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TROPICAL STORM ISAIAS BRIEFING 7:00 AM ET Monday, August 3, 2020 Prepared by: WFO New York/New York

Next Briefing: Monday Aug 3, 600 pm EDT Disclaimer: The information contained within is time-sensitive. Do not use after 5:00pm EDT Monday.

@NWSNewYorkNY www.weather.gov/nyc Situation Overview New York, NY Tropical Storm Isaias WEATHER FORECAST OFFICE

Hazard Impacts Location Timing

Flooding Rain Urban, poor drainage, creek/small stream Flash Entire Tri-State Late Tonight into Tuesday 2-4”, locally 4-6” Flooding threat likely Highest threat across NE NJ Night Watch Rises on larger stem rivers possible and the Lower Hudson Valley

Strong Winds Downed trees and tree limbs, with power Entire Tri-State Tuesday Afternoon and Tropical Storm outages possible Highest winds across the coast Tuesday Night Watch/Warning Minor damage to roof and siding possible

Coastal/Shoreline Dune Erosion and Localized Washovers Likely Vulnerable Tri-State shoreline, Inundation Tuesday Evening into Moderate Coastal Flood Impacts Likely coastal, and tidally influenced Coastal Flood Tuesday Night 1 to 2 ft AGL, locally 2 to 3 ft AGL riverine areas Watch

Marine Ocean Waters, LI Sound, Dangerous marine conditions expected across Tonight into Wednesday Tropical Storm nearshore bays, and NY the coastal waters Morning Warning Harbor

High Surf/ Dangerous Dangerous Surf Conditions for anyone entering Ocean Beaches Today through Wednesday Rip Currents the water Expected

8/3/2020 7:18 AM www.weather.gov/nyc Threat Levels New York, NY Tropical Storm Isaias WEATHER FORECAST OFFICE

For information on specific hazards in this area, please go to https://www.weather. gov/srh/tropical?office

=okx Increasing Threat Increasing

Wind Surge Rainfall/ River Tornadoes Marine Flash Flooding Flooding 8/3/2020 7:18 AM www.weather.gov/nyc Situation Overview New York, NY Tropical Storm Isaias WEATHER FORECAST OFFICE . What has Changed? . A Tropical is now in effect for coastal counties . A Tropical Storm Watch in effect for inland counties . Coastal Flood Watch is now in effect for Lower New York Harbor and south shore back bays of western Long Island . Isaias is a 70 mph Tropical Storm, east of Florida/Georgia Border as of 5 AM . It is expected to regain hurricane strength before reaching the Carolina coast tonight. Isaias will then slowly weaken as it accelerates and curves NE over the Carolinas Tuesday AM and then over the area Tuesday afternoon and evening. . Keep in mind, there is still some timing and NOTE: Do not focus on the exact track. Impacts can occur well outside the area intensity uncertainty, but confidence is increasing enclosed by the cone. on magnitude of local hazards and impacts.

8/3/2020 7:18 AM www.weather.gov/nyc Tropical Storm Watch and Warnings New York, NY Tropical Storm Isaias WEATHER FORECAST OFFICE

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8/3/2020 7:18 AM www.weather.gov/nyc Expected Storm Total Rainfall New York, NY Tropical Storm Isaias WEATHER FORECAST OFFICE

Note: There will likely be locally higher amounts . What’s Changed? . Watch in Effect Tuesday into Tuesday Night . Likely Hazards: . Storm Total Rainfall Forecast: 3-6”, except 1 to 3 inches for Eastern LI and SE CT. . Timing- . Potential for narrow bands of heavy rain to precede Isaias, bringing a localized flash flood threat starting Late Monday into Monday Night . Heaviest rain, and most widespread flood threat will likely be in a 6-8 hr period Tuesday Afternoon Into Tuesday Night (12pm-2am) . Likely Impacts: . Urban, poor drainage, creek and small stream Flash Flooding threat. . Significant rises on larger stem rivers possible.

8/3/2020 7:18 AM www.weather.gov/nyc into Tuesday Night New York, NY Tropical Storm Isaias WEATHER FORECAST OFFICE

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8/3/2020 7:18 AM www.weather.gov/nyc TS Wind Speed Probabilities New York, NY Tropical Storm Isaias WEATHER FORECAST OFFICE

Whats Changed? - The probability of seeing sustained tropical storm force winds is increasing.

Potential Hazards • 60-70% chance of sustained Tropical Storm Force winds (40-50g70 mph) at a location along the Coast. • 50 to 60% chance of sustained Tropical Storm Force winds (40g50 mph) at a locations across the Interior.

Potential Impacts • Downed trees and tree limbs, with power outages possible • Minor damage to roof and siding possible

Uncertainty/Scenario • Strongest winds and greatest potential to see the above impacts will be along the coast and for areas on the east side of the storm

8/3/2020 7:18 AM www.weather.gov/nyc Earliest Reasonable Time of Arrival New York, NY Tropical Storm Isaias WEATHER FORECAST OFFICE

. The earliest reasonable time of arrival of Tropical Storm Force Winds is Late morning/early afternoon Tuesday

. Preparedness actions for high risk groups and assets should be made by this time.

8/3/2020 7:18 AM www.weather.gov/nyc Most Likely Time of Arrival New York, NY Tropical Storm Isaias WEATHER FORECAST OFFICE

. The most likely time of arrival of Tropical Storm Force Winds is Late Tuesday Afternon/Tuesday Evening.

. All preparedness actions should be completed by this time!

8/3/2020 7:18 AM www.weather.gov/nyc Coastal Flood Watch Tuesday Night New York, NY Tropical Storm Isaias WEATHER FORECAST OFFICE

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8/3/2020 7:18 AM www.weather.gov/nyc Potential New York, NY Tropical Storm Isaias WEATHER FORECAST OFFICE Reasonable Worst Case Storm Surge Inundation Scenario. • Areas of Moderate impacts are likely. – 2 to locally 3 ft inundation – NY/NJ Harbor, Jamaica Bay, South shore of LI (Bay and barrier island), Southern CT coast • Low and localized potential for Life threatening coastal flooding (Along South Shore Bay of Nassau and Queens. – 3+ft inundation

Timing - Tuesday Night High Tide • LI Sound – 11pm – 1am • South - 9pm – midnight

Uncertainty- • Will surge coincide with high tide? • Heavy rain will exacerbate flash flood threat

8/3/2020 7:18 AM www.weather.gov/nyc Potential Storm Surge Inundation New York, NY Tropical Storm Isaias WEATHER FORECAST OFFICE

Potential Storm Surge Inundation Areas - Shaded in Blue. • Inundation of 1 to 2 ft above ground level possible.

Low lying areas, that are not showing explicit inundation – Shaded in Green.

Areas circled in red have a moderate potential for 1 to 2 ft of inundation above ground level, with a low probability of 3 ft of inundation above ground level.

8/3/2020 7:18 AM www.weather.gov/nyc Potential Storm Surge Inundation New York, NY Tropical Storm Isaias WEATHER FORECAST OFFICE Potential Storm Surge Inundation Areas - Shaded in Blue. • Inundation of 1 to 2 ft above ground level possible.

Low lying areas, that are not showing explicit inundation – Shaded in Green. Area circled in red have a moderate potential for 1 to 2 ft of inundation above ground level, with a low probability of 3 ft of inundation above ground level.

8/3/2020 7:18 AM www.weather.gov/nyc Potential Storm Surge New York, NY Tropical Storm Isaias WEATHER FORECAST OFFICE

Potential Storm Surge Inundation Areas - Shaded in Blue. • Inundation of 1 to 2 ft above ground level possible.

Low lying areas, that are not showing explicit inundation – Shaded in Yellow.

8/3/2020 7:18 AM www.weather.gov/nyc Potential Storm Surge New York, NY Tropical Storm Isaias WEATHER FORECAST OFFICE

Potential Storm Surge Inundation Areas - Shaded in Blue. • Inundation of 1 to 2 ft above ground level possible.

Low lying areas, that are not showing explicit inundation – Shaded in Yellow.

8/3/2020 7:18 AM www.weather.gov/nyc High Surf and Dangerous Rip Current New York, NY Tropical Storm Isaias WEATHER FORECAST OFFICE • High Surf – 10-15 ft breaking surf possible Tuesday afternoon into evening – Areas of dune erosion and localized washovers are likely for the ocean beachfront during the Tuesday Morning and particularly Tuesday Night high tides.

• High Risk of Rip Currents through Wednesday. – Worst conditions on Tuesday.

• Marine – Tropical storm conditions becoming likely – Peak Wind Potential – 40-50g55-64kt • 13-19 ft seas ocean • 4-8 ft LI Sound

8/3/2020 7:18 AM www.weather.gov/nyc Key Take-Aways New York, NY Tropical Storm Isaias WEATHER FORECAST OFFICE Confidence is HIGH that the event will occur Confidence is MODERATE regarding track, intensity and impacts Impacts may extend into early Wednesday morning

60-70% chance of seeing Tropical Storm Force sustained winds for a point, highest for city and coast. Could see tropical storm force winds as early as Tuesday morning, but likely Tuesday afternoon.

Heavy rainfall and Flash Flood potential Late Tonight into Tuesday Night. Flood Watch in effect for NYC, NE NJ, Lower Hudson Valley and southwestern CT.

Moderate Coastal Flood and Shoreline impacts likely Tuesday into Tuesday Night

High Surf Tuesday into Tuesday Night. Dangerous Rip Currents thru Wed.

Dangerous marine conditions are likely across the coastal waters Tuesday

8/3/2020 7:18 AM www.weather.gov/nyc The Next Briefing: Monday 6:00 PM EDT Method: Powerpoint

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