Weather forecast for Wednesday April 27

April 27, 2011

By JOHN LINDSEY from PG&E

A ridge of high pressure in the upper atmosphere is producing  gentle to moderate (8- to 18-mph) and at time gusty northeasterly (offshore) winds this morning.

This offshore flow will produce clear and warmer weather today with temperatures reaching the mid- and high-70s and maybe even the low 80s in the North County and coastal valleys. Temperatures along the beaches will be cooler, ranging between the mid 60s and low 70s at Avila Beach and Cayucos.

A 1,028 millibar Eastern Pacific High is currently located 500 miles to the west of San Luis Obispo. This area of high  pressure will move northward towards Cape Mendocino and  will strengthen to 1,036 millibars. At the same time, a thermal trough will develop over the San Joaquin Valley producing a steep pressure gradient along the California coast.

This condition will produce moderate gale to fresh gale force (32- to 46-mph) northwesterly winds along our coastline  on Thursday afternoon through Friday. These onshore winds  will produce cooler temperatures throughout San Luis Obispo County.

Another high pressure ridge will develop over California this weekend. This condition will produce northeasterly (offshore) winds during the morning hours on Saturday and Sunday.  This offshore flow will give clear and warmer weather with temperatures reaching into the 80s across the interior and 70s closer to the coast. Slightly cooler weather is forecast for early next week, then warmer weather may  return by the middle part of next week.

Yesterday’s         Today’s          Tomorrow’s
Min    Max        Min    Max         Min     Max
52.5°   59.7°     51.4°   64.0°      51.0°    59.0°

PG&E San Francisco Met Office predicted temps:

Inland Temperatures, Paso Robles

Actual                    Predicted

Tue         Wed         Thu         Fri          Sat         Sun         Mon         Tue
45 74      39 78  42 75     39 73    37 77    40 82     43 82      44 81

Coastal Valleys Temperatures, San Luis Obispo

Tue           Wed        Thu         Fri            Sat        Sun          Mon        Tue
48 69     46 72     47 67     45 66      44 70    45 76    47 75     46 73

SEA/SWELL:

This morning’s 5- to 7-foot northwesterly (310-degree deep-water) sea and swell (with a 5- to 11-second period) will continue at  this height and period through Thursday morning.

Another round of moderate gale- to fresh-gale (32- to 46-mph) northwesterly winds along the Central Coast on Thursday afternoon and Friday will generate 7- to 9-foot northwesterly (310-degree deep-water) sea and swell (with a 5- to 11-second period) on Thursday afternoon and night, further increasing to 8- to 10-feet with the same period on Friday.

The northwesterly sea and swell will decrease to 6- to 8-feet  on Saturday, further lowering to 4- to 6-feet (with a 7- to 11-second period) on Sunday.

WINDS:

This morning’s gentle to moderate (8- to 18-mph) and at times gusty northeasterly (offshore) winds will increase out of the northwest to strong to gale force  (25- to 38-mph) levels this afternoon through Thursday morning.

These winds will further increase to moderate gale to fresh gale (32- to 46-mph) levels along our coastline on Thursday afternoon through Friday.

Gentle to moderate (8- to 18-mph) northeasterly (offshore) winds will develop on Saturday and Sunday morning, followed by fresh  to strong (19- to 31-mph) northwesterly winds during the afternoon and evening hours.

Moderate to fresh (13- to 24-mph) northwesterly winds are forecast  on Monday, increasing to strong to gale force  (25- to 38-mph) levels next Tuesday and Wednesday.

DIABLO CANYON METEOROLOGICAL TOWER WIND DATA:

Today’s winds:

Max peak winds:      NE       17.2 mph at    4:15 a.m.
Max sustained wind:  NE        7.8 mph at    4:15 a.m.

Yesterday’s Maximum Winds:

Max peak winds:      NW       41.2 mph at    4:15 p.m.
Max sustained wind:  NW       33.1 mph at    4:15 p.m.

SEAWATER TEMPERATURES:

The Diablo Canyon waverider buoy is reporting a sea surface  temperature of 55.6 degrees while the Nortek AWAC current meter is reporting 49.1 degrees.

Intake seawater temperatures will range between 48- and 51 -degrees through Thursday morning , decreasing to 47- and 50-degrees on Thursday afternoon through Monday.

OCEAN CURRENTS:

A southerly (offshore) current will continue to flow southward through Monday.

SEAWATER VISIBILITY:

Seawater visibility was 20- to 22-feet at the Diablo Canyon Intake.

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24-Hour Ocean Condition Outlook for Wednesday 04/27 to Thursday 04/28

Sea/Swell       DIR. NW      HT.   5-7   PER.   5-11  This morning
Remaining  at:  DIR. NW      HT.   5-7   PER.   5-11  This afternoon
Remaining  at:  DIR. NW      HT.   5-7   PER.   5-11  Tonight

WINDS:          DIR. NE      SPEED 10-15 + 25         This morning
Increasing to:  DIR. NW      SPEED 25-30 + 40         This afternoon
Decreasing to:  DIR. NW      SPEED 20-25              Tonight
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48-Hour Ocean Condition Outlook for Thursday 04/28 to Friday 04/29

Sea/Swell       DIR. NW      HT.   5-7   PER.   5-11  Thursday morning
Increasing to:  DIR. NW      HT.   7-9   PER.   5-11  Thursday afternoon
Remaining  at:  DIR. NW      HT.   7-9   PER.   5-11  Thursday night

WINDS:          DIR. NW      SPEED 15-20 + 25         Thursday morning
Increasing to:  DIR. NW      SPEED 30-35 + 40         Thursday afternoon
Increasing to:  DIR. NW      SPEED 30-40 + 45         Thursday night
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Extended Ocean Condition Outlook:

Moderate gale- to fresh-gale (32- to 46-mph) northwesterly winds are
forecast to continue into Friday.

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The 24 – Hour Ocean Data From The Diablo Canyon Wave rider Buoy
MONTH  DAY  TIME  SIG.HEIGHT   PERIOD   SWELL DIRECTION     SST
04    24    2312     6.7        8            275          51.4
04    25    0442     5.2        7            278          55.2
04    26    2142     7.4        8            288          52.7
04    27    0212     5.4        9            278          55.6

(cm) (sec)  22+   20    17    15    13     11    9    7
———————————————————————
04 24  2312  204    7     2     8    78   144    80    37   557  721
04 25  0442  159    7     1     7    77   103    78    55   190  364
04 26  2142  224    9     2     3     6    24    84   570  1019  686
04 27  0212  164    9     1     5     6    25    72   222   487  438

Daily Swell Inspection Program

NAME                      DAY   TIME    HEIGHT   PERIOD     SST
(PST)   (FEET)  (SECONDS) (DEG. F)
# 166  Ocean Station Papa      27    0402       6       10       43.0
# 06   SE Papa                 27    0250       7       11       52.7
# 59   California Buoy         27    0250       7       11       56.3
# 01   Point Reyes Waverider   27    0246      10       12       51.6
# 15   Monterey Waverider Buoy 27    0250       7       13       52.2
# 28   Cape San Martin, Ca     27    0250       9       11       54.0
# 50   DCPP Waverider Buoy, Ca 27    0212       5        9       55.6
# 63   Harvest Buoy            27    0220      10        9       51.8
# 01   NW Hawaii               27    0250      10        9       76.8

* Note: Height (significant swell height) is the average height of     the waves in the top third of the wave record. Maximum wave height may be up to TWICE the height in the data shown in the above     table.

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): 25.98 inches
Average season rainfall at DIP to date:            23.93 inches

Ocean Lab Barometer:  30.15 in/Hg or 1020.9 mb  +0.0 mb (Steady)
Sunrise and Sunset

Today’s         Sunrise 6:16 AM      Sunset 7:45  PM
Tomorrow’s      Sunrise 6:15 AM      Sunset 7:46  PM

Tides:
Low Tide                 High Tide
AM          PM           AM          PM
27 Wednesday   1:27  1.7    1:22  0.6    7:03 3.8    7:58  4.4
28 Thursday    2:13  1.2    1:57  0.9    8:00 3.7    8:23  4.7
29 Friday      2:52  0.8    2:27  1.1    8:49 3.7    8:47  4.9
30 Saturday    3:27  0.4    2:55  1.4    9:33 3.7    9:10  5.1
1 Sunday      4:00  0.0    3:22  1.6   10:15 3.7    9:34  5.2
2 Monday      4:34 -0.2    3:49  1.8   10:56 3.6   10:00  5.4
3 Tuesday     5:08 -0.4    4:17  2.0   11:38 3.5   10:28  5.4
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This day in weather history

1931 – The temperature at Pahala, located on the main island of Hawaii, soared to 100 degrees to establish a state record.

1987 – Forty-two cities in the western and south central U.S.  reported record high temperatures for the date. The afternoon high of 87 degrees at Olympia WA was an April record, and highs of 92 degrees at Boise ID, 95 degrees at Monroe LA, and 96 degrees at Sacramento CA tied April records.

More than 300 daily temperature records fell by the wayside  during a two week long heat wave across thirty-four states in the southern and western U.S. Thirteen cities established
records for the month of April. (Sandra Sanders – 1987)

2007 – Clear and warm weather will continue through Saturday with temperatures in our inland areas reaching into the upper 80’s and low 90’s with widespread 70’s not too far from
the coast as an upper-level high builds over California.

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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.

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