Unsettled conditions after and unseasonably early hot and dry spell

Filed in Uncategorized by on May 4, 2013 24 Comments

What a strange winter it has been here in California! Intense December rains in the northern part of the state tapered off by the end of the calendar year, and our usually well-defined rainy season simply hasn’t returned since. NorCal has set numerous new records for minimum precipitation over various intervals since January–including, assuming provisional numbers hold up–the driest January-April period on record. SoCal has been quite dry too, on average, though occasional very dry years are less exceptional down south. Now that we’ve entered May, our typical rainy season should be well on its way out. Fire weather conditions over the past week have been disconcertingly extreme for so early in the year, with large, wind-driven wildfires both in far NorCal and SoCal. I don’t think this bodes well for the coming summer and fall.

NASA MODIS imagery of SoCal wildfire on 5/3/2013

NASA MODIS imagery of SoCal wildfire on 5/3/2013

Over the coming week or so, however, it does appear that a very unusual large-scale pattern will allow for some more unsettled conditions than we’ve seen in quite some time here in CA. By tomorrow, a cutoff low will retrograde over NorCal from Nevada under a rather strong Rex block. Cutoff lows are not uncommon near CA–in fact, our region is well-known for its propensity to produce these slow-moving features–but it is far from typical for a cutoff to form over the Great Basin and make it all the way off the coast of San Francisco, as is expected to happen over the next couple of days.

NAM depiction of precip early next week

NAM depiction of precip early next week

As it does so, this initially weak low will deepen and entrain some moisture over the ocean, slowly increasing lift and instability over a broad region of the state. Scattered showers and probably some thunderstorms should develop over the higher terrain by Sunday afternoon, slowly becoming more widespread Monday and Tuesday. Just about every part of the state stands the chance of an isolated thunderstorm at some point this week, though most places will see very little precip and lightning is most likely in the mountains. It is possible, as sometimes happens with spring/fall cutoff lows in CA, that some mid-level instability develops and produces more widespread thunderstorm activity than currently expected. If that happens, I anticipate the possibility of significant fire weather concerns, as such storms tend to be rather dry and we’ve seen how dry conditions already are throughout the week by the fires that have occurred. Could be an interesting week ahead!

© 2013 WEATHER WEST

  • Dan the Weatherman

    More stations are finally reporting light rain in Socal and the radar is now showing some light rain bands developing and moving onshore. It is been drizzling here off and on for the last hour or so, but just barely enough to wet the ground.

  • Nicholas

    Got some heavy rain off and on in my location. Flow is very good for the Whittier area. Already >0.50 with a few drops still falling.

  • alan

    .81″ since it started at midnight last night, much needed rain but in 10 days it’ll become unnoticed….

  • sc100

    There’s a really strong cell going right through the middle of Sacramento right now. I’m just at the northern end of it. I’m getting some of it right now. Hopefully it’ll strengthen more up where I’m at.

    • sc100

      I’m definitely getting some action right now!

  • Ken K.

    Picked up .45 at the house today, some pretty good heavier showers today, nice little break. Enjoy it looks to warm up again, like Dan has said in the past one last rainfall to kick in the summer mode.

  • Dan the Weatherman

    There was some pretty good steady rain here in Orange last night and early this morning, along with a few showers late this afternoon. This is the most rain that has fallen here since early March, and was much needed, too, as it helped to douse any remnant of last week’s fires. I will report a total for the area when the storm moves out later tomorrow.

  • Nicholas

    There must be strong subsidence over my area today. Every shower that has tried to make to eastern la county or IE has died. Yet showers near the coast have exploded.

  • Nicholas

    … Measurable precipitation finally falls in Bishop…

    Yesterday… may 6th… a total of 0.11 inch of rain fell at the
    eastern Sierra regional Airport in Bishop California. This marked
    the first time this year that measurable precipitation has fallen in
    Bishop which ties may 6th 1972 for the latest ever in the calendar
    year to go for the first measurable precipitation of the year.

    The last time Bishop saw measurable precipitation prior to may 6th
    was back on December 26th of 2012. This 130 consecutive day stretch
    ties with a stretch from December 28th 1971 through may 5th 1972 for
    the 5th longest stretch ever with measurable precipitation in
    Bishop. The longest such stretch ever was 199 days from April 23rd
    2003 through November 7th 2003.

    Finally so far today… may 7th… a total of 0.45 inch of
    precipitation has fallen in Bishop which ties the daily record last
    set in 1955.

    Records at Bishop date back to September 1943.

    The above information is preliminary and is subject to a final
    review before being certified by the National climatic data center.

  • Dan the Weatherman

    .28″ fell here in Orange from this latest storm, not bad for May, but I thought the area received a bit more than that as there was a good period of some moderate rain overnight Sunday night into early Monday morning.

  • alan

    .82 early in the week and .16 Thursday from a 10 min thunderstorm including hail

  • alan

    It’s a disturbingly warm start to the ‘summer’ – while the n. plans are recording record high temps and to the south in tx – record low temps…

    Hope somehow this bodes well for an active monsoon…considering we had summer like tstorms last week, earliest in the year I’ve experienced that here…

  • Ken K.

    Hot day ,100 at the house (Granite Hills) and 98 yesterday with RH’s in the lower teens, fires in our area the last 3 days, if this an indicator, looks to be a hot summer, Alan, last week I talked to one of the meteorologist out of San Diego office, his thoughts were for a normal monsoon while the meteorologist out south OPS,predictive services thought it would be below normal as the four corners high would be placed further west than normal. Will have to wait and see.

  • Dan the Weatherman

    I don’t necessarily believe that multiple hot spikes of weather in April and/or May are any indication of what the upcoming summer will be like, since we don’t usually settle into the usual summer pattern until later in June. At least from what I have noticed the last 15 years or so, it seems that this type of early season heat occurs when the rainy season ends earlier than usual. A quick late season storm well after the rains end such as last week’s event, for example, can occur in these types of seasons as well. Years that have behaved similarly to this year have been 1996-97, 2003-04, 2007-08, 2008-09 (to an extent). I will point out that there was a thunderstorm outbreak sometime in May, 2008 after there had been several spikes of heat in April and May after the rainy season ended at the end of February or early March.

    The summers of 2004 and 2008 were relatively mild to average as far as I can remember, while 1997 was warm and humid (due to El Nino) and 2009 was warm to hot. There is definitely a chance this summer could be very hot and brutal, but it could also turn out cooler than average to average as well.

    • Dan the Weatherman

      I do agree that the fire season will be more severe than normal from now until fall due to the ultra-dry conditions from the past couple of winters, especially during really hot spells, dry lightning situations, and fall Santa Ana wind events.

  • Nicholas

    GFS and Euro showing a small piece of energy moving down the coast. It would be rather late in the season for a winter like storm but its taken place a handful of times.

  • Might be time for a new update? Possible brief but potentially extremely hot event in interior NorCal this weekend with widespread Central Valley temps in excess of 110 possible. Also, there’s an increasing chance of some elevated convection early next week on the diffluent side of cutoff low over the far E. Pac. Stay tuned!

  • Shady Blues

    And here we go with the boring weather. Anybody have guess about the upcoming winter? Dan you were spot on about last winter. So, I am looking forward to your thoughts.

    • Dan the Weatherman

      I think next year will be wetter than this last year, but I think it will still be drier than average but closer to average than this year. Los Angeles doesn’t usually have two consecutive years with less than 7 inches of rain.

      I am concerned that this upcoming fall and possibly early winter could really be dry, especially during November, December, and possibly early January. Comet ISON is expected to reach perihelion toward the end of November and it has been really dry around here lately whenever a comet has passed through the inner Solar Syatem. I have never seen any scientific evidence that comets affect the weather in any manner, but I have noticed that Socal has been especially dry during these time periods. I do think that later in January it will turn wetter and that we will get more rain during the rest of the winter and early spring once the comet is out of the picture.

  • sc100

    It looks like Sacramento will end the rain year with 16.13 inches of rain, 80% of average. Not too bad, considering how bad 2013 has been so far. I see how LA is going to end the year with 5.85 inches. Ouch.

  • David

    SPECIAL WEATHER STATEMENT
    NATIONAL WEATHER SERVICE SACRAMENTO CA
    1130 AM PDT THU JUN 20 2013

    CAZ013>019-063-064-066>069-211300-
    SHASTA LAKE AREA / NORTHERN SHASTA COUNTY-
    BURNEY BASIN / EASTERN SHASTA COUNTY-NORTHERN SACRAMENTO VALLEY-
    CENTRAL SACRAMENTO VALLEY-SOUTHERN SACRAMENTO VALLEY-
    CARQUINEZ STRAIT AND DELTA-NORTHERN SAN JOAQUIN VALLEY-
    MOUNTAINS SOUTHWESTERN SHASTA COUNTY TO NORTHERN LAKE COUNTY-
    CLEAR LAKE/SOUTHERN LAKE COUNTY-
    NORTHEAST FOOTHILLS/SACRAMENTO VALLEY-MOTHERLODE-
    WESTERN PLUMAS COUNTY/LASSEN PARK-
    WEST SLOPE NORTHERN SIERRA NEVADA-
    1130 AM PDT THU JUN 20 2013

    …WET AND COOLER WEATHER SUNDAY INTO WEDNESDAY…

    AN UNSEASONABLY STRONG LOW PRESSURE SYSTEM WITH ABUNDANT TROPICAL
    MOISTURE IS FORECAST TO IMPACT INTERIOR NORTHERN CALIFORNIA EARLY
    NEXT WEEK. AHEAD OF IT…A WEAKER STORM WILL MOVE THROUGH SUNDAY BRINGING
    A THREAT OF MAINLY LIGHT SHOWERS…GENERALLY NORTH OF INTERSTATE 80.
    WIDESPREAD PRECIPITATION THEN DEVELOPS BY MONDAY MORNING AND
    CONTINUES INTO TUESDAY AS THIS ANOMALOUS LOW PRESSURE SYSTEM
    IMPACTS THE AREA. GIVEN THE TIME OF YEAR…SIGNIFICANT
    PRECIPITATION IS POSSIBLE WITH THE POTENTIAL FOR DAILY RAINFALL
    RECORDS TO BE BROKEN. UNCERTAINTIES EXIST WITH PRECIPITATION
    AMOUNTS AT THIS TIME…BUT UPWARDS OF AN INCH OF RAIN MAY FALL IN
    PORTIONS OF THE CENTRAL VALLEY THROUGH TUESDAY WITH HIGHER AMOUNTS
    POSSIBLE IN THE FOOTHILLS AND MOUNTAINS. SNOW LEVELS ARE EXPECTED
    TO REMAIN ABOVE PASS LEVELS WITH THIS RELATIVELY WARM STORM.

    PERSONS WITH OUTDOOR ACTIVITIES PLANNED SUNDAY THROUGH TUESDAY
    SHOULD BE PREPARED FOR THE POSSIBILITY OF SIGNIFICANT RAINFALL.
    PRECIPITATION IS EXPECTED TO DECREASE WEDNESDAY AND LIFT NORTHWARD.
    DRY AND WARMER WEATHER FORECAST THURSDAY INTO NEXT WEEKEND AS HIGH
    PRESSURE RETURNS.

  • Well…looks like we might get a very impressive summer rain event in NorCal early next week. In fact…there are increasing indications of a full-blow atmospheric river impacting the state, with rain totals of several inches possible. I have never seen a setup this moist and dynamic during the California warm season, and if this pans out some sites will certainly break daily rainfall records and perhaps all-time monthly records for summer, as well. Expect a full update either tomorrow or Saturday as the details become more clear. Bonus: extreme heat wave may be on the horizon for the week after next.

    • Dan the Weatherman

      The latest SFO AFD is indicating that the North Bay region could receive as much as 1 to 1.5″ of rain from this event with even higher totals in Norcal and southern Oregon. They are now calling it a potential atmospheric river event, and I don’t know if I have ever heard of an atmospheric river event (or Pineapple Express as it is often called) this time of year before in Norcal, especially given that this is the beginning of the dry season up there. Of course these are more common during the rainy season. It would be very interesting if this verifies and just how much rain does manage to fall. It is sorely needed and would help with the fire danger in the short term.

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