Tuesday, September29, 2020
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Marine Weather and Tides
Dennis Port, MA

Version 3.4
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8/26/2020 The 7 day forecast is taking about 5 seconds to load but it will eventually load. NOAA is still working on it.
8/18/2020 NOAA continues to have trouble. Wind guest will occasionally be left off graphs. I am working with NOAA to resolve the issue.
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 6:35AMSunset 6:26PM Tuesday September 29, 2020 10:47 AM EDT (14:47 UTC) Moonrise 5:56PMMoonset 4:06AM Illumination 93% Phase: Waxing Gibbous; Moon at 12 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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ANZ232 Nantucket Sound- 1016 Am Edt Tue Sep 29 2020
.gale watch in effect from late tonight through Wednesday evening...
This afternoon..S winds 5 to 10 kt. Seas 2 to 3 ft. Patchy fog. A slight chance of showers. Isolated tstms. Some tstms may produce gusty winds and heavy rainfall. Vsby 1 nm or less.
Tonight..S winds 10 to 15 kt, increasing to 15 to 20 kt with gusts up to 30 kt after midnight. Seas 2 to 4 ft. Patchy fog. A chance of showers. Vsby 1 nm or less.
Wed..SW winds 20 to 25 kt with gusts up to 40 kt. Seas 3 to 5 ft. Patchy fog. Showers likely. Vsby 1 to 3 nm.
Wed night..SW winds 15 to 20 kt, diminishing to 10 to 15 kt after midnight. Gusts up to 25 kt. Seas 2 to 4 ft.
Thu and Thu night..SW winds 10 to 15 kt with gusts up to 20 kt. Seas 2 to 4 ft.
Fri and Fri night..SE winds 5 to 10 kt, becoming n. Seas 2 to 3 ft. A chance of rain.
Sat and Sat night..NW winds 5 to 10 kt. Seas around 2 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 1016 Am Edt Tue Sep 29 2020
Synopsis for massachusetts and rhode island coastal waters.. High pressure remains centered south of newfoundland Tuesday morning. Meanwhile a cold front will move slowly along the east coast. Low pressure develops on this front over the mid atlantic region tonight and then intensfies as it tracks north up the eastern seaboard and into northern new england Wednesday morning. Southerly gales may accompany this low along with periods of heavy rain. A cold front sweeps across the waters Wednesday with improving weather conditions as winds shift from south to west. Dry, tranquil weather follows in the wake of the front Thursday. Weak low pressure tracks across the new england waters Fri from southwest to northeast. Behind the low, dry west winds follow Saturday. For additional information on possible hazardous weather for the week ahead, please visit www.weather.gov/boston/ehwo .


7 Day Forecast for Marine Location Near Dennis Port, MA
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location: 41.65, -70.12     debug


Area Discussion for - Boston, MA
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FXUS61 KBOX 291332 AFDBOX

Area Forecast Discussion National Weather Service Boston/Norton MA 932 AM EDT Tue Sep 29 2020

SYNOPSIS. Humid and unseasonably mild weather will continue Today with a few showers possible from time to time. An approaching cold front will bring widespread heavy rain and possibly damaging winds late tonight into early Wednesday, with highest rainfall totals across western Massachusetts and Connecticut. Cooler, less humid and drier air then moves in later Wednesday into Thursday. More scattered showers are possible Thursday night into Friday, followed by a cool dry weekend. Another round of showers is possible Sunday night into Monday.

NEAR TERM /UNTIL 6 PM THIS EVENING/. 930 AM update .

Another warm and humid morning in progress with dew pts in the 60s. This combined with light southerly winds has resulted in low clouds and patchy dense fog along the south coast of MA and RI, including Cape Cod and the Islands. Will continue the dense fog advisory here until 8 am, then expecting slowly improving conditions thereafter.

Otherwise, band of showers with embedded thunder east of Nantucket and Cape Cod will continue moving east away from the region, as weak short wave trough exits out to sea. Behind this trough, weak short wave ridging advects across the area. Given the mid level flow becomes slightly anticyclonic, expected enough subsidence to erode the cloud cover and give way to a mainly dry day and at least partial sunshine this afternoon. Already beginning to see drier air from 925 mb to 700 mb on SPC mesoanalysis just upstream south of New England over the ocean. Can't rule out an isolated shower or two, but the bulk of the day should be dry. HREF cloud cover product captures this well and simulates breaks of sunshine here this afternoon. Given warm airmass remains in place (925 mb temps of +17C to +19C) expecting highs this afternoon to climb to 75-80, cooler south coast. However low clouds may hang tough along the immediate south coast and especially Cape Cod. Thus, sunshine if any looks limited across this area.

SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/. Tonight:

* Potentially high-impact night of weather with heavy rainfall and strong winds associated with a rapidly intensifying surface cyclone. * Wind Advisory issued for most locations east of the East Slopes of the Berkshires.

A busy night of weather looks to be in store for much of our area. PWATS rise to over 2 inches, which is higher than the daily max value for Chatham, MA according to SPC sounding climatology. The key to producing heavy rainfall lies in a 70-80 kt 850mb low level jet that noses into S New England shortly after midnight. Around the same time, the H500 trough goes negatively tilted with an impressive baroclinic gradient developing near the surface. The associated cyclone undergoes rapid intensification, and it is not out of the question that we actually achieve bombogenesis criteria, i.e. a drop of 24 mb in 24 hours! 925mb winds are also forecast to be as high as 4 to 5 standard deviations above normal according to GEFS with 925mb winds as high as 65-70 kts.

So the question is: Can the 60-70 kt winds at 3000 ft mix down to the surface? Because the cold front comes through overnight, the lack of diurnal heating would argue against a more widespread damaging wind threat. However, indications are that a fine line of convection could develop and bring down some of the damaging winds. Given that most trees are still fully leaved, and that the nose of the jet is pointed towards the more densely populated areas of Eastern MA and RI, have decided to go with a Wind Advisory for most locations east of the East Slopes of the Berkshires. Later shift would monitor for the need to expand or upgrade the wind headline.

Wednesday:

Following the cold front passage, dew points fall rapidly into the 50s during the day. Expect breezy conditions to persist through much of the day as lapse rates steepen though risk for damaging winds should decrease as jet dynamics become less impressive. Currently have used a blend of guidance to derive the forecast daytime highs, with Western MA topping out in the 60s and Eastern MA in the low to mid 70s. The highs could well be reached early in the day as cold air advection commences in earnest. Should be a mostly dry day but with plenty of cold stratocumulus clouds.

LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/. 340 am update .

Highlights .

* Humidity finally breaks along with temps trending cooler

* Chance of rain Thu night/Fri & again Sun night into Monday

* Dry pleasant weather Wed night/Thu & much of this weekend

Precipitation .

Dry weather returns Wed afternoon and continues into Thu with post frontal airmass overspreading the region behind the departing frontal wave from Wed morning. However mean mid level trough axis doesn't move much from the Great Lakes/OH Valley region, as new jet energy dives into the mean trough. This induces developing low pressure south of New England Friday, with deformation rains over NYS into CT and western-central PA. Less rain likely across RI and eastern MA. All ensemble guidance from CMC/GEFS and ECENS in good agreement on timing, location and qpf with best clustering from ECENS and CMC. Thus above average confidence on a period of rain Thu ngt into Fri, highest pops over CT into western-central MA. Mean qpf from ECENS and CMC ensembles range from 0.30-0.40 inches, with 0.10- 0.20 over RI and eastern MA. Not blockbuster qpf but beneficial rains indeed. Dry weather returns for the weekend behind this departing short wave. However ensembles suggest mean trough will not move very much with axis remaining over Great Lakes and another short wave trough ejecting northeast toward New England Sun ngt into Mon, accompanied by another chance of rain.

Temperatures .

Mean trough axis remains well west of New England, so despite post frontal airmass overspreading the region late Wed into Thu, core of cold air advection remains west of New England and fades as it advects eastward. Thus, near seasonable temps Thu with highs in the upper 60s to lower 70s. Very pleasant with dew pts in the 40s and 50s. Amount of sunshine Thu a bit uncertain given SSW flow overrunning cooler/drier low level airmass. Thus could be some mid/high clouds obscuring the sun at times. Cooler Friday given overcast conditions and showers likely especially inland. Highs 65- 70, low 60s well inland. Modest cold air advection behind Friday's short wave trough, which will likely result in temps slightly cooler than normal this weekend despite mainly dry weather. Highs should range in the low to mid 60s. Normal high, 65-70. Temps continue to trend downward early next week with 1030+ mb high likely over Maritimes along with risk for showers.

AVIATION /14Z TUESDAY THROUGH SATURDAY/. Forecaster Confidence Levels .

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

11z update: Moderate confidence.

IFR/MVFR lifts to VFR by 16z-17z. However south coast of MA/RI may only see IFR/LIFR lift to MVFR with areas dense fog at 11z along the south coast burning off mid to late morning. Otherwise a mainly dry day other than an isolated shower or two. Earlier discussion below.

===================================================================

Today: Moderate confidence.

Improving to VFR for interior terminals but Cape terminals may only improve to MVFR. After 18z, interior terminals deteriorate to MVFR and localized IFR from west to east as cold front and line of locally heavy rain approaches from the west. S winds 5 to 10 kts with gusts 15 to 20 kts.

Tonight: Moderate confidence.

Widespread IFR to localized LIFR with heavy rain from the cold frontal passage. S winds 15 to 20 kts with gusts 25 to 30 kts and localized 35 kts.

Wednesday: High confidence.

IFR to start but improving to MVFR and then VFR after 18z. Winds turning to SW and W at 10 to 15 kts with gusts 20 to 25 kts.

KBOS Terminal . Moderate confidence in TAFs.

KBDL Terminal . Moderate confidence in TAFs. Outlook /Wednesday Night through Saturday/ .

Wednesday Night: Mainly VFR, with local MVFR possible. Breezy.

Thursday: VFR. Breezy.

Thursday Night: Mainly VFR, with local MVFR possible. Slight chance RA.

Friday: Mainly MVFR, with areas VFR possible. Chance RA.

Friday Night: Mainly VFR, with local MVFR possible. Chance RA.

Saturday: VFR.

MARINE.

930 AM UPDATE .

We didn't change much to the forecast at this time. The only change that we made was to keep visibility along the south coast of MA/RI lower, generally less than 1-2 miles.

See previous discussion below .

* Gale Watches issued for all coastal waters on Wednesday.

Rather tranquil conditions with seas and winds generally below Small Craft criteria on Tuesday. By Tue night, conditions steadily deteriorate. Expect areas of fog to develop but the main story will be an approaching cold front and a 70 kt low level jet leading to periods of heavy rainfall early Wednesday morning and possibly gale- force winds, with gusts possibly as high as 40 kt at times, especially early Wed morning. Winds turn to the west by Wed afternoon and remain gusty at about 20 to 25 kt.

Outlook /Wednesday Night through Saturday/ .

Wednesday Night through Thursday: Winds less than 25 kt. Rough seas up to 8 ft.

Thursday Night: Winds less than 25 kt. Areas of rough seas.

Friday: Winds less than 25 kt. Seas up to 5 ft. Chance of rain.

Friday Night: Winds less than 25 kt. Seas up to 5 ft. Slight chance of rain.

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

BOX WATCHES/WARNINGS/ADVISORIES. CT . Wind Advisory from 11 PM this evening to 8 PM EDT Wednesday for CTZ003-004. MA . Dense Fog Advisory until 10 AM EDT this morning for MAZ021>024. Wind Advisory from 11 PM this evening to 8 PM EDT Wednesday for MAZ005>007-012>024. RI . Dense Fog Advisory until 10 AM EDT this morning for RIZ008. Wind Advisory from 11 PM this evening to 8 PM EDT Wednesday for RIZ001>008. MARINE . Gale Watch from late tonight through Wednesday evening for ANZ230>237-250-251-254>256.

SYNOPSIS . Nocera/Chai NEAR TERM . Nocera/Chai SHORT TERM . Chai LONG TERM . Nocera AVIATION . Nocera/Chai MARINE . Nocera/Chai/Gaucher


Weather Reporting Stations
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Stations Dist Age Wind Air TempWater Temp WavesPressureDewPt
CHTM3 9 mi47 min SSW 6 G 9.9 66°F 65°F1015.2 hPa (+0.9)
44020 - NANTUCKET SOUND 14 mi27 min S 5.8 G 7.8 66°F
44090 17 mi20 min 65°F
WAXM3 - Waquoit Bay Reserve, MA 22 mi62 min S 1 69°F 1015 hPa69°F
NTKM3 - 8449130 - Nantucket Island, MA 25 mi47 min SSW 5.1 G 7 68°F 66°F1015.5 hPa (+1.1)
BZBM3 - 8447930 - Woods Hole, MA 30 mi47 min 66°F 67°F1015.2 hPa (+1.2)
44018 - SE Cape Cod 30NM East of Nantucket, MA 38 mi57 min SSE 7.8 G 7.8 64°F 2 ft1014.8 hPa (+0.6)64°F

Wind History for Nantucket Island, MA
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Airport Reports
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AirportDistAgeWind ktVisibilitySky/WeatherTempDewPtHumidityPressure
Chatham, Chatham Municipal Airport, MA8 mi55 minVar 30.25 miFog67°F66°F100%1015.7 hPa
Hyannis, Barnstable Municipal-Boardman Airport, MA9 mi51 minSSW 52.50 miFog/Mist69°F69°F100%1014.7 hPa
Otis Air National Guard Base, MA21 mi62 minSSW 57.00 miOvercast68°F68°F100%1014.9 hPa

Link to 5 minute data for KCQX

Wind History from CQX (wind in knots)
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2 days ago533S444S4S3S3Calm3SE4SE4S4CalmS4CalmS5CalmCalmSE3S44S5

Tide / Current Tables for Dennis Port, Nantucket Sound, Massachusetts
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Dennis Port
Click for Map
Tue -- 04:06 AM EDT     Moonset
Tue -- 04:55 AM EDT     0.16 feet Low Tide
Tue -- 06:35 AM EDT     Sunrise
Tue -- 11:36 AM EDT     3.41 feet High Tide
Tue -- 05:07 PM EDT     0.32 feet Low Tide
Tue -- 05:55 PM EDT     Moonrise
Tue -- 06:24 PM EDT     Sunset
Tue -- 11:49 PM EDT     3.63 feet High Tide
Tide / Current data from XTide NOT FOR NAVIGATION
Sorry tide depth graphs only, please select another station.

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3.42.92.11.10.40.20.30.81.52.333.33.432.41.50.70.30.40.91.52.33.13.5

Tide / Current Tables for Pollock Rip Channel, Massachusetts Current
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Pollock Rip Channel
Click for Map
Tue -- 02:09 AM EDT     0.00 knots Slack
Tue -- 04:06 AM EDT     Moonset
Tue -- 05:45 AM EDT     2.23 knots Max Flood
Tue -- 06:34 AM EDT     Sunrise
Tue -- 08:44 AM EDT     -0.00 knots Slack
Tue -- 11:46 AM EDT     -1.71 knots Max Ebb
Tue -- 02:43 PM EDT     0.00 knots Slack
Tue -- 05:55 PM EDT     Moonrise
Tue -- 06:08 PM EDT     2.02 knots Max Flood
Tue -- 06:24 PM EDT     Sunset
Tue -- 08:58 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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-1.6-1-0.10.81.62.12.21.80.8-0.3-1.1-1.6-1.7-1.4-0.60.31.11.721.81-0-1-1.5

Weather Map
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GEOS Local Image of    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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Ground Weather Radar Station Boston, MA
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