Intense, prolonged, and potentially record-breaking June heatwave

Filed in Uncategorized by on June 16, 2016 3,083 Comments

 

An amplified atmospheric configuration: Pacific low; desert high

After an extended period of quiescent weather in California, an unusually amplified atmospheric pattern will bring a potentially prolonged period of very hot conditions to a large portion of the American Southwest.

A very deep early-summer low is currently centered just west of the Pacific Coast. (NCEP via tropicaltidbits.com)

A very deep early-summer low is currently centered just west of the Pacific Coast. (NCEP via tropicaltidbits.com)

As of this writing, a very deep and cold (for June) low pressure system was situated over the far eastern Pacific Ocean just offshore of the West Coast. This slow-moving system has brought very active weather to the Pacific Northwest in recent days–including heavy rainfall in British Columbia, thunderstorms and very late-season snowfall in the Cascades, and even some frozen precipitation in California’s own Sierra Nevada. Some showers may yet occur as far south as the Bay Area and Sacramento region later on Thursday, though precipitation in these areas is expected to be minimal.

This won’t be the last we’ll see of this deep low, however. Instead of dissipating or moving eastward with the prevailing winds, this system will likely “retrograde” back toward the west and southwest over the next few days–setting up shop well southwest of Central California over the weekend. Meanwhile, an increasingly strong region of high pressure will build and expand westward from the Desert Southwest. California will be situated in a region of warm southerly/southeasterly flow between these two anomalously strong systems–allowing a warm desert airmass to slowly encroach upon coastal areas and advecting an increasing amount of mid to high-level subtropical moisture into the state.

The pressure differential between an unusually strong Pacific low and Southwestern high will drive winds from the southeast over California. (NCEP via tropicaltidbits.com)

The pressure differential between an unusually strong Pacific low and Southwestern high will drive winds from the southeast over California. (NCEP via tropicaltidbits.com)

 

Extreme, possibly record-breaking heat possible across a wide region

While there is still some uncertainty regarding exactly how hot it will get–and precisely where records are most likely to be broken–it is now abundantly clear that numerous locations throughout southern Arizona , Nevada, and California will exceed (and in some cases shatter) existing daily high temperature records. In fact, the magnitude of the upcoming ridge and associated heatwave may be sufficient to threaten a handful of all-time monthly temperature records. The magnitude of the coming heat is made all the more remarkable given that mid-June is not climatologically the warmest part of the calendar year in this part of the world, where temperatures typically peak later in the summer (or even in the autumn, closer to the coast). In the lower deserts of southern Arizona (including Phoenix) and far southeastern California, this likely means temperatures approaching 120 degrees. Most of the major urban centers in Southern California will probably see temperatures near or above 100 degrees on consecutive days (except along the immediate coastline), which further elevate already extreme fire danger and possibly threaten the local/regional electricity grid. As an increasing amount of subtropical moisture begins to move across the region by early next week (see below), even slight increases in surface dewpoints will make for very warm (and uncomfortable) overnight low temperatures–further exacerbating the risk of heat stress.

Unfortunately, this very hot weather regime will probably be here to stay for quite some time. In fact, latest weather model ensemble guidance (from both GFS and ECMWF) suggest that the anomalously strong Southwestern ridge will persist in some form for at least the next 10 days, and perhaps through the end of June. There may be some temporary relief from the most extreme heat in some areas by Tuesday or Wednesday of next week, but it does appear that a resurgence of extremely hot temperatures may occur once again by the end of next week.

Model ensemble forecasts suggest a high likelihood of very warm temperatures persisting through the rest of June. (NCEP via tropicaltidbits.com)

Model ensemble forecasts suggest a high likelihood of very warm temperatures persisting through the rest of June. (NCEP via tropicaltidbits.com; click to animate)

This second surge of heat next week may be focused a bit further north, expanding to include most of Northern California as well. The Central Valley may be particularly affected, and the cities of Bakersfield, Fresno, Sacramento, and Redding may all endure a prolonged streak of days with temperatures exceeding 100 degrees. If the GFS is to believed, there may even be a few days near or above 110 degrees in these inland valley cities next week. The magnitude of the mid-tropospheric ridge for much of next week is expected to be essentially unprecedented for June, so it is possible that the eyebrow-raising temperatures coming out of recent model guidance might actually come to fruition. While it will also be hot in the Bay Area, the risk of extreme heat there will be somewhat mitigated by a lingering marine influence (though there is some potential for temperatures to be much warmer than forecast, should offshore flow be slightly stronger than expected).

The magnitude of the Southwestern ridge will be unprecedented for mid-June. (NAEFS via NCEP)

The magnitude of the Southwestern ridge will be unprecedented for mid-June. (NAEFS via NCEP)

 

Needless to say: this upcoming heat event is one to take seriously, particularly given its expected longevity and the relative lack of relief expected next week.

 

Subtropical moisture: increasing risk of elevated convection, dry lightning, and associated fire risk

The prolonged southeasterly flow over California next week will bring an increasing amount of subtropical moisture in the middle to upper levels of the atmosphere. This setup strongly resembles that commonly associated with moisture surges later in the summer associated with the North American Monsoon, which bring thunderstorms mainly to mountain and desert regions but occasionally also to regions closer to the coast. Recent model runs have increased the amount of moisture during the middle to late portion of next week across much of California–meaning that some elevated convection (and perhaps some dry or mostly dry thunderstorms) may be possible at times nearly anywhere in the state in the 5-10 day period.

Mid and upper-level subtropical moisture will stream northward across California, leading to a risk of high-based thunderstorms at times next week. (NCEP via tropicaltidbits.com)

Mid and upper-level subtropical moisture will stream northward across California, leading to a risk of high-based thunderstorms at times next week. (NCEP via tropicaltidbits.com; click to animate)

It’s virtually impossible to be more specific at this time, as any convection would probably be associated with relatively subtle atmospheric perturbations that are difficult to discern more than a couple days in advance. The lightning potential next week will certainly be of considerable concern from a fire weather perspective, given both the persistence of what will by then be an ongoing severe heat wave and the broader context of California’s still extremely drought-stressed vegetation.

As always, follow Weather West on Twitter for more frequent micro-updates on California weather and climate in real time!

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  • FolsomPrisonBlues

    Was driving from Folsom to Morgan Hill this past weekend and went past the San Luis Reservoir near Pacheco Pass. I was surprised with how low it was. I have never seen it at the level it has now been reduced to. Looks more like a glorified pond now than anything else.

    • Dang stop buy and we’ll have a few beers next time! Bob G knows a ton about San Luis. All I can tell you is a vast majority of the water is pumped up and into the reservoir from the forebay which is connected to the State Water Project. It has for all intent no watershed and is used as storage and release during the summer for San Joaquin Valley Ag use. Some water is also used by Santa Clara and San Benito counties, too. As with Lake Mead, a lowering of the low point of extraction is being discussed.

      • FolsomPrisonBlues

        Ah so I am guessing a lot of its water doesn’t come from actual rainfall? The forebay actually looked to be in very decent shape. I used to drive past the reservoir all the time when I lived in Santa Clara and would go out to the valley. Since moving out to Folsom, this is the first time I had driven past in quite some time. Was a shocker. Hopefully some of this water can be replenished at some point.

    • 12% full I believe.

    • Thirsty Nick (Santa Maria)

      Looks like Cachuma.

  • craig(Big Sur/Carmel Valley)

    If the PacNW trough allows the 4 corners Ridge to elongate from se to nw up the great basin around 10 days from now, could be the beginnings of an active month ahead. The “A” looks like its right over Lake Havasu 😉

    • annette johnson

      Looks good to me! Some of the best monsoon storms in memory here in Havasu have come from the west in Socal and from the south in Parker. If we get a combination of both it’s probably a good idea to break out the candles and flashlights. Hope it happens!

  • craig(Big Sur/Carmel Valley)

    Just felt a small earthquake in CV. Map shows somewhere south of Hollister.

    • craig(Big Sur/Carmel Valley)

      Preliminary is 4.2 11 miles sse of Hollister

      • For the WW crowd I felt it in Morgan Hill. I’m in a two story office building. A little shaking and rolling.

        • craig(Big Sur/Carmel Valley)

          Was wondering….You’re the closest one in the WW crowd to that shaker. Was barely noticeable in C.V.

          • Gotta tell my secretary I’m really not nuts…LOL

          • craig(Big Sur/Carmel Valley)

            Lol. It was a small shake, rattle and roll in the market.

          • craig(Big Sur/Carmel Valley)

            Map now showing 2 earthquakes occurred around 2:38pm and 2:39pm. in same general area. One 4.2 11 miles sse of Hollister, and the other a 4.0, 8 miles nne of Chular. I didn’t feel a second one did you?

          • I felt one of ’em

          • Nate Wire

            There were definitely two events, but the second one happened immediately after the first (~40 sec). The two earthquakes are pretty distinct on this seismogram from Anderson Dam.

    • rob b-Truckee/East Bay

      Hollister has been pretty active the last few days.

      • craig(Big Sur/Carmel Valley)

        There were a few up near San Louis Res. too in last day.

      • Pfirman

        Hollister may be the most active location in California for shaking, so all in all, not an immediate concern.

  • rob b-Truckee/East Bay

    AlTahoe are you seeing any action? Sounds like South Lake Tahoe/Nat’L FS/Cal Fire are working a fire around Montreal rd and asking Heavenly to stop sending customers up the gondola but to let ppl head down to clear the area.

    • AlTahoe

      Hmm I dont see anything out of my office window that faces North. If you go here you can see it. Maybe a structure fire? Winds are still breezy as well.
      http://alerttahoe.seismo.unr.edu/firecams.html

      • rob b-Truckee/East Bay

        Listening to radio traffic Camino Dispatch is using the camera you’re looking at. There’s 2 columns showing on the camera.

        • AlTahoe

          I just heard a bunch of Firetrucks go down 50 towards that area. Hopefully the strong winds dont give them to much trouble.

          • rob b-Truckee/East Bay

            CHP reporting they plan to reopen roads-hopefully a good sign they have it contained.

  • DelMarSD

    Scripps Peir water temperature hit 76 degrees. Current temp is 76.38. Nice.

    • Tyler Price (Van Nuys)

      Pretty impressive, hopefully we don’t have too many more NW flow events that cause upwelling of colder water along our coasts! If this trend continues with warm SST’s along the immediate coasts than i wonder what they will hit in August? 78? 79? 80 again?! ?

      • WarmEpoch4California

        I’m loving how the warm SST are surviving the transition into La Nina (I feared another summer like 2010).

        Here’s the ECMWF prediction for the placement of the next hurricane (after Estelle) 8 days from now. Do you think he could bring us some remnants? With warm SST and the placement of the 4 corners high, what are the chances of getting some weather action from “Frank”?

        • Tyler Price (Van Nuys)

          Well in general recieving Precip from hurricane remnants all the way to the coasts and valleys and not exclusive to deserts and mountains is generally rare any year.. Even more so during La Niña years, but weather is unpredictable and it can still happen. We have a better chance at seeing moisture From ex hurricanes or TS during the latter months of summer, such as August and September. Sure would be nice to get a good soaking in SoCal before the summer and monsoon season wraps up!

      • Yo! Tyler!

    • RandomTreeInSB

      Correct me if I’m wrong.
      I love warm SST’s, but it seems like warmer than average sst is one culprit behind the Baja high…

      • FolsomPrisonBlues

        It looks like that warm pool near Baja could slowly dissipate as the cooler water is starting to move in all around it. Would be nice. A winter with some below average SST’s might be nice. A nice crisp fall/winter perhaps? 🙂

  • Barney

    The carrot continues to be dangled way out there in the long term, each run of each day it sits right about 13-16 days out. Laughable that it’s even discussed here with continuity.

    • Thirsty Nick (Santa Maria)

      The carrot has been dangling over California for the last few years and did we get much rain??? Nope, just a black cloud of disappointment over our heads.

      I predict a huge winter…when Moonbeam exits like 1983.

      • Barney

        On this comment section where there is no California above the Bay area you are correct sir.

    • 805 Weather (Camarillo)

      The GOA low seems to be slowly loading it’s ammunition for this fall… Would love a cold, ominous autumn like the ones we used to get in the early 2000s. Eyes peeled. I’m curious to hear from the veteran fisherman in the Bering Sea and what their take is on this year in comparison to previous years. Anybody know a guy? Deadliest Catch lol.

      • They hit it hard in October

      • FolsomPrisonBlues

        Man a nice cold, wet ominous autumn would rock! I can’t remember the last time we had one of those. Been way too long.

    • rob b-Truckee/East Bay

      Seeing a bit more discussion about the lack of monsoon rains over the Sierra into Tahoe/Reno area. This seems to be the least amount of summer storms in the last 5+ years……..maybe it will coincide with a “big” winter…whatever that may be.

      • RSmofo

        5000″ of snow.

      • FolsomPrisonBlues

        It does seem that during the last few years of drought that the monsoons have been quite prevalent. Perhaps the lack of them this year might indicate a different setup for the our upcoimng fall/winter. This summer is definitely different than the past few we have had. Even if we do get a bit of monsoon action, it is a lot less than previous years.

  • Thirsty Nick (Santa Maria)

    Fire broke out near the Hollywood sign today. So fortunate there wasn’t a Santa Ana event or it’ll be much worse.

    • RSmofo

      I dunno, Hollywood could use a good cleansing….

  • 805 Weather (Camarillo)

    Anybody else eyeballing the chance the monsoon slightly pays a little visit in about 8-9 days? It’s vague, but something has been there getting closer and closer since early Monday. More wait and see of course.

  • FolsomPrisonBlues

    Man looking at SST anomalies, the cool water is starting to dominate in the EPAC! massive amount of cooling going on from around the equator and northward of CA. The warm water up toward the GOA is being isolated out and cool water is slowly moving in. If this cooling holds up, I wonder what kind of an effect this would have on our Fall and Winter.

    • IMO
      Better than last year in the Northeast Pacific (for any year). The cooling from about 40N to 20N might allow some AR’s to punctuate a La Nina/weak Neutral year if there is good intraseasonal timing with MJO in WPAC. The EPAC’s recent TC and Hurricane activity is cooling some of that area now. The Baja area is still warm. Neutral -ENSO in around Baja…meh.. Analysis can be shown a correlation between +SST above HI to lead to a less than average precip year in both + – and neutral ENSO years. (right AlTahoe! :)) High pressure will tend to dominate somewhere in the NE PAC usually above 30N and out to —and in rare occasions straddling the dateline. The further away from the mainland and north of 40N the better. One of the big puzzle pieces will be where that height anomaly trends for the winter season. Probably a -PNA, -AMO and -AO wouldn’t hurt either :0

      • RSmofo

        It would be interesting to see what the SSTs looked like in Dec 2010.

        • From Global Ocean Data Assimilation System (GODAS)

          • FolsomPrisonBlues

            If the EPAC cools some more this wouldnt be too dissimilar. A lot more cooling would need to happen in the GOA though. The water along the coast there is currently quite warm.

          • http://iridl.ldeo.columbia.edu/
            This was apparently the SSTA for July 1861 and January 1862. via KAPLANv2 reconstruction …so GOA cool down might
            be necessary. PRAECISO before drawing any conclusions, though. A repeat would be a nightmare for CA.

          • FolsomPrisonBlues

            Wow nice link! I am going to be like a kid in a candy store checking all this data out!

      • CHeden

        A couple of excellent points to ponder. IMHO, a -AMO and -AO would have the largest impact since the hemispheric flow pattern would likely remain more progressive than what we’ve been seeing. Unfortunately, the LR models for the Atlantic are not biting (ATTM, anyway).

        • FolsomPrisonBlues

          One thing that has surprised me is that body of cold water south of Greenland is now pretty much gone. I know there was a lot of talk about the disruption that it could cause. That pool of water seemed to warm in a hurry.

          • CHeden

            Good pick up…but note the cooling is only south of 50N. Virtually everywhere north of there hemispherically, warmth continues. Western Greenland in particular is still broiling.

          • FolsomPrisonBlues

            I know that the circulation up there controls a lot of the climate for Europe (them having it nice and warm despite their high latitude), but does that have any impact on the weather out on our end? If nothing else, I have been learning that all climate on the planet seems somewhat connected in some way.

          • Charlie B

            Broiling is relative, of course. Nuuk is at 40 degrees, Quqontog (southern tip) 41, Manitsoq 42, Aasloat 39. I don’t know what “normal” is. Most others are in upper 30’s and lower 40’s. I couldn’t find Thule, which falls right in the middle of the red anomaly. Definitely wet suit water.

      • FolsomPrisonBlues

        Scary thing are the height anomaly predictions showing ridging over most NA for the upcoming winter. Daniel posted an image of this some time back.

      • Dan the Weatherman

        I think it would help when the AMO finally goes negative. I thought that was on the verge of happening a couple of years ago, but it just went back to positive like it has been for the most part since the spring of 1995.

  • CHeden

    LR forecasts from the CPC seems aligned with the GFS in bringing good PW’s all the way north to Tahoe. Western Nevada looks interesting as well.

    • I think the SoCal folks are jaded? 😉

      • SoCalWXwatcher

        July has been somewhat disappointing, but it’s looking to me like August will be quite active, which is the opposite of last year’s busy July followed by a less-active August.

        • RSmofo

          And the year before where I am. July is typically our dry month with August into early September bringing the best chances for tstorms.

          We’ve forgotten what normal is LOL

        • Dan the Weatherman

          It seems that quite often when one month such as July is active one year, that very same month the following year is completely opposite of the year before. This applies during winter as well.

        • Mike Stephenson (Riverside)

          Hopefully September has a little action left too!

    • Thirsty Nick (Santa Maria)

      Monsoon or mirage?

  • molbiol

    The monsoon continues to stay just out of reach and I wholeheartedly agree with NWS San Diego:

    “The high pressure ridge weakens
    slightly early next week for a subtle cooling trend and probably a
    few more coastal clouds. Monsoon moisture stays mostly too far
    south for us, but appears to increase around the middle of next
    week. Funny thing about that, I clearly remember saying this exact
    same thing last Wednesday.”

    Typical…

    • SoCalWXwatcher

      Oddly/Ironically, Oxnard actually appears more optimistic than the SD Office regarding Monsoon influence later next week, probably due to the fact there is better consensus among models/ensembles now:

      ”The middle-to-end of next week is looking hot once more as both the GFS and ECMWF (with good agreement in the ensembles) show the
      core of the ridge settling into Nevada by Wednesday and strengthening. This is also a textbook monsoonal position for the high and upper level clouds and convection possibilities may be on the rise.”

  • alanstorm

    Well, the nice, unseasonally cool period will be over. Enjoy it while it lasts, because a
    HEAT WAVE A COMETH
    Ukiah :
    Mon 102°
    Tues 103°
    Wed. 101°
    Thurs 101°
    Fri 100°
    Of course, thus means above 105° for every day in Red Bluff

    • FolsomPrisonBlues

      Folsom is also going to be 101 to 107 for the next 9 days at least =/

    • RSmofo

      104 when I was in San berdoo yesterday – it wasn’t bad, knowing I was driving home where it was 76. 😀

  • All is quiet. But still pretty! Between waves of fog…
    http://i.imgur.com/MpUsFR3.gif