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September 29, 2018/report

September 29, 2018

Summary:  The marine layer along the coast is now 4,000 feet deep and has completely pooled the San Joaquin Valley with modified marine air.  This will lead to a much cooler day.  In fact, readings in  most areas will probably struggle into the low 80s today and Sunday.


The culprit is a low pressure system which is approaching the northern California coast.  There are bands of high clouds as evidence it is there as there is no rain associated with it.  The on shore flow will continue through Sunday then the low will weaken and move into the Pacific Northwest.  A new low is moving rapidly southeastward and is gaining strength.  By the time it reaches northern California, its dynamics will certainly be strong enough for widespread shower activity, spreading into central California later Monday night and continuing through Wednesday.  In fact, most models track the low right through central California Tuesday and Wednesday then it will open up into a trough over the western states Thursday.


In the meantime, Hurricane Rosa, which is now slowly decreasing in strength with maximum sustained winds down to 100 MPH, is chugging northward well off the southern Baja coast.  It will move inland as a tropical storm through northern Baja Monday and into Arizona Tuesday.  Flash flood watches are out for much of Nevada, parts of southern California, and parts of Arizona.  It appears the northern limit of Rosa’s moisture will reach into southern Kern County, but there may not be enough deep tropical moisture to produce showers that far north.  Still, even this close, it’s a tricky call.


For now, the main low I alluded to earlier is the main challenge with the likelihood of showers and a slight chance of isolated thunderstorms later Monday night through Wednesday.  Models are also picking up on a new low moving through northern and central California Thursday.  Some models actually show a slight chance of showers for Thursday, but for now we’ll go with a dry forecast.  It will, though, keep temperatures below average through at least Friday with only marginal recovery next weekend.


Forecast: Other than occasional high clouds, it will be mostly clear through Sunday night and much cooler.  Increasing clouds later Monday.  Mostly cloudy Monday night through Wednesday with a chance of showers Monday night, becoming likely Tuesday through Wednesday with a slight chance of thunderstorms.  A slight chance of showers Wednesday night.  Becoming partly cloudy Thursday.   Mostly clear Thursday night through Saturday.


Short Term:                                                                            

Madera 81/50/81/49/85 Reedley 82/51/81/50/86 Dinuba 80/49/79/48/85
Porterville 82/51/81/50/85 Lindsay 81/49/81/48/85 Delano 82/53/81/51/86
Bakersfield 81/57/82/58/87 Taft 82/59/83/60/86 Arvin 83/55/83/57/87
Lamont 82/56/83/57/86 Pixley 82/52/81/51/86 Tulare 81/50/81/51/85
Woodlake 82/50/81/51/85 Hanford 81/53/81/54/86 Orosi 82/49/81/49/86


Seven Day Forecast:


Showers likely



Showers likely



Partly cloudy



Mostly clear



Mostly clear



Two Week Outlook:  October 6 through October 12:  This model shows strong high pressure along the Pacific coast.  It also, however, indicates the possibility of moisture moving into Arizona and southern California from the south.  Temperatures under this regime would again be above average with a low chance of precipitation.


September:  This model indicates there will be a higher than active monsoon over the Desert Southwest and possibly central and southern California.  This typically does not affect the valley floor other than cloud cover but could result in a larger number of days of thunderstorms over the Sierra Nevada and possibly even the Kern County mountains.  With generally high pressure over the southwest, temperatures will likely be somewhat above seasonal average.


September, October, November:  The first part of this time frame will see a more active than usual monsoon in place for above average rain over the Sierra Nevada and possibly the mountains and deserts of southern California.  October and November’s conditions aren’t as easy to determine.  At this time we’ll call for generally average values for both rain and temperatures.


Winds:  Winds will be mainly out of the northwest at 10 to 20 MPH at times with locally stronger gusts today with gusts to 35 MPH possible along the west side.  Winds tonight and Sunday will be mainly out of the northwest at 5 to 15 MPH, becoming generally less than 12 MPH Sunday night through Monday.  Winds Monday night and Tuesday will again be out of the northwest at 10 to 20 MPH with stronger gusts.


Rain:  It now appears likely we will have our first rain event since April 16 beginning possibly as early as later Monday night.  A low pressure system with strong dynamics will be off the northern California coast Monday, spreading showers into north/central California.  Later Monday night and Tuesday, showers will spread southward with the low pegged by some models to be directly over central California Tuesday and Tuesday night.  Models show a fairly significant moisture field wrapped around the low, so as much as .10 to .25 is certainly possible in some areas.  Thunderstorms appear unlikely with this event, but I’ll add a small chance to the forecast, especially if any clearing occurs Tuesday and Wednesday.  If clearing occurs at any given location, as much as .50 could not be ruled out.


The timing of all this will be later Monday night through the day Wednesday with decreasing activity Wednesday night.  Some  models indicate a new low will develop Thursday with a chance of showers.  I’m going with a dry forecast at this time for Thursday until evidence of possible rain shows up.  For now, expect dry weather for Thursday and beyond.

Afternoon Dew Points Today: Mid to upper 40s.  Kern: Mid to upper 40s.

Humidity: Visalia: 35%/90%  Bakersfield: 35%/70%

Actual Humidity September 28, 2018: Delano, 80%/26%, Porterville, 89%/18%


Percentage of Sunshine Today/Tomorrow: Visalia: Today: 70%  tomorrow 70%  Bakersfield: Today: 80% Tomorrow: 70%


ET Rates Over the Past Seven Days: Stratford 1.45, Parlier NA, Blackwell 1.53, Lindcove 1.28, Arvin 1.52, Orange Cove 1.41, Porterville 1.18, Delano 1.27,   Courtesy University of California *=estimate, NA=not available. 


Seven Day Soil Temperatures: Stratford 71, Parlier 72, Blackwell 82, Lindcove, 73, Arvin, 72, Orange Cove 73, Porterville 79, Delano 71


Record Temperatures: 102/43. Average Temperatures: 87/55

Cooling Degree Days this Season: 2046  +469

Courtesy of the NWS

Average temperature for September so far: 75.7 +2.0


Precipitation:  Seasonal total/average/above or below average

Since Oct 1, 2017  Fresno: 6.73 season. or -4.75.  Month to Date: .00

Since Oct 1, 2017,  Bakersfield:  3.93, or -2.51.  Month to Date: .00

Water year season is from October 1st through September.


Chilling Hours November 1st through February 28: Orange Cove,  Parlier,  Arvin,  Shafter,  Stratford,  Madera two,  Lindcove,  Porterville,   Hours at 45 or below 45.


Sunrise: 6:53 am  Sunset: 6:44 pm. Hours of Daylight:  11:52

Yesterday’s Weather:

MAE   : Madera               253 : DH1700 /  97 /  59 / 0.00 /

FAT   : Fresno Airport       333 : DH1700 /  96 /  65 / 0.00 /

HJO   : Hanford Airport      242 : DH1700 /  97 /  57 / 0.00 /

NLC   : Lemoore Naval AS     234 : DH1700 /  98 /  57 / 0.00 /

BFL   : Bakersfield Airport  496 : DH1700 /  98 /  68 / 0.00 /

VIS   : Visalia Airport      292 : DH1700 /  96 /  59 / 0.00 /

ATEC1 : Avenal               787 : DH1700 /  96 /  64 / 0.00 /

PTV   : Porterville Airport  442 : DH1700 /  97 /  61 / 0.00 /

TFTC1 : Taft                 759 : DH1658 /  96 /  74 / 0.00 /

LOSC1 : Los Banos            120 : DH1600 /  86 /  59 / 0.00 /


Rainfall:  Water year Oct 1st through September 30th

Year              %          Last Y.        %                Ave.             Annual ave.

STOCKTON                      0.00    9.22    66   21.79   155    14.03    14.06

MODESTO                       0.00    8.17    62   16.93   129    13.08    13.11

MERCED                        0.00    7.06    57   16.05   129    12.48    12.50

MADERA                        0.00    7.22    60   14.26   119    12.00    12.02

FRESNO                        0.00    6.73    59   17.36   151    11.48    11.50

HANFORD                       0.00    4.70    47   11.21   111    10.08    10.10

BAKERSFIELD                   0.00    3.95    61    8.34   129     6.46     6.47

BISHOP                        0.00    3.08    60    9.18   178     5.15     5.18

SALINAS                          T    7.16    56   16.49   129    12.81    12.83

PASO ROBLES                   0.00    9.62    75   16.17   127    12.75    12.78

SANTA MARIA                   0.00    6.01    43   18.91   136    13.93    13.95


Next report:  Saturday, September 29/pm