast Monday, then drops SE along the coast Tuesday and Wednesday. Rosa’s moisture looks destined to affect Northern Baja to AZ, which is more climatically favored for this time of the year. As mentioned below, it is still September and models do not do as great a job in the medium range as they do during the winter. Nevertheless, this mornings guidance still suggest that at least a quarter of an inch of precip is possible and that would translate to a few inches in the high country. This may flip-flop several times in the coming days so back country travelers do not let your guard down….. All in all, it looks like at the least, a good dusting for the high country!
Stay tuned!
Dr Howard and the Dweebs………………….:-)
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Although High pressure aloft will strengthen the next few days bringing warmer temperatures. The upper high is expected to build north over AK over the weekend as a vigorous belt of westerlies for Late September and Early October undercut and drive into California. With antecedent warmth well established over the Eastern California, there is no doubt that at least moderate to possibly strong winds will develop on Saturday. Pray the Aspens hold on to their leaves this weekend! 🙂
The pattern is complicated as Hurricane Rosa, now gathering strength west of Manzanillo MX, is expected to track NW, west of Baja, CA. Although this storm by the end of the week will be weakening as it moves over colder waters, its moisture is suggested to get somewhat entrained into the southern part of the westerlies. It is not completely known how much of it will get into California at this time, but the models are starting to turn wetter. There is also a cold part of the storm expected to come in Monday night or Tuesday. This would no doubt bring significant snowfall for the backcountry with any additional moisture from Rose.
The principle point here is that anyone planning a trip to the back country, leaving this weekend and traveling next week will need to have their winter gear ready! Snow, Winds Chills, hypothermia are all possible in a snow storm in the high elevations of the backcountry. Some model simulations bring up to a foot in the back country and if more moisture gets involved from Rosa, those amounts would rise. If the opposite occurs, then less snowfall would be expected. The Town of Mammoth will have much lighter amounts. Especially on the roads that are very warm from the Summer. Will update later this week on snow amounts in town if appropriate.
Note:
Going this strong with a forecast of the possibility of snowfall in the backcountry in late September is dicey. Forecast models are not as trustworthy as they would be in December through Mid March timeframe, However, I have to say that as of this time, the Global Models all show snowfall in our back country beginning Monday night and for several days thereafter…..so stay tuned to future developments… For those of you that are headed for the backcountry, you need to keep especially informed…
Dr Howard and the Dweebs……………….:-)
First week of fall to end on a Summery note then cooler, breezy weather developing over the weekend…..First week of October looks cooler than normal with showers possible…..
Tuesday September 25, 2018
Dweebs were back at it this morning with our first fall forecast. Of note, the MJO is amplifying in phase space 8 and is expected to track east into phase space 1. This area of tropical forcing moves through the Western Hemisphere and Africa next week. Highlights of this action now, are the intense mesoscale clusters developing from the ITZ, drenching parts of the Hawaiian Islands. In looking at the IR Satellite & 200-hpa Velocity Potential Anomalies for the 25th of September, this is possibly in reaction to a developing Wave-1 configuration and strong upper divergence centered SE of the Hawaiian islands over the ITZ. This is likely in relation to the developing MJO projection into Phase Space 8.
This would be classic Pineapple Connection, a form of an AR) for west coast except that it is late September and the results from the jet stream are much weaker. However, they are substantial enough to build Upper High now off the coast of the Pacific NW, Northwestward, forcing the Negative Phase of the Eastern Pacific Oscillation blocking pattern (-EPO). This results in the undercutting of the westerlies and a relatively minor closed or cutoff low for Northern California Sunday. Sensible weather for Mammoth will be breezy, cooler weather and a chance of showers early next week. As a note, There is a TS that will track up the Baja Coast this weekend and as a long shot, get entrained within the Trof off the west coast. This pattern is only remotely possible at this time as model simulations do not favor it at any significant degree…..However, it is possible. San Diego would benefit at best, but more likely northern Baja CA to AZ and possibly Las Vegas early next week.
Longer Range outlook for October favors periods of cooler than normal weather with some possible cold storms, during the month. Mammoth will likely get a few periods of snowfall during the month of October.
Dr Howard and the Dweebs……………:-)
