Thursday, June21, 2018 L-36.com


Marine Weather and Tides
Siasconset, MA

Version 3.4
What's New / NOTES
5/20/2018 -- NOAA is having problems with the data feed that I use to draw the graphs. They are aware of the issue and working to resolve it. Sometimes changing the location by about a mile will give a correct graph. 3/3/2018 - There is a new GOES Satellite for the east coast that required rewriting that part of the code. Please report any issues.

Sunrise 5:10AMSunset 8:24PM Thursday June 21, 2018 4:06 AM EDT (08:06 UTC) Moonrise 1:55PMMoonset 1:25AM Illumination 54% Phase: First Quarter Moon; Moon at 8 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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ANZ005 311 Am Edt Thu Jun 21 2018
Synopsis for eastport me to stonington me out 25 nm.. A cold front will cross the waters this morning. High pres will build toward the waters today and then move E on Fri.

7 Day Forecast for Marine Location Near Siasconset, MA
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location: 38.84, -69.85     debug


Area Discussion for - Boston, MA
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Fxus61 kbox 210305
afdbox
area forecast discussion
national weather service boston norton ma
1105 pm edt Wed jun 20 2018

Synopsis
Showers are likely overnight S of the ma ct ri border as a low
pressure center sweeps W to E just S of new england. Bit cooler
with a spot showers Thursday. Seasonable Friday while turning
unsettled Saturday, continuing through early Monday with the
chance of showers and thunderstorms. Dry weather thereafter
through Thursday, with a renewed chance of wet- weather Friday
into the following weekend.

Near term until 6 am Thursday morning
1030 pm update...

as low pressure approaches the nj coast this evening, noting
very spotty shower activity across S coastal ct and long island
on latest kbox and NE regional 88d radar imagery. Only ground
truth seen at 02z was across central long island, where both
kisp and khwv were reporting -ra. Pretty dry airmass in place
away from the S coast, with t TD spreads from 10 to 16 degrees.

00z NAM and rap bufkit soundings also showing a dry airmass
through the layer, especially on the rap model data.

Clouds AOB 5000 ft were reported across a few spots on long
island, while mid and high clouds were the rule further n.

Noting clearing line moving slowly but steadily S on latest
goes-east rgb microphysics composite and IR satellite imagery.

With these drier trends, have pushed the northern edge of the
precip further s, but did keep mention of mainly chc pops
across central ct central ri and S coastal mass. Have lkly pops
confined to the immediate S coast and islands after midnight.

With a mainly stable airmass, as well as no lightning being
reported anywhere across the NE u.S., have removed mention of
thunder from this update.

Have updated near term to bring conditions current and
incorporated current thinking into the overnight forecast.

Previous discussion...

rain moving in just around midnight, exiting the early morning
hours on Thursday. Latest radar returns just a pre-cursor, acting
to moisten the environment, however low-levels still considerably
dry as surface high pressure retreats off to the e.

Short term 6 am Thursday morning through Thursday night
Thursday into Thursday night...

precipitation along the south coast will be ongoing early in the
morning as surface low pressure continue to move across the southern
waters. Approaching wave from the northeast will drive this low
south and offshore leading to an end of the precip. Will have to
watch for a spot shower or two during the day across the interior.

Increasing low level moisture combined with steep lapse rates and
upper level trigger could lead to a few showers especially along the
higher terrain. Thus have insert a slight chc for a shower during
the afternoon.

Temperatures on Thursday will be warmer across the ct valley, but
quite cool along the east coast. Winds will switch from the
southwest to the northeast a front passes through. This will bring
the cooler maritime airmass onshore. Could see over a 10 degree
difference across the region.

Temperatures overnight will cool off, but not as much as prev
through. Increasing low level moisture trapped within the inversion
will result in stratus and fog across the area. Still trying to
narrow down best location, but something to watch for in the coming
shifts.

Long term Friday through Wednesday
* highlights...

- Saturday perhaps not a washout, skirting rains S e
- showers t'storms N W Sunday, sweeping SE into Monday morning
- prolonged dry conditions during the week
- watching weeks-end for additional wet-weather disturbances
* overview...

summer is coming. Prevailing N pacific h5 trof downstream of which a
split flow regime emerges over western N america. S tug by cascading
systems into a baffin bay gyre, h85 temperature warm anomalies build
into the great lakes st. Lawrence river valley per 5-day averages.

Subsequent higher heights, more dominant N atlantic high especially
towards bermuda, invoking a S warm, moist pump from the gulf. Would
appear seemingly that a general h5 trof pattern remains over the ne
conus, however weaker under an increasing weight of high pressure,
subsidence. Weak frontal boundary passages with uncertain outcomes,
where precipitation looks prominent upstream only to wash out upon
arrival. Confident warming trend into july, while a nod of concern
of drier than average precip, perhaps enhancing ongoing abnormally
dry conditions. Some unknowns, a NE atlantic rex-block evolving into
w europe, and tropical activity off africa into the caribbean. Will
hit on any targets of opportunity below.

* discussion...

Saturday...

lean away from heavy rain with wedging high pressure, drier air, as
the sub-tropical, +2" precipitable water airmass resides s, perhaps
skirting SE new england. Have seen this before with winter systems
in where isallobaric flow dams up against an approaching oh river
valley low. Can't rule out scattered shower, thunderstorm activity
towards days end, but leaning with 20.12z GFS nam in SE skirting
outcomes fueled by low-level convergent inflow towards a held-up
warm frontal boundary. De-amplifying mid-level trof, weak frontal
boundary parent, pushes the sub-tropical axis offshore ahead of an
oncoming sharper h5 trof axis for Sunday into Monday. Not ready to
call the day a washout.

Sunday into Monday...

afternoon showers and thunderstorms into evening, however mainly N w
interior locales. Possibly strong but not thinking severe per shear
and 0-6 km mean wind accompanying along with marginal instability.

Better sub-tropical, unstable and muggy airmass S e, offshore, yet
enough moisture that with destabilization should allow activity to
pop within cyclonic regime out ahead of overnight sharp cold front,
pushing offshore around Monday morning. Accompanying vortmax, strong
deep layer ascent, may have to watch SE new england into Monday up
against a more muggy airmass lingering offshore as to potential out-
comes. Thinking a majority of activity is nuisance.

Overall, for the 3-day period Saturday through Monday, could be a
situation of interior N W destabilization with s-shoreline skirting
soakers. High pressure wedge from the e, locations up the me coast
down into northeast ma may end up being the precipitation losers.

End of the week...

series of frontal boundaries, slowing, stalling against the building
wall of atlantic high pressure. Have to watch closely strength of
synoptic features round the convergence boundary, whether there is
the possibility of prolonged outcomes over any one particular area.

Noteworthy is a sudden tick upward of precipitation within ensemble
members.

Aviation 03z Thursday through Monday
Forecaster confidence levels...

low - less than 30 percent.

Moderate - 30 to 60 percent.

High - greater than 60 percent.

Short term through Thursday night ... High confidence.

Overnight...

mainlyVFR. May see local MVFR at times along the immediate s
coast, CAPE cod and the islands in any -shra and patchy fog. Low
risk of brief ifr conditions across the islands mainly in cigs
after 06z or so. SW winds up to about 10 kt shifting to light nw
after 08z or so.

Thursday...

vfr. Lingering s-coastal island -shra with MVFR cigs, a brief
threat of ifr CIGS for ack around 12-18z. Improvement during the
afternoon hours, CIGS lifting 4-7 kft agl, as spot -shra develops
across interior S new england around orh. N winds turning ne.

Thursday night...

vfr to start but with northeast flow believe low levels will
saturate dropping CIGS and vsbys to MVFR conditions.

Kbos terminal...

keep -shra S of the terminal overnight.VFR prevailing.

Kbdl terminal...

expect -shra to be immediately S of the terminal. Will go low
endVFR overnight however there is a risk of some MVFR possibly
sneaking in prior to morning.

Outlook Friday through Monday ... Moderate confidence.

Friday:VFR.

Friday night:VFR. Breezy. Slight chance shra.

Saturday through Saturday night: shra likely, chance tsra.

Sunday through Sunday night: breezy. Chance shra, slight chance
tsra.

Monday: breezy. Chance shra.

Marine
Forecaster confidence levels...

low - less than 30 percent.

Moderate - 30 to 60 percent.

High - greater than 60 percent.

Short term through Thursday night ... High confidence.

Passing low pressure system across the southern waters will
bring scattered showers which could briefly reduce visibility.

Seas could build to 3 feet. May see brief gusts up to 20 kt
across the southern near shore waters through 06z tonight.

Otherwise, SW winds will shift to a more NE direction th
lasting into Thu night. Could see local vsby restrictions in
patchy fog. Conditions remain below sca.

Outlook Friday through Monday ... Moderate confidence.

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

Friday night: winds less than 25 kt. Areas of seas approaching
5 ft. Slight chance of rain showers.

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

Chance of rain showers, slight chance of thunderstorms.

Saturday night: winds less than 25 kt. Seas locally approaching
5 ft. Rain showers likely, chance of thunderstorms.

Sunday: winds less than 25 kt. Local rough seas. Chance of rain
showers.

Sunday night: winds less than 25 kt. Local rough seas. Chance
of rain showers, slight chance of thunderstorms.

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

Chance of rain showers.

Box watches warnings advisories
Ct... None.

Ma... None.

Ri... None.

Marine... None.

Synopsis... Dunten
near term... Sipprell evt
short term... Dunten
long term... Sipprell
aviation... Dunten sipprell evt
marine... Dunten sipprell evt


Weather Reporting Stations
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Airport Reports
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AirportDistAgeWind ktVisibilitySky/WeatherTempDewPtHumidityPressure
Nantucket, Nantucket Memorial Airport, MA168 mi73 minWSW 510.00 miOvercast62°F60°F93%1008.1 hPa

Wind History from ACK (wind in knots)
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Last 24hrCalmCalmCalmSW5SW6SW6SW8S5S7S9S10S11S12S11S9S6S4S4SW6SW6SW6SW7SW5SW6
1 day agoSW14SW12W10W10W8N13N13N14N11
G19
N13N10N9N94SW4SW6W5CalmSW3CalmSW34CalmNW3
2 days agoSW7SW7SW9SW10SW11SW11SW9SW14
G19
SW12SW10SW12SW14SW13SW16S15SW13SW17SW15SW16
G23
SW14SW14SW14SW15SW14

Tide / Current Tables for
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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 (4,6,7,8)
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Ground Weather Radar Station Upton, NY
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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.