Archive for year 2018

The Atmospheric River Drums beating stronger now for Friday into Saturday as high PWAT’s move toward Hawaii then Central and Northern CA Friday….

Tuesday 4:00PM

 

Stage is set for record or near record strength “AR” for the Central Sierra, “For the Month of April”. Rain and very high elevation snowfall will increase both in coverage and intensity Friday into Saturday. PWAT of 1.5 to 2.00 inches forecasted Early Saturday AM adjusted for climatology are some 500% of normal for Oakland, CA, nearing all time values for early April.  Although this atmospheric river is in the strong category and would be moderate to strong for any time of the Winter, the fact that it is coming within the strength forecasted in April is very unusual.  QPF amounts are in the 3 to 5 inches range over the west side of the sierra and up to the crest. Amounts in the town of Mammoth are likely to be in the 2:00 to 3:00 inches of rain with some light snowfall accumulations in town Saturday afternoon…..At the end of the storm. This storm may be similar to the storm we had last November 17th , 2017 when the top of Mammoth Mt picked up 4 to 5 feet at 11,000 feet and set up the snow pack in the upper bowls for the winter.  However, it is more likely to be in the range of 1 to 2 feet as most of the precip will fall as rain before it get cold enough to snow.

 

The Dweeber……………..:-)

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Tuesday AM:

More comments from WSFO Redwood City:

An excerpt from this WSFO mornings discussion.

Just look at the last AR event that shifted N impacting the Central Coast and not as much on Santa Barbara. That being said the 00Z suite of models bring rather impressive PWATs to the Bay Area by 12Z Friday and increase them through the day. PWAT values of 1.8-2″ are actually being forecast. To put that in perspective that is nearly 500% of normal, 7 to 9 standard deviations and nearing all-time record values for KOAK (Oakland) sounding climatology. AR guidance puts IVT values 700-1000+ kg/m/s, which clearly fits in the moderate to strong and possibly extreme categories. Simply put, WOW.

 

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Monday AM:

Comment from WSFO Redwood City, CA this Morning….

Indications are that the leading edge of a very well organized long fetch of subtropical moisture will first arrive later Thursday, an atmospheric river with maximum integrated water vapor transport values meeting or temporarily exceeding 1,000 kg/m/s from Friday into Saturday. On a scale from 1 (weak) to 5 (exceptional) this atmospheric river will last approximately 48 hours at category 3 or category 4 which means it`ll be borderline mostly hazardous with respect to hydro considerations, but also of course bring beneficial rain.

 

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Sunday PM:

The second strongest MJO of the year has created strong westerly wind bursts north of the equator near 150 East. The RIMM Phase Space has the envelope of upper divergence over the western pacific. There maybe a connection of the MJO to the strong -WPO as a blocking high over AK and the Bering Sea is now established in the 5 day means.  MJO composites show the block in a couple of Lagged composites for Phase 8 in April, However, the MJO is still officially in late Phase 7.

An eastward extension of the East Asian subtropical jet moves north of Hawaii and couples with a weak branch of the polar mid-week. Thereafter, the coupled jets shifts east to the west coast. This ties in with the strengthening MJO as it shifts into Phase space 8 then 1. Looking at the GFS and ECMWF’s PWAT’s,  the AR will extend from the Solomon Island to Hawaii this week and eventually reach Northern and Central CA regions Friday into Saturday AM. In the Fetch well off shore are PWATs in the 1.5 to 2 inch range. The moisture fetch is not subtropical, but rather tropical. So precipitation Friday will likely be rain except for only the highest elevations of the Sierra.  There is a colder system following the tropical AR for Saturday afternoon so the freezing level will lower and rain will turn to snow later Saturday afternoon in town. On another note, the AK blocking highs early in the winter were not associated with a California AR. The pattern across the pacific was all Meridional flow. That has now changed to Zonal Flow which is more like what we had the winter of 2017.

Potentially this could be a big deal with Hydro-Concerns. However, the key will be the forcing or the lack of in the AR Friday and where the AR spends most of its time.

So where the thinking is at the moment is that there will be little forcing Friday AM but lots of moisture and then strong forcing by Early Saturday morning. Also the GFS has the main part of the river into the Central CA area and the Euro has it near Tahoe.  Amounts in the meat of the AR could easily be 5 or 6+ inches of water. Most areas are in the 2 to 3 inch range at this time.  More confidence in where to place the Bull’s-eye by this Tuesday or Wednesday……Stay Tuned.

 

Dr Howard and the Dweebs………………..:-)

Spring has Sprung w/Warming Trend in full swing; 50s and low 60s possible the next 3 to 5 days….MJO Amping Eastward spells excitment for possible pattern change to wet….

Friday:

 

Models continue trend of focusing main thrust of Precipitation of an approaching “AR” for next Friday over Northern CA and Central CA. Snow levels look very high, at and above 9000 feet.  So rain a good bet for the town if the models hold on to that idea for next week, The MJO is amplified in phase spaces 7 and remains amped through phase 1. So above normal temperatures are likely under the subtropical high….. highs at 8000 ft will range depending upon cloud cover between 57 and 62 degrees in Mammoth with lows in the 30s. These temps are primarily for just above the nighttime inversion..

 

 

The Madden Julian Oscillation is Amping now in phase 7, and accordingly,  the Eastern Pacific Ridge is Amping as well along the west coast bringing the warm up. This upper ridge will move over CA Friday and weaken due to short wave action and peak out the warming trend with highs about 60 . Lots of high cloudiness will result over the weekend, however, temps will remain above normal.  Highs in the upper 50s in Mammoth and upper 70s in Bishop. lows in the 30s at resort levels.

The MJO is forecasted to translate east over the following two weeks. For week one, that means a continuing period of warmer than normal temps according to the RIMM composites.  As the MJO shifts from Phase 8 to 1 and possibly 2, the composites suggest the possibility of precipitation moving back into the Southern half of CA and the teleconnection WPO going negative with the “possibility of a blocking high near or just east of the Bering Sea. Undercutting of the westerlies with zone flow, may make it to the central west coast thereafter.  This brings the possibility of an AR as well. Although It is still too soon to count on from a climate perspective, it is interesting that both ECMWF and GFS global models suggest a strong negative phase of the WPO developing (Upper Level High Pressure blocking)  during the first week of April. In fact the standard deviation of normal for the -WPO is off the chart for the ECMWF and about -5 Deviation of normal for the GFS for that same time period.  Their ensemble members during the 2nd half of next week support a possible AR during the time frame Thursday and Friday next week.

On another note, DWP just posted the update on the Mammoth Pass water wise. It indicated that the pass was 95% of normal for the water year ending April 1st.   Again this is just telemetry and I suspect that when the manual survey is done, it will be considerably less.  Nevertheless, it is certainly encouraging! It shows that the pass went from about 5 inches up until the 3rd week of February to 40.5 inches. Now that’s amazing…almost a Miracle?  Again, this does not include the final manual core sampling that will likely be taken just after the first of April. Also noted that the Central Sierra was 70% of normal to date with about 16 inches of water eq. (Quite a difference).   I feel that the main point here,  is that Mammoth Pass possibly picked up the lions-share of the last AR event in California.

 

Enjoy the great weather over the coming days with spring conditions returning to the lower slopes…..

Get it while its cold……………..

 

Dr Howard and the Dweebs……………………..:-)

Current Stormy Pattern winding down as the last shoe to drop comes through Sunday….Associated with below Normal Temps through Monday…..A warming trend mid-week will Lead to beautiful Spring Weather……Miracle March in the Bag……

A lot of folks have asked me lately what is a “Miracle March”.  What it is, is a colloquial term not scientific, that relates to a very dry winter followed by a wet March. There are no guidelines for this term and it has nothing to do with ending a drought, although it certainly can take the edge off one.  As an example, the term Pineapple Express or Mango Express and several other such colloquial terms, now have been defined by Meteorologists as Atmospheric River’s. The term Atmospheric River is a scientific term with guidelines as to intensity; water vapor transport within a baroclinic band on a time scale. Wind speeds of greater than 12.5 meters per second in the lowest 2 kilometers; and a shape that is long and narrow, no more than 400–500 kilometers wide, and extending for thousands of kilometers, sometimes cross entire ocean basins.  Recent research at Stanford has even put Category’s on the Atmospheric River like Hurricane’s,  which may catch on and become mainstream at a later time.

So far this wet season, Mammoth Mt reports between 122 inches of snow and 204 inches of snow for the month of March. A bit more will come this weekend. When you consider that for all the months of the Fall and Winter through the end of February, the total was 81.5 inches.  It is pretty amazing that over the Course of the winter of 2018, on the average, only 16 inches of snow fell a month!  So to me, as in comparison to the rest of the winter it is a Miracle!  Was this a record Miracle March?….No.  The winter of 1991 totaled 176 inches at the Main Lodge.  Additionally, this tally is in inches of snow fallen and not water content, which may also make a difference for comparison purposes.

Going forward:

Were approaching the end of March and weather patterns during the month of April are beginning to emerge.  To begin with, the remains of the current pattern shows the cold portion of the pattern of the past several days coming through this weekend with snow showers and light accumulations. IE (1 to 6 inches)  Colder than normal temperatures are expected to continue through Monday with highs in the low 30s today through Monday then moderating to the 40s by Tuesday and 50s by Thursday and Friday. Nights will be in the teens and 20s.  Expect gusty winds this  weekend with continued wind chills.

 

Longer Range:

Something to watch;  The MJO is in an amplification mood. See:  http://www.cpc.noaa.gov/products/precip/CWlink/MJO/CLIVAR/ncfs.shtml

The MJO Amping in this area will set up a strong (-WPO) (Blocking High pressure over the Bering Sea). Looking at both ECMWF and GFS teleconnections, it is noted that the WPO is forecasted to go strongly negative this end of this month, while the AO and NAO are only weakly negative and the PNA is weakly negative.  This pattern change is a lot different from what we have experienced this winter. The past Winter has been highlighted by Meridional flow (N/S) while the upcoming pattern for early April looks more Zonal in nature across the Pacific. With the MJO moving into Phases 7, 8 then 1, look for strong amplification of the eastern pacific ridge first, leading to -WPO, then the possibility of undercutting of the westerlies during the end of March or the first week of April. This may lead itself to another west coast “AR” event around the 4th of April. With La Nina weakening, and ENSO trending neutral, this is another teleconnection that may lend a hand in its evolution.  By the way, this pattern the first week of April for week 2 looks similar to what we experienced during the Winter and early Spring of 2017…..Miracle April anyone?  😉

 

DR Howard and the Dweebs…………………:-)