Saturday, August19, 2017 L-36.com


Marine Weather and Tides
West Chatham, MA

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 5:53AMSunset 7:35PM Saturday August 19, 2017 2:28 PM EDT (18:28 UTC) Moonrise 3:19AMMoonset 6:09PM Illumination 7% Phase: Waning Crescent; Moon at 27 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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ANZ254 Coastal Waters From Provincetown Ma To Chatham Ma To Nantucket Ma Out 20 Nm- 116 Pm Edt Sat Aug 19 2017
.small craft advisory in effect until 5 pm edt this afternoon...
This afternoon..SW winds 5 to 10 kt. Seas 2 to 4 ft. Patchy fog. Vsby 1 to 3 nm.
Tonight..SW winds 10 to 15 kt, becoming W 5 to 10 kt with gusts up to 20 kt after midnight. Seas 2 to 4 ft. Patchy fog. Vsby 1 nm or less.
Sun..W winds 5 to 10 kt. Seas 2 to 4 ft.
Sun night..W winds 5 to 10 kt. Seas 2 to 3 ft.
Mon..W winds around 5 kt, becoming sw in the afternoon. Seas around 2 ft. Patchy fog. Vsby 1 to 3 nm.
Mon night..SW winds 5 to 10 kt. Seas 2 to 3 ft.
Tue..SW winds 10 to 15 kt. Seas 2 to 4 ft.
Tue night..SW winds 15 to 20 kt. Seas 3 to 5 ft.
Wed..SW winds 15 to 20 kt with gusts up to 25 kt. Seas 3 to 5 ft. A chance of showers.
Wed night..W winds 10 to 15 kt. Seas 2 to 4 ft. A chance of showers. Seas are reported as significant wave height, which is the average of the highest third of the waves. Individual wave heights may be more than twice the significant wave height.
ANZ200 116 Pm Edt Sat Aug 19 2017
Synopsis for massachusetts and rhode island coastal waters.. A cold front will push thru the waters late today and this evening bringing mainly dry conditions after the current round of showers and Thunderstorms move east this morning. High pressure will return with dry weather during Saturday night through Tuesday. A cold front will then approach the waters midweek. For information on possible hazardous weather beyond the 24-36 hour forecast period, please visit www.weather.gov/boston and follow the current hazards link above the map on the left.

7 Day Forecast for Marine Location Near West Chatham, MA
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location: 41.73, -69.97     debug


Area Discussion for - Boston, MA
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Fxus61 kbox 191403
afdbox
area forecast discussion
national weather service taunton ma
1003 am edt Sat aug 19 2017

Synopsis
A cold front will slowly cross the region today, shifting
offshore by evening. High pressure brings fair seasonable
weather Monday and Tuesday. Another cold front sweeps through
new england Wednesday, followed by more dry weather Thursday and
Friday.

Near term until 6 pm this evening
10 am update...

not much change from previous forecast. Post frontal airmass
continues to slowly overspread the region with nnw winds across
ct-ri and western-central ma. SPC mesoanalysis shows winds at
925 mb westerly all the way to the coastline. So as solar
heating increases westerly winds just above the surface will
help mix down drier air aloft to the surface.

However the process will be slower across eastern ma as very
moist low level airmass with dew pts into the lower 70s across
southeast ma will remain trapped given drier air aloft. Although
eventually westerly winds and drier air aloft will win out with
low clouds eroding late morning into early afternoon with at
least partial sunshine developing across all of eastern ma. Cape
cod and islands will likely be the slowest regarding this trend.

Given southwest flow aloft cold front either gets hung up or
washes out across eastern ma this afternoon. This will result in
an area of surface convergence enhanced by afternoon seabreeze
along the eastern ma coastline. Thus low risk for a few low top
(given dry air aloft) showers later this afternoon across
eastern ma. All hi res guid including the ncar ensembles, arw,
nmm and hrrr in agreement on this.

Otherwise a warm summer afternoon with highs well into the 80s.

Less humid across western ma ct but remaining somewhat humid
across eastern ma with seabreeze precluding drier less humid air
from advecting seaward.

Previous discussion...

otherwise, cold front still very slowly moving into S new
england just within the last hour or so, and has likely only
just recently reached the box CWA per latest msas obs. Wv
imagery suggests a slight shift to the mid-upper flow such that
its likely now more parallel to this steering flow. Therefore
expect a very slow passage of the sfc front through the day
today, and it may wash out in-situ, as drier air is already
filtering in aloft per goes-16 low-upper lvl WV products. This
is supported by laps rap data as well, with k-indices already in
the 20s across w-ma and ct. While the dry air aloft continues
to build, it will trap the lower lvl moisture, maintaining the
high dwpts through the day today. While this will maintain the
humid conditions across S new england, the capping implied by
the dry air should limit further redevelopment of convection
today in spite of CAPE holding thanks to rising mid lvl lapse
rates under cyclonic curvature. There is one short window this
afternoon, when the remnants of the front reach E ma ri where
modest moisture pooling could allow for a few shra to develop,
hinted at in latest mesoscale guidance. Given the dry air
however, capped pops at slight chance.

Warm and humid today, even with early cloud debris, gradual
clearing and afternoon mixing should still allow temps to reach
well into the 80s, with dwpts even at peak mixing remaining in
the mid-upper 60s.

Short term 6 pm this evening through 6 am Sunday
Cold front continues to move offshore and wash out, but drier
air at the sfc will still lag well behind due to the inability
to mix it out during the daylight hours. Meanwhile, low pres
continues to wrap up in quebec as fairly robust upper lvl
shortwave rotates toward new england during the late evening
hours, shifting E of the area by early am sun. This is
accompanied by a secondary spike in k-indicies and pwats through
the column as it shunts the initial dry slot to the e, similar
to comma-head style wrap-around. While forcing attendant to the
wave is relatively strong, the remnant dry air should mitigate
shower development, but the risk is non-zero. Some QPF on recent
model runs, but given the initial drying, and the moisture spike
mentioned above is quite modest, will maintain a generally dry
forecast with this update and only suggest slightly more clouds
than previous forecast. Day crew can reassess if pops might be
needed.

With little change in low-lvl moisture, maintaining dwpts in the
60s, and increased cloud cover expected, overnight mins should
once again only fall into the mid 60s at the coolest spots.

Long term Sunday through Friday
Big picture...

subtropical high maintains sultry summer weather over the
southern usa. Zonal flow over the northern usa and canada early
week amplifies during the mid and late week. Contour heights
are normal to a little above normal early week, but fall below
normal by late week. This supports warm summery weather early
week, followed by cooler, drier air moving into new england late
week.

Model upper contour fields are similar through much of next
week. Thermal fields and surface pressure fields show a similar
distribution. This maintains confidence in the forecast data
for our area.

Details...

Sunday through Tuesday...

high pressure builds over the region during this period. Upper
trough is directly overhead Sunday morning with lingering
moisture below 800 mb but dry air above. Mid level air is at
-10c or warmer, while the destabilizing part of the cold pool is
near the canadian border. Expect dry weather Sunday with some
diurnal clouds but otherwise a fine day. Temps aloft at 13-14c
should support MAX sfc temps in the low to mid 80s.

Expect dry weather Sunday night to Tuesday, although increasing
mid and high clouds during Tuesday. Light wind flow will allow
sea breezes on Monday afternoon, but gradient on Tuesday
suggests a general southwest flow.

Mixing should reach between 800 mb and 850 mb each day. Temps
of 14-16c Monday and 16-18c on Tuesday suggest MAX sfc temps in
the 80s Monday and 85-90 Tuesday... Cooler along the coast. Slow
increase in humidity with dew points in the 60s. Winds in the
mixed layer Tuesday suggest southwest gusts 15-20 knots.

Tuesday night-Wednesday...

closed low digs over quebec and the northeast usa with
shortwave driving a cold front into through new england. Expect
showers scattered tstms with the front Tuesday night Wednesday.

Cold FROPA Wednesday brings an end to the showers, but
sufficient mixing to bring northwest gusts to 20 knots behind
the cold front.

Thursday-Friday...

surface high pressure builds over the region while upper trough
moves overhead. Cold pool in the upper trough moves in with
500-mb temps forecast to reach -16c to -18c by Friday. Temps at
850 mb will be 8-10c. Moisture profiles show lots of dry air
during that time but with a moist layer at 850 mb. Expect dry
weather with potential for some diurnal clouds. Expect MAX temps
in the 70s, possibly near 80 in spots.

Aviation 14z Saturday through Wednesday
Forecaster confidence levels...

low - less than 30 percent.

Moderate - 30 to 60 percent.

High - greater than 60 percent.

Short term through tonight ...

10 am 14z update...

only change to the forecast is for a slightly slower erosion to
the low clouds across eastern ma. Earlier discussion below.

====================================================================
through 15z... Moderate confidence.

Mix of ifr MVFR with the continuation of low CIGS and areas of
fog. After sunrise, conditions will gradually improve especially
across W ma ct, but this may take until mid morning to fully
break out to more widespreadVFR. Shra tsra mainly CAPE islands
continue through 10z this morning, then shift offshore. Ifr
remains through that area through 15z. Winds gradually shift to
w-sw and recede.

After 15z through tonight... Moderate confidence.

Gradual improvement toVFR all terminals winds mainly w-sw,
with sea breezes possible E coast.

Kbos terminal... Moderate confidence.

Mix of ifr this morning will gradually give way to improvement
toVFR. Sea breeze possible but with a late start.

Kbdl terminal... High confidence in taf.

Outlook Sunday through Wednesday ...

Sunday through Tuesday... High confidence.

Vfr. Areas of ifr in early morning fog low clouds, then improving
toVFR by each mid morning and continuing the remainder of each day.

Tuesday night-Wednesday... Moderate confidence.

Vfr with areas of MVFR CIGS vsbys in showers and scattered
thunderstorms. Ifr CIGS possible in early morning fog low clouds
especially in areas that have had some rain.

Marine
Forecaster confidence levels...

low - less than 30 percent.

Moderate - 30 to 60 percent.

High - greater than 60 percent.

Short term through tonight ... Moderate confidence.

Winds and seas will diminish this morning. Timing of current
small craft advisories seems reasonable, although conditions may
drop off more quickly than current advisories suggest. After
advisories are dropped boating conditions should remain
relatively quiet into the overnight hours, with the only issue
being some localized marine fog which may restrict visibilities,
especially on the S waters.

Outlook Sunday through Wednesday ...

Sunday through Tuesday... High confidence.

High pressure builds over the waters. Winds remain 15 knots or
less, and seas 3 feet or less. Winds pick up a little on
Tuesday, but remain 20 knots or less with seas 4 feet or less.

Tuesday night-Wednesday... Moderate confidence.

A cold front approaches from the great lakes, crossing the
waters late Wednesday or Wednesday night. Southwest winds
increase with gusts 20 to 25 knots during Wednesday. Winds shift
from the northwest Wednesday night. Seas build Tuesday night
and Wednesday reaching 5 to 6 foot heights on the outer waters.

The southwest flow may also nudge those higher seas into ri
sound as well. A small craft advisory may be needed on some of
the waters during this time.

Climate
Highest recorded dew points on august 18 in any year
pvd 76 in 2002
bdl 82 in 2002
bos 77 in 1994
orh 75 in 1987
highest dew points yesterday
pvd 76 from about 1130 to midnight edt
bdl 76 from about 630 pm to midnight edt
bos 74 from about 11 pm to 1 am edt
orh 72 from about 740 pm to 1220 am edt
so the pvd value ties highest for august 18.

Highest value at pvd for august is 80.

Highest value at pvd for anytime is 81.

Box watches warnings advisories
Ct... None.

Ma... None.

Ri... None.

Marine... Small craft advisory until 11 am edt this morning for anz235-
237.

Small craft advisory until 5 pm edt this afternoon for anz250-
254.

Small craft advisory until 8 pm edt this evening for anz255-
256.

Synopsis... Wtb doody
near term... Wtb nocera doody
short term... Doody
long term... Wtb
aviation... Wtb nocera doody
marine... Wtb doody
climate...



Weather Reporting Stations
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Stations Dist Age Wind Air TempWater Temp WavesPressureDewPt
44090 20 mi54 min 69°F1 ft
44020 - NANTUCKET SOUND 23 mi38 min SW 9.7 G 9.7 70°F 71°F1 ft1009.5 hPa (-0.4)70°F
NTKM3 - 8449130 - Nantucket Island, MA 31 mi40 min WSW 11 1010 hPa
WAXM3 - Waquoit Bay Reserve, MA 31 mi103 min 2.9 78°F 1010 hPa74°F
BZBM3 - 8447930 - Woods Hole, MA 40 mi40 min 75°F 72°F1009.5 hPa

Wind History for Nantucket Island, MA
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Airport Reports
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AirportDistAgeWind ktVisibilitySky/WeatherTempDewPtHumidityPressure
Chatham, Chatham Municipal Airport, MA2 mi36 minSSW 510.00 miOvercast79°F75°F88%1009.8 hPa
Hyannis, Barnstable Municipal-Boardman Airport, MA17 mi32 minS 710.00 miFair79°F73°F85%1009 hPa
Provincetown Municipal Airport, MA23 mi32 minN 510.00 miOvercast70°F66°F87%1009.6 hPa

Wind History from CQX (wind in knots)
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SW6SW7SW4SW4SW5SW6SW4S64NW34SW5
1 day agoSW5SW6S7SW84SW6SW7SW4S4SW5SW6SW4SW3S4S4S34355S8S9
G17
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2 days ago64NE7NE4E3SW4CalmCalmCalmCalmCalmNW3N4N4CalmCalmCalmCalmE3SE3SW54S4SW6

Tide / Current Tables for Pleasant Bay, Quonset Pont, Massachusetts
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Pleasant Bay
Click for Map
Sat -- 03:19 AM EDT     Moonrise
Sat -- 05:52 AM EDT     Sunrise
Sat -- 06:45 AM EDT     -0.27 feet Low Tide
Sat -- 12:08 PM EDT     3.23 feet High Tide
Sat -- 06:08 PM EDT     Moonset
Sat -- 07:00 PM EDT     -0.02 feet Low Tide
Sat -- 07:33 PM EDT     Sunset
Tide / Current data from XTide NOT FOR NAVIGATION
Sorry tide depth graphs only, please select another station.
12am1am2am3am4am5am6am7am8am9am10am11am12pm1pm2pm3pm4pm5pm6pm7pm8pm9pm10pm11pm
3.63.22.621.30.5-0.1-0.30.1122.93.23.12.62.11.60.90.3-00.312.13.1

Tide / Current Tables for Pollock Rip Channel, Massachusetts Current
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Pollock Rip Channel
Click for Map
Sat -- 01:11 AM EDT     0.00 knots Slack
Sat -- 03:19 AM EDT     Moonrise
Sat -- 04:49 AM EDT     2.08 knots Max Flood
Sat -- 05:53 AM EDT     Sunrise
Sat -- 07:57 AM EDT     -0.00 knots Slack
Sat -- 10:41 AM EDT     -1.63 knots Max Ebb
Sat -- 01:48 PM EDT     0.00 knots Slack
Sat -- 05:16 PM EDT     1.85 knots Max Flood
Sat -- 06:08 PM EDT     Moonset
Sat -- 07:33 PM EDT     Sunset
Sat -- 08:11 PM EDT     -0.00 knots Slack
Sat -- 11:01 PM EDT     -1.81 knots Max Ebb
Tide / Current data from XTide NOT FOR NAVIGATION
Sorry tide depth graphs only, please select another station.
12am1am2am3am4am5am6am7am8am9am10am11am12pm1pm2pm3pm4pm5pm6pm7pm8pm9pm10pm11pm
-1-0.20.81.522.11.81-0.1-1-1.5-1.6-1.3-0.70.211.61.81.71.20.2-0.9-1.6-1.8

Weather Map and Satellite Images
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Weather Map
wmap_A
IR Satellite Image from GEOS
east_satellite

GOES Local Image of Northeast    EDIT
Geos

Wind Forecast for Boston, MA (14,3,4,5)
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Ground Weather Radar Station Boston, MA
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Disclaimer:
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.