Wednesday, August21, 2019 L-36.com


Marine Weather and Tides
Nantucket, MA

Version 3.4
NOTICE
7/25/2019 New feature in the Airports section gives a link to 5 minute updates for data reports.
6/2/2019. Many thanks to a user for reporting an error on one of the Edit pages. The switch to PHP 7.2 caused many pages that previously worked to quit working. I fixed many but I still depend on users to report ones I missed. Please report errors HERE or send an email to me at L-36.com. Allen

Sunrise 5:54AMSunset 7:34PM Wednesday August 21, 2019 3:30 AM EDT (07:30 UTC) Moonrise 10:43PMMoonset 11:32AM Illumination 69% Phase: Waning Gibbous; Moon at 20 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- 116 Am Edt Wed Aug 21 2019
Rest of tonight..S winds around 5 kt. Seas around 2 ft.
Wed..S winds 5 to 10 kt, increasing to 10 to 15 kt with gusts up to 20 kt in the afternoon. Seas 2 to 4 ft. A chance of showers.
Wed night..SW winds 10 to 15 kt with gusts up to 20 kt. Seas 4 to 6 ft. Patchy fog. A chance of showers. Vsby 1 nm or less.
Thu..SW winds 10 to 15 kt with gusts up to 20 kt. Seas 4 to 6 ft. A chance of showers. Vsby 1 to 3 nm.
Thu night..SW winds 10 to 15 kt with gusts up to 20 kt, becoming nw 5 to 10 kt after midnight. Seas 2 to 4 ft. A chance of showers and tstms.
Fri and Fri night..N winds 5 to 10 kt. Seas 3 to 5 ft.
Sat..NE winds 5 to 10 kt. Seas 2 to 4 ft.
Sun..NE winds 10 to 15 kt with gusts up to 20 kt. Seas 3 to 5 ft. 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 116 Am Edt Wed Aug 21 2019
Synopsis for massachusetts and rhode island coastal waters.. A warm front will move north Wednesday morning and draw warm and very humid air over the waters. This will bring patchy fog as well as showers and scattered Thunderstorms Wednesday through Thursday. A cold front then sweeps across the waters sometime Thursday night into early Friday morning afterwhich dry weather and good vsby follows for Friday into the weekend. 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 210541
afdbox
area forecast discussion
national weather service boston norton ma
141 am edt Wed aug 21 2019

Synopsis
High pressure over southern new england moves offshore tonight
providing seasonable dry weather. A warm front moves across the
region Wednesday providing scattered showers and thunderstorms along
with increasing heat and humidity. A cold front Thursday will bring
another round of scattered showers and thunderstorms. The front
moves offshore Friday with dry weather to follow into the weekend
with mild days and cool nights along with comfortable humidity.

Near term until 6 am this morning
Satellite imagery shows clouds in western ny and pa. Northeast
radar mosaic shows showers thunder moving into western pa and
approaching the i-79 corridor. Movement of the clouds and
showers would bring them into the ct valley at about 10-12z 6-8
am, assuming that they hold together through that time. There
are also a couple of isolated showers farther east in pa, but
they are moving in to more stable air and should diminish.

9 pm observations show dew points in the low to mid 60s. No
expectation that they will get any lower than that overnight.

Hourly observed temperatures were 3-4f lower than forecast, but
dew points suggest the min temperature forecast remains
reasonable and so no changes planned. Extrapolation of observed
showers is a couple of hours slower than the forecast, but
within the margin of uncertainty. Low risk for some elevated
convection toward sunrise along the south coast of ma ri and
over western ma ct as warm front aloft surges northeastward.

So no changes in timing for this update, but the potential for
a slower onset is noted.

Short term 6 am this morning through 6 pm Thursday
Wednesday ...

very complex forecast especially afternoon convection and severity.

Warm front lifts northward into the region Wed morning. Some of the
guidance suggest an active warm front with lots of showers t-storms.

If this verifies lots of cloud debris would linger into the
afternoon and could suppress afternoon convection. In addition lots
of morning convection could delay warm frontal passage and thus
diminish risk of strong afternoon storms.

Conversely some of the guidance does not have much if any warm
frontal precip during the morning followed by warm sector
overspreading southern new england with 12z href and ec offering up
to 2500 j kg of sb cape. Thus robust warm sector combined with up to
30 kt of deep layer shear. These high CAPE and modest shear profiles
combined with forcing for ascent from short wave trough moving from
ny to vt nh would support a low to moderate risk of strong to severe
storms. However this convective forecast will hinge on warm frontal
morning convection and how quickly warm sector can overspread
ma ri ct. Some morning warm frontal convection could enhance diurnal
storms with leftover boundaries along with differential heating from
leftover cloud debris. So overall lots of uncertainty regarding
severe potential tomorrow. Hopefully 00z runs show a trend.

Otherwise gradually becoming more humid tomorrow especially if warm
front lifts north of the area.

Long term Thursday night through Tuesday
Highlights...

* hot and humid Thu with a risk for a few showers t-storms near and
south of the pike, shifting to the south coast Thu night
* cooler and less humid fri
* pleasantly warm days and cool nights this weekend into early next
week
details...

Thursday into Thursday night...

another robust mid level shortwave will be rotating across the great
lakes with downstream SW flow aloft across new eng. Cold front moves
into the interior Thu but slows and eventually gets hung up near the
south coast Thu evening. Models show some drier air aloft moving
into sne Thu morning before moisture gradually deepens later Thu thu
evening, especially south of the pike. It will be a hot and humid
day with partly to mostly sunny skies. 925 mb temps 22-24c support
highs around 90, except cooler near the south coast and higher
terrain in ma. Dewpoints lower 70s in the coastal plain but falling
through the 60s interior behind the front.

Marginal instability develops Thu with forecast capes around 1000
j kg, focused south of the pike. Models are not very bullish on
convective precip, likely due to presence of mid level dry air which
may limit convective activity during the day. Best chance for a few
afternoon t-storms will likely be near and south of the pike ahead
of the front, and there is enough deep layer shear for an isolated
strong to severe storm. While instability diminishes after dark,
better chance for showers and a few t-storms may be Thu night along
the south coast as deeper moisture with pwat plume nearing 2 inches
moves up along the south coast ahead of a shortwave and along the
stalled frontal boundary which eventually pushes south and offshore
by late Thu night.

Friday...

there is some uncertainty regarding how quickly clearing occurs near
the south coast. It is possible clouds may linger into Fri near the
south coast with a risk of a few showers. Otherwise, more sunshine
likely north of the pike. Cooler post frontal airmass will yield
highs mainly mid 70s to around 80 with low humidity.

Saturday through Tuesday...

ecmwf appears to be an outlier with development of closed low over
new eng this weekend into early next week and not really supported
by majority of its ensemble members. Trend is for mid level ridging
to develop across the NE late in the weekend into early next week,
with shower threat possibly increasing by Tue depending on timing of
next shortwave. Coolest days likely Sun Mon with high pres in the
maritimes with NE flow and will have to watch for some lower clouds
during this time period. Overall, looking at highs mostly in the 70s
and lows in the 50s this weekend into early next week, with highs in
the 60s possible along the east coast Sun mon.

Aviation 06z Wednesday through Sunday
Forecaster confidence levels...

low - less than 30 percent.

Moderate - 30 to 60 percent.

High - greater than 60 percent.

Short term through Thursday ... Moderate confidence.

Rest of tonight ... VFR.

Today...

vfr, with MVFR CIGS vsbys in showers and scattered
thunderstorms. A few showers are possible this morning in ct
and western ma, and are possible in all areas this afternoon and
evening. The best chance for showers tstms will be in northern
ct and western central ma in the afternoon and evening. A few
strong storms are possible with gusty winds, frequent lightning,
and heavy downpours.

Tonight...

MVFRVFR with scattered showers tstms especially in the evening.

Southwest winds gusting to 20 kt, especially over CAPE cod and
islands.

Thursday...

vfr MVFR in the morning...VFR in the afternoon with brief MVFR
in showers tstms possible.

Kbos terminal...

moderate to high uncertainty in timing and coverage of
showers tstms. A few showers storms possible mid to late
morning, but best chance will be mid to late afternoon.

Kbdl terminal... Moderate to high uncertainty in timing and
coverage of showers tstms. A few showers storms possible after 7
am, but best chance will be mid to late afternoon.

Outlook Thursday night through Sunday ... Moderate confidence
Thursday night: mainlyVFR, with local MVFR possible. Slight
chance shra.

Friday through Sunday:VFR.

Marine
Forecaster confidence levels...

low - less than 30 percent.

Moderate - 30 to 60 percent.

High - greater than 60 percent.

Short term through Thursday ... High confidence.

Tonight ... Tranquil weather with 1020 mb high over pa drifting
eastward. Dry weather and good vsby expected along with
tranquil seas.

Wednesday ... Warm front lifts into the waters with scattered showers
and t-storms. Low prob for a few strong storms.

Wednesday night ... Warm front lifts north into nh me waters with
evening scattered showers t-storms possible. Patchy fog
possible.

Outlook Thursday night through Sunday ... Moderate confidence.

Thursday: winds less than 25 kt. Seas locally approaching 5 ft.

Slight chance of rain showers, slight chance of thunderstorms.

Thursday night: winds less than 25 kt. Seas locally approaching
5 ft. Chance of rain showers, chance of thunderstorms.

Friday through Friday night: winds less than 25 kt. Areas of
seas approaching 5 ft.

Saturday: winds less than 25 kt. Seas locally approaching 5 ft.

Saturday night: winds less than 25 kt.

Sunday: winds less than 25 kt. Areas of seas approaching 5 ft.

Box watches warnings advisories
Ct... None.

Ma... None.

Ri... None.

Marine... None.

Synopsis... Kjc nocera
near term... Wtb kjc nocera
short term... Nocera
long term... Kjc
aviation... Wtb kjc nocera
marine... Wtb kjc nocera


Weather Reporting Stations
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Stations Dist Age Wind Air TempWater Temp WavesPressureDewPt
NTKM3 - 8449130 - Nantucket Island, MA 2 mi42 min SSW 4.1 G 5.1 77°F1018 hPa
44020 - NANTUCKET SOUND 19 mi20 min SSW 9.7 G 9.7 73°F 76°F71°F
WAXM3 - Waquoit Bay Reserve, MA 33 mi105 min S 1 73°F 1018 hPa71°F
BZBM3 - 8447930 - Woods Hole, MA 37 mi42 min 74°F1017.7 hPa
44090 42 mi30 min 71°F

Wind History for Nantucket Island, MA
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Airport Reports
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AirportDistAgeWind ktVisibilitySky/WeatherTempDewPtHumidityPressure
Nantucket, Nantucket Memorial Airport, MA1 mi37 minSSW 65.00 miFog/Mist68°F66°F96%1018 hPa

Link to 5 minute data for KACK

Wind History from ACK (wind in knots)
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Last 24hr------W8NW6NW6NW7NW7NW8NW9NW6N9NW5CalmS5S6----SE3SE5SE3SE4--S4
1 day agoS8--S6----SW4SW5SW5SW6S5--S8SW8S9S9--S10S6SW7W10SW9W9----
2 days agoSE5CalmCalm--CalmW3SW3W3----3SW8SW5SW10SW6SW6S6SE7S4S4S7S5S4S6

Tide / Current Tables for Nantucket, Nantucket Island, Nantucket Island, Massachusetts
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Tide / Current data from XTide NOT FOR NAVIGATION
Sorry tide depth graphs only, please select another station.


Tide / Current Tables for Nantucket Harbor Entrance Channel, Massachusetts Current
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Nantucket Harbor Entrance Channel
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Wed -- 12:48 AM EDT     1.25 knots Max Flood
Wed -- 03:18 AM EDT     -0.00 knots Slack
Wed -- 05:55 AM EDT     Sunrise
Wed -- 09:02 AM EDT     -1.19 knots Max Ebb
Wed -- 11:09 AM EDT     0.00 knots Slack
Wed -- 11:32 AM EDT     Moonset
Wed -- 01:11 PM EDT     1.32 knots Max Flood
Wed -- 03:44 PM EDT     -0.00 knots Slack
Wed -- 07:31 PM EDT     Sunset
Wed -- 09:29 PM EDT     -1.18 knots Max Ebb
Wed -- 10:43 PM EDT     Moonrise
Wed -- 11:36 PM EDT     0.00 knots Slack
Tide / Current data from XTide NOT FOR NAVIGATION
Sorry tide depth graphs only, please select another station.

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11.20.80.2-0.3-0.5-0.6-0.7-1-1.2-0.9-0.20.81.31.10.5-0.1-0.4-0.5-0.6-0.9-1.1-1.1-0.6

Weather Map and Satellite Images
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GOES Local Image of Northeast    EDIT
NOTE: East coast views moved to GEOS-16. They are experimental and not well supported by NOAA so they may not be correct so be warned. This change required redoing a large amount of the GOES code. If the image you are expecting is not showing, please let me know. You may need to use the EDIT function to update your location.
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Wind Forecast for Boston, MA (3,6,7,8)
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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.