September 28, 2018
Summary: It’s time to take the threat of precipitation beginning Monday night more seriously. Models this morning show the high which has resulted in hot September weather the past few days beginning to break down as the first of two low pressure systems bears down on California. The first will move inland Saturday with no precipitation but cooler air will begin to move in aloft and a strong push of marine air will surge down the valley. Actually, the beginning of that process is already underway as the marine layer has jumped 600 feet over the past few hours. It will begin to spill through the Delta and Pacheco Pass this afternoon, quickly moving inland tonight with gusty winds along the west side of the valley. Temperatures will plummet, reaching only the mid 80s Saturday and low 80s Sunday. By Sunday, the low will move northward into the Pacific Northwest.
In the meantime, we are still watching Hurricane Rosa which now has maximum sustained winds of 145 MPH, making it a category 4. Rosa, which had been moving west, is now showing signs of turning to the northwest and eventually moving through northern Baja as a tropical storm late Monday night and Tuesday. As of now, it appears southeast California will receive heavy amounts of rain with possible flooding, as will southwest Arizona. It’s still unclear how far north the remnants of Rosa will progress.
A new low, this one with much stronger dynamics, will race southeastward out of the Gulf of Alaska and will be in northern California by late Monday and central California Tuesday. Models do show this system weakening somewhat, but with a sufficient moisture shield for at least scattered showers and possibly a few isolated thunderstorms. The risk factor for this system for measurable precipitation will begin to increase Monday night with the greatest risk being Tuesday through the first half of the day Wednesday.
If Rosa’s moisture happens to get caught up in the circulation of this system, it would be possible we could have a major rain event. At this point, though, it appears unlikely. I would now put the chance of precipitation during this time frame at roughly 50%, but if models continue with current trends, that factor may rise over the next 72 hours.
By Wednesday night, this system will have moved out of the area, returning dry weather, but not before temperatures sink into the 70s Tuesday and Wednesday with only a slow recovery Thursday and beyond. In fact, a trough of low pressure is projected by models to remain over the western states with below average temperatures. If that isn’t enough, a new hurricane is projected to develop and move northwestward along the Baja coast next weekend, possibly moving inland through central Baja. That’s much to far out to project potential precipitation. As of now it looks like most of its moisture would move into the Desert Southwest.
Forecast: Outside of occasional high clouds, it will be mostly clear through Sunday. Becoming partly cloudy Sunday night. Increasing cloudiness Monday with an increasing chance of showers and isolated thunderstorms Monday night through roughly midday Wednesday. A slight chance of showers Wednesday afternoon then mostly clear to occasionally partly cloudy Thursday through Friday.
Short Term:
| Madera 94/55/82/52/81 | Reedley 94/56/83/53/82 | Dinuba 93/56/82/51/80 | |
| Porterville 95/56/84/52/82 | Lindsay 95/55/84/51/83 | Delano 96/59/85/54/83 | |
| Bakersfield 96/65/85/57/84 | Taft 95/68/86/58/84 | Arvin 97/62/87/57/84 | |
| Lamont 96/61/86/57/84 | Pixley 95/55/84/55/82 | Tulare 93/55/83/51/80 | |
| Woodlake 94/56/83/51/81 | Hanford 95/57/83/54/82 | Orosi 94/54/83/50/81 | |
Seven Day Forecast:
| Monday
PM showers possible 57/83 |
Tuesday
Increasing chance of showers 61/78 |
Wednesday
AM showers 56/76 |
Thursday
Partly cloudy 50/79 |
Friday partly cloudy 51/80 |
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 this morning will be light. By this evening, winds will be out of the west to northwest at 10 to 15 MPH with stronger gusts possible. Winds along the west side may gust as high as 35 MPH, continuing Saturday. Winds will be mainly out of the northwest Saturday through Monday at 10 to 15 MPH with stronger gusts possible.
Rain: Needless to say, there is a lot to talk about this morning. I now consider the chance of measurable precipitation from Monday night through the first half of the day Wednesday to be higher. The first of two low pressure systems will move in Saturday. This one will be dry, just resulting in a down turn in temperatures. System number two appears to have strong dynamics as it races out of the Gulf of Alaska, entering northern California Monday and central California Monday night and Tuesday. Even though this system will have weakened, most of the model information now indicates the moisture content around the low is pretty decent and may be enough for showers and isolated thunderstorms over the entire valley late Monday night into Wednesday. In the meantime, hurricane Rosa, which is a major hurricane, is continuing to be projected to move inland as a tropical storm Monday night through Tuesday through northern Baja then northeastward into Arizona. Heavy precipitation is projected for the Imperial Valley, possibly northward into the Coachella Valley, but models still show the moisture remaining slightly to our south. This is a hurricane we’re dealing with and they have a mind of their own, so I’m not yet ready to rule out remnants of Rosa possibly being tugged northward by that low which would be over central California. If this does occur, we would have a major precipitation event. It probably won’t happen, but even without Rosa’s moisture, the chance of measurable rain appears to be right at 50% and this may continue to rise as each set of models seems to pay more respect to that system.
Dry weather will return by Wednesday night, continuing through the following weekend. A could of models show a new hurricane developing and moving up the Baja coast by a week from Sunday, possibly moving through central Baja which would keep central California dry. Nevertheless, we’ll keep our eyes to the south as the tropics have come alive.
Afternoon Dew Points Today: Low to mid 50s. Kern: Low to mid 50s.
Humidity: Visalia: 25%/85% Bakersfield: 25%/70%
Actual Humidity September 27, 2018: Delano, 83%/26%, Porterville, 86%/18%
Percentage of Sunshine Today/Tomorrow: Visalia: Today: 80% tomorrow 70% Bakersfield: Today: 90% Tomorrow: 70%
ET Rates Over the Past Seven Days: Stratford 1.46, Parlier 1.30, Blackwell 1.49, Lindcove 1.30, Arvin 1.53, Orange Cove 1.43, Porterville 1.19, Delano 1.28, 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: 104/43. Average Temperatures: 87/55
Cooling Degree Days this Season: 2033 +462
Courtesy of the NWS
Average temperature for September so far: 75.6 +1.8
Precipitation: Seasonal total/average/above or below average:
Since Oct 1, 2017 Fresno: 6.73 season. or -4.74. 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: 6:45 pm. Hours of Daylight: 11:53
Yesterday’s Weather:
MAE : Madera 253 : DH1700 / 99 / 58 / 0.00 /
FAT : Fresno Airport 333 : DH1700 / 98 / 64 / 0.00 /
HJO : Hanford Airport 242 : DH1700 / 98 / 56 / 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 / 58 / 0.00 /
ATEC1 : Avenal 787 : DH1656 / 98 / 62 / 0.00 /
PTV : Porterville Airport 442 : DH1700 / 97 / 63 / 0.00 /
TFTC1 : Taft 759 : DH1657 / 98 / 75 / 0.00 /
LOSC1 : Los Banos 120 : DH1600 / 95 / 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 14.01 14.06
MODESTO 0.00 8.17 63 16.93 130 13.06 13.11
MERCED 0.00 7.06 57 16.05 129 12.47 12.50
MADERA 0.00 7.22 60 14.26 119 11.99 12.02
FRESNO 0.00 6.73 59 17.36 151 11.47 11.50
HANFORD 0.00 4.70 47 11.21 111 10.07 10.10
BAKERSFIELD 0.00 3.95 61 8.34 129 6.46 6.47
BISHOP 0.00 3.08 60 9.18 179 5.14 5.18
SALINAS 0.00 7.16 56 16.49 129 12.80 12.83
PASO ROBLES 0.00 9.62 76 16.17 127 12.74 12.78
SANTA MARIA 0.00 6.01 43 18.91 136 13.92 13.95
Next report: Friday, September 28/pm