Friday, August18, 2017 L-36.com


Marine Weather and Tides
Nantucket, 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 5:52AMSunset 7:36PM Friday August 18, 2017 5:58 PM EDT (21:58 UTC) Moonrise 2:17AMMoonset 5:15PM Illumination 12% Phase: Waning Crescent; Moon at 26 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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ANZ255 Coastal Waters Extending Out To 25 Nm South Of Marthas Vineyard And Nantucket- 342 Pm Edt Fri Aug 18 2017
.small craft advisory in effect through Saturday evening...
Tonight..S winds 20 to 25 kt with gusts up to 30 kt. Seas 4 to 6 ft. A chance of showers with a slight chance of tstms this evening, then showers with tstms likely after midnight. Patchy fog after midnight. Some tstms may produce heavy rainfall. Vsby 1 nm or less after midnight.
Sat..S winds 15 to 20 kt with gusts up to 25 kt, becoming sw 10 to 15 kt in the afternoon. Seas 4 to 6 ft. Patchy fog. Vsby 1 nm or less.
Sat night..SW winds 10 to 15 kt. Gusts up to 20 kt in the evening. Seas 2 to 4 ft. Patchy fog. Vsby 1 to 3 nm.
Sun..W winds 10 to 15 kt. Seas 2 to 3 ft. Patchy fog. Vsby 1 to 3 nm.
Sun night..W winds 5 to 10 kt. Seas 2 to 3 ft.
Mon..W winds 5 to 10 kt. Seas around 2 ft.
Mon night..SW winds 5 to 10 kt. Seas around 2 ft.
Tue..SW winds 5 to 10 kt. Seas 2 to 3 ft.
Tue night..SW winds 10 to 15 kt with gusts up to 20 kt. Seas 2 to 4 ft.
Wed..SW winds 15 to 20 kt. Seas 4 to 6 ft. A chance of showers.
Wed night..W winds 10 to 15 kt with gusts up to 20 kt. Seas 4 to 6 ft. A chance of showers. Winds and seas higher in and near tstms. 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 342 Pm Edt Fri Aug 18 2017
Synopsis for massachusetts and rhode island coastal waters.. A cold front will approach the waters from the west tonight, prompting showers and scattered Thunderstorms with areas of fog. The front will push thru the waters Saturday, bringing mainly dry conditions for the day. 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 Nantucket, MA
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location: 41.27, -70.06     debug


Area Discussion for - Boston, MA
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Fxus61 kbox 182008
afdbox
area forecast discussion
national weather service taunton ma
408 pm edt Fri aug 18 2017

Synopsis
Widespread rain with embedded heavier showers and thunderstorms
overnight. Main threat of localized flooding. Drying out into
Saturday ahead of a cold front which moves offshore Saturday
night. High pressure returns with fair seasonable weather Sunday
through Tuesday. Another cold front sweeps through new england
Wednesday, followed by more dry weather Thursday into Friday.

Near term until 6 am Saturday morning
* highlights (4p update)...

- severe thunderstorm watch 455 in effect over far W ma and ct.

- flooding concerns across the area, especially with regards to
the present train of rain with embedded heavier showers over
n W ma, and over S E new england as convection out of SE pa,
nj and the DELMARVA region advects N E fueled and maintained
by a convergent low level jet of tropical moisture. Rainfall
rates of around 1-2 inches with storm total rainfall amounts
up to around 3 inches.

- lower risk with respect to strong to severe storms. Greater
focus over S W portions of ma and ct. Potential of gusty
winds. Lower risk of a brief tornado given the environment.

- no headlines will be issued with this update.

* overview (4p update)...

ahead of a deep low center over the N great lakes region, tropical
moisture is surging n, converging and over-running along a warm
frontal boundary presently hung up along the e-waters immediately
offshore of new england as discerned via h925-85 SPC mesoanalysis.

Meanwhile the atmosphere has destabilized ahead of a pre-frontal
trough where partial clearing has occurred in an area of higher
surface dewpoints, deeper tropical moisture, and modest shear. All
of this activity is forecast to converge over S E new england and
adjacent waters this evening and overnight out ahead of a surface
cold front and attendant h5-7 mid-level dry punch. The h925-85 low
level jet intensifying per isallobaric response out ahead of the mid-
upper level ridge over the NW atlantic, maintaining convection and
heavy rain threats N E through Saturday morning prior to cold frontal
passage. Drying out NW to SE as winds turn westerly. Any dense fog
that develops during the overnight period as it is expected with
the very humid, muggy, moist airmass, eroding. Lows around the low
70s.

* discussion (4p update)...

straight-forward, continued forecast of widespread rain with embedded
heavier downpours and thunderstorms. Two things of continued concern:
1.) localized flooding, and 2.) strong to severe storms.

Near-term high-res guidance such as the hrrr is preferred. However,
18.12z NAM and WRF models are only partially considered given poor
initialization.

Localized flooding...

while all of S new england remains under threat, higher confidence
of potential impacts is across S E ma and ct and all of ri. Expect
thunderstorms over SW pa into nj to advect N E with the mean wind,
maintained and fueled by an inflow of low-level h925-85 tropical
moisture. A measure of instability running up against the warm
front still lingering along the immediate E waters as discerned
via h925-85 SPC mesoanalysis, and out ahead of a sweeping cold
front and mid-level dry punch, a convergence of moisture leading
to heavy rain is progged. This along with high freezing level
heights and h85 dewpoints well in excess of +12c (up to +17c),
efficient warm-rain processes signaled .As we have seen already
with prior heavy showers storms, rainfall rates of around 1-2
inches per hours are easily possible. Quick dousing amounts up
to 3 inches within 2 hours is not out of the question. The
propensity of flash flooding is there but thinking isolated,
localized rather than widespread. Will forego any headlines at
this point and focus on short-fused products.

Strong to severe storms...

watching closely as to whether we need to coordinate with SPC on
a severe thunderstorm watch for portions of S new england. Per
spc mesoanalysis, instability has manifested across S W ma and
ct. However marginal, the better environment still resides well
s W where partial clearing has allowed for better low-level lapse
rates and subsequent destabilization which has resulted in present,
ongoing convection. Still convinced that ongoing activity presently
is going to rob the environment to the n. However, not ignoring the
low lcls, high shear, and measure of instability across the region.

While the greater threat is S w, still need to maintain a watch for
portions of our area. Somewhat banking on the convection over se
pa and nj as it advects N E across SE areas of new england to have
some strong, possibly severe elements. Heavy rain and frequent
lightning the main threats, but gusty winds also possible.

Short term 6 am Saturday morning through Saturday night
Not a washout. Widespread rain with embedded heavier showers,
possibly a thunderstorms, lingers over SE ma during the morning
period, eroding with the influx of mid-level h5-7 drier air
despite the cold front lagged. This is easily evident within the
k-indices, contrary to other convective parameters such as cape.

Should see gradual clearing across the region for a brief period
before comma-wrap moisture sweeps through the region behind the
low filling back in the dry punch. Some scattered cumulus through
the day, however the cyclonic flow and some favorable mid level
lapse rates with a weak cold pool aloft, could see some shower
activity over the N W ma and ct overnight by which point the
surface cold front will have pushed offshore, winds becoming w
and turning light as high pressure builds into the region of the
oh river valley behind the low.

Lower surface dewpoints during the day but still out ahead of
the cold front, should turn a bit more comfortable with highs
into the mid to upper 80s. Clouds
lingering overnight with the
comma-low, may hamper what might be a favorable night of
radiational cooling given light winds. Lows back down into the
60s.

Long term Sunday through Friday
Much of this period will feature a mid level ridge across the
southern usa. For our neck of the woods, nearly zonal flow should
prevail through early next week. Expecting a potent mid level trough
to get close to our region towards late next week.

Latest guidance suite is in reasonable agreement with the overall
pattern, with the typical detail differences. Favoring a consensus
blend to smooth over the less predictable details.

Thinking heat and humidity slowly builds from Sunday on, peaking
Wednesday before a cold front moves through our region. Temperatures
during this period should be near to above normal. Once this cold
front passes Wednesday night, expecting near to below normal
temperatures which much more comfortable humidity levels.

Increasing risk for showers and possible thunderstorms Tuesday night
into Wednesday, otherwise mainly dry much of next week.

Aviation 19z Friday through Wednesday
Forecaster confidence levels...

low - less than 30 percent.

Moderate - 30 to 60 percent.

High - greater than 60 percent.

Short term through Saturday night ...

through tonight... Moderate confidence.

Conditions lowering ifr-lifr over much of the region as the
threat of ra +ra with embedded tsra becomes more widespread.

Tempo vsby impacts with ra +ra and expected dense fog, more
likely over S E coastal terminals. Clearing out towards morning.

Blustery S SW winds with gusts up to 30 kts, strongest over the
s SE coastal terminals. Despite, llws impacts possible especially
over far SE ma with 40 kts SW at 2 kft agl. Gradual improvement
nw to SE across the interior towards Saturday morning.

Saturday into Saturday night... Moderate confidence.

Gradual improvement for S E terminals, lowest ifr-lifr conditions
with -ra ra lingering for SE coastal terminals. SW winds prevailing
turning W towards evening. Sct 4-5 kft low-endVFR CIGS during
the day, becoming bkn-ovc N W overnight with the low risk of -ra.

Kbos terminal... Moderate confidence.

MVFR-ifr mix through morning. Feel there is a threat of ra +ra
this evening around 0-6z. Tempo ifr vsby impacts possible. Low
risk of tsra, feel that may stay S of the terminal, so will
continue vcts mention.

Kbdl terminal... Moderate confidence.

MVFR-ifr through the overnight period with the threat of ra +ra
along with tsra roughly 21-03z. Should see improvement after
midnight into the Saturday morning hours with CIGS lifting.

Outlook Sunday through Wednesday ...

Sunday through Tuesday... High confidence.

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

Tuesday night and Wednesday... Moderate confidence.

MainlyVFR. Scattered MVFR is shra tsra, especially Wednesday.

Marine
Forecaster confidence levels...

low - less than 30 percent.

Moderate - 30 to 60 percent.

High - greater than 60 percent.

Short term through Saturday night ... Moderate confidence.

S winds will be on the increase, gusting up to 25 kts across
the S SE waters. Small craft advisory remain as winds will
result in heightened seas up around 5 feet.

Heavy rain with embedded thunderstorms sweeping SW to NE across
the waters today and tonight. Will likely be some visibility
restrictions.

Conditions improving Saturday into Saturday night as a cold
front sweeps the waters late in the period with winds turning w.

Outlook Sunday through Wednesday ...

Sunday through Tuesday... High confidence.

High pressure builds over the waters. Winds remain 20 knots or less,
and seas 4 feet or less.

Tuesday night and Wednesday... Moderate confidence. Increasing
southwest winds ahead of a cold front should lead to rough seas
across the outer coastal waters, especially on the southern coastal
waters. There may be a few gusts to 25 kt on Wednesday, too.

Box watches warnings advisories
Ct... None.

Ma... None.

Ri... None.

Marine... Small craft advisory until 9 am edt Saturday for anz231>234.

Small craft advisory until 2 am edt Saturday for anz236.

Small craft advisory until 11 am edt Saturday for anz235-237.

Small craft advisory from 8 pm this evening to 5 pm edt
Saturday for anz250-254.

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

Synopsis... Belk sipprell
near term... Sipprell
short term... Sipprell
long term... Belk
aviation... Belk sipprell
marine... Belk sipprell


Weather Reporting Stations
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Stations Dist Age Wind Air TempWater Temp WavesPressureDewPt
NTKM3 - 8449130 - Nantucket Island, MA 2 mi40 min S 7 G 15 1012.6 hPa
44020 - NANTUCKET SOUND 13 mi68 min S 16 G 18 72°F 71°F2 ft1011.7 hPa (-1.6)71°F
WAXM3 - Waquoit Bay Reserve, MA 33 mi133 min 2.9 73°F 1013 hPa72°F
BZBM3 - 8447930 - Woods Hole, MA 37 mi40 min 73°F 71°F1011.3 hPa
44090 42 mi24 min 69°F2 ft

Wind History for Nantucket Island, MA
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Airport Reports
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AirportDistAgeWind ktVisibilitySky/WeatherTempDewPtHumidityPressure
Nantucket, Nantucket Memorial Airport, MA1 mi65 minS 116.00 miFog/Mist72°F70°F94%1012.3 hPa

Wind History from ACK (wind in knots)
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Last 24hrS6SW5S5S6S6S6SW6S4S5S6S6S6S8S7SE8S10SE10SE13SE11S11S11S12S12S11
1 day agoNE7SW5SW7SW6SW5CalmSE3CalmN3N3N7N7N9N5NE6NE6NE6CalmSE9S7SE8S7S7S7
2 days agoS6CalmSE4S3CalmCalmSW3W4W3SW4W4W4W6W5NW4NW6N10N11N14N16N13NE13N10--

Tide / Current Tables for Nantucket, Nantucket Island, Nantucket Island, Massachusetts
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Nantucket
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Fri -- 02:18 AM EDT     Moonrise
Fri -- 03:12 AM EDT     -0.07 feet Low Tide
Fri -- 05:52 AM EDT     Sunrise
Fri -- 09:44 AM EDT     3.04 feet High Tide
Fri -- 03:15 PM EDT     0.18 feet Low Tide
Fri -- 05:15 PM EDT     Moonset
Fri -- 07:34 PM EDT     Sunset
Fri -- 10:00 PM EDT     4.10 feet High Tide
Tide / Current data from XTide NOT FOR NAVIGATION
Sorry tide depth graphs only, please select another station.
12am1am2am3am4am5am6am7am8am9am10am11am12pm1pm2pm3pm4pm5pm6pm7pm8pm9pm10pm11pm
2.31.20.4-0.10.10.61.21.92.52.932.72.11.40.60.20.311.82.63.33.94.13.9

Tide / Current Tables for Nantucket Harbor Entrance Channel, Massachusetts Current
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Nantucket Harbor Entrance Channel
Click for Map
Fri -- 01:17 AM EDT     -1.35 knots Max Ebb
Fri -- 02:18 AM EDT     Moonrise
Fri -- 03:26 AM EDT     0.00 knots Slack
Fri -- 05:21 AM EDT     1.19 knots Max Flood
Fri -- 05:52 AM EDT     Sunrise
Fri -- 08:45 AM EDT     -0.00 knots Slack
Fri -- 01:50 PM EDT     -1.37 knots Max Ebb
Fri -- 04:00 PM EDT     0.00 knots Slack
Fri -- 05:15 PM EDT     Moonset
Fri -- 05:47 PM EDT     1.03 knots Max Flood
Fri -- 07:34 PM EDT     Sunset
Fri -- 08:34 PM EDT     -0.00 knots Slack
Tide / Current data from XTide NOT FOR NAVIGATION
Sorry tide depth graphs only, please select another station.
12am1am2am3am4am5am6am7am8am9am10am11am12pm1pm2pm3pm4pm5pm6pm7pm8pm9pm10pm11pm
-1-1.3-1.2-0.40.51.11.10.60.2-0-0.1-0.3-0.7-1.2-1.4-0.900.810.70.2-0.1-0.2-0.3

Weather Map and Satellite Images
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Weather Map
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IR Satellite Image from GEOS
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GOES Local Image of Northeast    EDIT
Geos

Wind Forecast for Boston, MA (17,4,5,8)
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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.