textproduct: Los Angeles

SYNOPSIS

01/136 AM.

Stagnant pattern through Friday, with below normal temperatures, patchy marine layer clouds, and moderate Sundowner winds. Several potential scenarios for the Labor Day weekend, with anything from benign conditions, tropical rain, or even hot offshore winds.

LONG TERM (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.

AVIATION

01/1108Z.

At 0406Z at KLAX, the marine layer was 1500 feet deep. The top of the inversion was at 3700 feet with a temperature of 20 Celsius.

High confidence on VFR TAFs at KWJF and KPMD.

High confidence in MVFR conds at KPRB/KSBP/KSMX through the morning and moderate confidence for return late tonight at KSBP/KPRB. 30% chance for IFR-MVFR cigs at KPRB after 10Z/02.

Low to moderate confidence in TAFs south of Point Conception with BKN MVFR conds possible at all sites through the morning. Patchy marine layer may cause sites to bounce between SCT and BKN. Lower chances of MVFR conds returning late tonight.

KLAX...Moderate confidence in TAF with SCT-BKN 012-018 through the morning, then good confidence in VFR conds through at least 06Z/02. Then low to moderate confidence in return of cigs of similar heights between 06Z-12Z/02. High confidence in an east winds staying under 8 knots.

KBUR...Low confidence in TAF through the morning with a 30% chance of 1-3 hours of BKN012-018 cigs through the morning. High confidence in TAF otherwise, with a 15% chance for a return of low clouds after 10Z/02.

MARINE

01/725 AM.

For the Outer Waters, moderate to high confidence in current forecast. Today through Friday, high confidence in Small Craft Advisory (SCA) level winds and short-period seas across PZZ673 and PZZ676 with a 30-40% chance of SCA level winds across PZZ670. For Saturday, there is a 30-40% chance of SCA level wind across all of the Outer Waters.

For the Inner Waters north of Point Sal, moderate to high confidence in current forecast. Today through Wednesday, high confidence in winds and seas remaining below SCA levels. For Thursday through Saturday, there is a 40-50% chance of SCA level winds (especially in the afternoon and evening hours).

For the Inner Waters south of Point Conception, moderate to high confidence in current forecast. Today through Thursday, there is a 60-80% chance of SCA level winds across the western half of the Santa Barbara Channel with high confidence in winds and seas remaining below SCA levels elsewhere. For Friday through Saturday, high confidence in winds and seas remaining below SCA levels.

Expecting increasing southerly swell this weekend due to tropical activity to the south. The details and timing are very much dependent on the track of the soon to be formed tropical cyclone, but confidence is moderate to high that the coastal waters will see a larger than normal in southerly swell over Labor Day Weekend.

BEACHES

01/725 AM.

There is growing confidence for significant impacts at the coast this Labor Day weekend. While there remains a range of outcomes in terms of the track the soon to be formed tropical cyclone takes, SoCal is likely to see an increasing southerly swell, with the south-southeast swell most likely pumping this weekend into Tuesday, especially considering the swells from the current Hurricane Karina hanging around. This 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. Additionally, evening high tides are 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 around evening high tides. If peak surf happens to coincide with times of high tide, there is the potential for moderate coastal flooding and beach erosion which could require coastal flood advisories. A few areas that could be especially susceptible to south-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.

LOX WATCHES/WARNINGS/ADVISORIES

CA...NONE. PZ...Small Craft Advisory in effect from 3 PM this afternoon to 3 AM PDT Wednesday for zone 650. (See LAXMWWLOX). Small Craft Advisory in effect until 3 AM PDT Thursday for zones 673-676. (See LAXMWWLOX).