27/1109 PM.
Beach impacts from Tropical Cyclones well south of the region are expected through Tuesday in the form of high surf, beach erosion, and possible coastal flooding. A significant warming trend is expected to begin Tuesday with increasing heat concerns through at least the following weekend.
(tdy-Wed), 28/1201 AM.
The primary forecast concerns for the short term are the building surf along south facing beaches and potential for moderate coastal flooding as well as very dangerous swimming conditions. Please see the Beaches discussion below for more details.
A 566 dam upper low embedded at the base of a pos tilt trof will move over the state from the NW to SE today. Hgts will drop about 10 dam during the day today. There is only weak onshore flow to the east and actual offshore flow from the north these two things combined with a weak marine inversion will inhibit low cloud formation this morning with only patchy low clouds at some LA coastal sites as well as the Central Coast. The falling hgts will bring 4 to 8 degrees of cooling today to all areas save for the Central Coast which will not see much change from Sunday's cool down.
The upper low will be to the east of the area on Tuesday and the wrap around flow from the low will bring northerly flow aloft to the area. At the sfc building high pressure to the NNE will bring offshore flow to the area esp from the north. This offshore flow will prevent any morning low clouds. It will also bring 3 to 6 locally 8 degrees of warming to the area and most of the csts/vlys will warm into the 80s with lower 90s in the warmest vlys. For the first time in a while there will be a widespread offshore wind event with north to northeast winds affecting a large portion of the area. The strongest winds will be through the i-5 corridor and the area a few miles either side of the VTA/LA county line in the morning. There is a 40 percent chc that the gusts will reach low end advisory criteria.
An east pac ridge will approach the state on Wednesday and hgts will rise to 588 dam. There will be another round of offshore winds in the morning but without much upper support they will be weaker than Tuesday's winds. Oddly an eddy is supposed to form as well driven by strong NW winds across the outer waters. Right now am betting that the offshore flow will keep the low clouds away but if the eddy is strong enough there could be some low clouds in the morning with the best odds across southern LA county. Since the offshore is weaker cst/vly temps will cool a couple of degrees while the mtns and far interior will see another 3 to 6 degrees of warming as the upper high builds in overhead.
(Thu-Sun), 28/220 AM.
High pressure will remain draped over Srn CA through the Thu-Sun xtnd period. Hgts will be around 590 dam through the period. The big question will revolve around the sfc gradients. There will likely be offshore flow from both the N and E in the morning, but there is quite a bit of disagreement on how strong the offshore push will be. Similarly in the afternoon there is disagreement with the EC showing weak offshore flow continuing in the afternoon while the GFS shows weak onshore flow. In the past the actual values have mostly come in in between the two.
Regardless of the exact magnitude of the offshore push the forecast will very likely be one of minimal or zero morning clouds and very warm temperatures. Max temps will mostly be in the 80s across the coasts and in the 90s in the vlys. There is a 40 percent chc that the warmest vly temps will reach triple digits Friday or Saturday. Heat advisories are almost a certainty for many areas and warnings may be necessary as well. Stay tuned to the NWS for the latest on this developing heat risk.
Of note: the AI enhanced version of the EC shows above to well above normal temps continuing into the middle of next month.
The National Hurricane Center (NHC) is tracking the newly formed Tropical Storm Rachel in the Eastern Pacific Ocean. The latest NHC track brings a Hurricane nearing our swell window by Friday. If this west to northwest track holds, it could enter our swell window by early next week. The potential surf or coastal flood impacts would probably occur after October 4th.
28/1101z.
At 0822Z at KLAX, the marine layer was around 900 ft deep. The top of the inversion was at 1900 feet with a temperature of 22 Celsius.
High confidence in TAFs for KBUR, KVNY, KWJF, and KPMD.
Moderate confidence in TAFs for KSBP/KSMX low cloud arrival timing may be off by 2 hours and cig hgt may be off by +/- 300 ft.
Good confidence in TAFs for KSBA, KOXR and KCMA with a 10 percent chc of MVFR cigs 13Z-16Z.
Moderate confidence in TAFs for KSMO, KLAX and KLGB with a 15 percent chc of MVFR cigs 13Z-16Z.
KLAX, Fair confidence in TAF. There is a 15 percent chance BKN012 conds 13Z-17Z. High confidence in no significant east wind component.
KBUR, High confidence in TAF.
28/235 AM.
High confidence in Small Craft Advisory (SCA) winds and steep seas affecting the outer waters through late least Tuesday night. Local Gale Force gusts will be possible at times, especially this afternoon and evening across the outer waters south of Point Conception. There is a 25% chance for a Gale Warning to be issued for that time period. Nearshore along the Central coast will see SCA winds and steep seas each afternoon and evening through Tuesday.
For the nearshore waters south of Point Conception, SCA winds are expected across the entirety of the Santa Barbara Channel and portions of the inner waters adjacent to Los Angeles and Orange Counties on today, with moderate chances Tuesday.
Southerly swells from Hurricanes Odalys (SSW) and Polo (SSE) will continue to affect the region through Tuesday. These swells will create larger waves and surf nearshore, which could impact some harbor entrances.
Conditions are likely to improve to below SCA levels Wednesday into next weekend, except for occasional northwest SCA winds near Point Conception in the afternoon/evening hours.
27/803 PM.
Southerly swells from Tropical Storm Odalys and Hurricane Polo will affect the waters through the middle of this coming week, with Hurricane Polo likely sending the more impactful swell from the SSE (160-170 degrees) affecting our coastline Monday and Tuesday. This swell timing will line up with very high tides Monday and Tuesday in the late morning hours. Some south- facing shores are more vulnerable because of the lingering erosion effects from Hurricane Marie earlier this month.
Surf heights across Los Angeles and Ventura Counties are likely to peak around 4-7 feet Monday and Tuesday, while the Santa Barbara south coast should see surf in the 3-5 foot range. High tides build and peak Monday and Tuesday, likely reaching around 7 feet (MLLW) in the late morning hours - which is higher by almost a foot over astronomical tides due to ongoing effects of El Nino.
While this swell is slightly smaller than the swell from Marie, there is still significant concern of Coastal Flooding over vulnerable south-facing beaches. The areas of most concern include Avalon, Long Beach, Malibu, and to a lesser extent 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 possible in the most vulnerable areas. Minor tidal overflow may affect west facing beaches due to very high tides.
Beach Hazards Statements (BHS) are in effect for LA and Ventura coasts through early Monday morning, and for the Santa Barbara south coast into Wednesday. Then a Coastal Flood Advisory and High Surf Advisory are in effect for LA and Ventura Monday and Tuesday. A BHS may need to be issued for the LA and Ventura coasts for Tuesday afternoon through Wednesday (lining up with Santa Barbara) due to the very high tides.
Ca, Beach Hazards Statement in effect until 5 AM PDT early this morning for zones 87-354-362-366. (See LAXCFWLOX). Coastal Flood Advisory in effect until 5 PM PDT Tuesday for zones 87-354-362-366. (See LAXCFWLOX). High Surf Advisory in effect until 5 PM PDT Tuesday for zones 87-354-362-366. (See LAXCFWLOX). Beach Hazards Statement in effect through Wednesday afternoon for zones 349-350. (See LAXCFWLOX). Wind Advisory in effect from 6 PM this evening to 6 AM PDT Tuesday for zones 349>353-376>378. (See LAXNPWLOX). PZ, Small Craft Advisory in effect from noon today to 11 PM PDT this evening for zone 645. (See LAXMWWLOX). Small Craft Advisory in effect from noon today to midnight PDT tonight for zones 650-655. (See LAXMWWLOX). Small Craft Advisory in effect until 3 AM PDT Wednesday for zones 670-673-676. (See LAXMWWLOX).
