26/154 AM.
High temperatures will remain above normal through today with areas of low clouds and fog this morning. Substantial cooling is expected Sunday and Monday. Beach impacts from Tropical Cyclones well south of the region will be 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), 26/307 AM.
Not too much change in the forecast today compared to yesterday. Only a few areas are seeing marine layer clouds this morning, and really only South of Point Conception. These clouds may expand a bit more by sunrise, but will be pretty limited to the coasts and inland coasts thanks to some light offshore flow due to surface pressure gradients trending offshore. These gradient trends are leading to a mini Santa Ana- like pattern for LA/Ventura, with light winds and 3-6 degrees warmer for these areas. High temperatures today for areas south of Point Conception/away from the coast will range in the 80s and to high 90s, with temperatures near the coast and north of Point Conception in the 70s and 80s.
A bit of an odd situation synoptically starting Sunday, with quite a bit of uncertainty. An upper level trough will start to drop into the region from the NW, and continue to move slowly through the region into next week. Meanwhile, two strong hurricanes are currently affecting the eastern Pacific (Polo and Odalys), well to the south of California. There is quite a bit of uncertainty in the forecast due to the uncertainties in the evolution and tracks of these storms. The low pressure system may funnel some of the moisture from the into the region, however there is quite a spread in the ensembles as some members show Precipitable Water values (PWATs) of 0.5 inches, and some show PWATs up to near 2 inches. As a result, there may be possibility of light, spotty showers for areas south of Point Conception starting Sunday. While the official forecast does have a slight chance of rain for interior areas Sunday and Monday, there also is the possibility that most of the moisture stays south of Los Angeles County. As for temperatures, a cool down is expected Sunday and Monday with temperatures 10 to 20 degrees lower by Monday compared to today.
Ultimately, the biggest local impacts from the hurricanes to the south are still expected to be confined to the beaches with increasing swells from the hurricanes, though this is also quite uncertain pending the track of both hurricanes.
(Tue-Fri), 26/310 AM.
Still a lot of uncertainty in the weather forecast Tuesday and beyond. More than 50 percent of the models are indicating high pressure building over the state behind the exitting trough, with offshore flow and a fairly substantial warming trend through at least Thursday. There's at least a 30 to 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.
26/0642z.
At 0546Z over KLAX, the marine layer was 800 ft deep. The top of the inversion was at 2000 feet with a temperature of 27 Celsius.
High confidence TAFs for KPRB, KWJF, and KPMD.
Low to moderate confidence in remainder of TAFS. There is a 30% chance of LIFR/IFR conds at KSBP, and a 30% chance of conds remaining VFR through the period at KSMX. There is a 20% chance for short- lived IFR/MVFR cigs at KBUR and KVNY. Moderate confidence in timing (plus or minus 3 hours).
KLAX, Moderate to high confidence in TAF through 18Z Sat, then high confidence. Timing of flight cat changes could be off by +/- 3 hours. High confidence in any east winds staying under 8 knots.
KBUR, Moderate to high confidence in TAF through 17Z, then high confidence. There is a 30% chance of shor-lived BKN005-008 conds 10-16Z Saturday.
26/251 AM.
Through this weekend, moderate to high confidence in Small Craft Advisory (SCA) winds and steep seas affecting the outer waters off the Central Coast to near Point Conception. The SCAs currently go through late Sunday night but will likely be extended through Tuesday night. SCA conds are also forecast over the waters southward to San Nicolas Island (PZZ676) starting late this afternoon afternoon. Gale force gusts will be possible at times, especially Monday afternoon and evening across PZZ676. Nearshore along the Central coast will see SCA conditions this afternoon into evening and short period seas (7-8 feet at 7-8 seconds).
Moderate to high confidence in widespread gusty winds Monday into Tuesday extending into the nearshore waters at times, with the highest confidence in the Central Coast waters and Santa Barbara Channel. SCA conds over PZZ655 may be limited to Monday afternoon and evening.
Southerly swells from Hurricanes Odalys (SSW) and Polo (SSE) will affect the region this weekend through the middle of next week. These swells will create larger waves and surf nearshore, which could impact some harbor entrances, especially Sunday through Tuesday.
Some dense fog is possible on the Central Coast this weekend.
25/819 PM.
Southerly swells from Hurricanes Odalys and Polo will affect the waters this weekend through the middle of next week. This is a complex 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 west for its waves to have a clear path to southern California. This means that the swells will have a 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 from Hurricane Marie earlier this month.
While the surf heights will likely range in the 4 to 7 foot range for south facing beaches 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 of 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 to those from Hurricane Marie, 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 where 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 will be minimal if the lower-end surf outcome materializes.
Due to rather high uncertainty, have gone with Beach Hazard Statements through Wednesday afternoon. This covers the coastline from Santa Barbara South coast down to LA county, including 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 from 3 PM this afternoon to 9 PM PDT this evening for zone 645. (See LAXMWWLOX). Small Craft Advisory in effect until 3 AM PDT Monday for zones 670-673. (See LAXMWWLOX). Small Craft Advisory in effect from 3 PM this afternoon to 3 AM PDT Monday for zone 676. (See LAXMWWLOX).
