Marine Weather and Tides
10/6/2018 Colors of tide XTide graphs changed to emphasize that they were upgraded. See next note. Comments welcome.
10/4/2018 I have fixed XTide and updated the harmonic files. There were some name changes so you might have to click EDIT to find the new station name.
|Sunrise 5:51AM||Sunset 5:22PM||Monday December 17, 2018 10:22 AM CST (16:22 UTC)||Moonrise 1:58PM||Moonset 1:17AM||Illumination 76%|
7 Day Forecast for Marine Location Near Pole Ojea, PRHourly EDIT Help
Area Discussion for - San Juan, PR  (on/off)  Help NOTE: mouseover dotted underlined text for definition
|Fxca62 tjsj 171515|
area forecast discussion
national weather service san juan pr
1115 am ast Mon dec 17 2018
Mostly sunny skies and fair weather conditions will prevail across
the region today with limited or no shower activity expected in
and around the islands. Mid to upper level ridge will hold across
the region although slightly erode today as a short wave trough
will move across the west atlantic and north of the region. Upper
ridge is to build once again across the region by mid week to
maintain stable conditions aloft and limit convective development.
Surface high pressure located over the central atlantic will shift
into the eastern atlantic during the next few days, as a cold front
moves over the western atlantic and stalls well north of the region
by midweek. This will cause winds to diminish through at least Wednesday
night. Winds will again increase during the latter part of the week
as another surface high pressure builds over the western atlantic bringing
breezy conditions to the region. No change made to the inherited forecast
package and reasoning at this time. Mostly fair weather skies and overall
dry and stable conditions will prevail except for the occasional periods
of passing clouds and trade wind showers especially during the late
evening and early morning hours.
Aviation update Vfr conds durg entire prd. No change to
previous avn discussion.
Marine update Winds and seas will continue to gradually diminish
and subside during the rest of today and Tuesday. However, still
a slight chop over most of the offshore atlantic waters and
anegada passage today, therefore small craft operators should
exercise caution at least until later this afternoon. No change
to previous marine discussion.
Prev discussion issued 458 am ast Mon dec 17 2018
synopsis... Ridge aloft will keep a dry air mass over the region
throught the week. This will promote fair weather conditions
across puerto rico and the u.S. Virgin islands. No significant
rainfall is expected during the next several days. Winds will
diminish through mid week as a frontal boundary stalls north of
the region and a surface high over the central atlantic moves
further east. Another surface high behind the front will increase
winds once again during the second part of the week.
Short term... Today through Wednesday...
a dry and stable air mass is expected to prevail across the forecast
area today and Tuesday. Precipitable water values are expected to
range between 0.80 and 1.00 inches, which would be near 2 standard
deviations below normal for this time of the year. In addition,
relative humidity values between the 850 and 700 mb layer are
expected to be below 50%. These two factors alone suggest that the
environment will be very hostile for shower development. Therefore,
most areas across the region should experience rain-free conditions.
If any showers do manage to develop, the area that would most likely
see some activity would be across northwest pr during the afternoon
hours due to sea breeze influence and diurnal heating. Either way,|
with the very dry air mass in place, any showers that do manage to
develop should be brief and lead to very light accumulations.
On Wednesday, a patch of low-level moisture embedded within the
trade wind flow is set to move over the region. Therefore, an
increase in shower activity is possible. However, given that the
synoptic pattern continues to feature a mid to upper-level ridge
maintaining the mid to upper-levels of the atmosphere very dry, any
showers that do develop should be brief and lead to minor rainfall
Long term... Thursday through Monday...
an upper level ridge will continue to dominate the region through
the long term period. Another drier air mass is expected to move
from the east on Thursday and linger through Saturday morning,
keeping moisture below 850 mb. This will limit shower activity
across the islands. Moisture increases to 700 mb on Saturday
afternoon and continues through early next week. A return to light
passing showers across the usvi and eastern pr during the night
time and early morning hours, followed by diurnally induced
afternoon showers over western pr can be expected during this
period. However, no significant rainfall accumulations are
expected at the moment.
Aviation...VFR conditions are expected to prevail across all
terminals throughout the forecast period. A few shra may affect
tjbq and tjmz terminals after 17 16z. Low-level winds will be
mainly from the SE between 10 and 15 knots with sea breeze
variations developing after 17 14z.
Marine... Small crafts should exercise caution today due to seas
up to 6 feet across the atlantic waters and caribbean passages.
East to southeast winds will prevail between 10-15 kt. Winds and
seas will gradually diminish through Wednesday. A long period
northerly swell is expected to enter the atlantic waters during
the end of the work week. A surface high pressure will increase
winds once again on Thursday.
There is a risk o rip currents for the northern beaches of puerto
rico and culebra today due to a fading northerly swell.
Preliminary point temps pops
Sju 86 73 85 74 10 0 0 20
stt 87 72 87 74 10 0 10 20
Sju watches warnings advisories
Pr... High rip current risk until 6 pm ast this evening for culebra-
north central-northeast-northwest-san juan and vicinity-
Short term... Ram
long term... .Ram
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