• This week's San Luis Obispo Tribune's Weather Watch Column “Exploding trees? Here’s why we see big branches fall during hot summer days." www.sanluisobispo.com/news/weather/weather-watch/ • You can catch live weather forecasts weekday mornings from 6-9 a.m. on KVEC 920 AM on First Look with Andy Morris • For weather updates, charts and photos, along with power outage information and other events you can follow me at: https://twitter.com/pge_john ========== PG&E DCPP Weather Forecast for Thursday 09/03/20 ========== SEA/SWELL: Today's 3- to 5-foot northwesterly (305-degree, deep-water) sea and swell (with a 5- to 15-second period) will increase to 4 to 6 feet (with a 5- to 12-second period) on Friday. This northwesterly sea and swell will remain at this height but (with a 5- to 8-second period) on Saturday through Wednesday. Arriving from the Southern Hemisphere: A 1-foot Southern Hemisphere (215-degree, deep-water) swell (with a 20- to 22-second period) is forecast to arrive along our coastline on Sunday, increasing to 1 to 2 feet (with an 18- to 20-second period) by Monday. This Southern Hemisphere swell is expected to peak at 1 to 3 feet (with a 16- to 18- second period) on Tuesday. ATMOSPHERIC CONDITIONS: A patchy 800 foot marine layer with areas of mist and fog covers about half of the beaches and coastal valleys and a few areas of the North County by way of the Salinas Valley. The low coastal clouds will quickly clear later this morning as strong to gale-force (25 to 38 mph) northwesterly winds develop along the coastline. Today' high temperatures will range from the high 90s in the inland valleys (Paso Robles), and low-80s in the coastal valleys (San Luis Obispo). The beaches will range between the mid 60s and low 70s. Meteorologists determine the thickness of the atmosphere by analyzing 500-millibar upper-level charts. This chart will tell you how high the pressure is three or four miles above the Earth’s surface. The higher the 500-millibar line, the thicker the atmosphere, and the warmer it will be. Anything above 580 decameters (dm) will usually give hot temperatures, if near 600 dm, record-breaking. The 500 millibar line may increase to 598 dm over the Central Coast this Labor Day weekend. This condition will produce warm to hot temperatures on Friday through Tuesday. Along the coastline, strong to gale-force (25 to 38 mph) northwesterly winds will develop during the afternoon, while in the morning, moderate to fresh (13 to 24 mph) Santa Lucia (northeasterly) winds will drive the marine layer out to sea, leaving behind clear skies on Friday through Tuesday. Along the beaches and many of the coastal valleys, the warmest part of day should occur during the late morning, before the northwesterly winds bring cooler air from the Pacific during the afternoon. High temperatures along most of the beaches will range between the high 70s and low 80s. However, the southerly facing beaches of Cayucos, Avila Beach and Shell Beach will reach the 90s on Saturday, Sunday and Monday. High temperatures in the coastal valleys will range between the low to high 90s on Saturday, Sunday and Monday. There is a chance that San Luis Obispo could hit triple-digit levels on Sunday. The record high in San Luis Obispo on Sunday is 101 degrees set in 2004. North County temperatures will increase to the 103 degrees on Friday and 107 by Saturday. The Paso Robles Airport is forecast to reach the 113 degrees on Sunday, and 112 on Monday. If these daily high temperatures develop on Sunday and Monday, they will be record breaking. The record high on Sunday is 109 degrees set back in 1988 and 107 on Monday set in 2008. This heat is expected to continue through Tuesday, before the high pressure ridge weakens and the marine layer deepens and moves inland for cooler weather. WILDFIRE INDEX RATINGS: COASTAL: FIA 508 INLAND: FIA 497, 510, 575, 580, 582 and 590 The PG&E Fire Index Ratings will be at high (R3) levels along the Coastline, and very high (R4) level in the Coastal and Inland Valleys and Far Inland Areas today. The PG&E Fire Index Ratings will be at very high (R4) levels along the Coastline, and extremely high (R5) levels in the Coastal and Inland Valleys and Far Inland Areas on Friday. The PG&E Fire Index Ratings will be at very high (R4) levels along the Coastline, and extremely high (R5) levels in the Coastal Valleys. The Inland Valleys and Far Inland Areas will be at very high (R4) levels on Saturday. DIABLO CANYON METEOROLOGICAL TOWER TEMPERATURE DATA: Yesterday's Today's Tomorrow's Min Max Min Max Min Max 58.2° 62.1° 56.7° 65.0° 59.0° 72.0° PG&E Weather Office in San Francisco predicted temperatures for San Luis Obispo County Inland Temperatures, Paso Robles Actual Predicted Wed Thu Fri Sat Sun Mon Tue Wed Thu 54 96 57 99 56 103 61 107 64 113 65 112 62 103 60 98 58 97 Coastal Valleys Temperatures, San Luis Obispo Wed Thu Fri Sat Sun Mon Tue Wed Thu 58 75 58 81 52 85 55 90 59 98 59 95 59 86 59 81 59 79 WINDS: Strong to gale-force (25 to 38 mph) afternoon northwesterly winds are expected today through Tuesday. Moderate to fresh (13 to 24 mph) Santa Lucia (northeasterly) winds are forecast during the morning on Friday, Saturday and Sunday. DIABLO CANYON METEOROLOGICAL TOWER WIND DATA: Today's Maximum Winds: Max peak winds: NW 26.0 mph @ 2:15 a.m. Max sustained wind: NW 17.0 mph @ 2:15 a.m. Yesterday's Maximum Winds: Max peak winds: NW 32.0 mph @ 1:30 p.m. Max sustained wind: NW 26.0 mph @ 1:30 p.m. SEAWATER TEMPERATURES: Seawater temperatures will range between 58 and 62 degrees through this morning, decreasing to 56 to 58 degrees this -afternoon through Saturday. Seawater temperatures will father lower to 54 to 57 degrees on Sunday through Tuesday. OCEAN CURRENTS: A southerly (offshore) flowing current is forecast to continue to flow southward through Tuesday. SEAWATER VISIBILITY: Seawater visibility was 32 feet (top to bottom) at the Diablo Canyon Marina. ========================================================================== 24-Hour Ocean Condition Outlook for Thursday 09/03 to Friday 09/04 SEA/SWELL: DIR. NW HT. 2-4 PER. 5-15 This morning Increasing to: DIR. NW HT. 3-5 PER. 5-15 This afternoon Remaining at: DIR. NW HT. 3-5 PER. 5-14 Tonight WINDS: DIR. NW SPEED 15-20 This morning Increasing to: DIR. NW SPEED 25-30 + 40 This afternoon Decreasing to: DIR. NW SPEED 15-20 Tonight ========================================================================== 48-Hour Ocean Condition Outlook for Friday 09/04 to Saturday 09/05 SEA/SWELL: DIR. NW HT. 4-6 PER. 5-13 Friday morning Remaining at: DIR. NW HT. 4-6 PER. 5-12 Friday afternoon Remaining at: DIR. NW HT. 4-6 PER. 5-11 Friday night WINDS: DIR. NE SPEED 15-20 + 25 Friday morning Increasing to: DIR. NW SPEED 25-30 + 40 Friday afternoon Decreasing to: DIR. N SPEED 15-20 Friday night ========================================================================== Extended Ocean Condition Outlook: Decreasing northwesterly winds are forecast next Wednesday and Thursday. ========================================================================== The 24 - Hour Ocean Data from the Diablo Canyon Waverider Buoy: MONTH DAY TIME SIG.HEIGHT PERIOD SWELL DIRECTION SST 09 01 2200 3.7 11 281 58.3 09 02 2130 3.4 9 282 56.7 09 03 0630 3.1 15 227 59.4 DCPP Ocean Lab Waverider Buoy Energy Spectral Analysis: Mo. daytime sig.ht. sig.per. energy (cm.sq.) (cm) (sec) 22+ 20 17 15 13 11 9 7 -------------------------------------------------------------------------- 09 01 2200 112 9 0 1 9 12 35 247 374 61 09 02 2130 104 9 1 2 5 14 32 75 343 131 09 03 0630 95 4 1 3 6 31 21 53 92 262 Daily Swell Inspection Program for today: NAME DAY TIME HEIGHT PERIOD SST (PST) (FEET) (SECONDS) (DEG. F) # 66 Ocean Station Papa 3 0600 7 11 57.6 # 06 SE Papa The buoy at this station has gone adrift. # 05 West Washington State 3 0600 6 11 66.0 # 59 California 3 0600 6 12 67.6 # 44 Humboldt Bay Waverider 3 0608 6 13 52.5 # 94 Cape Mendocino 3 0632 5 13 53.2 # 29 Point Reyes Waverider 3 0603 4 14 60.4 # 42 San Francisco Sandbar 3 0630 3 14 59.4 # 15 Monterey Waverider Buoy 3 0630 4 14 57.2 # 28 Cape San Martin No recent wave reports. 61.3 # 76 DCPP Waverider 3 0630 3 15 59.4 # 22 Santa Lucia Escarpment 3 0600 5 5 62.4 # 11 Point Arguello 3 0600 5 5 61.0 # 63 Harvest Buoy 3 0630 5 5 61.9 # 19 San Nicolas Island 3 0633 7 7 66.0 # 20 Scripps 3 0622 3 6 66.0 # 10 Waimea Bay, Hawaii 3 0600 3 11 80.6 # 33 Pearl Harbor Entrance 3 0600 3 14 81.1 # 04 SE Hawaii 3 0600 6 9 79.5 Precipitation at the Diablo Canyon Ocean Lab: Tuesday 1500 through Wednesday 1500 0.00 inches Wednesday 1500 through Thursday 1500 0.00 inches Precipitation this rain season (July 1 - June 30): 0.08 inches Average season rainfall at DCPP to date: 0.04 inches Ocean Lab Barometer: 30.00 in/Hg or 1015.6 0.0 mb (study) Today's Sunrise 6:38 AM Sunset 7:26 PM Tomorrow's Sunrise 6:38 AM Sunset 7:25 PM Tides: Low Tide High Tide AM PM AM PM 3 Thursday 5:33 0.4 5:29 1.8 11:53 4.6 11:28 5.2 4 Friday 6:00 0.7 6:08 1.7 ----- --- 12:18 4.7 5 Saturday 6:26 1.2 6:51 1.7 12:07 4.8 12:44 4.7 6 Sunday 6:52 1.6 7:40 1.6 12:49 4.3 1:12 4.7 7 Monday 7:18 2.1 8:40 1.6 1:40 3.9 1:44 4.7 8 Tuesday 7:48 2.5 9:54 1.5 2:50 3.5 2:23 4.7 ======================================================================== This day in weather history 1961 - Denver, CO, received 4.2 inches of snow, their earliest snow of record. (Sandra and TI Richard Sanders - 1987) 2007 - Compressional heating off the Santa Lucia Mountains produced hot coastal temperatures. Temperatures at 1430 hours yesterday afternoon were 105°F at Avila Beach and 64.6°F degrees at Diablo Canyon. A fishing boat reported a 37°F temperature drop. This temperature gradient occurred off Port San Luis between the breakwater and the wind shift line in less than 1/4 of a mile. That's what you call a temperature gradient! The Diablo Canyon Meteorological Tower showed a very strong temperature inversion (A warmer, less dense air mass over a cooler, more dense air mass at the surface) from 76 meters to 10 meters during this time. One could write a American Meteorological Society Bulletin on yesterday's temperatures gradients. At 1600 hours very gusty northerly winds mixed out the inversion layer, causing sea level air temperatures at Diablo Canyon to increase to the low 90s from 1600 through 1800 hours. ======================================================================== This weather forecast is a service provided by Pacific Gas and Electric Company (PG&E) to our energy customers. The forecast is valid only for the Diablo Canyon Power Plant coastline area (approximately a one-half mile radius surrounding the plant). Some of the information in this forecast is provided by Pacific Weather Analysis, with their permission. Replication of this email must be in its entirety. You may view and copy material from this forecast, provided you retain all copyright, trademark, and other proprietary notices displayed on the materials. Use of these materials in publications, radio, television, other media presentations, or other websites is prohibited without PG&E's express written consent. PG&E is a subsidiary of PG&E Corporation, one of the largest natural gas and electric utilities in the United States, delivering some of the nation's cleanest energy to 15 million people in Northern and Central California. If you would like to subscribe or unsubscribe to this daily forecast, please send an email to PGEweather@pge.com. Any questions about this forecast, please E-mail John Lindsey at jcl5@pge.com