Weather forecast for Saturday April 16

April 16, 2011

By JOHN LINDSEY from PG&E

SEA/SWELL:

Strong to gale force (25- to 38-mph) northwesterly winds along the Central Coast will continue to generate 4- to 6-foot northwesterly (310-degree deep-water) sea and swell (with a 7- to 12-second period) through Sunday.

A 3- to 5-foot northwesterly (285-degree deep-water) swell (with an 8- to 15-second period) will develop on Monday, building to 4- to 6-feet (with an 8- to 13-second period) on Tuesday. This swell will decrease to 2- to 4-feet on Wednesday.

Another round of strong to gale force (25- to 38-mph) northwesterly winds later next week, will produce a 4- to 6-foot northwesterly (310-degree deep-water) sea and swell (with a 7- to 11-second period) late Thursday through next Sunday.

Arriving from the southern hemisphere:

A 1-foot southern hemisphere (205-degree deep-water) swell (with a 16- to 18-second period) will arrive along our coastline Monday, increasing to 2- to 4-feet (with a 15- to 17-second period) on Tuesday and will continue at this height and period through Wednesday.

ATMOSPHERIC CONDITIONS:

A 1,028-millibar Eastern Pacific High is parked about 600 miles to the west-southwest of San Luis Obispo and will gradually weaken over the next 96 hours.

A few areas of marine low clouds developed along our coastline this morning and along highway 101 from Atascadero northward through the Salinas Valley, but will clear later this morning.

Temperatures will warm into the low to high 70s throughout San Luis Obispo County. Expect similar morning conditions Sunday, with mild temperatures and low coastal clouds.

Rain will develop across Northern California and spread southward towards Monterey Bay late Sunday into Monday, as a cold front moves onshore. This cold front will produce decreasing northwesterly winds, night and morning low clouds, fog and drizzle along with cooler temperatures along the Central Coast on Monday. This system is expected to be relatively warm and snow levels will remain above 5,500 to 8,000 feet north to south.

A weak 1,012 millibar low pressure system will approach the Central Coast later on Tuesday, producing night and morning coastal low clouds and fog. As the system moves over the Central Coast on Wednesday, its expected to produce gentle southerly winds and mostly cloudy conditions with a few sprinkles.

A return to dry and warm weather along with strong to gale force northwesterly winds along the coastline is expected Thursday through next weekend.

Yesterday’s         Today’s          Tomorrow’s
Min    Max        Min    Max         Min     Max
55.7°   71.2°     51.2°   64.0°      52.0°    60.0°

PG&E San Francisco Met Office predicted temps:

Inland Temperatures, Paso Robles

Actual                    Predicted

Fri        Sat   Sun   Mon   Tue   Wed   Thu   Fri   Sat
40 78      49 78 50 76 49 72 41 74 41 75 40 74 39 76 43 76

Coastal Valleys Temperatures, San Luis Obispo

Fri        Sat   Sun   Mon   Tue   Wed   Thu   Fri   Sat
47 79      48 73 49 73 49 69 49 68 45 69 46 68 45 68 46 68

WINDS:

Today’s strong to gale force (25- to 38-mph) northwesterly winds
will continue through Sunday.

The northwesterly winds will decrease on Monday and Tuesday to
moderate to fresh (13 to 24-mph) levels, than shifting out of
the south on Wednesday.

Strong to gale force (25- to 38-mph) northwesterly winds are
forecast on Thursday through next Saturday.

DIABLO CANYON METEOROLOGICAL TOWER WIND DATA:

Today’s winds:

Max peak winds:      NW       19.5 mph at    6:30 a.m.
Max sustained wind:  NW       13.0 mph at    6:30 a.m.

Yesterday’s Maximum Winds:

Max peak winds:      NW       29.3 mph at    1:45 p.m.
Max sustained wind:  NW       21.5 mph at    2:00 p.m.

SEAWATER TEMPERATURES:

The Diablo Canyon waverider buoy is reporting a sea surface temperature of 55.0 degrees while the Nortek AWAC current meter is reporting 49.4 degrees.

Intake seawater temperatures will range between 49- and 51 -degrees through Friday.

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 Friday.

SEAWATER VISIBILITY:

Seawater visibility was 22- to 24-feet at the Diablo Canyon Intake.

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24-Hour Ocean Condition Outlook for Saturday 04/16 to Sunday 04/17

Sea/Swell       DIR. NW      HT.   4-6   PER.   7-12  This morning
Remaining  at:  DIR. NW      HT.   4-6   PER.   7-12  This afternoon
Remaining  at:  DIR. NW      HT.   4-6   PER.   7-12  Tonight

WINDS:          DIR. NW      SPEED 10-15 + 20         This morning
Increasing to:  DIR. NW      SPEED 25-30 + 40         This afternoon
Decreasing to:  DIR. NW      SPEED 20-25              Tonight
===========================================================================
48-Hour Ocean Condition Outlook for Sunday 04/17 to Monday 04/18

Sea/Swell       DIR. NW      HT.   4-6   PER.   7-12  Sunday morning
Remaining  at:  DIR. NW      HT.   4-6   PER.   7-12  Sunday afternoon
Remaining  at:  DIR. NW      HT.   4-6   PER.   7-12  Sunday night

WINDS:          DIR. NW      SPEED 10-15              Sunday morning
Increasing to:  DIR. NW      SPEED 25-30 + 40         Sunday afternoon
Decreasing to:  DIR. NW      SPEED 20-25              Sunday night
===========================================================================

Extended Ocean Condition Outlook:

Decreasing northwesterly winds.

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

The 24 – Hour Ocean Data From The Diablo Canyon Wave rider Buoy
MONTH  DAY  TIME  SIG.HEIGHT   PERIOD   SWELL DIRECTION     SST
04    10    0043     6.2       11            285          52.7
04    11    0613     3.7       14            230          50.2
04    12    0413     5.0       13            263          52.5
04    13    0243     7.0       13            271          54.0
04    13    0843     6.0       13            270          54.9
04    14    0512     5.0       12            275          51.6
04    15    1212     4.9       11            285          52.7
04    16    0442     4.8        8            288          55.0

(cm) (sec)  22+   20    17    15    13     11    9    7
———————————————————————
04 10  0043  189   11     1     8    31    98   251   523   443  446
04 11  0613  112    4     1     3    19    62    85    93    91  294
04 12  0413  152    7     1     3    23    69   151    84   205  430
04 13  0243  214    7     2     4    11   114   641   469   416  560
04 13  0843  183   11     1     4     9   110   438   526   382  305
04 14  0512  154    4     1     4    28    30   102   262   211  432
04 15  1212  150   11     1     5    15    21    79   476   253  181
04 16  0442  146    7     1     5     4    20    81   154   260  439

Daily Swell Inspection Program

NAME                      DAY   TIME    HEIGHT   PERIOD     SST
(PST)   (FEET)  (SECONDS) (DEG. F)
# 166  Ocean Station Papa      16    0402       3        7       42.1
# 06   SE Papa                 16    0450       7       10       52.3
# 59   California Buoy         16    0450       7       11       55.4
# 01   Point Reyes Waverider   16    0446       8       13       53.4
# 15   Monterey Waverider Buoy 16    0450       7       12       52.3
# 28   Cape San Martin, Ca     16    0450      11        7       55.2
# 50   DCPP Waverider Buoy, Ca 16 0443 5 8 55.0
# 63   Harvest Buoy            16    0420       9       13       51.8
# 01   NW Hawaii               16 0450 6 8 74.5

* 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.

Thursday  1500 through Friday      1500   0.00 inches
Friday    1500 through Saturday    1500   0.00 inches

Precipitation this rain season (July 1 – June 30): 25.84 inches
Average season rainfall at DIP to date:            23.52 inches

Ocean Lab Barometer:  30.05 in/Hg or 1017.7 mb  -1.0 mb (Falling)
Sunrise and Sunset

Today’s         Sunrise 6:30 AM      Sunset 7:36  PM
Tomorrow’s      Sunrise 6:28 AM      Sunset 7:37  PM

Tides:
Low Tide                 High Tide
AM          PM           AM          PM
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
20 Wednesday   6:42 -1.3    6:02  2.0   —– —    1:20  3.8
21 Thursday    7:39 -1.1    6:55  2.4   12:14 5.9    2:29  3.6
22 Friday      8:40 -0.7    8:02  2.6    1:05 5.4    3:46  3.5
23 Saturday    9:45 -0.4    9:32  2.7    2:04 4.9    5:03  3.6
24 Sunday     10:50 -0.1   11:09  2.5    3:15 4.4    6:06  3.8
25 Monday     11:50  0.1   —–  —    4:36 4.1    6:53  4.0
26 Tuesday    12:29  2.1   12:40  0.4    5:55 3.9    7:29  4.2
=========================================================================

This day in weather history

1851 – The famous “Lighthouse Storm” raged near Boston Harbor. Whole gales and gigantic waves destroyed Minot Light with its two keepers still inside. The storm resulted in great
shipping losses and coastal erosion. (David Ludlum)

1880 – A tornado near Marshall, MO, carried the heavy timbers of an entire home a distance of twelve miles.

1990 – Thunderstorms developing along a stationary front produced large hail and damaging winds across Oklahoma, with 99 reports of large hail and damaging winds during the evening and early nighttime hours. Thunderstorms produced baseball size hail south of Carney, and wind gusts to 100 mph in the Oklahoma City area which swept away many Federal tax returns being transported from a mail cart to a waiting truck about the time of the midnight deadline.

Will Rogers Airport in Oklahoma City reported a record wind gust of 92 mph. (Storm Data)

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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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