Hurricane Isaias
LOCATED
40 MI WSW OF NASSAU
WINDS
80 MPH
PRESSURE
987 MB
MOVING
NW AT 12 MPH
From the National Hurricane Center at 1100 AM EDT Sat Aug 01 2020
ISAIAS MAKING LANDFALL ON NORTHERN ANDROS ISLAND
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key messages
Alerts
hazards
summary
DISCUSSION

1. Hurricane conditions and dangerous storm surge will continue in portions of the northwest Bahamas today and tonight.

2. Hurricane conditions are expected along portions of the Florida east coast by late tonight and Sunday. Preparations to protect life and property should be rushed to completion.

3. Dangerous storm surge is possible along the Florida east coast from Jupiter Inlet to Ponte Vedra Beach where water rises of 2 to 4 feet above ground level are possible along the immediate coastline and adjacent waterways. Residents there should follow advice given by local emergency officials.

4. Isaias will produce heavy rains and potentially life-threatening flash flooding in the Bahamas, and flash urban flooding, especially in low-lying and poorly drained areas, in eastern Florida, and from the Carolinas to the mid-Atlantic and Northeast U.S. Minor river flooding is possible across portions of the Carolinas and Virginia early next week.

5. Tropical storm watches and warnings are in effect for portions of the northeast Florida and southern Georgia coasts. Additional watches and warnings will likely be issued later today and Sunday along the U.S. east coast as the risk of wind, heavy rainfall, and storm surge impacts continues to increase.

1. Hurricane conditions and dangerous storm surge will continue in portions of the northwest Bahamas today and tonight.

2. Hurricane conditions are expected along portions of the Florida east coast by late tonight and Sunday. Preparations to protect life and property should be rushed to completion.

3. Dangerous storm surge is possible along the Florida east coast from Jupiter Inlet to Ponte Vedra Beach where water rises of 2 to 4 feet above ground level are possible along the immediate coastline and adjacent waterways. Residents there should follow advice given by local emergency officials.

4. Isaias will produce heavy rains and potentially life-threatening flash flooding in the Bahamas, and flash urban flooding, especially in low-lying and poorly drained areas, in eastern Florida, and from the Carolinas to the mid-Atlantic and Northeast U.S. Minor river flooding is possible across portions of the Carolinas and Virginia early next week.

5. Tropical storm watches and warnings are in effect for portions of the northeast Florida and southern Georgia coasts. Additional watches and warnings will likely be issued later today and Sunday along the U.S. east coast as the risk of wind, heavy rainfall, and storm surge impacts continues to increase.

CHANGES WITH THIS ADVISORY:

The Tropical Storm Watch from the Volusia/Flagler County Line to Ponte Vedra Beach Florida has been changed to a Tropical Storm Warning.

A Tropical Storm Watch has been issued from north of Ponte Vedra Beach Florida to Altamaha Sound Georgia.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT:

A Hurricane Warning is in effect for...
- Boca Raton to the Volusia/Flagler County Line Florida
- Northwestern Bahamas

A Hurricane Watch is in effect for...
- Hallandale Beach to south of Boca Raton Florida

A Storm Surge Watch is in effect for...
- Jupiter Inlet to Ponte Vedra Beach Florida

A Tropical Storm Warning is in effect for...
- North of Ocean Reef to south of Boca Raton Florida
- Lake Okeechobee
- Volusia/Flagler County Line to Ponte Vedra Beach Florida

A Tropical Storm Watch is in effect for...
- North of Ponte Vedra Beach Florida to Altamaha Sound Georgia

Interests elsewhere along the southeast coast of the United States should monitor the progress of Isaias. Additional watches or warnings may be required later today.

A Hurricane Warning means that hurricane conditions are expected somewhere within the warning area. A warning is typically issued 36 hours before the anticipated first occurrence of tropicalstormforce winds, conditions that make outside preparations difficult or dangerous. Preparations to protect life and property should be rushed to completion.

A Hurricane Watch means that hurricane conditions are possible within the watch area. A watch is typically issued 48 hours before the anticipated first occurrence of tropicalstormforce winds, conditions that make outside preparations difficult or dangerous.

A Storm Surge Watch means there is a possibility of life threatening inundation, from rising water moving inland from the coastline, in the indicated locations during the next 48 hours. For a depiction of areas at risk, please see the National Weather Service Storm Surge Watch/Warning Graphic, available at hurricanes.gov.

A Tropical Storm Warning means that tropical storm conditions are expected somewhere within the warning area within 36 hours.

A Tropical Storm Watch means that tropical storm conditions are possible within the watch area, generally within 48 hours.

For storm information specific to your area in the United States, including possible inland watches and warnings, please monitor products issued by your local National Weather Service forecast office. For storm information specific to your area outside of the United States, please monitor products issued by your national meteorological service.

CHANGES WITH THIS ADVISORY:

The Tropical Storm Watch from the Volusia/Flagler County Line to Ponte Vedra Beach Florida has been changed to a Tropical Storm Warning.

A Tropical Storm Watch has been issued from north of Ponte Vedra Beach Florida to Altamaha Sound Georgia.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT:

A Hurricane Warning is in effect for...
- Boca Raton to the Volusia/Flagler County Line Florida
- Northwestern Bahamas

A Hurricane Watch is in effect for...
- Hallandale Beach to south of Boca Raton Florida

A Storm Surge Watch is in effect for...
- Jupiter Inlet to Ponte Vedra Beach Florida

A Tropical Storm Warning is in effect for...
- North of Ocean Reef to south of Boca Raton Florida
- Lake Okeechobee
- Volusia/Flagler County Line to Ponte Vedra Beach Florida

A Tropical Storm Watch is in effect for...
- North of Ponte Vedra Beach Florida to Altamaha Sound Georgia

Interests elsewhere along the southeast coast of the United States should monitor the progress of Isaias. Additional watches or warnings may be required later today.

A Hurricane Warning means that hurricane conditions are expected somewhere within the warning area. A warning is typically issued 36 hours before the anticipated first occurrence of tropicalstormforce winds, conditions that make outside preparations difficult or dangerous. Preparations to protect life and property should be rushed to completion.

A Hurricane Watch means that hurricane conditions are possible within the watch area. A watch is typically issued 48 hours before the anticipated first occurrence of tropicalstormforce winds, conditions that make outside preparations difficult or dangerous.

A Storm Surge Watch means there is a possibility of life threatening inundation, from rising water moving inland from the coastline, in the indicated locations during the next 48 hours. For a depiction of areas at risk, please see the National Weather Service Storm Surge Watch/Warning Graphic, available at hurricanes.gov.

A Tropical Storm Warning means that tropical storm conditions are expected somewhere within the warning area within 36 hours.

A Tropical Storm Watch means that tropical storm conditions are possible within the watch area, generally within 48 hours.

For storm information specific to your area in the United States, including possible inland watches and warnings, please monitor products issued by your local National Weather Service forecast office. For storm information specific to your area outside of the United States, please monitor products issued by your national meteorological service.

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 a dangerous 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...

Jupiter Inlet to Ponte Vedra Beach FL...24 ft North Miami Beach to Jupiter Inlet FL...13 ft

The deepest water will occur along the immediate coast near and to the right of the center, where the surge will be accompanied by large waves. Surgerelated 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.

A dangerous storm surge will raise water levels by as much as 3 to 5 feet above normal tide levels in areas of onshore winds in the Northwestern Bahamas.

WIND: Hurricane conditions will continue to spread over the Northwestern Bahamas through today.

Hurricane conditions are expected to reach the coast within the hurricane warning area in Florida tonight and will spread northward through Sunday. Winds are expected to first reach tropical storm strength later today, making outside preparations difficult or dangerous. Preparations to protect life and property should be rushed to completion. Tropical storm conditions are expected within the tropical storm warning area, and are possible within the watch area, over southern Florida by this afternoon or evening. Tropical storm conditions are expected in the warning area in northeast Florida by late Sunday, and are possible in the watch area in northeast Florida and southeast Georgia by Monday morning.

RAINFALL: Isaias is expected to produce the following rain accumulations:

Bahamas: 4 to 8 inches.

Cuba: 1 to 2 inches, with isolated maximum totals of 4 inches.

These rainfall amounts could lead to lifethreatening flash and urban flooding, especially in lowlying and poorly drained areas.

From Friday night through Tuesday:

South Florida into eastcentral Florida: 2 to 4 inches, with isolated maximum totals of 6 inches.

Northeast Florida into coastal Georgia: 1 to 2 inches.

Carolinas into the mid Atlantic, including the southern and central Appalachians: 2 to 4 inches, with isolated maximum totals of 6 inches.

Heavy rainfall from Isaias could result in potentially life threatening flash and urban flooding, especially in lowlying and poorly drained areas. Minor river flooding is possible across portions of the Carolinas and Virginia.

SURF: Swells generated by Isaias are affecting portions of Hispaniola, eastern Cuba, the Turks and Caicos, and the Bahamas. These swells will spread along the east coast of Florida and the southeastern United States coast today. These swells are likely to cause lifethreatening surf and rip current conditions. Please consult products from your local weather office.

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 a dangerous 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...

Jupiter Inlet to Ponte Vedra Beach FL...24 ft North Miami Beach to Jupiter Inlet FL...13 ft

The deepest water will occur along the immediate coast near and to the right of the center, where the surge will be accompanied by large waves. Surgerelated 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.

A dangerous storm surge will raise water levels by as much as 3 to 5 feet above normal tide levels in areas of onshore winds in the Northwestern Bahamas.

WIND: Hurricane conditions will continue to spread over the Northwestern Bahamas through today.

Hurricane conditions are expected to reach the coast within the hurricane warning area in Florida tonight and will spread northward through Sunday. Winds are expected to first reach tropical storm strength later today, making outside preparations difficult or dangerous. Preparations to protect life and property should be rushed to completion. Tropical storm conditions are expected within the tropical storm warning area, and are possible within the watch area, over southern Florida by this afternoon or evening. Tropical storm conditions are expected in the warning area in northeast Florida by late Sunday, and are possible in the watch area in northeast Florida and southeast Georgia by Monday morning.

RAINFALL: Isaias is expected to produce the following rain accumulations:

Bahamas: 4 to 8 inches.

Cuba: 1 to 2 inches, with isolated maximum totals of 4 inches.

These rainfall amounts could lead to lifethreatening flash and urban flooding, especially in lowlying and poorly drained areas.

From Friday night through Tuesday:

South Florida into eastcentral Florida: 2 to 4 inches, with isolated maximum totals of 6 inches.

Northeast Florida into coastal Georgia: 1 to 2 inches.

Carolinas into the mid Atlantic, including the southern and central Appalachians: 2 to 4 inches, with isolated maximum totals of 6 inches.

Heavy rainfall from Isaias could result in potentially life threatening flash and urban flooding, especially in lowlying and poorly drained areas. Minor river flooding is possible across portions of the Carolinas and Virginia.

SURF: Swells generated by Isaias are affecting portions of Hispaniola, eastern Cuba, the Turks and Caicos, and the Bahamas. These swells will spread along the east coast of Florida and the southeastern United States coast today. These swells are likely to cause lifethreatening surf and rip current conditions. Please consult products from your local weather office.

At 1100 AM EDT (1500 UTC), the center of Hurricane Isaias was located by an Air Force Reserve Hurricane Hunter aircraft and Bahamas radar near latitude 24.7 North, longitude 77.9 West. Isaias is moving toward the northwest near 12 mph (19 km/h). A general northwestward motion with some decrease in forward speed is expected for the next day or so, followed by a northnorthwestward motion by late Sunday. On the forecast track, the center of Isaias will move over northern Andros Island during the next few hours and move near or over Grand Bahama Island in the Northwestern Bahamas later today. Isaias is forecast to move near the east coast of the Florida peninsula tonight through Sunday.

Reports from the reconnaissance aircraft indicate that maximum sustained winds have decreased slightly to near 80 mph (130 km/h) with higher gusts. Little change in strength is expected through Sunday, and Isaias is forecast to remain a hurricane during this time. Slow weakening is expected to begin by late Monday.

Hurricaneforce winds extend outward up to 25 miles (35 km) from the center and tropicalstormforce winds extend outward up to 115 miles (185 km). Reports from a U.S. Navy site on Andros Island indicate that sustained winds of 45 mph (76 km/h) and a gust to 69 mph (111 km/h) occurred about 3 hours ago. More recently, a sustained wind of 35 mph (56 km/h) and a gust to 48 mph (77 km/h) were measured at Nassau, Bahamas.

The estimated minimum central pressure is 987 mb (29.15 inches).

At 1100 AM EDT (1500 UTC), the center of Hurricane Isaias was located by an Air Force Reserve Hurricane Hunter aircraft and Bahamas radar near latitude 24.7 North, longitude 77.9 West. Isaias is moving toward the northwest near 12 mph (19 km/h). A general northwestward motion with some decrease in forward speed is expected for the next day or so, followed by a northnorthwestward motion by late Sunday. On the forecast track, the center of Isaias will move over northern Andros Island during the next few hours and move near or over Grand Bahama Island in the Northwestern Bahamas later today. Isaias is forecast to move near the east coast of the Florida peninsula tonight through Sunday.

Reports from the reconnaissance aircraft indicate that maximum sustained winds have decreased slightly to near 80 mph (130 km/h) with higher gusts. Little change in strength is expected through Sunday, and Isaias is forecast to remain a hurricane during this time. Slow weakening is expected to begin by late Monday.

Hurricaneforce winds extend outward up to 25 miles (35 km) from the center and tropicalstormforce winds extend outward up to 115 miles (185 km). Reports from a U.S. Navy site on Andros Island indicate that sustained winds of 45 mph (76 km/h) and a gust to 69 mph (111 km/h) occurred about 3 hours ago. More recently, a sustained wind of 35 mph (56 km/h) and a gust to 48 mph (77 km/h) were measured at Nassau, Bahamas.

The estimated minimum central pressure is 987 mb (29.15 inches).

Data from an Air Force Reserve reconnaissance aircraft around 1410 UTC indicated that the center of the eye of Isaias was located along the southern coast of northern Andros Island about 15 nmi south-southwest of Andros Town. The eye appearance in Bahamas and aircraft radar data, along with the visual reports from the flight crew, has gone from nearly closed a few hours ago to open in the southwestern quadrant more recently. However, the diameter of the eye has been has been holding steady between 20-22 nmi, an indication that Isaias has been able to fight off some modest southwesterly wind shear. The initial intensity has been lowered to 70 kt based on maximum 700-mb flight-level winds of 77 kt, which equals about 70-kt surface wind speed, and the central pressure fluctuating between 987-990 mb.

The initial motion estimate remains 315/10 kt. The latest NHC model guidance is now tightly packed about the previous 18-h worth of official track forecasts, and as a result, no significant changes were made to the previous advisory track. The global and regional models have come into much better agreement compared to 24 hours ago in taking Isaias northwestward slowly for the next 36 h or so, and moving the center near or keeping it just offshore the east-central Florida coast. By 48 hours, the hurricane is expected to turn northward around the western portion of the Bermuda-Azores ridge that will slowly be eroded by an approaching mid-level shortwave trough currently situated over the central United States. By 60 h and beyond, the aforementioned trough is expected to gradually accelerate Isaias northeastward near or along the coast from South Carolina to New England. The new NHC track forecast is basically an extension of the previous one, and lies very close to an average of the simple consensus model TVCA, and the corrected- consensus models NOAA-HCCA and FSSE.

In the near term, Isaias could weaken a little bit this afternoon while passing over northern Andros Island. However, the still impressive vertical structure of the cyclone should allow for some re-strengthening after the center moves back over the warm Gulf Stream by this evening. The current SHIPS analyzed westerly vertical wind shear of 25 kt could be too high due to the model incorporating some of the storm's outflow. The models forecast the shear to weaken somewhat over the next 36 h while Isaias is moving over the Gulf Stream, and the 06Z UKMET shows Isaias moving underneath a 200-mb anticyclone, which would normally favor some strengthening. Given all of these factors, the official forecast maintains a steady intensity through Monday night. Slow weakening is forecast when Isais encounters more significant southwesterly vertical wind shear ahead of a strong upper-level trough that will be approaching the U.S. east coast on days 3-5.

Data from an Air Force Reserve reconnaissance aircraft around 1410 UTC indicated that the center of the eye of Isaias was located along the southern coast of northern Andros Island about 15 nmi south-southwest of Andros Town. The eye appearance in Bahamas and aircraft radar data, along with the visual reports from the flight crew, has gone from nearly closed a few hours ago to open in the southwestern quadrant more recently. However, the diameter of the eye has been has been holding steady between 20-22 nmi, an indication that Isaias has been able to fight off some modest southwesterly wind shear. The initial intensity has been lowered to 70 kt based on maximum 700-mb flight-level winds of 77 kt, which equals about 70-kt surface wind speed, and the central pressure fluctuating between 987-990 mb.

The initial motion estimate remains 315/10 kt. The latest NHC model guidance is now tightly packed about the previous 18-h worth of official track forecasts, and as a result, no significant changes were made to the previous advisory track. The global and regional models have come into much better agreement compared to 24 hours ago in taking Isaias northwestward slowly for the next 36 h or so, and moving the center near or keeping it just offshore the east-central Florida coast. By 48 hours, the hurricane is expected to turn northward around the western portion of the Bermuda-Azores ridge that will slowly be eroded by an approaching mid-level shortwave trough currently situated over the central United States. By 60 h and beyond, the aforementioned trough is expected to gradually accelerate Isaias northeastward near or along the coast from South Carolina to New England. The new NHC track forecast is basically an extension of the previous one, and lies very close to an average of the simple consensus model TVCA, and the corrected- consensus models NOAA-HCCA and FSSE.

In the near term, Isaias could weaken a little bit this afternoon while passing over northern Andros Island. However, the still impressive vertical structure of the cyclone should allow for some re-strengthening after the center moves back over the warm Gulf Stream by this evening. The current SHIPS analyzed westerly vertical wind shear of 25 kt could be too high due to the model incorporating some of the storm's outflow. The models forecast the shear to weaken somewhat over the next 36 h while Isaias is moving over the Gulf Stream, and the 06Z UKMET shows Isaias moving underneath a 200-mb anticyclone, which would normally favor some strengthening. Given all of these factors, the official forecast maintains a steady intensity through Monday night. Slow weakening is forecast when Isais encounters more significant southwesterly vertical wind shear ahead of a strong upper-level trough that will be approaching the U.S. east coast on days 3-5.

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