Weather forecast for Tuesday April 19

April 19, 2011

By JOHN LINDSEY from PG&E

The Eastern Pacific High has moved towards the southwest and is now halfway between California and Hawaii.

This weather pattern will continue to produce relatively fast upper-level (jet stream) winds which will steer a series of low pressure systems into Northern California this week.

Along the Central Coast, marine low clouds along with areas of fog and drizzle will develop during night and morning hours partially clearing during the afternoon hours.

Combined with the deep marine layer will be variable mid to high-level clouds today. Today’s high temperatures will reach the 60s throughout San Luis Obispo County.

A 1,010-millibar low-pressure system will approach the Central Coast on Wednesday. It’s expected to produce gentle southerly winds and mostly cloudy conditions with a few
sprinkles or light rain showers on Wednesday afternoon through Thursday morning.

This systems will have little in the way of any upper-level support and most Central Coast locations shouldn’t have any measurable rainfall.

A return to dry and warmer weather along with strong- to gale-force northwesterly winds along the coastline is expected Thursday afternoon through Friday.

The northwesterly (onshore) winds will decrease and temperatures will warm Saturday into Monday with many areas reaching the low 80s.

Yesterday’s         Today’s          Tomorrow’s
Min    Max        Min    Max         Min     Max
49.1°   59.6°     51.7°   61.0°      52.0°    61.0°

PG&E San Francisco Met Office predicted temps:

Inland Temperatures, Paso Robles

Actual                    Predicted

Mon        Tue   Wed   Thu   Fri   Sat   Sun   Mon
51 76      46 69 43 67 41 66 39 70 42 74 49 80 45 81

Coastal Valleys Temperatures, San Luis Obispo

Mon        Tue   Wed   Thu   Fri   Sat   Sun   Mon
52 63      52 66 45 63 47 65 46 67 45 70 49 77 48 78

SEA/SWELL:
Low swell conditions, fairly uncommon during the month of April, will continue through Thursday morning. The predominate wave train during this period will be coming
from the southern hemisphere.

This morning’s 1- to 2-foot northwesterly (290-degree deep -water) swell (with a 7- to 11-second period) will continue at this height through this morning, building to 2- to 3-feet
(with an 8- to 11-second period) this afternoon through tonight. This swell will decrease to 1- to 3-feet on on Wednesday and will continue a this height and period through Thursday morning.

Another round of strong to gale force (25- to 38-mph) northwesterly winds Thursday afternoon, will produce a 4- to 6-foot northwesterly (310-degree deep-water) sea and swell
(with a 7- to 11-second period) Thursday afternoon through Friday, decreasing to 3- to 4-feet on Saturday through Sunday.

Arriving from the southern hemisphere:

Today’s 2- to 3-foot southern hemisphere (200-degree deep -water) swell (with a 15- to 17-second period) will remain at this height but with a gradually shorter period through
Wednesday.

Another, but longer period southern hemisphere swell will overlap Wednesday’s wave train, and will continue to produce a 2- to 3-foot southern hemisphere (205-degree deep-water)
swell (with a 13- to 20-second period) on Thursday. This 2- to 3-feet swell will continue at this height but with a gradually shorter period through Sunday.

WINDS:

Moderate to fresh (13 to 24-mph) northwesterly winds will develop this afternoon, shifting and decreasing out of the south to gentle to moderate (8 and 18-mph) levels tonight
and remaining at this level through Thursday morning.

Strong to gale force (25- to 38-mph) northwesterly winds are forecast on Thursday afternoon through Friday, decreasing over the weekend.

DIABLO CANYON METEOROLOGICAL TOWER WIND DATA:

Today’s winds:

Max peak winds:      SE        3.0 mph at    5:30 a.m.
Max sustained wind:  SE        1.6 mph at    5:30 a.m.

Yesterday’s Maximum Winds:

Max peak winds:      NW       33.6 mph at    4:45 p.m.
Max sustained wind:  NW       23.7 mph at    4:45 p.m.

SEAWATER TEMPERATURES:

The Diablo Canyon waverider buoy is reporting a sea surface temperature of 51.4 degrees while the Nortek AWAC current meter is reporting 49.6 degrees.

Intake seawater temperatures will range between 49- and 51 -degrees through today, increasing to 52- to 54-degrees on Wednesday into Thursday.

Intake seawater temperatures will decrease to 50- and 52 -degrees on Friday and will remain at this level through 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) current will develop tonight and will continue to flow northward through Thursday morning.

A southerly (offshore) current will develop on Thursday afternoon and will continue to flow southward through the weekend.

SEAWATER VISIBILITY:

Seawater visibility was 24- to 26-feet at the Diablo Canyon Intake.

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24-Hour Ocean Condition Outlook for Tuesday 04/19 to Wednesday 04/20

Swell           DIR. NW      HT.   1-2   PER.   7-11  This morning
Increasing to:  DIR. NW      HT.   2-3   PER.   7-11  This afternoon
Remaining  at:  DIR. NW      HT.   2-3   PER.   7-11  Tonight

(Combined with:  DIR. SW      HT.   2-3   PER.  15-17  All day today)

WINDS:          DIR. SE      SPEED  5-10              This morning
Increasing to:  DIR. NW      SPEED 15-20 + 25         This afternoon
Decreasing to:  DIR. VAR.    SPEED  5-10              Tonight
===========================================================================
48-Hour Ocean Condition Outlook for Wednesday 04/20 to Thursday 04/21

Sea/Swell       DIR. NW      HT.   1-3   PER.   8-11  Wednesday morning
Increasing to:  DIR. NW      HT.   1-3   PER.   8-11  Wednesday afternoon
Remaining  at:  DIR. NW      HT.   1-3   PER.   8-11  Wednesday night

(Combined with:  DIR. SW      HT.   2-3   PER.  14-16  All day Wednesday)

WINDS:          DIR. SE      SPEED 10-15              Wednesday morning
Remaining  at:  DIR. SE      SPEED 10-15              Wednesday afternoon
Remaining  at:  DIR. SE      SPEED 10-15              Wednesday night
===========================================================================

Extended Ocean Condition Outlook:

Increasing northwesterly winds will develop on Thursday afternoon through 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    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
04    17    1912     5.8        7            279          52.5
04    18    0612     4.7       15            220          52.2
04    19    0212     2.6       17            215          51.4

(cm) (sec)  22+   20    17    15    13     11    9    7
———————————————————————
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
04 17  1912  176    7     3     9    81    53    22   154   185  670
04 18  0612  143    4     2    19    20   108    20    68   163  446
04 19  0212   78    4     2    11    62    44    40    13    35  116

Daily Swell Inspection Program

NAME                      DAY   TIME    HEIGHT   PERIOD     SST
(PST)   (FEET)  (SECONDS) (DEG. F)
# 166  Ocean Station Papa      18    1002       4       14       43.0
# 06   SE Papa                 19 0250 7 9 51.4
# 59   California Buoy         19 0250 7 8 55.6
# 01   Point Reyes Waverider   19    0246       5       18       53.8
# 15   Monterey Waverider Buoy 19    0250       2       13       54.0
# 28   Cape San Martin, Ca     19    0250       4       17       56.3
# 50   DCPP Waverider Buoy, Ca 19    0212       3       17       51.4
# 63   Harvest Buoy            19    0220       3       17       52.2
# 01   NW Hawaii               19    0250       6       12       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.

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

Precipitation this rain season (July 1 – June 30): 25.84 inches
Average season rainfall at DIP to date:            23.70 inches

Ocean Lab Barometer:  29.99 in/Hg or 1015.6 mb -0.8 mb (Falling)
Sunrise and Sunset

Today’s         Sunrise 6:26 AM      Sunset 7:39  PM
Tomorrow’s      Sunrise 6:25 AM      Sunset 7:40  PM

Tides:
Low Tide                 High Tide
AM          PM           AM          PM
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

1775 – The first engagement of the Revolutionary War took place under clear crisp weather at Lexington-Concord. (Sandra and TI Richard Sanders – 1987)

1973 – Glenrock, WY, received 41 inches of snow in just 24 hours, and a storm total of 58 inches, to establish two state records. (18th-20th) (David Ludlum)

1989 – A dozen cities in the southwestern U.S. reported new record high temperatures for the date. The afternoon high of 98 degrees at Hanksville UT equalled their record for April.
Tucson AZ reported their earliest 100 degree reading of record. (The National Weather Summary)

1996 – One of the most memorable tornado outbreaks in Illinois history occurred on April 19, 1996. During the day, 33 tornadoes were reported as supercells erupted and moved across the state during the afternoon and evening hours. Wind estimates in excess of 170 mph were associated with some of the stronger tornadoes, one of which ripped through nearby Ogden, IL. (University of Illinois WW2010)

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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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