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Tropical Storm Isaias Update Statement

2020-08-04 17:57:15| National Hurricane Center (Atlantic)

Issued at 1200 PM EDT Tue Aug 4 2020 000 WTNT64 KNHC 041557 TCUAT4 Tropical Storm Isaias Tropical Cyclone Update NWS National Hurricane Center Miami FL AL092020 1200 PM EDT Tue Aug 4 2020 ...1200 PM EDT POSITION UPDATE... ...STRONG WINDS...HEAVY RAINFALL...AND TORNADOES OCCURRING OVER SOUTHERN NEW JERSEY AND SOUTHEASTERN PENNSYLVANIA WILL CONTINUE TO SPREAD NORTHWARD ALONG THE MID-ATLANTIC COAST THIS AFTERNOON... A Weatherflow weather station at Long Beach Island Surf, New Jersey, recently reported a sustained wind of 46 mph (74 km/h) and a gust to 59 mph (94 km/h). Around 1053 AM EDT, this same weather observing station measured a wind gust of 109 mph (176 km/h), which was associated with a tornadic thunderstorm. Doppler weather radar data from Ft. Dix, New Jersey, indicated Doppler velocities as high as 112 mph (180 km/h) at an altitude of 1,590 above ground level at this same location. However, this wind is not considered to be representative of Isaias' larger wind field. Also, a Weatherflow observing site located at Rutgers/Little Egg Harbor, New Jersey, recently reported a sustained wind of 52 mph (84 km/h) and a gust to 70 mph (113 km/h). SUMMARY OF 1200 PM EDT...1600 UTC...INFORMATION ----------------------------------------------- LOCATION...39.6N 75.8W ABOUT 10 MI...20 KM WSW OF WILMINGTON DELAWARE ABOUT 35 MI...55 KM WSW OF PHILADELPHIA PENNSYLVANIA MAXIMUM SUSTAINED WINDS...70 MPH...110 KM/H PRESENT MOVEMENT...NNE OR 25 DEGREES AT 35 MPH...56 KM/H MINIMUM CENTRAL PRESSURE...993 MB...29.32 INCHES $$ Forecaster Stewart/Roberts

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Tropical Storm Isaias Probabilistic Storm Surge Graphics

2020-08-04 17:13:46| National Hurricane Center (Atlantic)

Probabilistic Storm Surge Graphics last updated Tue, 04 Aug 2020 15:13:46 GMT

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Tropical Storm Isaias Forecast Discussion Number 30

2020-08-04 16:59:12| National Hurricane Center (Atlantic)

Issued at 1100 AM EDT Tue Aug 04 2020 000 WTNT44 KNHC 041459 TCDAT4 Tropical Storm Isaias Discussion Number 30 NWS National Hurricane Center Miami FL AL092020 1100 AM EDT Tue Aug 04 2020 Doppler radar data from Dover, Delaware (KDOX), and Ft. Dix, New Jersey (KDIX) this morning continue to indicate 70-80 kt winds between 4000-7000 ft over the ocean just offshore the Delmarva peninsula and the southeastern coast of New Jersey, which would normally correspond to 65-70 kt surface winds. However, these velocity values have been collocated with only 15-25 dBZ reflectivity echoes, so the typical 80-85 percent reduction factors likely don't apply. Sustained observed surface winds of 50-55 kt have been reported, so the initial intensity will be held at 60 kt, but that is only for winds over the ocean and near the coast. Isaias is moving north-northeastward or 020/30 kt. The cyclone will continue to accelerate north-northeastward today and tonight within strong southwesterly flow ahead of a deep-layer trough and associated cold front approaching the mid-Atlantic and New England areas from the west. By 24 h, the Isaias is expected to slow down and degenerate into a post-tropical cyclone over Maine before it is absorbed by a larger extratropical low located over southeastern Canada. The new NHC track forecast is just an extension of the previous advisory, and lies very close to the tightly clustered consensus track models. As Isaias moves north-northeastward through the Mid-Atlantic coast, interaction with a strong upper-level jet maximum is forecast to maintain the tropical storm's intensity longer than what typically would be expected for inland decaying tropical cyclone. The global models continue to indicate that Isaias is likely to produce widespread tropical-storm conditions, with hurricane-force wind gusts possible along the mid-Atlantic coast through this afternoon. As a result, the gust factor at 12 h remains above the standard 20-percent value in the Forecast/Advisory Product (TCMAT4). In addition to the wind threat, Isaias is expected to produce heavy rainfall along and just west of the I-95 corridor today, and the Weather Prediction Center has placed a portion of this area in a high risk for life-threatening flash flooding. There also remains a significant risk of tornadoes across the mid-Atlantic coast and southeastern New York this afternoon, possibly spreading into southern New England tonight. Key Messages: 1. Widespread sustained tropical storm force winds and gusts to hurricane force are expected along the mid-Atlantic coast, including portions of the Chesapeake Bay region, through this afternoon, which could cause tree damage and power outages. Tropical storm conditions are expected to spread across New England tonight. 2. Heavy rainfall along the East Coast, near the path of Isaias, will result in flash flooding, some of which may be significant in the mid-Atlantic and Northeast through tonight. Potentially life-threatening urban flooding remains possible in Philadelphia and elsewhere along and just west of the I-95 corridor today. Scattered minor to moderate river flooding is likely across portions of the and the Mid-Atlantic. Quick-responding rivers in Northeast will also be susceptible to minor river flooding. 3. Numerous tornadoes have already occurred over portions of the mid-Atlantic coast this morning. The threat of tornadoes will continue along the mid-Atlantic coast spread into New England this afternoon. FORECAST POSITIONS AND MAX WINDS INIT 04/1500Z 39.1N 76.1W 60 KT 70 MPH...INLAND 12H 05/0000Z 43.2N 73.8W 50 KT 60 MPH...INLAND 24H 05/1200Z 48.2N 71.7W 35 KT 40 MPH...POST-TROP/INLAND 36H 06/0000Z 52.0N 71.1W 30 KT 35 MPH...POST-TROP/EXTRATROP 48H 06/1200Z 53.6N 69.5W 20 KT 25 MPH...POST-TROP/EXTRATROP 60H 07/0000Z...DISSIPATED INLAND $$ Forecaster Stewart

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Tropical Storm Isaias Public Advisory Number 30

2020-08-04 16:52:12| National Hurricane Center (Atlantic)

Issued at 1100 AM EDT Tue Aug 04 2020 000 WTNT34 KNHC 041451 CCA TCPAT4 BULLETIN Tropical Storm Isaias Advisory Number 30...Corrected NWS National Hurricane Center Miami FL AL092020 1100 AM EDT Tue Aug 04 2020 Corrected reference location to Fredericktown, Maryland ...CENTER OF ISAIAS MOVING RAPIDLY ACROSS EASTERN MARYLAND... ...STRONG WINDS...HEAVY RAINFALL...AND TORNADOES WILL CONTINUE TO SPREAD NORTH-NORTHEASTWARD ALONG THE MID-ATLANTIC COAST TODAY... SUMMARY OF 1100 AM EDT...1500 UTC...INFORMATION ----------------------------------------------- LOCATION...39.1N 76.1W ABOUT 20 MI...30 KM SSW OF FREDERICKTOWN MARYLAND ABOUT 70 MI...110 KM SW OF PHILADELPHIA PENNSYLVANIA MAXIMUM SUSTAINED WINDS...70 MPH...110 KM/H PRESENT MOVEMENT...NNE OR 20 DEGREES AT 35 MPH...56 KM/H MINIMUM CENTRAL PRESSURE...993 MB...29.33 INCHES WATCHES AND WARNINGS -------------------- CHANGES WITH THIS ADVISORY: The Tropical Storm Warning has been discontinued south of Duck, North Carolina, including the Pamlico and Albemarle Sounds. The Storm Surge Warning has been discontinued. SUMMARY OF WATCHES AND WARNINGS IN EFFECT: A Tropical Storm Warning is in effect for... * North of Duck North Carolina to Eastport Maine * Chesapeake Bay * Tidal Potomac River * Delaware Bay * Long Island and Long Island Sound * Martha's Vineyard, Nantucket, and Block Island A Tropical Storm Warning means that tropical storm conditions are expected somewhere within the warning area, in this case within the next 12 to 18 hours. For storm information specific to your area, including possible inland watches and warnings, please monitor products issued by your local National Weather Service forecast office. DISCUSSION AND OUTLOOK ---------------------- At 1100 AM EDT (1500 UTC), the center of Tropical Storm Isaias was located by NOAA Doppler weather radars and surface observations near latitude 39.1 North, longitude 76.1 West. Isaias is moving toward the north-northeast near 35 mph (56 km/h), and this general motion accompanied by some increase in forward speed is expected through tonight. On the forecast track, the center of Isaias will continue to move near or along the coast of the mid-Atlantic states today, and move across the northeastern United States into southern Canada tonight. Data from Doppler weather radars along with surface observations indicate that maximum sustained winds remain near 70 mph (110 km/h) with higher gusts. Only gradual weakening is anticipated while Isaias moves north-northeastward near the mid-Atlantic coast today. A faster rate of weakening is expected to begin tonight, and the system is forecast to become post-tropical tonight or early Wednesday. Tropical-storm-force winds extend outward up to 140 miles (220 km) from the center. During the past hour, a sustained wind of 55 mph (89 km/h) and a gust to 65 mph (105 km/h) were reported by a Weatherflow site at Ocean City, Maryland. A sustained wind of 45 mph (72 km/h) and a gust to 57 mph (92 km/h) were reported at Ocean City-South Beach, New Jersey. The estimated minimum central pressure based on surface observations is 993 mb (29.33 inches). HAZARDS AFFECTING LAND ---------------------- Key messages for Isaias can be found in the Tropical Cyclone Discussion under AWIPS header MIATCDAT4, WMO header WTNT44 KNHC, and on the web at www.hurricanes.gov/text/MIATCDAT4.shtml. STORM SURGE: The combination of storm surge and the tide will cause normally dry areas near the coast to be flooded by rising waters moving inland from the shoreline. The water could reach the following heights above ground somewhere in the indicated areas if the peak surge occurs at the time of high tide... Ocracoke Inlet NC to the North Carolina/Virginia border including Pamlico Sound, Albemarle Sound, Pamlico and Neuse Rivers...1-2 ft North of the North Carolina/Virginia border to Martha's Vineyard including the Chesapeake Bay, the Tidal Potomac River, Delaware Bay, Long Island Sound, Block Island Sound, Narragansett Bay, Buzzards Bay, and Vineyard Sound...1-3 ft The deepest water will occur along the immediate coast in areas of onshore winds, where the surge will be accompanied by large waves. Surge-related flooding depends on the relative timing of the surge and the tidal cycle, and can vary greatly over short distances. For information specific to your area, please see products issued by your local National Weather Service forecast office. WIND: Widespread tropical-storm conditions are expected in the tropical storm warning area in the mid-Atlantic states, including portions of the Chesapeake Bay region today, with wind gusts to hurricane force possible. These winds could cause significant tree damage and power outages. Tropical storm conditions are expected to reach southern New England this afternoon and northern New England tonight. Gale-force winds are expected to spread into southeastern Quebec tonight and Wednesday. See products issued by Environment Canada for more information. RAINFALL: The following rainfall accumulations are expected along and near the track of Isaias: Central and Northern Mid-Atlantic: Additional 2 to 4 inches, isolated maximum storm totals of 8 inches. Eastern New York into Vermont: 2 to 4 inches, isolated maximum totals 6 inches. Western Connecticut, western Massachusetts, New Hampshire and western Maine: 1 to 3 inches. Heavy rainfall along the East Coast, near the path of Isaias, will result in flash and urban flooding, some of which may be significant in the mid-Atlantic and Northeast through tonight. Potentially life-threatening urban flooding remains possible Philadelphia, and elsewhere along and just west of the I-95 corridor today. Scattered minor to moderate river flooding is likely across portions of the Mid-Atlantic. Quick-responding rivers in the Northeast will also be susceptible to minor river flooding. TORNADOES: A few tornadoes are possible across northern New Jersey and southeastern New York, through southern New England, by late afternoon. A risk for tornadoes may continue across northern New England through this evening. SURF: Swells generated by Isaias will spread northward along the mid-Atlantic and Northeast coasts of the United States today. These swells are likely to cause life-threatening surf and rip current conditions. Please consult products from your local weather office. NEXT ADVISORY ------------- Next intermediate advisory at 200 PM EDT. Next complete advisory at 500 PM EDT. $$ Forecaster Stewart

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