Transition to Summer WX still occurring….Couple More NW Trofs…Then Summer WX Weekend following July 4th……Some Models Hinting at Stronger EL Nino Next Fall/Winter
Thursday June 28, 2012
Posted at 9:17 am by Howard
Friday AM Update:
Transition to Summer WX almost complete.
GFS 5 day means +3,5,8 and (7 day mean) day + 11 shows a growing positive height anomaly in the higher Lat’s west of the dateline that will transit us to a full-on Summer pattern by the end of next week. The ECMWF is similar as well.
As the positive height anomaly builds north at 170E near Kamchatka, Russia, it apparently retrogrades the old trof in the mean off the coast of the pacific northwest westward to about 155W/60N and allows a portion of the continental upper high to retrograde or at least expand westward as well to the Great Basin. This really doesn’t occur until later this upcoming week. This essentially completes the transition to Summer WX over the far west by the end of following weekend…the weekend of the 8th. This spells the end of the remains of the stronger Spring like Trofs for the Pacific NW that has also intensifyed our local zephyr wind by gradient force circulation aloft.
Although the AZ monsoon has already begun over the desert southwest, some monsoonal flow would then have “the chance” to be directed more into the Great Basin and the Sierra via Southern Ca-and AZ, the week of the 10th-16th as the upper flow becomes more South-Easterly by the end of next week. Hot weather is likely to precede the moisture next weekend (8th) so expect 100s in the Owens Valley and 80s in Mammoth just prior to or next weekend.
In the meantime…..we still have a few trofs and dry southwest flow to deal with through mid-week. Temps will be (seasonal), in the low to upper 70s at 8000 ft…..with periods of Zephyr (west) winds……15 to 25mph Monday-Tuesday and possibly a bit stronger Thursday.
The without upper trofing next weekend and as heights increase next weekend further west…..there will no gradient wind to intensify the zephier and the thermal trof at the surface will focus more over the sierra crest. Monsoon moisture will move into the eastern sierra that following week.
If you have not seen the latest CFSv2 charts on the developing El Nino, the’re are at the bottom of yesterdays discussion below.
Here is the Plan…..
The Long Wave Trough in the mean will gradually weaken and is forecast to eventually retrograde over the next 6 to 10 days. This means that we will still have to deal with periods of afternoon wind through early next week. Temps are pretty much seasonal now with highs in Mammoth in the mid 70s. Lows at night in the low 40s. Great sleeping weather. Dry and cool!!!
The WX Maps at 500mb show two trofs that will move through the Pacific NW. One on the 1st and the other the 3rd. No doubt preceding land fall, those systems will kick up extra SW flow and add to the usual gradient wind. So, although each afternoon will be Breezy, there will be extra wind Saturday PM followed by 3 to 4 degrees of cooling Sunday. Overall…..temps will remain in the 70s but low to mid 70s while Saturday night may be extra breezy. The next trough will be about the 3rd. It is weaker and so heights well remain higher. So a boost to both afternoon winds as well as temps. Expect highs in the mid to upper 70s Tuesday into July 4th. Going into the following weekend, there is suggestion in the day +11 means that a substantial weakening of the G of AK and northwest trof will occur plus retrogression as well. Thus the westerlies will migrate back up into there usual Canadian home north of 50N.
If that occurs we can expect high temps to move into the low 80s with low 100+ heat in the Owens Valley. Additionally and is normally the case….the continental upper high will develop more westward as well, so a little seasonal wind may be in our future, shortly after that weekend as well. (TSRWs)
With all said… the -PDO is still providing cooler then normal SSTs over the Eastern Pacific. The nature of the overlying atmosphere is more comfortable with west coast trofing than not over the chilly waters and it will be interesting to see how that all works out. By the middle of July, the westerlies are usually well up into Canada……Climo-wise.
On another note, it will be very interesting to see if the upcoming El Nino disrupts or weakens the -PDO. IE (Warms) the current negative phase PDO.
EL Nino Update:
Here is a follow up with the new CFSv2 model. The latest update shows quite the significant EL Nino Brewing.
Check out the links below….for strength, timing.
Then look at the precip Anomaly for California Dec, Jan, Feb.
Latest June 28th, 2012 Update:
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.