flood related hazards high impact/long duration … · boston, ma weather forecast ... very low...

Boston, MA Weather Forecast Office Presentation Created

3/1/2018 8:22 AM Follow us on Twitter Follow us on Facebook

Flood Related Hazards

Wind Related Hazards

Severe Weather Related Hazards

National Weather Service

Thursday, March 01, 2018 8:21 AM

What Has Changed?

Hurricane Force Wind Gusts likely

across Cape/Islands. Property

damage and numerous power

outages possible.

Hurricane Force Wind Watches

across the southeast New England

waters.

Winter Storm Watch Issued for the

east slopes of the Berkshires and

Worcester Hills.

High Impact/Long Duration Coastal

Storm Friday Into Saturday

Hazards

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Main Points Hazard Impacts Location Timing

Coastal

Flooding

Significant flooding of shore

roads/severe beach erosion. Major

coastal flooding possible, which may

result in some property damage &

flood areas that are not usually

impacted.

Eastern MA coast including

Nantucket.

Late Friday morning,

Friday night and

Saturday high tide

cycles.

Marine 25 to 35 foot seas across the eastern

waters possible with NEwind gusts of

55 to 65 knots.

All Coastal Waters with

strongest wind gusts. Friday into Saturday.

Strong Winds

Tree damage/scattered power

outages possible. Strongest

Cape/Islands with possible property

damage + numerous power outages.

Eastern MA and RI and

especially Cape/Islands. Friday into Saturday

Heavy Rain/

Fresh Water

Flooding

Heavy Rain with urban/poor drainage

street flooding threat. A few

rivers/small streams may approach or

exceed flood stage.

Eastern MA/RI.

Heavy rain threat Friday

but some river flooding

possible into the

weekend.

Rain changing

To Wet Snow

Rain changes to wet snow in some

locations. Very low confidence on

snow accumulations, but power

outages possible if higher amts occur.

Greatest Risk Interior high

terrain, but can not be ruled

out across other locations.

Mainly Friday afternoon

into Friday night.







None Limited Elevated Significant Extreme





Summary of Greatest Impacts Coastal Flooding/Beach Erosion: Eastern MA

Wind Damage: Highest Risk Eastern MA/RI

Fresh Water Flooding: Highest Risk Eastern MA/RI

Wet Snow - Low Confidence: Greatest Risk High Terrain

Marine: All southern New England Waters







Timing

• Several tide cycles will be impacted. Especially

Friday mid day into Saturday mid-day.

Minor Coastal Flooding

• Partial inundation within the flood zone, especially for low-lying

areas.

• Vulnerable shore roads with up to a foot of water inundation

possible. May be flooding of a few vulnerable basements.

• Some beach erosion with heavy surf.

Timing

• Some impacts possible late tonight, but most likely Wednesday

peaking Wednesday morning

Moderate to Major Coastal Flooding

• Inundation within the flood zone. Vulnerable shore roads inundated at least a foot

of water up to 3 feet. Road closures. Vulnerable basements flooded as well.

• Beach erosion with heavy surf. A few sections of near-shore escape roads

weakened or washed out, especially in historically vulnerable low spots.

• Storm surge breaching dunes and possibly seawalls in scattered locations to result

in damage to shoreline buildings, mainly in historically vulnerable spots.

• Moderate damage to marinas, docks, and piers. Several small craft broken away

from moorings (especially unprotected areas).

• Shoreline road washouts are possible due to the combination of storm surge and

large breaking waves.

High Impact (5-7 ft Depth)

• Large areas of deep inundation in the flood zone.

• Severe beach erosion. Several sections of near-shore roads washed out.

• Low-lying escape routes severely flooded.

• Breaching of dunes and possibly seawalls in scattered locations.

• Structural damage to shoreline buildings, with a few washing into the sea.

• Moderate to major damage to marinas, docks, and piers. Many small craft broken away from moorings and lifted onshore and stranded.

Extreme/Catastrophic Impact (7ft+ Depth)

• Widespread deep inundation within flood zone.

• Water possibly reaching several miles inland.

• Extreme beach erosion. Several new cuts. Many large sections of near-shore roads washed out.

• Low-lying escape routes severely flooded.

• Surge breaching dunes and possibly seawalls in widespread locations.

• Structural damage to shoreline buildings, several washing into the sea.

• Extensive damage to marinas, docks, and piers.

• Numerous small craft broken away from moorings, lifted onshore and stranded.

Low Impact (1-3 ft Depth)

• Partial inundation within the flood zone, especially for low-lying areas.

• Moderate to locally major beach erosion.

• Very heavy surf breaching dunes in isolated locations, mainly in historically vulnerable spots.

Moderate Impact (3-5 ft Depth)

• Partial inundation within the flood zone.

• Major beach erosion. A few sections of near-shore escape roads weakened or washed out, especially in historically vulnerable low spots.

• Storm surge breaching dunes and possibly seawalls in scattered locations to result in damage to shoreline buildings, mainly in historically vulnerable spots.

• Moderate damage to marinas, docks, and piers. Several small craft broken away from moorings (especially unprotected areas).

Minor Coastal Flooding

• Vulnerable shore roads flooded with up to a foot of

water.

• Most roads remain passable but some may be

closed briefly around high tide.

• Some basements may flood.

• Beach erosion possible due to rough surf.

Moderate to Major Coastal Flooding

• Shore roads flooded with up to 3 feet of water.

• Many shore roads impassable and closed around

high tide. Some may be washed out due to storm

surge and large breaking waves.

• Large debris washed ashore, including on shore

roads.

• Many basements flooded.

• Severe beach erosion. Dunes breached.

• Sea walls may be damaged.

• Damage possible to shoreline buildings, mainly in

historically vulnerable spots.

• Damage to marinas, docks, and piers. Smaller

craft may break away from moorings, especially in

unprotected areas.

Providence

495

95

95

195

3 to 4 Foot Surge Expected

Nantucket

Plymouth

Boston

Moderate to Major

Moderate to Major

Coastal Flooding – Surge / Inundation

Minor

Moderate

Major

Extreme







Forecast Maximum Wave Heights

Definitions Storm Surge Marine

None No coastal flood risk No marine hazard risk

Limited

< 1 foot of inundation

Localized vulnerable

shoreline roads &

property will briefly flood

Winds 15 to 24 knots

and/or

Waves ≥ 2 feet

Elevated

1-2 feet of inundation

Few shoreline roads &

property will flood

Low threat of

property damage


and/or

Waves ≥ 5 feet

Significant


Several shoreline roads

& property will flood

Risk to life; elevated

threat of property

damage


and/or

Waves ≥ 10 feet

Extreme


Many shoreline roads &

property will be damaged

Coastal community

flooding

Evacuations necessary

Winds ≥ 48 knots

and/or

Waves ≥ 20 feet

Impacts Storm Surge Marine

None None None

Limited

Inundated shore roads

Basement flooding,

Minor beach erosion

Difficult boating

conditions for small

boats

Elevated

Isolated road closures,

Scattered homes and

businesses flooded,

Moderate beach erosion

Low risk of rough seas,

Rough boating

conditions

Significant

Scattered road closures,

Numerous homes and

businesses flooded,

Major beach erosion

Medium risk of rough

seas, Hazardous boating

conditions

Extreme

Numerous road closures,

Widespread homes and

businesses flooded,

Extensive beach erosion

High risk of rough seas,

Dangerous, life-

threatening boating

conditions

Mariners

• Northeast wind gusts 65 to 75

mph (55 to 65 kts).

• Long duration of duration of

very strong winds Friday into

Saturday. Strongest winds

Friday afternoon and night.

• Hurricane force wind gusts

coupled with 25 to 35 foot seas

will result in a life threatening

situation for Mariners. Mariners

are urged tor return to port by

this evening.







Forecast Maximum Wind Gusts

Hurricane Force Wind Gusts may result in property damage and numerous power outages.







Forecast Storm Total Precipitation

Greatest Risk For Some Urban Flooding Along With A Few Rivers And Streams.







Forecast Storm Total Snowfall

These Specific Snow Accumulations Are Quite Uncertain. Please see best/worst case scenarios for a better idea of possible outcomes and impacts.







Forecast Storm Total Snowfall (Worst Case)

WORST CASE: Low probability but very high impact. Rain changes to heavy Wet snow. 6-12+ Inches falls resulting in power outages.







Forecast Storm Total Snowfall (Best Case)

BEST CASE: Precipitation remains all rain with just a very small snow accumulation in the high terrain with little impact.







Threat Event Summary

Confidence: High confidence in moderate to major coastal flooding along the

eastern MA coast. High confidence in damaging wind gusts across eastern

MA/RI and especially Cape/Islands. Very low confidence in wet snow

accumulations with a wide variety of possible outcomes and impacts.

What:

Where: All of Southern New England. Greatest concern Eastern MA.

When: Friday into Friday night but strong winds continue into Saturday.

Significant coastal flooding,

beach erosion across eastern

MA coast.

Heavy Rain may result in

urban/street flooding and a

few rivers may go into flood

across eastern MA/RI.

Damaging wind gusts eastern

MA/RI. Hurricane force wind

gusts Cape/Islands w/numerous

power outages possible.

Rain may eventually change to

wet snow in some locations.

Greatest risk high terrain+SE MA.

Snow accums highly uncertain.





flood related hazards high impact/long duration … · boston, ma weather forecast ... very low...

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