Stormy weather on Sunday

March 17, 2011

By JOHN LINDSEY from PG&E

Today is the last full day of dry weather for the next several days.

A cold front will produce rain showers and moderate to fresh (13 to 24-mph) southerly winds over our area on Friday evening into Saturday afternoon. snow levels initially at 3,500 to 5,000 feet north to south will lower to 2,500 to 3,500 feet north to south after frontal passage.

The Eastern Pacific High will move westward and take a position north of Hawaii. The upper-level (jet steam) winds will move southward over the Central Coast. This condition will open the door to a series of Gulf of Alaska low pressure systems that will produce increasing southerly winds and periods of heavy rain.

This afternoon’s models and charts are indicating an intense 989 millibar storm reaching the Central Coast on Sunday, the first day of spring.

If this storm develops as advertised, moderate gale to fresh gale (32 to 46-mph) southeasterly winds and periods of heavy rain is expected on Sunday into Monday. Rainfall totals of
2 to 3 inches is possible. Snow levels will rise to 4,000 to 5,500 feet north to south Sunday.

This storm may be followed by another potentially strong system next Wednesday. It continues to look like a wet week next week.

Weather Forecast for Thursday March 17

SEA SWELL:

Today’s 8 to 10-foot west-northwesterly (285-degree deep-water) swell (with a 13 to 17-second period) will decrease to 7 to 9-feet (with a 12 to 14-second period) on Friday.

A 10 to 12-foot northwesterly (290-degree deep-water) swell (with a 13 to 15-second period) is forecast along our coastline on Saturday, decreasing to 6 to 8-feet on Sunday morning.

Combined with this northwesterly swell on Sunday will be increasing southerly seas.

A 989 millibar storm off our coastline will generate moderate gale to fresh gale (32 to 46-mph) southeasterly winds. This winds will generate 11 to 13-foot southerly (190-degree shallow-water) seas (with a 4 to 8-second period) on Sunday afternoon through Sunday night.

A 936 millibar storm with hurricane force winds off the Kamchatka Peninsula will produce an 8 to 10-foot northwesterly (300-degree deep-water) swell (with a 20 to 22+ second period) on Monday, increasing to 9 to 11-feet (with an 18 to 20-second period) Tuesday.

Another round of increasing southerly winds will produce 5 to 7-foot southerly (190-degree shallow-water) seas (with a 4 to 6-second period) on Wednesday, followed by an 11 to 13-foot westerly (280-degree deep-water) swell next Thursday.

ATMOSPHERIC CONDITION:

Yesterday’s         Today’s          Tomorrow’s
Min    Max        Min    Max         Min     Max
53.9°   62.2°     53.4°   60.0°      51.0     59.0

PG&E San Francisco Met Office predicted temps:

Inland Temperatures, Paso Robles

Actual                    Predicted

Wed       Thu   Fri   Sat   Sun   Mon   Tue   Wed   Thu
49-68   38 64 35 60 46 56 46 55 47 57 46 60 46 60 46 64

Coastal Valleys Temperatures, San Luis Obispo

Wed     Thu   Fri   Sat   Sun   Mon   Tue   Wed   Thu
54 68   51 67 38 61 46 58 48 56 44 58 42 62 45 61 48 63

WINDS:

Today’s moderate to fresh (13 to 24-mph) northwesterly winds will decrease tonight.

Moderate to fresh (13 to 24-mph) southerly winds will develop on Friday and will continue at this level through Saturday.

Moderate gale to fresh gale (32 to 46-mph) southeasterly winds with gust over 50 mph will develop on Sunday, decreasing on Monday.

DIABLO CANYON METEOROLOGICAL TOWER WIND DATA:

Today’s winds:

Max peak winds:      NW       29.5 mph at   2:30 p.m.
Max sustained wind:  NW       21.0 mph at   2:30 p.m.

Yesterday’s Maximum Winds:

Max peak winds:      NW       38.0 mph at   5:15 p.m.
Max sustained wind:  NW       25.7 mph at   5:15 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 49.7 degrees.

Intake seawater temperatures will range between 49- and 52 -degrees through Friday, increasing to 51- and 53-degrees over the weekend.

OCEAN CURRENTS:

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

A northerly (onshore) flowing current will develop on Friday and will continue to flow northward through most of next week.

SEAWATER VISIBILITY:

Seawater visibility was 4 to 6 feet at the Diablo Canyon Intake.

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24-Hour Ocean Condition Outlook for Thursday 03/17 to Friday 03/18

Sea/Swell       DIR. WNW     HT.   9-11  PER.  14-17  This morning
Decreasing to:  DIR. WNW     HT.   8-10  PER.  13-16  This afternoon
Remaining  at:  DIR. WNW     HT.   8-10  PER.  13-15  Tonight

(Combined with:  DIR. NW      HT.   2-4   PER.   4-6   this afternoon)

WINDS:          DIR. NW      SPEED 10-15              This morning
Increasing to:  DIR. NW      SPEED 25-30              This afternoon
Decreasing to:  DIR. NW      SPEED  5-10              Tonight
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48-Hour Ocean Condition Outlook for Friday 03/18 to Saturday 03/19

Swell           DIR. WNW     HT.   8-10  PER.  12-14  Friday morning
Decreasing to:  DIR. WNW     HT.   7-9   PER.  12-14  Friday afternoon
Decreasing to:  DIR. WNW     HT.   7-9   PER.  12-14  Friday night

WINDS:          DIR. SE      SPEED  5-10              Friday morning
Increasing to:  DIR. SE      SPEED 10-15              Friday afternoon
Increasing to:  DIR. SE      SPEED 20-25              Friday night
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Extended Ocean Condition Outlook:

A potentially very heavy rain and wind event is expected Sunday.

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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    14    2013    11.6       14            263          50.7
03    15    0443     9.6       15            253          51.4
03    16    0713     7.1       13            267          52.0
03    16    1213     9.5       22+           243          52.2
03    16    2013    10.7       20            267          51.3
03    17    1213     9.4       17            240          52.0

(cm) (sec)  22+   20    17    15    13     11    9    7
———————————————————————-
03 14  2013  354   13    20   122   490  1838  2643  1574   540  293
03 15  0443  291   15    16    74   442  1452   844  1005   677  387
03 16  0713  216   13   244   124    67   539   672   463   401  211
03 16  1213  290   13   619   710   167   314  1169  1105   465  460
03 16  2013  325   20    73  1685   683  1271   489   715   473  610
03 17  1213  287   11    15    94   834   592  1043  1203   571  420

Daily Swell Inspection Program

NAME                      DAY   TIME    HEIGHT   PERIOD     SST
(PST)   (FEET)  (SECONDS) (DEG. F)
# 166  Ocean Station Papa      17    0402      12       13       41.5
# 06   SE Papa                 17    1250      22       12       50.9
# 59   California Buoy         17    1250      11       15       54.7
# 01   Point Reyes Waverider   17    1246      14       13       52.5
# 15   Monterey Waverider Buoy 17    1250       9       13       57.0
# 28   Cape San Martin, Ca     17    1250      13       16       55.2
# 50   DCPP Waverider Buoy, Ca 17    1213       9       17       52.0
# 63   Harvest Buoy            17    1220      14       13       50.4
# 01   NW Hawaii               17 1250 9 8 73.4

* 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   1500   0.04 inches

Precipitation this rain season (July 1 – June 30): 20.06 inches
Average season rainfall at DIP to date:            20.80 inches

Ocean Lab Barometer:   30.22 in/Hg or 1023.2 mb  -1.1 mb (Falling)

Sunrise and Sunset

Today’s         Sunrise 7:11 AM      Sunset 7:12  PM
Tomorrow’s      Sunrise 7:09 AM      Sunset 7:13  PM

Tides:
Low Tide                 High Tide
AM          PM           AM          PM
17 Thursday    2:30  1.6    3:31 -1.0    8:37 6.2    9:53  4.7
18 Friday      3:20  1.2    4:06 -0.8    9:25 6.1   10:27  5.1
19 Saturday    4:12  0.8    4:42 -0.4   10:15 5.7   11:03  5.4
20 Sunday      5:07  0.5    5:19  0.2   11:08 5.1   11:43  5.6
21 Monday      6:06  0.4    5:58  0.8   —– —   12:07  4.5
22 Tuesday     7:13  0.4    6:40  1.5   12:26 5.7    1:17  3.8
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This day in weather history

1906 – The temperature at Snake River, WY, dipped to 50 degrees below zero, a record for the U.S. for the month of March. (Sandra and TI Richard Sanders – 1987)

1989 – Strong northerly winds ushered snow and arctic cold into the north central U.S. Winds gusted to 58 mph at Sydney NE and Scottsbluff NE, Cadillac MI received 12 inches of snow, and International Falls MN reported a record low of 22 degrees below zero. (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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