Thursday, February20, 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 6:28AMSunset 5:21PM Thursday February 20, 2020 9:51 PM EST (02:51 UTC) Moonrise 5:57AMMoonset 3:25PM 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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ANZ255 Coastal Waters Extending Out To 25 Nm South Of Marthas Vineyard And Nantucket- 716 Pm Est Thu Feb 20 2020
Tonight..NW winds 5 to 10 kt, becoming N 10 to 15 kt with gusts up to 20 kt after midnight. Seas 2 to 4 ft. A slight chance of snow this evening with vsby 1 to 3 nm.
Fri..N winds 10 to 15 kt, diminishing to 5 to 10 kt in the afternoon. Gusts up to 20 kt. Seas 2 to 4 ft.
Fri night..W winds 5 to 10 kt, increasing to 10 to 15 kt with gusts up to 20 kt after midnight. Seas 2 to 4 ft.
Sat..W winds 10 to 15 kt with gusts up to 25 kt. Seas 3 to 5 ft.
Sat night..W winds 10 to 15 kt with gusts up to 20 kt, diminishing to 5 to 10 kt after midnight. Seas 3 to 5 ft.
Sun and Sun night..SW winds 10 to 15 kt. Seas 2 to 4 ft.
Mon..SW winds 5 to 10 kt. Seas 2 to 3 ft.
Mon night..SW winds 5 to 10 kt. Seas 2 to 3 ft. A chance of rain.
Tue..S winds 5 to 10 kt. Seas 2 to 4 ft. Rain likely.
Tue night..S winds 10 to 15 kt with gusts up to 20 kt. Seas 3 to 5 ft. Rain likely. 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 716 Pm Est Thu Feb 20 2020
Synopsis for massachusetts and rhode island coastal waters.. A large high pres will slowly build east through Fri, passing south of the waters this weekend. The high will continue to move east and away from our waters early next week as low pres over the southern plains slowly lifts northeast. 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 210234 AFDBOX

Area Forecast Discussion National Weather Service Boston/Norton MA 934 PM EST Thu Feb 20 2020

SYNOPSIS. High pressure will continue to bring dry but cold weather tonight and Friday. Conditions remain dry through early next week as temperatures rise to above normal levels. Next chance for wet weather arrives Monday night. Unsettled conditions may linger through the middle of next week with a couple of surface lows moving across.

NEAR TERM /UNTIL 6 AM FRIDAY MORNING/.

935 PM Update .

A moisture starved shortwave will act to turn surface winds from the NW to more of a NNW direction overnight. This combined with 850T near -16C and mainly clear skies will allow for one of the coldest nights of the winter. While that is not saying much considering how mild this winter has been, expect low temps to bottom out between 5 and 15 above in most locations by daybreak.

The exception to the mainly clear skies will be across portions of the Cape/Nantucket. As surface winds turn more to the NNW, ocean effect clouds will develop. Subsidence inversion will be quite low though, so despite moderate instability nothing more than a few passing flurries/light snow showers are expected across the outer-Cape/Nantucket.

SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/. 4 PM update .

Friday .

Very cold start to the day and temp recovery will be limited as given lack of thermal advection with ridge of high pressure overhead and associated subsidence inversion limiting boundary layer mixing. Thus similar highs as today (upper 20s and lower 30s) but it won't feel as cold given more sunshine and less wind. Sunshine may be delayed until the afternoon for Cape Cod and Nantucket as ocean effect clouds linger much of the morning.

Friday night .

Ridge axis moves east of the area with westerly winds developing. However after sunset where winds decouple (deeper valleys and possibly low lying spots of eastern MA) temps may fall quickly with dew pts in the single digits and clear skies. However not as cold along the coast especially Cape Cod and Islands where winds will not decouple, including Boston and high terrain.

Otherwise, dry and quiet weather conditions.

LONG TERM /SATURDAY THROUGH THURSDAY/. Highlights .

* Dry conditions with normal temperatures above normal late this weekend into early next week

* Next chance for precipitation begins Monday night, mainly rain event

* Potential for southern stream moisture shifting out of Ohio/Tennessee valleys toward the NE U.S. through the middle of next week with continued mild temps

* A changeover to light snow may occur Wed night into Thu across portions of the interior

Details .

Saturday through Monday .

Noting a general W-NW mid level steering flow from the northern Plains states through New England to the mid Atlc coast to start off Saturday morning. This keeps a dry flow across the northeast with a broad H5 ridge extending from Alberta and Saskatchewan through the E slopes of the Rockies to N Texas in place to start off. This patter will take a few days to break down, so will see an extended period of dry conditions as surface high pressure from eastern Texas to the mid Atlc coast will slowly shift E through the upcoming weekend, then pushes off the Carolina coast by around 12Z Monday.

With the general land based wind flow in place, along with gradually rising H5 heights, temps will start off close to seasonal levels on Saturday on W winds at 10 mph that may gust up to 20 mph. Readings will continue to moderate as winds gradually back to SW by Monday. Part of the backing winds will be the beginnings of a digging long wave trough through the central and northern Plains states that will merge with a weakening H5 cutoff low late Sunday and Monday. H5 heights will rise to around 558 dm on Monday. So, with the mild SW wind flow and rising heights, will see Monday's temps range from 5 to 10 degrees above seasonal levels. Highs will top off in the lower 50s across most areas, but only in the mid-upper 40s across the higher terrain and along the S coast with the onshore wind.

The SW winds will bring in some mid and upper level moisture, so clouds will increase from W-E during the day. However, with T/Td spreads around 10 degrees, have kept a dry forecast going through Monday

Monday night through Tuesday night .

With the SW wind in place bringing milder air at the surface and aloft, will slowly bring in a deepening moisture layer as a surface low approaches the OH valley by 12Z Tue. Should see light rain arrive across the CT valley by around midnight, then spreading E through the remainder of the night. Temps should remain above freezing, so not expect PTYPE issues at this point.

Looks like best shot for precip will occur along the RI coast, possibly reaching into N CT by around daybreak. Not seeing any southern stream moisture plume working in to start off, so should see light QPF values Mon night.

By Tuesday morning, however, will see increasing deep layer moisture heading toward the region as the central Plains H5 trough continues to dig. 12Z GEFS ensemble mean signaling a PWAT plume on the order of 1 to 2 SD above normal (around 1 to 1.25 inches). So, could see steadier rainfall mainly S of the Mass Pike from around 18Z Tue to 06Z Wed, with potential QPF totals around 0.5 to 0.6 inches across NE CT/RI/SE Mass during that timeframe. Should see precip start to taper off as the first low weakens as it moves across the northeast. So, should see precip tapering off around or after midnight Tue night from W-E.

Highs on Tuesday will run around 5 degrees above normal with readings mainly in the upper 40s to around 50, except a bit cooler across the higher terrain.

Wednesday and Thursday .

By 12Z Wednesday, will see deep, nearly meridional H5 trough from western Ontario southward through the MS river valley develop. 12Z models signaling a brief dry period between systems through midday Wednesday or so. This appears to be short lived as several model members developing another low pres wave in the Delmarva area by 00Z Thursday. With an E-SE wind flow in place, may see another area of showers move across. Could see up to 0.3 inches across the E slopes of the Berkshires after midnight Thu night, then pushes eastward during the day on Thursday. So, current forecast suggests another 0.3 to 0.5 inches of rainfall during the Wed night-Thu timeframe. Still quite a bit of uncertainty whether this scenario, however, as there is still quite a bit of model solution spread.

Another caveat may be how quickly colder air may filter in behind the departing second low on Thu. There is the possibility of a changeover to snow across the higher inland terrain Wed night that could shift SE during Thu. Depending upon how quickly this will occur, as well as whether it lasts across the higher terrain of the northern Worcester hills and E slopes of the Berkshires whether there could be some snow accumulation late Wed night/Thu.

AVIATION /03Z FRIDAY THROUGH TUESDAY/. Forecaster Confidence Levels .

Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. 00Z TAF Update . High confidence thru at least 12z Saturday.

VFR SCT-BKN clouds from 050-070, most clouds across N CT/RI/SE Mass terminals through 03Z-05Z. Exception will be across outer Cape Cod and Nantucket where MVFR CIGS develop in response to winds becoming N-NE 10-20 kt around or after 05Z. A few ocean effect snow showers or flurries possible across this area.

Friday . MVFR CIGS over mid to outer Cape Cod and Nantucket during the morning, along with a few snow showers/flurries possible, then should improve. Otherwise VFR, dry weather and light/variable winds.

Friday night . VFR. Dry conditions and light SW winds.

KBOS Terminal . High confidence in TAF. Period of SCT-BKN clouds at 050-060 through 03Z-04Z this evening.

KBDL Terminal . High confidence in TAF.

Outlook /Saturday through Tuesday/ .

Saturday through Saturday Night: VFR. Breezy.

Sunday through Monday: VFR.

Monday Night: Mainly MVFR, with areas VFR possible. Chance RA.

Tuesday: Chance RA.

MARINE. 4 PM update .

Tonight/Friday/Fri night .

Dry weather and good vsby. Only exception will be as winds shift from WNW late today to NNE overnight (10-20 kt) a few snow showers may impact the waters around Cape Cod and Nantucket. Light/variable wind Fri followed by developing modest west wind Fri night but may increase to 20-25 kt outer eastern MA waters late toward Gulf of ME waters.

Outlook /Saturday through Tuesday/ .

Saturday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Areas of seas approaching 5 ft.

Saturday Night: Winds less than 25 kt. Areas of seas approaching 5 ft.

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

Sunday Night through Monday: Winds less than 25 kt.

Monday Night: Winds less than 25 kt. Chance of rain.

Tuesday: Winds less than 25 kt. Rain likely.

BOX WATCHES/WARNINGS/ADVISORIES. CT . None. MA . None. RI . None. MARINE . None.

SYNOPSIS . Nocera/EVT NEAR TERM . Frank SHORT TERM . Nocera LONG TERM . EVT AVIATION . Nocera/EVT MARINE . Nocera/EVT


Weather Reporting Stations
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Stations Dist Age Wind Air TempWater Temp WavesPressureDewPt
NTKM3 - 8449130 - Nantucket Island, MA 2 mi52 min NNW 8 G 12 31°F 39°F1029.1 hPa (+0.5)
44020 - NANTUCKET SOUND 19 mi32 min 18 G 21 31°F 12°F
WAXM3 - Waquoit Bay Reserve, MA 33 mi67 min WNW 4.1 33°F 1029 hPa14°F
BZBM3 - 8447930 - Woods Hole, MA 37 mi52 min 30°F 38°F1029.1 hPa (+0.9)
44090 42 mi22 min 40°F2 ft

Wind History for Nantucket Island, MA
(wind in knots)    EDIT      (on/off)   Help
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Airport Reports
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AirportDistAgeWind ktVisibilitySky/WeatherTempDewPtHumidityPressure
Nantucket, Nantucket Memorial Airport, MA1 mi59 minNNW 1010.00 miFair31°F12°F45%1028.4 hPa

Link to 5 minute data for KACK

Wind History from ACK (wind in knots)
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1 day agoS11SW12W13W13W10W7NW8NW8NW9NW13NW13
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2 days agoNE5--NE6NE6NE6NE6E6E7E9E11E16
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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
Thu -- 01:16 AM EST     -1.54 knots Max Ebb
Thu -- 03:42 AM EST     0.00 knots Slack
Thu -- 04:56 AM EST     Moonrise
Thu -- 05:16 AM EST     0.62 knots Max Flood
Thu -- 06:29 AM EST     Sunrise
Thu -- 07:50 AM EST     0.28 knots Min Flood
Thu -- 09:00 AM EST     0.32 knots Max Flood
Thu -- 10:35 AM EST     -0.00 knots Slack
Thu -- 01:38 PM EST     -1.61 knots Max Ebb
Thu -- 02:25 PM EST     Moonset
Thu -- 04:02 PM EST     0.00 knots Slack
Thu -- 05:19 PM EST     Sunset
Thu -- 05:50 PM EST     0.79 knots Max Flood
Thu -- 08:10 PM EST     0.55 knots Min Flood
Thu -- 09:17 PM EST     0.58 knots Max Flood
Thu -- 11:22 PM EST     -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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-1.1-1.5-1.4-0.60.20.60.50.30.30.30.2-0.2-0.9-1.5-1.6-1-00.60.80.70.60.60.50.2

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.
Link to Loop

Other links: Northern Pacific     Contential US     Full GOES-East
Wind Forecast for Boston, MA (21,6,7,8)
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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.