September 27, 2018
Summary: After having it exceedingly easy in this chair for months, I now have a complex mess on my hands. One source of problems is from the northwest. The other is from the south and southeast. Short term, strong upper level high pressure right along the Pacific coast will result in hot weather through Friday with today being the hottest. Modeling for the weekend and on through Monday through Wednesday is literally like a chess game. The first major change will occur Saturday as a closed low several hundred miles to the west of San Francisco begins to move east/northeast. It should be centered over northwest California Saturday afternoon. Currently, the marine layer is only 1,500 feet deep but that will change rapidly Friday as the low moves closer, eventually pushing a major surge of marine air through the Delta and other gaps and passes along the Coast Range. Temperatures should drop by at least 10 degrees Saturday along with gusty winds, especially along the west side, where blowing dust along freshly plowed fields will occur.
By Sunday, this first low will move northward into the Pacific Northwest while another closed low develops off the northern California coast. This low will move into central California Monday night and Tuesday.
The third, and for now the most important piece in our game, is hurricane Rosa which is currently located several hundred miles of Cabo San Lucas and is chugging steadily towards the northwest. Satellite imagery indicates the cloud mass around Rosa is quite large and will begin moving into the lower deserts as early as late Sunday afternoon. Most models this morning continue to show this system moving inland through northern Baja. If I were to guess, it may move inland about 150 miles south of the California/Mexico border then continue northeastward. This scenario would move copious amounts of moisture into southeast California and into Arizona where flood concerns could be legitimate by early next week.
While all this is occurring, the northern system would be making its move into northern California with an increasing chance of showers over the northern part of the state, perhaps down to Fresno County. One solution we haven’t discussed much is that it is possible all of Rosa’s moisture may move into the south, by passing the growing area entirely. It’s also possible all of the moisture from the northern system could be confined to northern California. If these two scenarios occur, central California would be bypassed completely.
There are just too many variables involved to forecast a dry pattern as all this activity could explode in my face, bringing precipitation to the region. I feel we’re close enough now where afternoon updates are certainly in line as we study the projected path by the Hurricane Center for Rosa and watch that low forecast to move through northern California Monday night and Tuesday. A chance of showers is still very much appropriate to forecast for Monday afternoon through Wednesday morning. After Wednesday, a broad trough of low pressure will remain along the west coast, allowing some warming but by and large temperatures will remain below average for at least the next week and possibly longer.
Forecast: Mostly clear with occasional high clouds through Sunday. Partly cloudy Sunday night. Increasing cloudiness late Monday with a slight chance of showers late Monday afternoon. Mostly cloudy Monday night through Wednesday morning with a chance of showers and thunderstorms. A slight chance of showers Wednesday afternoon. Becoming partly cloudy Wednesday night. Mostly clear Thursday.
Short Term:
| Madera 99/55/93/56/84 | Reedley 99/57/93/57/85 | Dinuba 98/54/93/55/84 | |
| Porterville 100/56/94/57/86 | Lindsay 100/56/93/58/86 | Delano 99/63/96/61/87 | |
| Bakersfield 100/66/96/64/87 | Taft 99/68/96/64/87 | Arvin 101/64/97/63/87 | |
| Lamont 100/62/95/60/86 | Pixley 99/58/94/58/86 | Tulare 98/54/93/56/85 | |
| Woodlake 99/55/95/56/85 | Hanford 100/56/95/57/86 | Orosi 98/55/96/56/85 | |
Seven Day Forecast:
| Sunday
Partly cloudy 51/84 |
Monday
PM showers possible 55/80 |
Tuesday
Chance of showers 59/76 |
Wednesday
AM showers possible 55/77 |
Thursday
Mostly clear 50/80 |
Two Week Outlook: October 4 through October 10: 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 variable at 5 to 10 MPH through tonight with locally stronger gusts. By later Friday afternoon, winds will begin to pick up out of the west to northwest mainly along the west side at 15 to 25 MPH with gusts to 35 MPH, continuing Friday night. Elsewhere, winds will be out of the northwest at 10 to 15 MPH with stronger gusts. Winds Saturday through Monday will be mainly out of the northwest at 5 to 15 MPH with local gusts to 25 MPH, mainly along the west side.
Rain: It hasn’t rained in the valley since mid April. That may not change beginning early next week. There will be a chance of showers and thunderstorms from late Monday afternoon through about Wednesday morning. A complex pattern is evolving involving a closed low which will be moving into northern California Monday night and Tuesday and weakening hurricane Rosa which is projected to move onshore in northern Baja Sunday night and Monday.
There are many “what ifs” in this evolving pattern. If current model projections are correct, most if not all the precipitation from Rosa would move into roughly the southern one-third of California and into Arizona where flooding could be a concern Monday and Tuesday.
In the meantime, that closed low to our north is projected to have strong enough dynamics for a chance of showers for most of northern California with the possibility of showers spreading down to Fresno County.
There is also the possibility that neither of these systems will result in measurable rain as the hurricane and its moisture could move too far south and the closed low could move in too far to the north.
For now, the best option would be to call it roughly a 30% chance of precipitation at any given location beginning late Monday afternoon through about Wednesday morning.
After Wednesday, the pattern will again be dry.
I will be issuing an afternoon update.
Afternoon Dew Points Today: Mid to upper 40s. Kern: Low to mid 40s.
Humidity: Visalia: 20%/85% Bakersfield: 15%/55%
Actual Humidity September 26, 2018: Delano, 92%/24%, Porterville, 90%/15%
Percentage of Sunshine Today/Tomorrow: Visalia: Today: 90% tomorrow 70% Bakersfield: Today: 90% Tomorrow: 80%
ET Rates Over the Past Seven Days: Stratford 1.48, Parlier 1.30, Blackwell 1.48, Lindcove 1.30, Arvin 1.53, Orange Cove 1.43, Porterville 1.20, Delano 1.30, Courtesy University of California *=estimate, NA=not available.
Seven Day Soil Temperatures: Stratford 71, Parlier 72, Blackwell 81, Lindcove, 73, Arvin, 72, Orange Cove 73, Porterville 79, Delano 71
Record Temperatures: 105/44. Average Temperatures: 88/56
Cooling Degree Days this Season: 2021 +456
Courtesy of the NWS
Average temperature for September so far: 75.5 +1.6
Precipitation: Seasonal total/average/above or below average:
Since Oct 1, 2017 Fresno: 6.73 season. or -4.73. Month to Date: .00
Since Oct 1, 2017, Bakersfield: 3.93, or -2.50. 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: 6:52 am Sunset: 6:47 pm. Hours of Daylight: 11:56
Yesterday’s Weather:
MAE : Madera 253 : DH1700 / 98 / 57 / 0.00 /
FAT : Fresno Airport 333 : DH1700 / 97 / 62 / 0.00 /
HJO : Hanford Airport 242 : DH1700 / 98 / 54 / 0.00 /
NLC : Lemoore Naval AS 234 : DH1700 / 99 / 56 / 0.00 /
BFL : Bakersfield Airport 496 : DH1700 / 96 / 66 / 0.00 /
VIS : Visalia Airport 292 : DH1700 / 96 / 58 / 0.00 /
ATEC1 : Avenal 787 : DH1700 / 96 / 60 / 0.00 /
PTV : Porterville Airport 442 : DH1700 / 97 / 60 / 0.00 /
TFTC1 : Taft 759 : DH1657 / 95 / 72 / 0.00 /
LOSC1 : Los Banos 120 : DH1600 / 93 / M / 0.00 /
Rainfall: Water year Oct 1st through September 30th
Year % Last Y. % Ave. Annual ave.
STOCKTON 0.00 9.22 66 21.79 156 14.00 14.06
MODESTO 0.00 8.17 63 16.93 130 13.05 13.11
MERCED 0.00 7.06 57 16.05 129 12.45 12.50
MADERA 0.00 7.22 60 14.26 119 11.98 12.02
FRESNO 0.00 6.73 59 17.36 151 11.46 11.50
HANFORD 0.00 4.70 47 11.21 111 10.07 10.10
BAKERSFIELD 0.00 3.95 61 8.34 129 6.45 6.47
BISHOP 0.00 3.08 60 9.18 179 5.13 5.18
SALINAS 0.00 7.16 56 16.49 129 12.79 12.83
PASO ROBLES 0.00 9.62 76 16.17 127 12.73 12.78
SANTA MARIA 0.00 6.01 43 18.91 136 13.92 13.95
Next report: Friday, September 28