25/211 AM.
High temperatures will remain above normal through Saturday with areas of low clouds and fog each morning. Substantial cooling is expected Sunday and Monday. Beach impacts from Tropical Cyclone Polo are possible Monday and Tuesday in the form of high surf and possible beach erosion. A significant warming trend is expected Tuesday and Wednesday.
(tdy-Mon), 25/153 PM.
As expected temperatures today were generally within a few degrees of yesterday. The marine layer is hanging on along the beaches south of Pt Conception otherwise skies were mostly clear with just a few clouds over the mountain peaks.
There have been no significant changes to the 7 day forecast. A light northeast gradient will develop later tonight into Saturday, a sort of mini Santa Ana, mainly just impacting LA/Ventura coast and valleys with temperatures 3-6 degrees warmer than today. Highs near 90 are expected in Downtown LA and near 100 in the warmer valleys. No winds of significance expected. Most everywhere else across the 4 county area will experience 2-5 degrees of cooling Saturday.
There remains quite a bit of uncertainty in the forecast Sunday through early next week due to the two strong hurricanes (Polo and Odalys) in the eastern Pacific and the uncertainties with their evolution and respective tracks. There is high confidence in several degrees of cooling Sunday and Monday as most models bring an upper level trough California. And while most of the hurricane models are in pretty good agreement keeping the storms well south of California, there is a window of opportunity Sunday night into Monday for some mid level moisture to move into the area and create a few light showers south of Pt Conception. The biggest impacts locally are still expected to be confined to the beaches with increasing swells from the hurricanes, though this is also quite uncertain pending the ultimate track of both hurricanes.
(Tue-Fri), 25/208 PM.
Pretty big uncertainty in the weather forecast Tue and beyond. More than 50% of the models are indicating high pressure building over the state with a fairly substantial warming trend through at least Thursday. There's at least a 30-40 percent chance of near 100 degree temperatures in the valleys and similar chances for Downtown LA and San Luis Obispo reaching 90 or higher. There's also a lower but still significant chance of temperatures 5-10 degrees cooler than that. Will have to wait to see how the hurricanes track before having much confidence in the longer range.
25/1628z.
At 16Z over KLAX, the marine layer was 1400 ft deep. The top of the inversion was at 3000 feet with a temperature of 24 Celsius.
High confidence in VFR conditions through at least Saturday for KPRB, KPMD, and KWJF.
High confidence in clearing at all sites by 19Z today.
For tonight into tomorrow: LIFR/IFR conditions possible at KSBP (20%) and KSMX (60%). IFR/MVFR conditions possible at KOXR (30%), KCMA (30%), KSMO (50%), KLAX (70%), KLGB (70%), KBUR (30%), KVNY (20%). Moderate confidence in timing (plus or minus 3 hours).
High confidence in typical winds.
KLAX, VFR conditions likely to start 17-18Z. There is a 20% chance of brief MVFR ceilings 23-03Z. There is a 70% chance of OVC008-012 tonight, low-moderate confidence on timing. High confidence in any east winds staying under 8 knots.
KBUR, MVFR HZ possible through 20Z, otherwise high confidence in VFR conditions through at least 10Z. There is a 30% chance of IFR ceilings 12-16Z on Saturday.
25/1240 PM.
Through this weekend, moderate confidence Small Craft Advisory (SCA) winds and steep seas affecting the outer waters of the Central Coast. Winds will be strongest this evening, when the nearshore waters along the Central coast will see brief SCA conditions.
High confidence in widespread gusty winds Monday into Tuesday over most of the coastal waters, including nearshore. SCA likely everywhere, with a moderate risk for Gales between Point Sal and San Nicolas Island.
Southerly swells from Hurricanes Odalys and Polo will affect the region this weekend through the middle of next week. These swells will create larger waves nearshore, which could impact some harbor entrances, especially Sunday through Tuesday.
Some dense fog is possible on the Central Coast this weekend.
25/1240 PM.
Southerly swells from Hurricanes Odalys and Polo will affect the region this weekend through the middle of next week. This is a very complicated scenario with two hurricanes so close in proximity, with one of them (Odalys) poorly handled by our computer models. Another complexity is the relatively short window of time that Polo is far enough to the west for its waves to have a clear path towards southern California. This means that the swells will have a sharp peak and narrow window of time to line up with the high tides. Lastly, some south-facing shores are extra vulnerable because of the lingering erosion effects of Hurricane Marie from earlier this month.
While the surf heights will likely range in the 4 to 7 foot range for south facing beaches at times Sunday through Tuesday, there is a plus or minus in that potential of 2 feet or so due to the complications mentioned above. High tides will steadily build each day and peak Monday and Tuesday, likely reaching around 7 feet (MLLW) - which is higher by almost a foot over astronomical tides due to ongoing effects of El Nino.
There is a significant concern for Coastal Flooding over vulnerable south-facing beaches as a result, but the magnitude is still uncertain. The areas of most concern include Avalon, Long Beach, Malibu and Santa Barbara. The reasonable worst-case scenario is for impacts similar the Hurricane Marie from earlier this month, but the most likely outcome is for impacts to be a step less. The one exception being Avalon on Catalina Island, as the swells from Hurricane Polo will be more from a southeasterly direction than with Marie, which they are more exposed to. The same goes for Santa Barbara Harbor, but being the furthest away from the Hurricane, the risk is less but still present.
South-facing beaches should plan for shallow flooding of seawater over low lying beach walkways, parking lots, and roads as well as potential for significant beach erosion. Very localized damage to structures is also possible in the most vulnerable areas. With all that stated, there is a potential that impacts are minimal if the lower-end surf outcome materializes.
Due to rather high uncertainity, have went with Beach Hazard Statements from Now through Wednesday afternoon. This covers the coastline from Santa Barbara South coast down to LA county which includes Catalina island. A decision to upgrade to Coastal Flood Advisory will be made Saturday or Sunday. Refer to CFWLOX for more details.
Ca, Beach Hazards Statement in effect through Wednesday afternoon for zones 87-349-350-354-362-366. (See LAXCFWLOX). PZ, Small Craft Advisory in effect until 9 PM PDT this evening for zone 645. (See LAXMWWLOX). Small Craft Advisory in effect until 9 AM PDT Sunday for zones 670-673. (See LAXMWWLOX).
