31/751 PM.
Stagnant pattern through Friday, with below normal temperatures, coastal clouds, and moderate Sundowner winds. Several potential scenarios for the Labor Day weekend, with anything from benign conditions possible, tropical rain, to hot offshore winds.
(Mon-Thu), 31/748 PM.
With upper level trough across California and increasing onshore flow, we have seen a cooling trend across most areas today, with many areas seeing temperatures 5 to 10 degrees below normal for this time of year. Current satellite imagery showing low clouds off the Central Coast, and is expected to spread inland up there, as well as portions of the LA/Ventura coast later tonight. In addition to the lowering heights and stronger onshore flow, there will be a weak eddy circulation each night which will likely maintain a deeper marine layer depth around 2000 feet, with a few areas perhaps even seeing some drizzle in the morning.
Onshore winds will remain enhanced across the interior during the next few days, with gusts mostly in the 25 to 40 mph range. This will be most enhanced across the Antelope Valley and adjacent foothills, as well as the LA county mountains. In addition, there will be weak to moderate sundowner winds across southwest Santa Barbara county the next few nights. Tonight's event is trending weaker, with the 7 pm SBA-SMX gradient only at -1.8 mb as compared to -4 mb yesterday at this time. There will be a gradual increase in sundowner wind potential for Tuesday and Wednesday evenings, when wind advisories may be needed.
***From previous discussion***
Multiple large troughs of low pressure will drive the weather through the week. The core of the energy and moisture will stay far enough to the north to not be concern with any rain or strong winds, but it will maintain below normal temperatures. To clarify however, with this being the hottest time of the year, below normal temperatures does not mean it is time to dust off the jackets. It will still feel warm, but thankfully not hot like it was last week. Tropical moisture will stay away from the region as well so it will also not feel as muggy as it did last week. With ocean temperatures still in the 70s however, it will still feel more humid than usual.
A deep marine layer (2,000+ feet) will continue through the week as well, and should deepen a little more tomorrow as the trough sags to the south. Would expect a spot or two to see drizzle in the morning where the clouds develop, especially near the Central Coast foothills. Solid night through morning low clouds are most likely on the Central Coast, but coverage to the south should remain spotty thanks to the warmer ocean temperatures, despite the marine layer being just as deep. It is impossible to predict exactly where those random spots of clouds will form.
Sundowner winds will continue each night over southwest Santa Barbara County and flirt with an Advisory each time. Tonight looks just under Advisory levels, while Tuesday and Wednesday night look just over.
(Fri-Mon), 31/606 PM.
Little change expected on Friday compared to the first half of the week.
All eyes remain focused on the Labor Day holiday weekend period. A Hurricane is likely to develop by Wednesday or Thursday from the clump of clouds currently just off the Baja coast. Once it forms, it will likely move to the northwest through Saturday and towards southern California. The big question is where will it head after Saturday. Some deterministic models, like the current GFS, keeps the storm moving northward and right through southern California by Monday or Tuesday. Others, like the deterministic ECMWF, show the storm turning to the west and never even sniffing California. These are just two of many projections, but they do represent the two extreme scenarios between a major rain and wind event and little to nothing. Peering into the ensemble solutions, they suggest that the heavy rain scenario is the least likely outcome (5-10% of the 100 projections have 2+ inches of rain), but there are a fair number of solutions showing light to moderate rain (mostly under 1 inch) which would likely have minimal impacts. The completely dry scenario comprises 20-30% of the solutions. Which means in terms of rain, the most likely outcome is for some light to moderate rain impacting the holiday weekend. As far as timing is concerned, there is a small chance of showers starting as early as Saturday, with also a small potential for monsoonal thunderstorms over the mountains and deserts. From Sunday into Monday night, rain chances are somewhat higher.
The wind story is similar, with a low but non- zero chance of strong east to northeast winds causing fire and downed tree concerns. With all that said, this is definitely a period to monitor with a range of outcomes on the table. Due to the rarity of this storm, expecting there to be a lot of uncertainty even as we get to the weekend, but hopefully some details will come more into focus by mid-week once the storm actually form.
01/0000z.
At 2345Z at KLAX, the marine layer was 1300 feet deep. The top of the inversion was at 2900 feet with a temperature of 22 Celsius.
High confidence on VFR conditions through Tuesday at KWJF KPMD.
High confidence in IFR/MVFR conditions tonight through Tuesday at KPRB KSMX KSBP. Moderate confidence for KLAX KSMO KLGB, and low confidence for KOXR KCMA KSBA KBUR KVNY.
KLAX, High confidence in VFR conditions to follow through at least 06Z. Moderate confidence of MVFR cigs between 07z and 18z. High confidence in an east winds staying under 8 knots.
KBUR, High confidence in VFR conditions through at least 08Z. There is a 20% chance of 1-3 hours of MVFR ceilings between 10Z and 17Z, with very low confidence on timing.
31/1010 PM.
High confidence that Small Craft Advisory (SCA) winds and short period seas will be most common from Point Sal to San Nicolas Island through the majority of the week. The western Santa Barbara Channel will be flirting with SCA each evening. The nearshore Central Coast waters will likely stay under SCA through Tuesday, with a window of low-end SCA Wednesday and Thursday. Expecting increasing southerly swell starting around Friday/Saturday due to tropical activity.
31/749 PM.
There is growing confidence for significant impacts at the coast this Labor Day weekend. Unless the storm takes a full left turn after Saturday, the south-southeast swell will be pumping through the weekend into Tuesday, especially considering the swells from the current Hurricane Karina are also still around. The most likely scenario would result in high surf advisories for south facing beaches during a busy holiday weekend (especially Sunday into Monday night) with very strong rip currents. In addition, evening high tides are also expected to be 6.5 to 6.8 feet by Sunday evening, and around 7 feet by Monday evening. As a result, there is an increasing chance of at least minor coastal flooding of low-lying areas and beach erosion near times of high tides each evening. If peak surf happens to coincide with times of high tide, there is the potential for moderate coastal flooding/beach erosion which could require coastal flood advisories. At this time, the highest and most energetic swell energy will likely come from a more southeasterly direction. A few areas that could be especially susceptible to southeasterly swell include Catalina Island (including Avalon), Long Beach to Cabrillo Beach, Malibu and Point Mugu. If the storm gets closer to the coast, those coastal impacts will be amplified.
Ca, NONE. PZ, Small Craft Advisory in effect until 6 AM PDT Wednesday for zones 673-676. (See LAXMWWLOX).
