Tropical Storm Chantal

Tropical Depression Chantal Track 1100 Hours August 23 2019
Tropical Depression Chantal Track 1100 Hours August 23 2019

Tropical Storm Chantal Satellite 0500 Hours August 21 2019

NWS National Hurricane Center Miami FL 1100 AM AST Fri Aug 23, 2019

Chantal  (see Wednesday video below)is currently producing only small bursts of convection over the northern semicircle, and visible satellite imagery suggests that the low-level circulation is becoming less well defined. The initial intensity is held at 25 kt based on current satellite intensity estimates, but it is possible this is a little generous. A combination of dry air and large-scale subsidence is expected to prevent the return of persistent deep convection, and if current trends continue Chantal could degenerate to a remnant low later today or tonight. The remnant low is expected to dissipate by 72 h, which is unchanged from the previous forecast.

The initial motion is now 155/6. There is little change to either the forecast philosophy or the forecast track from the previous advisory. The cyclone is embedded in the subtropical ridge, and the core of the ridge is forecast to shift from southwest to northeast of Chantal during the next couple of days. This evolution should cause Chantal or its remnants to make a clockwise half loop before the system dissipates. Like its predecessor, the new forecast track lies near the various consensus models.

FORECAST POSITIONS AND MAX WINDS

INIT  23/1500Z 36.6N  40.8W   25 KT  30 MPH - Tropical Depression (WSW São Miguel Island)
 12H  24/0000Z 35.8N  41.0W   25 KT  30 MPH - Tropical Depression (WSW São Miguel Island)
 24H  24/1200Z 35.3N  42.1W   25 KT  30 MPH...POST-TROP/REMNT LOW
 36H  25/0000Z 35.3N  43.3W   20 KT  25 MPH...POST-TROP/REMNT LOW
 48H  25/1200Z 35.5N  44.1W   20 KT  25 MPH...POST-TROP/REMNT LOW
 72H  26/1200Z...DISSIPATED

NWS National Hurricane Center Miami FL 1100 AM AST Thu Aug 22, 2019

Tropical Storm Chantal  continues to produce an area of deep convection just northeast of the mostly exposed low-level center. Recent scatterometer data shows winds near 30 kt to the southeast east of the center, and the initial intensity is again held at 30 kt. The cyclone is moving toward warmer sea surface temperatures and into an area of decreasing vertical wind shear. However, abundant dry air and increasing upper-level convergence should cause the system’s convection to dissipate in 24 h or so. The new intensity forecast is similar to the previous forecast in calling for the cyclone to decay to a remnant low by 36 h and dissipating completely by 96 h.

The initial motion is 100/15 as Chantal is moving along the southern edge of the mid-latitude westerlies. A low- to mid-level ridge to the south is expected to build northward between the depression and the westerlies, leaving Chantal in weak steering flow and causing it to make a slow clockwise loop before it dissipates. The new NHC track forecast is similar to, but slightly north of the previous forecast.

FORECAST POSITIONS AND MAX WINDS

INIT  22/1500Z 38.8N  43.8W   30 KT  35 MPH - Tropical Depression (WSW São Miguel Island)
 12H  23/0000Z 38.0N  42.0W   30 KT  35 MPH - Tropical Depression (WSW São Miguel Island)
 24H  23/1200Z 36.9N  41.1W   30 KT  35 MPH - Tropical Depression (WSW São Miguel Island)
 36H  24/0000Z 36.1N  41.0W   25 KT  30 MPH...POST-TROP/REMNT LOW
 48H  24/1200Z 35.7N  41.7W   25 KT  30 MPH...POST-TROP/REMNT LOW
 72H  25/1200Z 36.6N  42.9W   20 KT  25 MPH...POST-TROP/REMNT LOW
 96H  26/1200Z...DISSIPATE

NWS National Hurricane Center Miami FL 500 AM AST Thu Aug 22, 2019

Tropical Storm Chantal has been able to sustain an area of convection just to the east of its low-level center since the last advisory, and final-T numbers are actually back up to a unanimous T2.0/30 kt from TAFB and SAB. The initial intensity is therefore held at 30 kt. The depression is getting ready to move over a tongue of slightly warmer waters, and vertical shear is forecast to decrease below 10 kt in a day or two. However, there is abundant dry air around the system, and upper-level convergence is expected to increase, both of which should extinguish Chantal’s organized deep convection in 24-36 hours. The NHC intensity forecast continues to most closely follow the global models, with Chantal expected to become a remnant low on Friday and degenerate into a trough on Sunday.

Chantal is moving south of due east and a little slower than before, or 100/15 kt. A low- to mid-level ridge to the south is expected to build over Chantal in the coming days, leaving the depression in weak steering flow and causing it to make a slow clockwise loop before it dissipates. The new NHC track forecast is mainly an update of the previous one and lies between the ECMWF, HCCA, and the multi-model consensus aids.

FORECAST POSITIONS AND MAX WINDS

INIT  22/0900Z 39.1N  45.7W   30 KT  35 MPH - Tropical Depression (WSW São Miguel Island)
 12H  22/1800Z 38.4N  43.5W   30 KT  35 MPH - Tropical Depression (WSW São Miguel Island)
 24H  23/0600Z 37.3N  41.8W   30 KT  35 MPH - Tropical Depression (WSW São Miguel Island)
 36H  23/1800Z 36.3N  41.3W   25 KT  30 MPH...POST-TROP/REMNT LOW
 48H  24/0600Z 35.6N  41.8W   25 KT  30 MPH...POST-TROP/REMNT LOW
 72H  25/0600Z 36.2N  43.5W   20 KT  25 MPH...POST-TROP/REMNT LOW
 96H  26/0600Z...DISSIPATED

NWS National Hurricane Center Miami FL 500 PM AST Wed Aug 21, 2019

Tropical Storm Chantal Deep convection associated with Chantal has diminished and is confined to some disorganized patches of showers and thunderstorms northeast of the center. The advisory intensity estimate is held at 35 kt, pending the arrival of new scatterometer data. The cyclone should continue to move through a dry mid- to low-level air mass, with humidities less than 40 percent, during the next few days. This is likely to cause weakening, and it is expected that Chantal will become a tropical depression tomorrow and a remnant low by Friday. Given the current appearance of the system, loss of tropical cyclone status and dissipation are now forecast to occur much sooner than earlier anticipated. This is in good agreement with the latest HWRF model run.

The storm is moving just south of east, or 100/17 kt. Little change has been made to the previous track forecast or reasoning. Chantal should follow a clockwise path, around the western periphery of a mid-level high-pressure area, at a slower forward speed over the next few days. In 3-4 days, what is left of the cyclone is likely to turn northwestward to northward.

FORECAST POSITIONS AND MAX WINDS

INIT  21/2100Z 39.8N  49.1W   35 KT  40 MPH - Tropical Storm (WSW St John's Newfoundland)
 12H  22/0600Z 39.4N  46.5W   35 KT  40 MPH - Tropical Storm (WSW St John's Newfoundland)
 24H  22/1800Z 38.5N  43.6W   30 KT  35 MPH - Tropical Depression (WSW São Miguel Island)
 36H  23/0600Z 37.3N  41.8W   30 KT  35 MPH - Tropical Depression (WSW São Miguel Island)
 48H  23/1800Z 36.3N  41.3W   25 KT  30 MPH - Tropical Depression (WSW São Miguel Island)
 72H  24/1800Z 35.4N  42.5W   20 KT  25 MPH - Tropical Depression (WSW São Miguel Island)
 96H  25/1800Z 36.0N  42.7W   20 KT  25 MPH - Tropical Depression (WSW São Miguel Island)
120H  26/1800Z...DISSIPATED

NWS National Hurricane Center Miami FL 1100 AM AST Wed Aug 21,  2019

Tropical Storm Chantal has changed little since last night. It remains a sheared tropical cyclone, with the low-level center exposed to the west of the deep convection. The current intensity estimate is held at 35 kt based on a blend of subjective and objective Dvorak estimates. Although the shear is forecast to gradually diminish, the system should remain in an environment of dry air at the low- to mid-levels for the next several days. This will likely cause weakening, and Chantal is forecast to become a depression within 48 hours and degenerate into a remnant low in 3 to 4 days. The official intensity forecast is the same as the previous one, and only slightly below the model consensus.

The motion continues eastward, or 090/17 kt. Chantal is forecast to turn clockwise and decelerate around the periphery of a mid-level anticyclone over the next few days. Later in the period, the cyclone is predicted to drift northward.

FORECAST POSITIONS AND MAX WINDS

INIT  21/1500Z 40.2N  51.6W   35 KT  40 MPH - Tropical Storm (WSW St John's Newfoundland)
 12H  22/0000Z 40.0N  48.3W   35 KT  40 MPH - Tropical Storm (WSW St John's Newfoundland)
 24H  22/1200Z 39.2N  44.7W   35 KT  40 MPH - Tropical Storm (WSW St John's Newfoundland)
 36H  23/0000Z 38.1N  42.3W   35 KT  40 MPH - Tropical Storm (WSW St John's Newfoundland)
 48H  23/1200Z 36.9N  41.4W   30 KT  35 MPH - Tropical Depression (WSW São Miguel Island)
 72H  24/1200Z 35.5N  42.5W   30 KT  35 MPH - Tropical Depression (WSW São Miguel Island)
 96H  25/1200Z 36.0N  43.3W   30 KT  35 MPH - Tropical Depression (WSW São Miguel Island)
120H  26/1200Z 37.0N  43.5W   30 KT  35 MPH - Tropical Depression (WSW São Miguel Island)

NWS National Hurricane Center Miami FL 500 AM AST Wed Aug 21, 2019

Tropical Storm Chantal has changed little overnight. A small area of deep convection has persisted northeast of the tropical storm’s exposed surface center. Given the steady-state structure of the cyclone, the initial intensity has been held at 35 kt based on earlier ASCAT data.

Only minor adjustments were made to the NHC track and intensity forecasts, the most substantial of which is that Chantal is now expected to become a remnant low within 96 h. The tropical storm is surrounded by dry air and will be moving over marginal SSTs for the next couple of days. As a result of this unfavorable environment, Chantal is expected to weaken to a tropical depression by 48 h. Most of the dynamical models indicate that the cyclone will lose all of its convection and become post-tropical soon after, but the official forecast conservatively maintains the system as a tropical cyclone for 72 h. The official intensity forecast is near a consensus of the GFS, HMON, and HWRF models.

The tropical storm is moving quickly eastward but is forecast to slow and turn southeastward by Thursday. It should then turn toward the south on Friday as it moves around the northeast periphery of a low- to mid-level ridge centered over the central Atlantic. The track guidance is in good agreement on the forecast, at least as long as Chantal remains a tropical cyclone. The uncertainty in the track forecast is higher after the cyclone becomes a remnant low, but most of the guidance generally suggests that Chantal will become trapped in weak steering flow and meander over the North Atlantic for a couple of days thereafter.

FORECAST POSITIONS AND MAX WINDS

INIT  21/0900Z 40.3N  53.7W   35 KT  40 MPH - Tropical Storm (WSW St John's Newfoundland)
 12H  21/1800Z 40.2N  50.4W   35 KT  40 MPH - Tropical Storm (WSW St John's Newfoundland)
 24H  22/0600Z 39.6N  46.3W   35 KT  40 MPH - Tropical Storm (WSW St John's Newfoundland)
 36H  22/1800Z 38.4N  43.4W   35 KT  40 MPH - Tropical Storm (WSW St John's Newvoundland)
 48H  23/0600Z 37.2N  42.0W   30 KT  35 MPH - Tropical Depression (WSW São Miguel Island)
 72H  24/0600Z 35.3N  42.4W   30 KT  35 MPH - Tropical Depression (WSW São Miguel Island)
 96H  25/0600Z 35.5N  44.0W   30 KT  35 MPH - Tropical Depression (WSW São Miguel Island)
120H  26/0600Z 37.5N  44.0W   30 KT  35 MPH - Tropical Depression (WSW São Miguel Island)

NWS National Hurricane Center Miami FL 1100 PM AST Tue Aug 20, 2019 

Recent scatterometer wind data and passive microwave satellite images indicate that the small low-pressure system that the NHC has been monitoring for the past few days has developed a well-defined surface wind circulation and contains tropical-storm-force winds south of the cyclone’s center. Therefore, the low has become Tropical Storm Chantal. 

The initial motion estimate is 085/19 kt. NHC model guidance is in excellent agreement that Chantal will move eastward around the northern periphery of the Bermuda-Azores high and gradually slow down during the next 48 hours. Thereafter, the cyclone is forecast to drop southward around the eastern portion of the ridge, possibly stalling over warmer waters. The NHC forecast track lies close to the consensus models HCCA and TVCN.

Chantal is expected to remain in a moderate southwesterly to westerly vertical wind shear regime for the next 48 hours or so, followed by a significant decrease in the shear through 120 h. After 48 hours, the southward motion is also expected to move Chantal over warmer water with SSTs around 27C. However, mid-level moisture is expected to be quite sparse with humidity values forecast to be less than 40 percent based on the GFS and ECMWF SHIPS intensity guidance. Therefore, little or no significant intensification is expected throughout the forecast period, and the official intensity forecast closely follows a blend of the HCCA and IVCN consensus models. Although the official forecast calls for Chantal to remain a tropical cyclone through the 120 h, the abundance of dry air that the cyclone will be moving through could result in erosion of the deep convection sooner than currently expected.

FORECAST POSITIONS AND MAX WINDS

INIT  21/0300Z 40.2N  56.2W   35 KT  40 MPH - Tropical Storm (WSW St John's Newfoundland)
 12H  21/1200Z 40.3N  52.6W   35 KT  40 MPH - Tropical Storm (WSW St John's Newfoundland)
 24H  22/0000Z 40.2N  48.5W   35 KT  40 MPH - Tropical Storm (WSW St John's Newfoundland)
 36H  22/1200Z 39.0N  44.7W   35 KT  40 MPH - Tropical Storm (WSW St John's Newfoundland)
 48H  23/0000Z 37.4N  42.3W   35 KT  40 MPH - Tropical Storm (WSW São Miguel Island)
 72H  24/0000Z 34.9N  42.5W   35 KT  40 MPH - Tropical Storm (WSW São Miguel Island)
 96H  25/0000Z 34.6N  44.8W   35 KT  40 MPH - Tropical Storm (WSW São Miguel Island)
120H  26/0000Z 36.0N  44.8W   35 KT  40 MPH - Tropical Storm (WSW São Miguel Island)

NWS National Hurricane Center Miami FL 800 PM EDT Tue Aug 20, 2019

For the North Atlantic…Caribbean Sea and the Gulf of Mexico:

A small low-pressure system is located more than 400 miles southeast of Halifax, Nova Scotia. Associated thunderstorm activity continues to shows signs of organization, and recent satellite data indicate that the circulation has become a little better defined. Although environmental conditions are only marginally conducive, any further development of this low could result in the formation of a tropical cyclone while it moves eastward at 15 to 20 mph across the open north Atlantic.

* Formation chance through 48 hours…medium…40 percent. * Formation chance through 5 days…medium…40 percent.

NWS National Hurricane Center Miami FL 200 PM EDT Tue Aug 20, 2019

For the North Atlantic…Caribbean Sea and the Gulf of Mexico:

A low-pressure system is located almost 400 miles southeast of Halifax, Nova Scotia. While the associated thunderstorm activity shows signs of organization, recent satellite wind data indicates the system does not currently have a well-defined circulation. Significant development of this low is unlikely as it moves eastward at 15 to 20 mph across the open north Atlantic.

* Formation chance through 48 hours…low…10 percent. * Formation chance through 5 days…low...10 percent.

NWS National Hurricane Center Miami FL 800 AM EDT Tue Aug 20, 2019

For the North Atlantic…Caribbean Sea and the Gulf of Mexico:

A low-pressure system located more than 300 miles south of Halifax, Nova Scotia, continues to produce an area of thunderstorms east of the center. Significant development of this low is unlikely as it moves eastward at 15 to 20 mph, away from the United States and Canada.

* Formation chance through 48 hours…low…10 percent. * Formation chance through 5 days…low...10 percent.

NWS National Hurricane Center Miami FL 800 PM EDT Mon Aug 19, 2019

For the North Atlantic…Caribbean Sea and the Gulf of Mexico:

An area of low pressure located more than 200 miles southeast of Cape Cod, Massachusetts, is producing a small area of thunderstorm activity northeast of the center. Significant development of this system is unlikely as it moves eastward at 15 to 20 mph, away from the United States.

* Formation chance through 48 hours…low…10 percent. * Formation chance through 5 days…low...10 percent.

NWS National Hurricane Center Miami FL 800 AM EDT Mon Aug 19 2019

For the North Atlantic…Caribbean Sea and the Gulf of Mexico:

1. Thunderstorm activity has decreased in association with a low-pressure system located a couple of hundred miles south of Nantucket, Massachusetts. Significant development of this system is now unlikely as it moves east-northeastward away from the United States.

* Formation chance through 48 hours…low…10 percent. * Formation chance through 5 days…low…10 percent.

NWS National Hurricane Center Miami FL 800 AM EDT Sun Aug 18,  2019

For the North Atlantic…Caribbean Sea and the Gulf of Mexico:

1. A small low-pressure system located over eastern North Carolina is producing disorganized showers and thunderstorms. Any tropical development today is expected to be limited due to the system’s proximity to land. By tonight, the low is expected to move northeastward over the Atlantic, where some further organization could occur before the system encounters cooler waters in a day or so.

The low is forecast to produce heavy rainfall along with a threat of flash flooding in coastal portions of North Carolina through this evening. Please see products from your local National Weather Service office or the Weather Prediction Center’s Excessive Rainfall Outlook for more information.

* Formation chance through 48 hours…low…30 percent. * Formation chance through 5 days…low…30 percent.

NWS National Hurricane Center Miami FL 800 PM EDT Sat Aug 17, 2019

For the North Atlantic…Caribbean Sea and the Gulf of Mexico:

1. A small low-pressure system located along the South Carolina coast about midway between Myrtle Beach and Charleston is producing disorganized showers and thunderstorms. Tropical development of this system is expected to be slow to occur tonight and Sunday due to proximity to land as the disturbance moves northeastward along or near the coast of the Carolinas.

By early Monday, however, the low is expected to move over the warmer Atlantic waters, where some further organization could occur. The low is forecast to produce heavy rainfall along with a threat of flash flooding in eastern portions of South and North Carolina through Sunday. Please see products from your local National Weather Service office or the Weather Prediction Center’s Excessive Rainfall Outlook for more information.

* Formation chance through 48 hours…low…20 percent. * Formation chance through 5 days…low…20 percent.

NWS National Hurricane Center Miami FL 200 PM EDT Sat Aug 17,  2019

For the North Atlantic…Caribbean Sea and the Gulf of Mexico:

A surface trough is producing a band of cloudiness and showers extending from the northeast Gulf of Mexico northeastward across the coasts of Georgia, South Carolina, and North Carolina. The shower activity is currently most concentrated near a small area of low pressure located along the trough near the South Carolina coast. Tropical development of this system, if any, is likely to be slow as the disturbance moves northeastward along the eastern coast of the United States with increasing forward speed during the few days.

Regardless of development, the disturbance is forecast to produce heavy rainfall along with a threat of flash flooding in that region. Please see products from your local National Weather Service office or the Weather Prediction Center’s Excessive Rainfall Outlook for more information.

* Formation chance through 48 hours…low…10 percent. * Formation chance through 5 days…low…10 percent.

NWS National Hurricane Center Miami FL 800 AM EDT Sat Aug 17 2019

For the North Atlantic…Caribbean Sea and the Gulf of Mexico:

1. Disorganized cloudiness and showers over the northeastern Gulf of Mexico and northeastern Florida are associated with a weak surface trough. Tropical development of this system, if any, is expected to be slow to occur while it moves northeastward at 5 to 10 mph near the coasts of Georgia, South Carolina, and North Carolina during the next few days. Regardless of development, the disturbance is forecast to produce heavy rainfall along with a threat of flash flooding in that region. Please see products from your local National Weather Service office or the Weather Prediction Center’s Excessive Rainfall Outlook for more information.

* Formation chance through 48 hours…low…10 percent. * Formation chance through 5 days…low…20 percent.

NWS National Hurricane Center Miami FL 800 PM EDT Fri Aug 16, 2019

For the North Atlantic…Caribbean Sea and the Gulf of Mexico: 

1. A surface trough of low pressure is producing a large but disorganized area of showers and thunderstorms over the northeastern Gulf of Mexico and across northeastern Florida. Any tropical development of this system is expected to be slow to occur over the next few days while it moves northeastward at 5 to 10 mph near the coasts of Georgia, South and North Carolina.

Regardless of development, the disturbance is forecast to produce heavy rainfall along with a threat of flash flooding in that region. Please see information from your local National Weather Service office or the Weather Prediction Center’s Excessive Rainfall Outlook for more information.

* Formation chance through 48 hours…low…10 percent. * Formation chance through 5 days…low...20 percent.

If this storm system is named, it will be Tropical Storm Chantal.

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Video: Tropical Storm Chantal forms in Atlantic; no threat to land

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