Marine Weather and Tides
6/25/2017 - NOAA is having a major issue that impact the 7 day forecast load times. Many users are reporting problems. The issue has been reported.
5/23/2017 - Worked with NOAA again to speed up the 7 day forecast load times. Thanks to them for being responsive.
5/19/2016 - There were issues with the 3 day airport observation history. I switched to another data source. Let me know if you see any issues with the data feeds.
|Sunrise 6:43AM||Sunset 5:56PM||Tuesday November 21, 2017 3:33 PM AST (19:33 UTC)||Moonrise 9:09AM||Moonset 8:35PM||Illumination 10%|
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|AMZ741 Mona Passage Southward To 17n- 1104 Am Ast Tue Nov 21 2017 |
Rest of today..East winds 10 to 15 knots. Seas 2 to 4 feet with occasional seas up to 5 feet. Dominant period 10 seconds. North swell around 4 feet.
Tonight..East winds 10 to 15 knots. Seas 2 to 4 feet with occasional seas up to 5 feet. Dominant period 7 seconds. North swell around 4 feet in the evening. Isolated showers through the night.
Wednesday..East winds 10 to 15 knots. Seas 3 to 5 feet with occasional seas up to 6 feet. Dominant period 7 seconds. Isolated showers.
Wednesday night..East winds 5 to 10 knots. Seas 3 to 5 feet with occasional seas up to 6 feet. Dominant period 8 seconds. Isolated showers through the night.
Thursday..East winds 5 to 10 knots. Seas 3 to 5 feet with occasional seas up to 6 feet. Dominant period 8 seconds. Isolated showers.
Friday..East winds 10 to 15 knots. Seas 2 to 4 feet with occasional seas up to 5 feet. Dominant period 10 seconds. Scattered showers.
Saturday..East winds 10 to 15 knots. Seas 2 to 4 feet with occasional seas up to 5 feet. Dominant period 11 seconds. Isolated showers.
|AMZ700 1104 Am Ast Tue Nov 21 2017 |
Synopsis for puerto rico and the uS. Virgin islands waters... Light to moderate easterly winds expected across the local waters, as a surface high pressure ridge will build and move eastward across the west atlantic through Wednesday. Seas will increase briefly up to 7 feet on Wednesday through Wednesday night across the atlantic waters and the anegada passage, as a cold frontal boundary sinks southward into the tropical atlantic.
7 Day Forecast for Marine Location Near El Combate, PRHourly EDIT Help
Area Discussion for - San Juan, PR  (on/off)  Help NOTE: mouseover dotted underlined text for definition
|Fxca62 tjsj 211549|
area forecast discussion
national weather service san juan pr
1149 am ast Tue nov 21 2017
Skies were partly cloudy to mostly sunny during the morning hours
as a drier airmass and high pressure ridge continued to filter in
and build across the region. Satellite imagery suggests remnant
moisture along old frontal boundary continued to lift north and
east of the region while dissipating. Recent tjsj 21 12z sounding
confirmed much drier and stable environment with layered precipitable
water now down to 1.55 inches compared to 2.00 inches or more in
recent days. Light to moderate low level southeast wind flow prevailed
over land areas. For the rest of the day, expect limited convective
development across the region, however pockets of residual moisture
combined with local and diurnal effects will give way to isolated
to scattered showers mainly across parts of the interior and northwest
sections of pr. Over the u.S. Virgin islands mostly fair weather skies
are forecast for the rest of the day, but one or two brief streamer
like showers will remain possible over or near some for the islands.
No changes made to the inherited forecast package at this time, which
had a good handle on the present and expected weather conditions.
A flash flood watch will continue for the communities downstream
from the guajataca dam, especially the low lying areas along the
river as the potential for dam failure will continue.
Aviation update No chg to previous avn discussion.VFR conds
expected across the local flying area and at all terminals durg
the prd. Few shra en route btw islands... Few cu... Sct cld lyrs nr
fl030... Fl050. No sig operational impacts attm.
Marine update No change to previous marine forecast discussion
at this time. Winds and seas 5-15 kts and 2 to 5 feet respectively
for the rest of today.
Prev discussion issued 457 am ast Tue nov 21 2017
synopsis... Drier air will reduce showers and thunderstorms today,
but moisture will return Thursday and Friday. Another break over
the weekend will occur before moisture returns from the south on
Monday. Cold fronts are still being restrained from reaching the
area by local trade winds during the next 7 to 10 days.
Short term... Today through Thursday...
mostly clear skies prevailed across the forecast area overnight and
early this morning. A few passing showers were observed across the
local waters but none over land areas. Coastal temperatures were in
the mid to upper 70s under east southeast winds at 10 mph or
Although a mid to upper level ridge will continue to build across
the forecast area today and hold through much of the week, easterly
winds will continue to bring patches of low level moisture at
The GFS is showing a drop in precipitable water to as
little as 1.1 inches tonight. Environmental conditions are
rapidly becoming hostile for organized deep convection under the
building ridge, but there will still be enough low level moisture
to assure shower activity, particularly late Wednesday into
Thursday. In fact, based on the latest guidance, today through
Wednesday afternoon is the driest period with precipitable water|
increasing to near two inches Wednesday night into Thursday.
Therefore, expect a fair and generally stable weather pattern
today and Wednesday with morning passing showers across usvi and
east pr followed by some afternoon showers across west puerto
rico. The chance for shower activity will increase Wednesday night
into Thursday as low level moisture increases across the eastern
The flash flood watch in northwest puerto rico is for the
downstream portion of rio guajataca below the lake. Recent rains
have raised the lake levels several feet and local authorities
want to maintain vigilance regarding the unstable condition of
Long term... Friday through Wednesday... High pressure that forms
just north of the mona channel Wednesday night will bring in
moisture on Thursday from the northeast that will linger until
early Saturday morning. This and the easterly wave that will move
through on Friday will continue the good chances for both night
and early morning showers in eastern puerto rico and the u.S.
Virgin islands and showers and isolated thunderstorms in western
puerto rico in the afternoon. A break in the moisture will occur
over the weekend. As a cold front sweeps down through the last of
the bahama islands on Monday a new surge of tropical moisture
invades the area from the caribbean sea to the south. Lower levels
will then see wet and dry periods during the first part of next
week and the front will lift to the north mid week next week before
reaching the area.
The ridge of high pressure at upper levels will continue just
east of the area and keep convection limited. The deep long wave
trough invading the western atlantic on Sunday will weaken in the
process of flattening that ridge in its passage through the area
on Wednesday of next week. Although good moisture will be
available during the week next week it will not be as strong as
has occurred in the last few days.
Aviation... MostlyVFR conds are expected to prevail at all taf
sites throughout the day. Brief MVFR conds will remain possible in
and around jmz jbq due to shra btw 21 16-22z. Ese winds at around 10
knots with some sea breeze variation to continue.
Marine... East northeast winds behind a front dipping toward the
tropical atlantic today will drive swell into the outer atlantic
waters late Wednesday. Seas will approach small craft advisory
conditions then. Small craft advisories are not expected through
the middle of next week after that.
Preliminary point temps pops
Sju 87 77 88 77 20 20 30 30
stt 86 77 85 76 20 30 30 50
Sju watches warnings advisories
Pr... Flash flood watch until 2 pm ast this afternoon for northwest-
Short term... Ram
long term... .Ram
Weather Reporting StationsEDIT (on/off)  Help NOTE: Click on distance to see the station location on a map
|Stations||Dist||Age||Wind||Air Temp||Water Temp||Waves||Pressure||DewPt|
|MISP4 - 9759938 - Mona Island, PR||0 mi||46 min||84°F||84°F||1012.3 hPa|
Wind History for Mayaguez, PR(wind in knots) EDIT (on/off)  Help
Airport ReportsEDIT (on/off)  Help Click EDIT to display multiple airports
Wind History from JMZ (wind in knots)
|1 day ago|
|2 days ago|
EDIT RT Ports Option Weekend mode (on/off) (on/off)  Help One Week of Data
|Mona Island |
Click for Map
Tue -- 01:00 AM AST -0.16 feet Low Tide
Tue -- 06:41 AM AST Sunrise
Tue -- 09:08 AM AST Moonrise
Tue -- 10:30 AM AST 0.87 feet High Tide
Tue -- 01:26 PM AST 0.73 feet Low Tide
Tue -- 03:22 PM AST 0.78 feet High Tide
Tue -- 05:54 PM AST Sunset
Tue -- 08:35 PM AST Moonset
Tide / Current data from XTide NOT FOR NAVIGATION
EDIT (on/off)  Help One Week of Data
|Puerto Real |
Click for Map
Tue -- 03:28 AM AST 0.06 feet Low Tide
Tue -- 06:38 AM AST Sunrise
Tue -- 09:05 AM AST Moonrise
Tue -- 10:38 AM AST 1.25 feet High Tide
Tue -- 05:30 PM AST 0.39 feet Low Tide
Tue -- 05:51 PM AST Sunset
Tue -- 08:32 PM AST Moonset
Tue -- 09:57 PM AST 0.66 feet High Tide
Tide / Current data from XTide NOT FOR NAVIGATION
Weather Map and Satellite Images(on/off)  Help
|Weather Map ||IR Satellite Image from GEOS|
GOES Local Image of Puerto Rico EDIT
Wind Forecast for (14,3,4,5)(on/off)  Help
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The information on this web site has not been checked for accuracy. It is for entertainment purposes only and should be independently verified before using for any other reason. There are five sources. 1) Documents and manuals from a variety of sources. These have not been checked for accuracy and in many cases have not even been read by anyone associated with L-36.com. I have no idea of they are useful or accurate, I leave that to the reader. 2) Articles others have written and submitted. If you have questions on these, please contact the author. 3) Articles that represent my personal opinions. These are intended to promote thought and for entertainment. These are not intended to be fact, they are my opinions. 4) Small programs that generate result presented on a web page. Like any computer program, these may and in some cases do have errors. Almost all of these also make simplifying assumptions so they are not totally accurate even if there are no errors. Please verify all results. 5) Weather information is from numerious of sources and is presented automatically. It is not checked for accuracy either by anyone at L-36.com or by the source which is typically the US Government. See the NOAA web site for their disclaimer. Finally, tide and current data on this site is from 2007 and 2008 data bases, which may contain even older data. Changes in harbors due to building or dredging change tides and currents and for that reason many of the locations presented are no longer supported by newer data bases. For example, there is very little tidal current data in newer data bases so current data is likely wrong to some extent. This data is NOT FOR NAVIGATION. See the XTide disclaimer for details. In addition, tide and current are influenced by storms, river flow, and other factors beyond the ability of any predictive program.