Sunday, August20, 2017

Marine Weather and Tides
Isle of Palms, SC

Version 3.4
What's New / NOTES
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 6:45AMSunset 7:59PM Sunday August 20, 2017 7:47 AM EDT (11:47 UTC) Moonrise 4:19AMMoonset 6:08PM Illumination 3% Phase: Waning Crescent; Moon at 28 days in cycle
NOTE: Some of the data on this page has not been verified and should be used with that in mind. It may and occasionally will, be wrong. The tide reports are by xtide and are NOT FOR NAVIGATION.
Marine Forecasts
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7 Day Forecast for Marine Location Near Isle of Palms, SC
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location: 30.97, -77.7     debug

Area Discussion for - Charleston, SC
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Fxus62 kchs 201121
area forecast discussion
national weather service charleston sc
721 am edt Sun aug 20 2017

A weak stationary front will gradually dissipate across the
region early this week. A stronger cold front is expected to
pass over the region on Thursday. Slightly cooler and drier
conditions are expected through the rest of the week into next

Near term through tonight
The biggest adjustment to the forecast was to include patchy
fog from inland berkeley county to hampton county.

Early this morning: low level convergence, plenty of moisture
and sufficient thermodynamics, plus isentropic ascent will
cause widely scattered or scattered showers and a few t-storms
over some of the barrier islands, mainly from tybee island to
portions of coastal charleston county.

Today: a tutt low will continue to slowly progress w-nw through
the gulf of mexico, allowing for an expansion of strong sub-
tropical ridging to spread across the local area, keeping short
wave energy off to the n. A weak stationary front located not
too far to the n-nw of the cwfa will meander nearby throughout
the day, as atlantic high pressure starts to build in. The
coastal convection will begin to diminish in coverage and
intensity by 12-13z, and with the oceanic high poking westward,
our synoptic flow backs around to the se, causing even higher
pwat to arrive from the atlantic. The sea breeze and the
proximity to the front looks to be the main focus for convection
during the afternoon, with coverage similar to yesterday and
mainly in the 20-30% range. We're not too concerned with any
severe potential due to warm mid levels, but dry air in roughly
the 750-450 mb layer will cause dcape values to peak around
1000-1200 j kg, enough for locally gusty winds. Pwat around
110-120% of normal and weak steering flow will cause a few of
the storms to produce hard downpours with minor flooding

The onshore trajectories and an early start to the sea breeze
will keep our coastal counties no higher than 90-94f, but still
into the middle 90s further inland. Heat indices will peak at
100-105f, maybe briefly a little higher near the us-17 corridor
if dew points can climb above 80f.

Tonight: a short wave located near the northern bahamas from
this morning will lift n-nw with a weakness in the sub-tropical
ridge, bringing with it a further increase in moisture from the
ocean. A deepening SE flow that extends through about 500 mb,
better isentropic ascent and larger scale forcing for ascent
with the short wave will produce an increasing chance of showers
and t-storms arriving overnight, probably after 2 or 3 am. By
daybreak Monday at least widely scattered to scattered activity
will be encompassing the coastal counties. Although the steering
flow is more progressive, given the abundance of moisture there
will be a heavy rain and localized flooding threat. Temps will
remain well above average for this time of year, which has been
the case most nights this month. Not completely convinced of
fog late at night since SREF probabilities are low and we may
not reach our cross-over temps. But MOS guidance is showing fog
along the NW tier of counties after 09z, so will make
adjustments in later forecasts if necessary.

Short term Monday through Wednesday
Monday: short range guidance shows a broad mid level low will track
across the western gulf of mexico as the center of ridge shifts near
the sc coast during the daylight hours Monday. A weak mid level
inverted trough is expected to run between the gulf low NE across fl
off the ga coast. GFS and ECMWF indicate that a band of enhanced
cloud cover will develop within the region of the weak mid level
trough. Simulated IR from the GFS indicates that the cloud cover
associated with the h5 trough will expand between the southeast
coast and bermuda between 15z through 0z today. It will be very
interesting to observe later today if the mid and high cloud cover
develops as guidance suggests. Otherwise, Mon will be a day where pw
values increase to around 2 inches with tall and thin instability.

This environment should support a healthy CU field with some degree
of cirrus level moisture. Overall, cloud cover and deep convection
will be a factor across the forecast area during the solar eclipse.

However, several gaps in the cloud cover should occur, more common
north of the edisto river basin. Scattered thunderstorms are
forecast across SE ga and west of i-95. Elsewhere, isolated
thunderstorms are possible. Guidance supports high temperatures
ranging from the low 90s across the mid savannah river valley to the
upper 80s near the beaches.

Tuesday and Wednesday: mid level ridge is forecast to remain
centered over the forecast area on Tuesday and will gradually weaken
as trough ripples over the mid west on Wednesday. Forecast soundings
show an inversion at h75 Tuesday afternoon, decreasing on Wednesday.

I will indicate low chc pops across the land zones on Tuesday,
increase to solid chc pops on Wednesday. High temperatures are
forecast to peak across the inland savannah river valley weds
afternoon, reaching the mid to upper 90s.

Long term Wednesday night through Saturday
A cold front should push across the forecast area on Thursday,
likely supporting a band of thunderstorms. Pops on Thursday have
been increase into the likely range across most of the forecast
area. High pressure sourced from canada will remain centered
well north of the region through the rest of the week.

Confidence in the day 5 through 7 forecast is low. Medium range
guidance indicates that the sfc high center will shift over new
england, ridging SW across the carolinas and ga. In addition,
both the GFS and ECMWF show a coastal low developing off the
ga sc coast by late this week. Guidance supports prolonged ne
winds, yielding afternoon dewpoints in the upper 60s inland by
the weekend. I will favor the marine and near shore zones for
chc pops through much of the day 5 through 7 period.

Aviation 12z Sunday through Thursday
Vfr to prevail through 12z Monday. Probabilities of direct
impacts at the terminals between about 18 and 22z from isolated
to maybe scattered shra tsra is too low to include mention at
this time.

Extended aviation outlook: thunderstorms may result in short periods
of flight restrictions, greatest potential during the afternoon and
early evening. Patchy fog is possible over wet soil Wednesday

Today: a stationary front will meander inland over the se, as
high pressure becomes more dominate from the e. The result is
for winds backing around from SW to SE through the day at no
higher than 10 or 15 kt. Even with a small 9-10 second swell,
combined seas will be no more than 2 or 3 ft.

Tonight: the stationary front becomes ill-defined as sub-
tropical high pressure continues to expand west, producing se
and S winds around 10 kt. Little change in seas.

Monday through Friday: western atlantic high pressure will yield a
weak pressure gradient over the coastal waters through mid week. A
cold front should sweep across the forecast area on Thursday. Sfc
winds are forecast to remain light from the SE through Tuesday, then
veering from the south-southwest Wednesday and Thursday. Wave
heights are expected to generally range between 2-3 feet Monday
through Thursday. Large high pressure centered over the great lakes
will build over the region on Friday. In addition, a coastal low may
develop off the ga and sc coast late Friday. Winds should shift from
the ne, increasing to around 10 kts by Friday afternoon. Four foot
wave are forecast across portions of amz350 and possibly beyond 20
nm offshore.

Waterspouts... The risk for waterspouts is a little less than
earlier expected given diminishing non-supercell tornado
parameter as per SPC and either too much convection or the lack
of a well defined land breeze boundary. However, since the local
waterspout index is in the moderate range we continue to
maintain a close watch should any form on the sea breeze later
this morning.

Rip currents... We considered a moderate risk of rip currents
today with the onshore flow and astronomical influences, but
since we anticipate swells no more than about 1 to maybe 1.5 ft
by the time they reach the beaches we went with a low risk.

Tides coastal flooding
Astronomical influences will continue to produce elevated tides
early next week. Only small tidal departures are necessary and
we could approach shallow coastal flooding levels with the
evening high tides through Tuesday along parts of the sc coast.

Coastal flood advisories might be necessary.

Record high minimums for august 20...

kchs... 78 set in 2010 and previous.

Kcxm... 80 set in 2009 and previous.

Ksav... 82 set in 1878.

The temperature and dew point sensors at the downtown charleston
observation site (kcxm) could periodically fail. Technicians
plan on fixing the problem.

Chs watches warnings advisories
Ga... None.

Sc... None.

Marine... None.

Near term...

short term...

long term...



tides coastal flooding...



Weather Reporting Stations
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Airport Reports
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AirportDistAgeWind ktVisibilitySky/WeatherTempDewPtHumidityPressure
Charleston Executive Airport, SC171 mi72 minN 010.00 miA Few Clouds81°F78°F94%1016.6 hPa

Wind History from JZI (wind in knots)
Last 24hrSW4W4S4S6S6S9S9S11S9S8
1 day agoSW5W7W7NW745S11S9
2 days agoW34W4W5W6S9W12

Tide / Current Tables for
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Tide / Current Tables for
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Weather Map and Satellite Images
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Weather Map
IR Satellite Image from GEOS

GOES Local Image of Southeast    EDIT

Wind Forecast for Charleston, SC (7,2,3,4)
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Ground Weather Radar Station Wilmington, NC
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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 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 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.