Weather forecast for Wednesday March 23

March 23, 2011

By JOHN LINDSEY from PG&E

A 999 millibar low pressure system currently spinning off Cape Mendocino will remain nearly stationary over the next 48 hours.

The associated cold front will passed over Diablo Canyon this morning at about 9 a.m. with periods of moderate rain and  strong to gale force (25 to 38 mph) southeasterly winds.

The southerly winds will decrease and the steady rain to will turn to scattered showers later this morning through tonight.

A brief break in the weather will develop on Thursday morning.

An intense 988 millibar Gulf of Alaska low pressure system will merge with the low off Cape Mendocino. The associated cold front will pass the Central Coast Thursday evening between 5 and 7 p.m. with another round of moderate rain and gusty southeasterly winds.

During this period (today through Thursday), snow levels are expected to be near 3,000 to 4,000 feet with precipitation totals near 1 to 3 inches for the higher elevations, and 0.75 to 1.5 inches for the lower elevations.

After a brief period of dry weather on Friday, another cold front is will drop southeastward on Saturday morning with moderate rain.

High pressure will build over our area on Sunday and should produce an extended period of dry weather. Strong to gale (25 to 31-mph) northwesterly “springtime” winds are forecast on Sunday through next Wednesday.

However, a few of the models are indicating a northeasterly (offshore) wind event developing on Monday morning. If this  condition develops, well above seasonal temperatures are
expected.

Yesterday’s         Today’s          Tomorrow’s
Min    Max        Min    Max         Min     Max
49.1°   54.8°     50.9°   57.0°      47.0     56.0

PG&E San Francisco Met Office predicted temps:

Inland Temperatures, Paso Robles

Actual                    Predicted

Tue     Wed   Thu   Fri   Sat   Sun   Mon   Tue   Wed
38 58   48 56 40 57 41 61 42 59 39 64 36 69 41 71 39 70

Coastal Valleys Temperatures, San Luis Obispo

Tue    Wed   Thu   Fri   Sat   Sun   Mon   Tue   Wed
39 60  50 57 41 58 43 59 42 60 43 63 43 68 45 67 44 69

SEA/SWELL:

This morning’s strong to gale force (25 to 31-mph) southeasterly winds have generated 6- to 8- foot southerly (190-degree shallow -water) seas (with a 4- to 6-second period) this morning, decreasing to 4- to 6-feet this afternoon but reaming at this height through Thursday.

These seas will be followed by an 8- to 10-foot west-northwesterly  (280-degree deep-water) swell (with a 13- to 15-second period) Thursday.

A 988 millibar Gulf of Alaska storm is forecast to move southeastward and merge with a 999 millibar storm off Cape Mendocino later today.  This storm will produce a 600 mile long
fetch (distance of water over which the wind blows) with  50 mph west-northwesterly winds. These winds will generate  a 13 to 15-foot northwesterly (290-degree deep-water) swell
(with a 14 to 17-second period) on Friday.

Note: Wave Heights at the offshore buoys should reach over 20 feet on Friday.

This northwesterly swell will decrease to 8- to 10 feet  (with a 12 to 14-second period) on Saturday.

Strong to gale force (25 to 38-mph) northwesterly winds and and yet another Gulf of Alaska storm will produce a 9 to 11-foot northwesterly (300-degree deep-water) sea and swell
(with a 7 to 15-second period) on Sunday, decreasing to  7 to 9-feet (with a 7 to 11-second period) on Monday.

An 8 to 10-foot northwesterly (300-degree deep-water) sea  and swell (with a 7 to 18-second period) is forecast along  our coastline on Tuesday through next Wednesday.

Look for another increase in northwesterly swell on March 31.

Arriving from the southern hemisphere:

A 1- to 2-foot southern hemisphere (200-degree deep-water) swell (with a 20 to 22-second period) will arrive along our  coastline later today, increasing to 2 to 4 feet (with a 15 to 17-second period) by Thursday.

WINDS:

This morning’s strong to gale force (25 to 38-mph) southerly winds will decrease to moderate to fresh (13 to 24-mph) levels this afternoon. These winds will further lower to
gentle to moderate (8 to 18-mph) levels tonight.

Moderate to fresh (13 to 24-mph) southerly winds will develop on Thursday morning, building to strong to gale force (25 to 38-mph) levels on Thursday afternoon and evening. These
winds will decrease Thursday night.

Moderate to fresh (13 to 24-mph) northwesterly winds will  develop on Friday, becoming light and variable on Saturday.

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

However, a few of the models are indicating a northeasterly (offshore) wind event developing on Monday morning.

DIABLO CANYON METEOROLOGICAL TOWER WIND DATA:

Today’s winds:

Max peak winds:      SE       42.1 mph at  03:30 a.m.
Max sustained wind:  SE       30.2 mph at  03:30 a.m.

Yesterday’s Maximum Winds:

Max peak winds:      SE       15.2 mph at  10:30 p.m.
Max sustained wind:  SE       29.3 mph at  10:30 p.m.

SEAWATER TEMPERATURES:

The Diablo Canyon waverider buoy is reporting a sea surface  temperature of 52.0 degrees while the Nortek AWAC current meter is reporting 51.1 degrees.

Intake seawater temperatures will range between 51 and 53 -degrees through Friday.

OCEAN CURRENTS:

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

This northerly (onshore) flowing current will continue to flow northward through Friday.

SEAWATER VISIBILITY:

Seawater visibility was 2 to 3 feet at the Diablo Canyon Intake.

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24-Hour Ocean Condition Outlook for Wednesday 03/23 to Thursday 03/24

Sea/Swell       DIR. S       HT.   6-8   PER.   4-6   This morning
Decreasing to:  DIR. SW      HT.   4-6   PER.   5-7   This afternoon
Remaining  at:  DIR. SW      HT.   4-6   PER.   5-7   Tonight

(Combined with:  DIR. NW      HT.   6-8   PER.  11-15  All day)

WINDS:          DIR. SE      SPEED 30-35 + 40         This morning
Decreasing to:  DIR. SW      SPEED 20-25              This afternoon
Decreasing to:  DIR. SW      SPEED 15-20              Tonight
===========================================================================
48-Hour Ocean Condition Outlook for Thursday 03/24 to Friday 03/25

Sea/Swell       DIR. WNW     HT.   8-10  PER.  13-15  Thursday morning
Remaining  at:  DIR. WNW     HT.   8-10  PER.  13-15  Thursday afternoon
Remaining  at:  DIR. WNW     HT.   8-10  PER.  13-15  Thursday night

(Combined with:  DIR. SW      HT.   4-6   PER.   5-7   All day Thursday)

WINDS:          DIR. S       SPEED 10-15              Thursday morning
Increasing to:  DIR. S       SPEED 30-35 + 40         Thursday afternoon
Remaining  at:  DIR. S       SPEED 30-35 + 40         Thursday night
===========================================================================

Extended Ocean Condition Outlook:

High pressure will build over our area on Sunday and should produce an extended period of dry weather. Strong to gale (25 to 31-mph) northwesterly “springtime” winds are forecast on Sunday through next Tuesday.

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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
03    18    0843     6.1       12            274          49.3
03    19    0543    11.1       14            271          50.2
03    20    0243    10.1        7            220          50.5
03    20    0643    12.9       12            275          50.9
03    21    1313     8.9       22+           268          52.5
03    22    0013    11.3       11            278          51.1
03    22    0813     7.0       17            263          50.7
03    23    0343     5.7       15            264          52.0

(cm) (sec)  22+   20    17    15    13     11    9    7
———————————————————————-
03 18  0843  187   11     2     9    28   219   471   714   380  192
03 19  0543  339   15     9    44   193  2176  2025  1128   562  445
03 20  0243  309    7     4     5    10   218   693   603  1289 2304
03 20  0643  393   11     6    12    38   288  1464  2668  2566  851
03 21  1313  271    9   383   506    36   202   566   920   980  427
03 22  0113  339   20    69  1756   356    82   334  1683  1619  505
03 22  0813  213   17    22   357   518    75   168   499   391  333
03 23  0343  175    4    11    94   165   227   116    40   110  856

Daily Swell Inspection Program

NAME                      DAY   TIME    HEIGHT   PERIOD     SST
(PST)   (FEET)  (SECONDS) (DEG. F)
# 166  Ocean Station Papa      23    0402      11       11       41.7
# 06   SE Papa                 23    0350      10       13       49.8
# 59   California Buoy         23    0350      15        9       56.1
# 01   Point Reyes Waverider   23    0346      13        9       51.8
# 15   Monterey Waverider Buoy 23    0350       9        8       53.6
# 28   Cape San Martin, Ca     23    0350      12        7       55.0
# 50   DCPP Waverider Buoy, Ca 23    0343       6       15       51.8
# 63   Harvest Buoy            23    0320       7       17       54.5
# 01   NW Hawaii               23    0350      10        8       73.2

* 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.

Monday    1500 through Tuesday     1500   0.00 inches
Tuesday   1500 through Wednesday   0600   0.04 inches

Precipitation this rain season (July 1 – June 30): 23.77 inches
Average season rainfall at DIP to date:            21.69 inches

Ocean Lab Barometer:   29.86 in/Hg or 1011.3 mb  -1.8 mb (Falling)

Sunrise and Sunset

Today’s         Sunrise 7:02 AM      Sunset 7:17  PM
Tomorrow’s      Sunrise 7:01 AM      Sunset 7:18  PM

Tides:
Low Tide                 High Tide
AM          PM           AM          PM
23 Wednesday   7:56 -0.5    7:13  2.0   12:46 5.8    2:26  3.6
24 Thursday    9:05 -0.3    8:12  2.4    1:36 5.6    3:55  3.3
25 Friday     10:22 -0.1    9:38  2.7    2:37 5.2    5:33  3.4
26 Saturday   11:38 -0.1   11:20  2.7    3:52 4.8    6:51  3.6
27 Sunday     —–  —   12:43  0.0    5:14 4.6    7:43  3.8
28 Monday     12:43  2.4    1:35  0.0    6:29 4.6    8:20  4.0
29 Tuesday     1:42  2.0    2:17  0.1    7:29 4.6    8:50  4.2
=========================================================================

This day in weather history

1987 – A blizzard raged across western Kansas, and the panhandle of  Texas and Oklahoma. Pampa TX received 21 inches of snow, and winds gusted to 78 mph at Dodge City KS Altus OK. Governor  Hayden declared forty-six counties in western Kansas a  disaster area. In southwest Kansas, the storm was described as the worst in thirty years.  (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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