Weather forecast for April 5

April 5, 2011

By JOHN LINDSEY from PG&E

The 1,024 millibar high over California responsible for yesterday’s beautiful weather will weaken and move eastward today.

A dry cold front will sweep southeastward over the Central Coast later today with cooler temperatures and coastal low clouds and fog tonight into Wednesday.

The main effect of this cold front will be to produce moderate gale to fresh gale (32 to 46-mph) northwesterly winds Wednesday.

The northwesterly winds will decrease to strong to gale force (25 to 31-mph) levels on Thursday, further decreasing on Friday and Saturday

An upper-level low may produce a few rain showers late Thursday night into Friday. Temperatures will continue to trend downward on Thursday with maximum temperatures struggling to get out of the 50s on  Thursday and again on Friday with overnight minimums in the 30s and 40s with frost possible in the inland valleys on Friday and again on Saturday morning as this low will produce much below normal temperatures for early April into next weekend.

The upper-level low moves out of the region over the weekend for fair and warmer weather, but temperatures will remain below normal and cool into next week.

Yesterday’s         Today’s          Tomorrow’s
Min    Max        Min    Max         Min     Max
57.8°   70.5°     54.2°   64.0°      52.0°    59.0°

PG&E San Francisco Met Office predicted temps:

Inland Temperatures, Paso Robles

Actual                    Predicted

Mon       Tue   Wed   Thu   Fri   Sat   Sun   Mon
41 78     42 79 43 73 40 62 36 59 33 62 35 65 39 69

Coastal Valleys Temperatures, San Luis Obispo

Mon       Tue   Wed   Thu   Fri   Sat   Sun   Mon
44 76     45 66 47 61 44 64 40 60 38 61 42 63 45 64

SEA/SWELL:

This afternoon’s strong to gale force (25 to-38 mph) northwesterly winds will generate 4- to 6-foot northwesterly (300-degree deep-water) sea and swell with a 4- to 11-second period this afternoon through tonight.

These winds will further increase to moderate gale to fresh gale (32 to 46-mph) levels later on Wednesday. These winds combined with a Gulf of Alaska swell will produce a 7- to
9-foot northwesterly (310-degree deep-water) sea and swell (with a 7- to 17-second period) on Wednesday morning, building to 10- to 12-feet (with a 7- to 16-second period) Wednesday afternoon and night.

The northwesterly winds will decrease to strong to gale force (25 to 31-mph) levels on Thursday and consequently the northwesterly (300-degree deep-water) sea and swell will decrease to 8- to 10-foot level (with a 7- to 13-second period) during this timeframe.

Arriving from the Southern Hemisphere:

A 1- to 2-foot Southern Hemisphere (225-degree deep-water) swell (with a 20- to 22-second period) will arrive along the coast Wednesday, increasing to 2 to 4 feet (with an 18- to 20-second period) Thursday through Friday.

WINDS:

Increasing northwesterly winds will develop this afternoon, reaching moderate gale to fresh gale (32 to 46-mph) levels on Wednesday.

Strong to gale force (25 to 31-mph) northwesterly winds are forecast on Thursday, decreasing on Friday and Saturday.

DIABLO CANYON METEOROLOGICAL TOWER WIND DATA:

Today’s winds:

Max peak winds:      NE       12.1 mph at   3:15 a.m.
Max sustained wind:  NE        4.5 mph at   3:15 a.m.

Yesterday’s Maximum Winds:

Max peak winds:      NE       25.2 mph at   6:00 a.m.
Max sustained wind:  NE       14.2 mph at   6:00 a.m.

SEAWATER TEMPERATURES:

The Diablo Canyon waverider buoy is reporting a sea surface temperature of 55.8 degrees while the Nortek AWAC current meter is reporting 52.2 degrees.

Intake seawater temperatures will range between 51- and 53
-degrees through tonight, decreasing to 49- and 52-degrees
on Wednesday and remaining at this level through Saturday.

OCEAN CURRENTS:

Both the DCPP Cal Poly CODAR stations and the DCPP Nortek AWAC meter are indicating a southerly (offshore) flowing current today.

This southerly (offshore) current will continue to flow southward through Saturday.

SEAWATER VISIBILITY:

Seawater visibility was 11 to 13-feet at the Diablo Canyon Intake.

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24-Hour Ocean Condition Outlook for Tuesday 04/05 to Wednesday 04/06

Sea/Swell       DIR. NW      HT.   3-5   PER.  10-12  This morning
Increasing to:  DIR. NW      HT.   4-6   PER.   4-11  This afternoon
Remaining  at:  DIR. NW      HT.   4-6   PER.   4-11  Tonight

WINDS:          DIR. NE      SPEED  5-10              This morning
Increasing to:  DIR. NW      SPEED 15-20 + 25         This afternoon
Increasing to:  DIR. NW      SPEED 20-25 + 30         Tonight
===========================================================================
48-Hour Ocean Condition Outlook for Wednesday 04/06 to Thursday 04/07

Sea/Swell       DIR. NW      HT.   7-9   PER.   7-17  Wednesday morning
Increasing to:  DIR. NW      HT.  10-12  PER.   7-16  Wednesday afternoon
Remaining  at:  DIR. NW      HT.  10-12  PER.   7-16  Wednesday night

WINDS:          DIR. NW      SPEED 15-20 + 25         Wednesday morning
Increasing to:  DIR. NW      SPEED 30-35 + 45         Wednesday afternoon
Decreasing to:  DIR. NW      SPEED 25-30 + 40         Wednesday night
===========================================================================

Extended Ocean Condition Outlook:

Decreasing northwesterly winds and seas.

===========================================================================

The 24 – Hour Ocean Data From The Diablo Canyon Wave rider Buoy
MONTH  DAY  TIME  SIG.HEIGHT   PERIOD   SWELL DIRECTION     SST
04    01    0712     7.8       20            268          54.5
04    01    1342     6.6       18            265          54.9
04    02    2142     9.4       13            272          54.7
04    03    0742    11.1       13            274          55.4
04    04    0543     6.0       13            270          53.1
04    05    0243     3.4       15            229          55.8

(cm) (sec)  22+   20    17    15    13     11    9    7
———————————————————————
04 01  0712  239   11    43   589    66   166   535   921   573  303
04 01  1342  202   20    38   498   276   105   232   433   469  238
04 02  2142  287   13     6    30   284   674  1117  1078   971  546
04 03  0742  338   13     3     9    30   655  2388  2025   996  557
04 04  0543  183   11     2     7    17   105   339   590   557  247
04 05  0243  105    4     9    32     8    88   100   122   109  146

Daily Swell Inspection Program

NAME                      DAY   TIME    HEIGHT   PERIOD     SST
(PST)   (FEET)  (SECONDS) (DEG. F)
# 166  Ocean Station Papa       5    0002      22       14       41.7
# 06   SE Papa                  5    0250      20       16       51.6
# 59   California Buoy          5 0250 6 5 55.2
# 01   Point Reyes Waverider    5    0246       8       11       50.4
# 15   Monterey Waverider Buoy  5    0250       3       14       55.4
# 28   Cape San Martin, Ca      5 0250 6 8 55.9
# 50   DCPP Waverider Buoy, Ca  5    0243       3       11       54.3
# 63   Harvest Buoy             5    0220       5       12       57.2
# 01   NW Hawaii                5    0250      14       11       75.2

* 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.

Sunday    1500 through Monday      1500   0.00 inches
Monday    1500 through Tuesday     1500   0.00 inches

Precipitation this rain season (July 1 – June 30): 25.82 inches
Average season rainfall at DIP to date:            23.01 inches

Ocean Lab Barometer:  29.99 in/Hg or 1015.7 mb  -1.3 mb (Falling)

Sunrise and Sunset

Today’s         Sunrise 6:44 AM      Sunset 7:27  PM
Tomorrow’s      Sunrise 6:43 AM      Sunset 7:28  PM

Tides:
Low Tide                 High Tide
AM          PM           AM          PM
5 Tuesday     5:58  0.1    5:21  1.8  (12:17 3.7)  11:32  5.1
6 Wednesday   6:38  0.1    5:46  2.1   ———    1:05  3.4
7 Thursday    7:24  0.1    6:14  2.4   12:02 5.0    2:03  3.2
8 Friday      8:18  0.1    6:50  2.6   12:38 4.9    3:20  3.0
9 Saturday    9:21  0.2    7:50  2.8    1:23 4.8    4:52  3.0
10 Sunday     10:28  0.1    9:35  2.9    2:23 4.6    6:04  3.2
11 Monday     11:31  0.0   11:19  2.6    3:40 4.5    6:46  3.5
12 Tuesday    —–  —   12:25 -0.1    5:04 4.4    7:19  3.9
13 Wednesday  12:36  2.1    1:12 -0.1    6:21 4.5    7:50  4.4
14 Thursday    1:36  1.3    1:55  0.0    7:28 4.6    8:21  4.9
15 Friday      2:29  0.6    2:35  0.2    8:29 4.7    8:54  5.4
16 Saturday    3:19 -0.2    3:14  0.5    9:26 4.6    9:29  5.9
17 Sunday      4:09 -0.8    3:54  0.8   10:23 4.5   10:07  6.2
18 Monday      4:58 -1.2    4:34  1.2   11:19 4.3   10:46  6.3
19 Tuesday     5:49 -1.3    5:16  1.6  (12:18 4.1)  11:28  6.2
=========================================================================

This day in weather history

1945 – The temperature at Eagles Nest, NM, plunged to 45 degrees below zero to establish an April record for the United States. (Sandra and TI Richard Sanders – 1987)

1989 – Unseasonably hot weather prevailed in the southwestern U.S. Afternoon highs of 100 degrees at Santa Maria CA and 105 degrees in Downtown Los Angeles established records for the month of April. (The National Weather Summary)

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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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