Wednesday, April8, 2020
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Marine Weather and Tides
Nantucket, MA

Version 3.4
NOTICE
12/16/2019 NOAA is having trouble with requests that include wind gusts. I am posting graphs without wind gusts until it gets fixed.
10/9/2019 Updated the Marine Zones.
9/4/2019 Fixed the weather maps due to NOAA moving them.
7/25/2019 New feature in the Airports section gives a link to 5 minute updates for data reports.

Sunrise 6:09AMSunset 7:15PM Wednesday April 8, 2020 10:57 AM EDT (14:57 UTC) Moonrise 8:06PMMoonset 6:49AM Illumination 100% Phase: Full Moon; Moon at 15 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- 1016 Am Edt Wed Apr 8 2020
.gale watch in effect from Thursday afternoon through Friday evening...
This afternoon..NE winds 5 to 10 kt. Seas 2 to 3 ft. A chance of rain this morning.
Tonight..NE winds 5 to 10 kt, becoming se after midnight. Seas 2 to 4 ft. Patchy fog. Vsby 1 to 3 nm.
Thu..SE winds 10 to 15 kt with gusts up to 20 kt, becoming S 20 to 25 kt with gusts up to 30 kt in the afternoon. Seas 5 to 8 ft. Patchy fog. A chance of showers. Vsby 1 to 3 nm.
Thu night..W winds 20 to 25 kt with gusts up to 35 kt. Seas 7 to 10 ft. Showers likely.
Fri and Fri night..W winds 25 to 30 kt with gusts up to 45 kt. Seas 8 to 11 ft.
Sat..W winds 15 to 20 kt with gusts up to 25 kt. Seas 5 to 8 ft.
Sat night..W winds 10 to 15 kt with gusts up to 20 kt. Seas 4 to 6 ft.
Sun..SW winds 5 to 10 kt. Seas 2 to 4 ft.
Sun night..S winds 15 to 20 kt with gusts up to 25 kt. Seas 3 to 5 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 1016 Am Edt Wed Apr 8 2020
Synopsis for massachusetts and rhode island coastal waters.. Low pressure south of new england early Wednesday exits into georges bank Wednesday afternoon and then out to sea. A strong cold front crosses new eng Thu afternoon and evening. Low pres develops on this front in new england, intensifying as it moves into the gulf of maine Thu night then into the maritimes Fri. High pressure will be centered southeast of the waters for Sat. 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 081450 AFDBOX

Area Forecast Discussion National Weather Service Boston/Norton MA 1050 AM EDT Wed Apr 8 2020

SYNOPSIS. Weak area of low pressure tracking over or just south of New England will spread a period of rain across the region this morning. As the low departs a drying trend develops this afternoon along with a few breaks of sunshine late in the day. Another system moves in Thursday, bringing more rain and scattered thunderstorms. Scattered showers are possible Thursday night through Friday. Drier weather for this weekend before our next wet weather system early next week.

NEAR TERM /UNTIL 6 PM THIS EVENING/.

1040 AM Update . We made two main changes to the near-term forecast. Firstly, the back edge of the main precipitation shield is moving out to sea a little faster so we adjusted the PoPs accordingly. Secondly, we bumped the temperatures up especially across interior MA and CT. There could be some breaks in the clouds for some inland locations, especially along the lower CT River valley to reach the upper 50s or even 60 late this afternoon. Otherwise, the rest of the forecast remains on track.

700 AM update .

The back edge of the precip is moving quickly into western/central MA and CT. Precip amounts have generally added up to a few hundredths in northern zones to a few tenths in north western CT. No major changes to the forecast this morning.

Previous Discussion .

Today .

Mid level warm front and associated surface wave moving across or just south of the region this morning. Given NW flow aloft deep layer moisture and instability will struggle to advect northeast. Therefore lowest pops and least qpf will be across northeast MA. In addition convection currently over southeast PA into NJ appears to be precluding deep layer moisture and instability from advecting northeast. Furthermore, leftover dry air (Dew pts in the 30s) from Tue initially eroding leading edge of precip as it attempts to enter eastern MA during the predawn hours. Thus leaning toward the lower qpf guidance. 00z HREF probability matched mean seems reasonable with greatest qpf from western MA into CT, RI and southeast MA including Cape Cod and Islands where up to 0.25 inches of qpf is possible. Meanwhile over Essex county of northeast MA only a few hundreds is likely.

Progressive NW flow aloft will result in a short duration period of rain with drying trend for the afternoon. Back edge of precip shield currently from Utica NY to Lake George area. Low level winds become light northeast this afternoon behind departing frontal wave. Typically this would keep low clouds lock in across the region. However given low level dry air currently over the region with dew pts in the 30s, lower clouds will be confined to western MA/CT into RI and southeast MA this morning. Thus partial clearing will advect from north-northeast to southwest this afternoon and especially late in the day when some breaks of sunshine are possible. Models have been trending milder with each run. As a result will follow these trends with highs today in the low to mid 50s, upper 50s possible Hartford to Springfield. Not as warm as the past two days but very close to normal. Coolest temps along the immediate eastern MA coastline including Boston given the northeast winds, limiting highs here to the upper 40s.

SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/. Tonight .

Weak short wave ridging provides the region with dry weather and seasonable temperatures. Given light winds and dew pts 35-40 (at or above the average nighttime lows), risk for patchy fog especially along the coast where highest dew pts will be observed.

Thursday .

Closed low just north of the Great Lakes into southern Ontario ejects a very strong short wave into New England during the afternoon. Very strong jet dynamics with this system that induces 979 mb triple pt/secondary over northeast MA around 21z Thu. Strong cyclonic curvature to the mid/upper level flow coupled with PWAT plume of 1+ inches and steep mid level lapse rates suggest a good bet for elevated convection and brief heavy showers. In fact could be a fine line of low top convection. Key for surface based convection will be how far north does warm sector track before triple pt low pinches off warm sector from advecting northward. Some of the high res guidance hint at warm sector briefly advecting into RI and eastern MA with surface temps and dew pts climbing into the 50s! Some of the guidance has trended farther north-northeast with triple pt/secondary low. This would result in warm sector surging farther north increasing the threat of strong to severe storms. SPC Day 2 forecast has also trended northward with marginal risk now into NYC area. Will just have to watch how this evolves. As of now SB instability appears to be lacking.

Breezy conditions will develop in the warm sector late Thu morning into Thu afternoon with south winds 10-15 mph gusting up to 25-35 mph at times, then abruptly shifts to the west late in the day with the FROPA.

LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/. Highlights .

* Gusty winds, light rain, and high elevation snow on Friday with a few rumbles of thunder possible

* Potential for minor coastal flooding through early Friday around high tide across the east and south coasts of MA and RI. See the Tides and Coastal Flooding section below for more details.

* Temperatures running near to below normal through Saturday, then a warm up Sunday- Tuesday

* Rain and gusty winds return Monday

Details .

Thursday night and Friday .

By late Thursday evening/early overnight hours the cold front will have exited offshore ushering in a drier airmass and leaving clearing skies in its wake. Strong jet dynamics remain, now out of the W/NW. This brings mid level CAA and steepening lapse rates, helping to mix down a strong 40-50 kt 850 mb LLJ. The strongest winds should remain aloft during the overnight hours, but with diurnal heating on Friday and the cold pool aloft the boundary layer should mix very well all the way up to at least 750 mb. This will allow for widespread very strong wind gusts to mix down, potentially necessitating a Wind Advisory or even a High Wind Warning; 40-50 mph gusts are likely.

Even though the sfc low will be well to our north, the upper low lingers overhead keeping cyclonic flow in place with wraparound moisture and the strong LLJ. This will mean scattered rain showers, especially during the day. This as diurnal heating of the sfc together with the cold pool aloft contribute to some sfc based instability which could bring about a thunderstorms or two as well.

Saturday and Sunday .

Nice weekend in store, though Sunday looks to be the nicer of the two days (warmer with less wind). A ridge of high pressure begins to move overhead early Saturday, and this means the pressure gradient will be slowly relaxing, so winds likely remain breezy on Saturday before calming Saturday night and Sunday. Temperatures remain in the low 50s on Saturday under NW flow on the downstream side of the ridge. By Sunday though, the ridge axis approaches and SW return flow warms us up into the upper 50s. Low temperatures on Sunday morning were trended toward the colder MOS guidance to account for likely radiational cooling under clear skies and light winds . into the upper 20s and low 30s.

Monday and Tuesday .

The mild temperatures continue on Monday and Tuesday. However, it comes with the return of widespread rain. A deep mid level trough and sfc low will bring rain and gusty winds around Monday, with another potentially wet disturbance right on its heels.

AVIATION /15Z WEDNESDAY THROUGH SUNDAY/. Forecaster Confidence Levels .

Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent.

15z update .

Today: High confidence.

VFR conditions with light NE wind. Not expecting marine stratus due to low-level dry air.

Tonight: Moderate confidence.

MVFR to IFR conditions with areas of fog developing along the south coast. Light SE wind.

Thursday . strong cold front approaches the region and sweeps thru the area late in the day. Mainly MVFR but IFR possible in hilly terrain. Widespread showers developing west to east thru the day with a fine line of low top showers/thunderstorms possible along and ahead of the front. LLWS likely given magnitude of low level southerly jet. Strong wind shift late in the day with the frontal passage from south to west.

KBOS Terminal . High confidence in the TAF.

KBDL Terminal . High confidence in the TAF.

Outlook /Thursday Night through Sunday/ .

Thursday Night: VFR. Strong winds with local gusts up to 40 kt.

Friday: VFR. Strong winds with gusts up to 45 kt. Slight chance SHRA, isolated TSRA.

Friday Night: Mainly VFR, with local MVFR possible. Windy with gusts up to 35 kt.

Saturday through Saturday Night: VFR. Breezy.

Sunday: VFR.

MARINE. 15z update . Have issued a Coastal Flood Advisory for Boston Harbor and the MA South Coast to cover the upcoming high tide cycle around local noon for possible minor flooding. All other marine headlines remain unchanged.

This afternoon . weak surface low tracks eastward to Georges Bank this afternoon. Morning rain gives way to a drying trend in the afternoon. Light SSW winds become NE this afternoon.

Tonight . Weak high pressure over the waters provides dry quiet weather.

Thursday . strong cold front sweeps across the water late Thu with widespread showers and embedded thunder likely. Strong SSW winds ahead of the front abruptly shifts to the WNW and remains strong and gusty.

Outlook /Thursday Night through Sunday/ .

Thursday Night: Moderate risk for gale force winds with gusts up to 40 kt. Rough seas up to 11 ft. Slight chance of rain showers.

Friday: Moderate risk for gale force winds with gusts up to 40 kt. Rough seas up to 12 ft. Slight chance of rain showers, isolated thunderstorms.

Friday Night: Moderate risk for Small Craft Advisory winds with gusts up to 30 kt. Areas of rough seas.

Saturday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Local rough seas.

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

Sunday: Winds less than 25 kt.

TIDES/COASTAL FLOODING. 4 AM Update:

Next 4 tides (Midday and midnight today and Thursday) are astronomically high and run the risk of minor coastal flooding/inundation. Midday today and then midnight tonight main risk is eastern MA and again tonight given light onshore flow. Then tomorrow with southerly surface winds risk shifts to the south coast of MA/RI.

BOX WATCHES/WARNINGS/ADVISORIES. CT . None. MA . Coastal Flood Advisory until 8 AM EDT Friday for MAZ007-015- 016-019-022. RI . Coastal Flood Advisory from 8 PM this evening to 8 AM EDT Friday for RIZ002-004>007. MARINE . Gale Watch from Thursday afternoon through Friday evening for ANZ232-250-254-255. Gale Watch from late Thursday night through Friday evening for ANZ233>235-237-256. Gale Watch from Thursday afternoon through Friday afternoon for ANZ231-251.

SYNOPSIS . Nocera/BW NEAR TERM . Chai SHORT TERM . Nocera LONG TERM . BW AVIATION . Nocera/BW/Chai MARINE . Loconto/Chai TIDES/COASTAL FLOODING .


Weather Reporting Stations
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Stations Dist Age Wind Air TempWater Temp WavesPressureDewPt
NTKM3 - 8449130 - Nantucket Island, MA 2 mi64 min NNE 7 G 8.9 46°F 47°F999.6 hPa
44020 - NANTUCKET SOUND 19 mi78 min
CHTM3 29 mi70 min NNE 8 G 8.9 46°F 51°F999.6 hPa
WAXM3 - Waquoit Bay Reserve, MA 33 mi73 min N 1.9 46°F 1000 hPa43°F
BZBM3 - 8447930 - Woods Hole, MA 37 mi64 min 47°F 45°F999.6 hPa
44090 42 mi58 min 43°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 mi65 minNE 910.00 miOvercast48°F46°F93%999.3 hPa

Link to 5 minute data for KACK

Wind History from ACK (wind in knots)
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Last 24hrW8W12W13W14W15SW13SW12SW11SW8SW10SW7SW6SW7SW5SW6CalmCalmSE3CalmCalmNE3E4CalmNE9
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2 days agoN5CalmS8S8S7SW7S8S9S7S6S8SW10SW9SW7S8S8SW6SW6W8W8N8N10N10N12
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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
Click for Map
Wed -- 12:11 AM EDT     -0.00 knots Slack
Wed -- 04:45 AM EDT     -1.64 knots Max Ebb
Wed -- 06:11 AM EDT     Sunrise
Wed -- 06:48 AM EDT     Moonset
Wed -- 07:03 AM EDT     0.00 knots Slack
Wed -- 09:06 AM EDT     1.42 knots Max Flood
Wed -- 12:22 PM EDT     -0.00 knots Slack
Wed -- 05:07 PM EDT     -1.67 knots Max Ebb
Wed -- 07:13 PM EDT     Sunset
Wed -- 07:26 PM EDT     0.00 knots Slack
Wed -- 08:06 PM EDT     Moonrise
Wed -- 09:31 PM EDT     1.49 knots Max Flood
Tide / Current data from XTide NOT FOR NAVIGATION
Sorry tide depth graphs only, please select another station.

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0.1-0.2-0.6-1-1.5-1.6-1.1-0.111.41.20.60.1-0.2-0.5-0.9-1.4-1.7-1.4-0.50.61.41.40.9

Weather Map
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wmap_A
GEOS 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 (10,2,3,4)
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Ground Weather Radar Station Boston, MA
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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 numerous 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.