Potential Tropical Cyclone Seven Advisory 1

1. 5 and T

2.0. Therefore, only an additional slight increase in convective organization and the low-level circulation closing off would make the system a tropical depression, and it could be at tropical storm strength when it approaches the Leeward Islands during the next couple of days. Therefore, advisories are being initiated on the system in order to issue Tropical Storm Watches for portions of the Leeward Islands at this time.Subtropical ridging extending across nearly the entire Atlantic is pushing the low along quickly toward the west, or 280/18 kt. In general this ridging is expected to persist into the middle part of next week. However, around the Sunday-Monday time frame, some mid-level troughing over the western Atlantic could allow the system to gain a little more latitude before it runs into additional ridging located near the east coast of the United States at the end of the forecast period. The GFS, which has perhaps one of the strongest solutions, is a northern outlier and shows the system turning farther into the weak troughing, while the ECMWF has a weaker solution and keeps the system on a westward track across the Lesser and Greater Antilles. At this time, the NHC official forecast lies close to the TVCN and HCCA consensus aids, and it is also relatively close to the ECMWF ensemble mean, which is farther north than its parent model.The biggest negative to the system becoming a tropical cyclone and strengthening is its fast motion of 15-20 kt. However, that motion is expected to gradually decrease in 2 to

3.days. At that same time, deep-layer shear has decreased a bit, and the system will be moving over warmer waters and toward a slightly more moist environment. Therefore, gradual strengthening is anticipated, and the NHC intensity forecast closely follows the HCCA and IVCN consensus aids through 72 hours, up until the system is near Hispaniola. After that time, land interaction is likely to disrupt the circulation, and the official forecast is below the model consensus aids on days

4.and 5.Key Messages1. Tropical storm conditions are possible in portions of the Leeward Islands late Saturday or early Sunday, and the risk of tropical storm conditions will spread westward to the Virgin Islands and Puerto Rico late Sunday and Sunday night.2. Heavy rainfall with this system may produce areas of scattered flash flooding over the northern Leeward Islands Saturday into Sunday.3. There is a risk of wind and rainfall impacts in portions of Hispaniola, the Turks and Caicos Islands, the southeastern Bahamas, and Cuba next week, and interests in those areas should monitor the progress of this system.

1. 5 and T

2.0. Therefore, only an additional slight increase in convective organization and the low-level circulation closing off would make the system a tropical depression, and it could be at tropical storm strength when it approaches the Leeward Islands during the next couple of days. Therefore, advisories are being initiated on the system in order to issue Tropical Storm Watches for portions of the Leeward Islands at this time.Subtropical ridging extending across nearly the entire Atlantic is pushing the low along quickly toward the west, or 280/18 kt. In general this ridging is expected to persist into the middle part of next week. However, around the Sunday-Monday time frame, some mid-level troughing over the western Atlantic could allow the system to gain a little more latitude before it runs into additional ridging located near the east coast of the United States at the end of the forecast period. The GFS, which has perhaps one of the strongest solutions, is a northern outlier and shows the system turning farther into the weak troughing, while the ECMWF has a weaker solution and keeps the system on a westward track across the Lesser and Greater Antilles. At this time, the NHC official forecast lies close to the TVCN and HCCA consensus aids, and it is also relatively close to the ECMWF ensemble mean, which is farther north than its parent model.The biggest negative to the system becoming a tropical cyclone and strengthening is its fast motion of 15-20 kt. However, that motion is expected to gradually decrease in 2 to

3.days. At that same time, deep-layer shear has decreased a bit, and the system will be moving over warmer waters and toward a slightly more moist environment. Therefore, gradual strengthening is anticipated, and the NHC intensity forecast closely follows the HCCA and IVCN consensus aids through 72 hours, up until the system is near Hispaniola. After that time, land interaction is likely to disrupt the circulation, and the official forecast is below the model consensus aids on days

4.and 5.Key Messages1. Tropical storm conditions are possible in portions of the Leeward Islands late Saturday or early Sunday, and the risk of tropical storm conditions will spread westward to the Virgin Islands and Puerto Rico late Sunday and Sunday night.2. Heavy rainfall with this system may produce areas of scattered flash flooding over the northern Leeward Islands Saturday into Sunday.3. There is a risk of wind and rainfall impacts in portions of Hispaniola, the Turks and Caicos Islands, the southeastern Bahamas, and Cuba next week, and interests in those areas should monitor the progress of this system.

CHANGES WITH THIS ADVISORY: The government of Antigua and Barbuda has issued a Tropical Storm Watch for Antigua and Barbuda, St. Kitts and Nevis, and Montserrat. The government of the Netherlands has issued a Tropical Storm Watch for Saba and Sint Eustatius. SUMMARY OF WATCHES AND WARNINGS IN EFFECT: A Tropical Storm Watch is in effect for...
- Antigua and Barbuda, St. Kitts and Nevis, and Montserrat
- Saba and Sint Eustatius A Tropical Storm Watch means that tropical storm conditions are possible within the watch area, generally within 48 hours.

Interests elsewhere in the Leeward Islands, the Virgin Islands, Puerto Rico should monitor the progress of this system. Tropical Storm Watches will likely be required for these areas later today or tonight.

For storm information specific to your area, please monitor products issued by your national meteorological service.

CHANGES WITH THIS ADVISORY: The government of Antigua and Barbuda has issued a Tropical Storm Watch for Antigua and Barbuda, St. Kitts and Nevis, and Montserrat. The government of the Netherlands has issued a Tropical Storm Watch for Saba and Sint Eustatius. SUMMARY OF WATCHES AND WARNINGS IN EFFECT: A Tropical Storm Watch is in effect for...
- Antigua and Barbuda, St. Kitts and Nevis, and Montserrat
- Saba and Sint Eustatius A Tropical Storm Watch means that tropical storm conditions are possible within the watch area, generally within 48 hours.

Interests elsewhere in the Leeward Islands, the Virgin Islands, Puerto Rico should monitor the progress of this system. Tropical Storm Watches will likely be required for these areas later today or tonight.

For storm information specific to your area, please monitor products issued by your national meteorological service.

Key messages for Potential Tropical Cyclone Seven can be found in the Tropical Cyclone Discussion under AWIPS header MIATCDAT2 and WMO header WTNT42 KNHC and on the web at www.hurricanes.gov/graphics_at2.shtml?key_messages.

WIND: Tropical storm conditions are possible within the watch area by Saturday night or early Sunday.

RAINFALL: The system is expected to produce rainfall of 3 to 6 inches across the northern Leeward Islands Saturday into Sunday. This rainfall may produce scattered areas of flash flooding.

Key messages for Potential Tropical Cyclone Seven can be found in the Tropical Cyclone Discussion under AWIPS header MIATCDAT2 and WMO header WTNT42 KNHC and on the web at www.hurricanes.gov/graphics_at2.shtml?key_messages.

WIND: Tropical storm conditions are possible within the watch area by Saturday night or early Sunday.

RAINFALL: The system is expected to produce rainfall of 3 to 6 inches across the northern Leeward Islands Saturday into Sunday. This rainfall may produce scattered areas of flash flooding.

At 1100 AM AST (1500 UTC), the disturbance was centered near latitude 15.3 North, longitude 49.3 West. The system is moving toward the west near 21 mph (33 km/h), and this general motion with a gradual decrease in forward speed is expected into early next week. On the forecast track, the system is expected to approach the Leeward Islands on Saturday, move over the Leeward Islands Saturday night and Sunday, and then be near the Virgin Islands and Puerto Rico Sunday night and Monday. Maximum sustained winds are near 35 mph (55 km/h) with higher gusts. Gradual strengthening is forecast during the next couple of days, and the disturbance is expected to become a tropical depression tonight and a tropical storm by Saturday. * Formation chance through 48 hours...high...80 percent. * Formation chance through 5 days...high...80 percent. The estimated minimum central pressure is 1010 mb (29.83 inches).

A tropical wave and small area of low pressure moving quickly westward across the central tropical Atlantic has been producing bursts of deep convection near and to the west of the wave axis. Scatterometer data from last evening indicated that the system did not quite have a closed circulation, but it is close. In addition, the convective organization has increased a bit since yesterday, with TAFB and SAB providing Dvorak classification of T1.5 and T2.0. Therefore, only an additional slight increase in convective organization and the low-level circulation closing off would make the system a tropical depression, and it could be at tropical storm strength when it approaches the Leeward Islands during the next couple of days. Therefore, advisories are being initiated on the system in order to issue Tropical Storm Watches for portions of the Leeward Islands at this time.

Subtropical ridging extending across nearly the entire Atlantic is pushing the low along quickly toward the west, or 280/18 kt. In general this ridging is expected to persist into the middle part of next week. However, around the Sunday-Monday time frame, some mid-level troughing over the western Atlantic could allow the system to gain a little more latitude before it runs into additional ridging located near the east coast of the United States at the end of the forecast period. The GFS, which has perhaps one of the strongest solutions, is a northern outlier and shows the system turning farther into the weak troughing, while the ECMWF has a weaker solution and keeps the system on a westward track across the Lesser and Greater Antilles. At this time, the NHC official forecast lies close to the TVCN and HCCA consensus aids, and it is also relatively close to the ECMWF ensemble mean, which is farther north than its parent model.

The biggest negative to the system becoming a tropical cyclone and strengthening is its fast motion of 15-20 kt. However, that motion is expected to gradually decrease in 2 to 3 days. At that same time, deep-layer shear has decreased a bit, and the system will be moving over warmer waters and toward a slightly more moist environment. Therefore, gradual strengthening is anticipated, and the NHC intensity forecast closely follows the HCCA and IVCN consensus aids through 72 hours, up until the system is near Hispaniola. After that time, land interaction is likely to disrupt the circulation, and the official forecast is below the model consensus aids on days 4 and 5.

A tropical wave and small area of low pressure moving quickly westward across the central tropical Atlantic has been producing bursts of deep convection near and to the west of the wave axis. Scatterometer data from last evening indicated that the system did not quite have a closed circulation, but it is close. In addition, the convective organization has increased a bit since yesterday, with TAFB and SAB providing Dvorak classification of T1.5 and T2.0. Therefore, only an additional slight increase in convective organization and the low-level circulation closing off would make the system a tropical depression, and it could be at tropical storm strength when it approaches the Leeward Islands during the next couple of days. Therefore, advisories are being initiated on the system in order to issue Tropical Storm Watches for portions of the Leeward Islands at this time.

Subtropical ridging extending across nearly the entire Atlantic is pushing the low along quickly toward the west, or 280/18 kt. In general this ridging is expected to persist into the middle part of next week. However, around the Sunday-Monday time frame, some mid-level troughing over the western Atlantic could allow the system to gain a little more latitude before it runs into additional ridging located near the east coast of the United States at the end of the forecast period. The GFS, which has perhaps one of the strongest solutions, is a northern outlier and shows the system turning farther into the weak troughing, while the ECMWF has a weaker solution and keeps the system on a westward track across the Lesser and Greater Antilles. At this time, the NHC official forecast lies close to the TVCN and HCCA consensus aids, and it is also relatively close to the ECMWF ensemble mean, which is farther north than its parent model.

The biggest negative to the system becoming a tropical cyclone and strengthening is its fast motion of 15-20 kt. However, that motion is expected to gradually decrease in 2 to 3 days. At that same time, deep-layer shear has decreased a bit, and the system will be moving over warmer waters and toward a slightly more moist environment. Therefore, gradual strengthening is anticipated, and the NHC intensity forecast closely follows the HCCA and IVCN consensus aids through 72 hours, up until the system is near Hispaniola. After that time, land interaction is likely to disrupt the circulation, and the official forecast is below the model consensus aids on days 4 and 5.

AL072021 Potential Tropical Cyclone Seven