Tropical Storm Joyce

Tropical Depression Joyce 1400 Hours September 18 2018
Tropical Depression Joyce 1400 Hours September 18 2018

NWS National Hurricane Center Miami FL 500 AM AST Tue Sep 18 2018

The latest convective burst associated with Sub-Tropical Storm Joyce (see 2 videos below) is weakening due to the effects of 35-40 kt of westerly vertical shear and very dry mid-level air. Satellite intensity estimates have changed little since the previous advisory, so the initial intensity remains 30 kt. The cyclone is expected to gradually weaken due to the ongoing shear and dry air entrainment, and the new intensity forecast again calls for the system to become a remnant low in 12-24 h. Dissipation of the remnants is forecast in 72-96 h in agreement with the global model guidance. As indicated in the previous discussion, there is an alternative scenario where interaction with an upper-level trough seen in water vapor imagery to the northwest of Joyce maintains organized convection longer than currently forecast.

The initial motion is now 165/5. Joyce is forecast to move around the eastern periphery of a deep-layer ridge located across the eastern Atlantic, with the cyclone or its remnants turning southwestward during the next 36 h and westward by 72 h. The new forecast track generally lies between the TVCA and HCCA consensus models.

FORECAST POSITIONS AND MAX WINDS

INIT  18/0900Z 32.9N  27.6W   30 KT  35 MPH - Tropical Storm (WNW Santa Cruz das Flores, Azores
 12H  18/1800Z 32.0N  27.7W   30 KT  35 MPH - Tropical Storm (WNW Santa Cruz das Flores, Azores
 24H  19/0600Z 31.0N  28.5W   25 KT  30 MPH - Tropical Storm (WNW Santa Cruz das Flores, Azores
 36H  19/1800Z 30.3N  29.5W   25 KT  30 MPH - Tropical Storm (WNW Santa Cruz das Flores, Azores
 48H  20/0600Z 29.8N  31.0W   25 KT  30 MPH - Tropical Storm (WNW Santa Cruz das Flores, Azores
 72H  21/0600Z 29.5N  34.5W   20 KT  25 MPH - Tropical Storm (WNW Santa Cruz das Flores, Azores
 96H  22/0600Z...DISSIPATED

NWS National Hurricane Center Miami FL 1100 AM AST Mon Sep 17 2018

Joyce  is gradually losing organization, with drier air entraining into the circulation. Visible satellite imagery this morning shows a few cloud swirls pivoting around a mean center with only a small amount of deep convection displaced about 90 miles northeast of the mean center. ASCAT scatterometer data indicate that winds of 25 to 30 kt remain on the southwestern side of the cyclone. Based on these data, Joyce remains a 30-kt tropical depression for this advisory. Dry air and strong vertical wind shear are expected to continue to weaken Joyce over the next few days, and the cyclone is expected to degenerate into a remnant low by 24 hours. The official intensity forecast is similar to the previous advisory and remains close to the model consensus. The only notable change is that Joyce is now expected to become a remnant low a little faster than the previous advisory.

The initial motion is 105/07 kt. Joyce has slowed down this morning as anticipated as it is now reaching the northeastern periphery of a mid-level high pressure area. Over the next couple of days, the cyclone is expected to turn southeastward, southward, and then southwestward around the eastern periphery of the high. The lastest track guidance is tightly clustered, with the NHC track forecast lying in the middle of the guidance envelope, and close to the previous official forecast track.

FORECAST POSITIONS AND MAX WINDS

INIT  17/1500Z 34.0N  28.4W   30 KT  35 MPH - Tropical Storm (WSW Santa Cruz das Flores, Azores)
 12H  18/0000Z 33.5N  27.2W   30 KT  35 MPH - Tropical Storm (WSW Santa Cruz das Flores, Azores)
 24H  18/1200Z 32.3N  26.6W   30 KT  35 MPH - Tropical Storm (WSW Santa Cruz das Flores, Azores)
 36H  19/0000Z 31.2N  27.2W   25 KT  30 MPH - Tropical Storm (WSW Santa Cruz das Flores, Azores)
 48H  19/1200Z 30.3N  28.3W   20 KT  25 MPH - Tropical Storm (WSW Santa Cruz das Flores, Azores)
 72H  20/1200Z 28.9N  31.3W   20 KT  25 MPH - Tropical Storm (WNW Santa Cruz das Flores, Azores)
 96H  21/1200Z...DISSIPATED

NWS National Hurricane Center Miami FL 1100 AM AST Sun Sep 16 2018

Tropical Storm Joyce  is barely a tropical cyclone at the moment. The cloud pattern consists of a low-level swirl with a small patch of deep convection located about 80 n mi northeast of the center and another patch of weakening convection well removed from the center in the northeast quadrant. Visible satellite images and a partial ASCAT pass indicate that the circulation of the cyclone has also become increasingly elongated from northeast to southwest. Based on the system’s appearance and the satellite intensity estimates, the initial wind speed is lowered to 30 kt, making Joyce a tropical depression.

The depression is moving east-northeastward at 16 kt within the mid-latitude westerlies, and this motion should continue through tonight. After that time, the shallow cyclone is expected to slow down and turn southeastward and then southwestward as it is moves in the flow on the east side of a building low- to mid-level ridge. The track models are in fairly good agreement, and little overall change was made to the previous NHC forecast.

Joyce is currently in a quite hostile environment of 30-40 kt of west-southwesterly shear. Even though SSTs are relatively warm, the ongoing strong shear and nearby dry air should continue to cause the cyclone to gradually weaken. Although the NHC forecast shows Joyce hanging on as a tropical depression for a couple of more days, it is very possible that the system could degenerate into a trough or a remnant low at any time during that period.

FORECAST POSITIONS AND MAX WINDS

INIT  16/1500Z 34.7N  34.3W   30 KT  35 MPH - Tropical Storm (WSW Santa Cruz das Flores, Azores)
 12H  17/0000Z 34.9N  31.4W   30 KT  35 MPH - Tropical Storm (WSW Santa Cruz das Flores, Azores)
 24H  17/1200Z 34.5N  28.7W   30 KT  35 MPH - Tropical Storm (WSW Santa Cruz das Flores, Azores)
 36H  18/0000Z 33.6N  27.0W   30 KT  35 MPH - Tropical Storm (WSW Santa Cruz das Flores, Azores)
 48H  18/1200Z 32.6N  26.7W   25 KT  30 MPH - Tropical Storm (WSW Santa Cruz das Flores, Azores)
 72H  19/1200Z 30.4N  29.2W   20 KT  25 MPH - Tropical Storm (WSW Santa Cruz das Flores, Azores)
 96H  20/1200Z...DISSIPATED

NWS National Hurricane Center Miami FL 500 AM AST Sun Sep 16 2018

What’s left of the Joyce’s  associated deep convection is now displaced about 80 miles to the north-northeast of the elongated surface circulation. There still may be some 35 kt winds in a small area of deep convection where the coldest cloud tops (-65C) are observed, therefore, the initial intensity is held at 35 kt for this advisory.

There is no change to the intensity forecast philosophy. The surrounding environment is forecast to remains quite unfavorable during the next 24 hours, although the warm 27C oceanic temperatures could slightly counteract the negative effects of the harsh vertical shear pattern. Afterward, decreasing sea surface temperatures, a more stable thermodynamic air mass, along with the stiff shear, is forecast to induce gradual weakening and, ultimately, dissipation in 4 days.

The initial motion is estimated to be east-northeastward, or 075/15 kt. The cyclone is embedded within the same mid-tropospheric steering flow as Tropical Storm Helene, and Joyce should move east-northeastward to eastward today. Through day 3, Joyce should turn southeastward to south-southwestward around the eastern periphery of a subtropical ridge to its west as a vertically shallow system. The NHC forecast is similar to the previous advisory, and is based on the better-performing consensus aids.

FORECAST POSITIONS AND MAX WINDS

INIT  16/0900Z 34.0N  36.1W   35 KT  40 MPH - Tropical Storm (WSW Santa Cruz das Flores, Azores)
 12H  16/1800Z 34.5N  33.4W   30 KT  35 MPH - Tropical Storm (WSW Santa Cruz das Flores, Azores)
 24H  17/0600Z 34.6N  30.1W   30 KT  35 MPH - Tropical Storm (WSW Santa Cruz das Flores, Azores)
 36H  17/1800Z 34.1N  27.8W   30 KT  35 MPH - Tropical Storm (WSW Santa Cruz das Flores, Azores)
 48H  18/0600Z 32.9N  26.8W   25 KT  30 MPH - Tropical Storm (WSW Santa Cruz das Flores, Azores)
 72H  19/0600Z 30.7N  28.5W   25 KT  30 MPH - Tropical Storm (WSW Santa Cruz das Flores, Azores)
 96H  20/0600Z...DISSIPATED

NWS National Hurricane Center Miami FL 500 PM AST Sat Sep 15 2018

The circulation of Tropical Storm Joyce  is elongated this afternoon, with the center partially exposed. It has been interesting to watch deep convection firing in the northeastern quadrant, kicking off new small swirls that rotate around the mean circulation. A blend of the Dvorak estimates from TAFB/SAB supports keeping the wind speed 40 kt on this advisory.

There is no change to the intensity forecast reasoning. The environment is predicted to be nearly steady-state around Joyce through Sunday, with strong shear being offset by waters near 27C. Thereafter, as the hostile shear continues, the mid-level air should become drier near the center, and SSTs cool off below 26C. These conditions should cause Joyce to slowly weaken early next week, and dissipate in 3 days or so. This forecast is basically the same as the previous one, but it isn’t out of the realm of possibility the cyclone could open up into a trough before that time.

Joyce continues to accelerate, now moving east-northeastward at about 15 kt. The storm remains embedded within the same trough as Tropical Storm Helene, and Joyce should move east-northeastward during the next day or so. Beyond that time, as Joyce becomes a shallow cyclone, it is forecast to turn southeastward due to low-level flow around the eastern side of a building ridge over the central Atlantic Ocean. The track forecast is simply an update to the previous one, and continues to be on the southern side of the guidance envelope.

FORECAST POSITIONS AND MAX WINDS

INIT  15/2100Z 33.1N  39.6W   40 KT  45 MPH - Tropical Storm (WSW Santa Cruz das Flores, Azores)
 12H  16/0600Z 34.1N  37.2W   40 KT  45 MPH - Tropical Storm (WSW Santa Cruz das Flores, Azores)
 24H  16/1800Z 34.8N  33.8W   40 KT  45 MPH - Tropical Storm (WSW Santa Cruz das Flores, Azores)
 36H  17/0600Z 34.8N  30.5W   35 KT  40 MPH - Tropical Storm (WSW Vila do Porto, Azores)
 48H  17/1800Z 34.0N  28.0W   30 KT  35 MPH - Tropical Storm (WSW Vila do Porto, Azores)
 72H  18/1800Z 31.5N  26.5W   25 KT  30 MPH - Tropical Storm (WSW Ponta Delgada, Portugal)
 96H  19/1800Z...DISSIPATED

NWS National Hurricane Center Miami FL 1100 AM AST Sat Sep 15 2018

Tropical Storm Joyce  is feeling the effects of shear this morning. The low-level center of the tropical storm has become exposed to the south of a area of deep convection. ASCAT data indicate the the maximum winds have dropped to 35-40 kt, and 40 kt is chosen as the initial wind speed since the resolution of ASCAT is likely causing an undersampling of the small storm.

The environment isn’t forecast to change much near Joyce during the next day or so, with strong shear being offset by waters near 27C. The NHC forecast is leveled off during that time, a bit lower than the previous prediction mostly to account for the initial wind speed. Thereafter, while the shear is forecast to continue, the mid-level air should become drier near the center, and SSTs cool off gradually below 26C. These conditions should cause Joyce to slowly weaken early next week, and dissipate in 3 days or so. This is the solution provided by much of the guidance, and the NHC forecast follows suit.

Joyce has accelerated overnight, now moving east-northeastward at about 12 kt. The storm remains embedded in the same trough as Tropical Storm Helene and it should follow that tropical cyclone east-northeastward to northeastward at increasing forward speeds during the next day or two. Beyond that time, as Joyce becomes a shallow cyclone, it is forecast to turn southeastward due to low-level flow around the eastern side of a building ridge over the central Atlantic Ocean. No significant changes were made to the forecast, which lies on the southern side of the guidance envelope.

FORECAST POSITIONS AND MAX WINDS

INIT  15/1500Z 32.0N  41.0W   40 KT  45 MPH - Tropical Storm (WSW Santa Cruz das Flores, Azores)
 12H  16/0000Z 32.9N  39.2W   40 KT  45 MPH - Tropical Storm (WSW Santa Cruz das Flores, Azores)
 24H  16/1200Z 34.0N  35.9W   40 KT  45 MPH - Tropical Storm (WSW Santa Cruz das Flores, Azores)
 36H  17/0000Z 34.5N  32.2W   35 KT  40 MPH - Tropical Storm (WSW Santa Cruz das Flores, Azores)
 48H  17/1200Z 34.0N  29.0W   30 KT  35 MPH - Tropical Storm (WSW Horta, Azores)
 72H  18/1200Z 32.0N  25.5W   25 KT  30 MPH - Tropical Storm (WSW Funchal, Madeira)
 96H  19/1200Z...DISSIPATED

NWS National Hurricane Center Miami FL 500 AM AST Sat Sep 15 2018

There has not much change with Joyce overnight. The tropical storm is producing a fair amount of deep convection to the north and west of the center, but there are some dry slots on the east side. A blend of the latest satellite intensity estimates supports holding the initial wind speed at 45 kt. Joyce is currently just east of an upper-level trough and the flow aloft is quite diffluent near the cyclone. This upper-level pattern could allow Joyce to strengthen slightly today. However, by tonight, southwesterly flow aloft is expected to increase over the cyclone. This increase in shear combined with decreasing mid-level humidities and cooling SSTs should lead to a steady weakening trend after 12 hours. The cyclone is forecast to dissipate in 3 to 4 days, but some of the models suggest that this could occur sooner.

The tropical storm is moving eastward at 7 kt. Joyce is embedded in the same trough as Helene and it should follow that tropical cyclone east-northeastward to northeastward at increasing forward speeds during the next day or two. Beyond that time, if there is anything left of Joyce, the system will likely turn back to the east or east-southeast as it moves within the mid-latitude westerlies. The models are in fairly good agreement, and this forecast lies close to the middle of the guidance envelope.

FORECAST POSITIONS AND MAX WINDS

INIT  15/0900Z 31.9N  42.2W   45 KT  50 MPH - Tropical Storm (SW Santa Cruz das Flores, Azores)
 12H  15/1800Z 32.7N  40.6W   50 KT  60 MPH - Tropical Storm (SW Santa Cruz das Flores, Azores)
 24H  16/0600Z 33.9N  37.8W   45 KT  50 MPH - Tropical Storm (SW Santa Cruz das Flores, Azores)
 36H  16/1800Z 34.6N  34.1W   40 KT  45 MPH - Tropical Storm (SW Santa Cruz das Flores, Azores)
 48H  17/0600Z 34.7N  31.0W   35 KT  40 MPH - Tropical Storm (SW Santa Cruz das Flores, Azores)
 72H  18/0600Z 33.0N  26.5W   30 KT  35 MPH - Tropical Storm (ENE Funchal, Madeira)
 96H  19/0600Z...DISSIPATED

NWS National Hurricane Center Miami FL 1100 PM AST Fri Sep 14 2018

Joyce   continues to look better organized on GOES-16 satellite imagery and the convective canopy has expanded. However, recent microwave data reveals that the cyclone is still tilted to the northeast due to nearly strong southwesterly wind shear. The most recent TAFB and SAB Dvorak classifications support raising the initial intensity to 45 kt. Despite the shear, most of the intensity guidance shows very slight strengthening over the next 12 to 24 hours, and the NHC intensity forecast is a little higher than the previous advisory at most forecast times. Persistent shear and decreasing SSTs along the forecast track should cause Joyce to weaken beyond that time, likely dissipating entirely shortly after 72 h. A few models, most notably the HWRF and UKMET, persist the cyclone a little beyond that, but only as a remnant low.

The storm has turned east as expected, and the initial motion is now 090/5 kt. As the larger Helene begins to accelerate away, a mid-latitude trough over the central Atlantic should cause Joyce to turn northeastward and speed up. A turn back toward the east, or possibly even east-southeast is possible by the end of the forecast period as Joyce weakens and follows the northern periphery of a subtropical high over eastern Atlantic. Very little change has been made to the track forecast through 48 h, but it has been adjusted to the south at 72 h, following the latest consensus guidance.

FORECAST POSITIONS AND MAX WINDS

INIT  15/0300Z 31.6N  43.6W   45 KT  50 MPH - Tropical Storm (SW Santa Cruz das Flores, Azores)
 12H  15/1200Z 32.2N  42.1W   50 KT  60 MPH - Tropical Storm (SW Santa Cruz das Flores, Azores)
 24H  16/0000Z 33.2N  39.8W   50 KT  60 MPH - Tropical Storm (SW Santa Cruz das Flores, Azores)
 36H  16/1200Z 34.4N  37.1W   45 KT  50 MPH - Tropical Storm (SW Santa Cruz das Flores, Azores)
 48H  17/0000Z 35.1N  33.6W   40 KT  45 MPH - Tropical Storm (SW Santa Cruz das Flores, Azores)
 72H  18/0000Z 34.0N  28.4W   35 KT  40 MPH - Tropical Storm (SW Santa Cruz das Flores, Azores)
 96H  19/0000Z...DISSIPATED

NWS National Hurricane Center Miami FL 500 PM AST Fri Sep 14 2018

Convection associated with Joyce has increased since the last advisory, with a vigorous band now near the center in the northern semicircle. In response, satellite intensity estimates have edged upward, and the initial intensity is increased to 40 kt as a blend between the TAFB subjective Dvorak estimates and the CIMSS satellite consensus. The cyclone now has good cirrus outflow in the northern semicircle as an upper-level low seen in water vapor imagery passes south of the cyclone.

The storm is starting its forecast turn toward the east and the initial motion is now 125/5. As Tropical Storm Helene to the east-northeast of Joyce moves away, Joyce is expected to turn northeastward with an increase in forward speed during the next 24 h, followed by an eastward turn after 48 h. The global models continue to trend faster, and after 48 h there has been a southward shift compared to the previous guidance. Therefore, the new forecast track will be notably faster than the previous track and the 72 h point will be shifted southward. The new track is still a little to the north of the various consensus models.

Southwesterly upper-level winds are still forecast to increase over the cyclone during the next day or two, and the forecast track takes Joyce over decreasing sea surface temperatures. This combination should lead to a weakening trend, especially after 24 h. The new intensity forecast is adjusted upward a little from the previous one based on the initial intensity, but it still calls for Joyce to dissipate by 96 h in agreement with most of the global models. It is possible that Joyce could strengthen a little more during the first 12 h while the upper-level low helps keep the stronger shear away from the storm.

FORECAST POSITIONS AND MAX WINDS

INIT  14/2100Z 31.4N  44.1W   40 KT  45 MPH - Tropical Storm (SW Santa Cruz das Flores, Azores)
 12H  15/0600Z 31.6N  43.1W   40 KT  45 MPH - Tropical Storm (SW Santa Cruz das Flores, Azores)
 24H  15/1800Z 32.6N  41.1W   40 KT  45 MPH - Tropical Storm (SW Santa Cruz das Flores, Azores)
 36H  16/0600Z 33.9N  38.7W   35 KT  40 MPH - Tropical Storm (SW Santa Cruz das Flores, Azores)
 48H  16/1800Z 35.0N  35.6W   30 KT  35 MPH - Tropical Storm (SW Santa Cruz das Flores, Azores)
 72H  17/1800Z 35.5N  28.5W   30 KT  35 MPH - Tropical Storm (SW Santa Cruz das Flores, Azores)
 96H  18/1800Z...DISSIPATED

NWS National Hurricane Center Miami FL 1100 AM AST Fri Sep 14 2018

Tropical Storm Joyce  has again changed little in organization since the last advisory, with several small bands of convection to the east and northeast of the partly exposed center. The initial intensity remains 35 kt in agreement with the latest satellite estimates from TAFB and the CIMSS satellite consensus.

The initial motion is now 180/7. Joyce is currently being steered by the larger and stronger Helene to its east, and a southward to southeastward motion is expected for the next 12 h or so. As Helene passes to the east-northeast of Joyce, Joyce should turn eastward and northeastward with a faster forward speed due to the approach of a mid-latitude trough from the west. The global models have again trended toward a faster northeastward motion after 24 h, and the NHC track forecast has been adjusted to be faster and a little farther to the east.

There is no change to the intensity forecast philosophy from the previous advisory. Southwesterly upper-level winds are forecast to increase over the cyclone within the next day or two, which should prevent Joyce from strengthening. The NHC forecast calls for little change in wind speed over the next 36 h, then shows weakening as the shear increases further. The global models mostly dissipate Joyce by day 4, but the system could lose its deep convection and become post-tropical before that time.

FORECAST POSITIONS AND MAX WINDS

INIT  14/1500Z 31.6N  44.6W   35 KT  40 MPH - Tropical Storm (SW Santa Cruz das Flores, Azores)
 12H  15/0000Z 31.3N  44.3W   35 KT  40 MPH - Tropical Storm (SW Santa Cruz das Flores, Azores)
 24H  15/1200Z 32.0N  42.9W   35 KT  40 MPH - Tropical Storm (SW Santa Cruz das Flores, Azores)
 36H  16/0000Z 33.2N  41.0W   35 KT  40 MPH - Tropical Storm (SW Santa Cruz das Flores, Azores)
 48H  16/1200Z 34.6N  38.4W   30 KT  35 MPH - Tropical Storm (SW Santa Cruz das Flores, Azores)
 72H  17/1200Z 36.0N  32.0W   30 KT  35 MPH - Tropical Storm (WSW Santa Cruz das Flores, Azores)
 96H  18/1200Z...DISSIPATED

NWS National Hurricane Center Miami FL AL102018 500 PM AST Thu Sep 13 2018

Joyce  has an exposed center this afternoon with no substantial deep convection anywhere nearby. The initial intensity remains 35 kt, consistent with the Hebert-Poteat ST2.5 classification from TAFB as well as the appearance of the very tight low-level center as seen in the GOES-16 visible satellite imagery. As Joyce still remains embedded within an upper-level trough, the system retains the subtropical storm label.

Joyce has now been devoid of deep convection for almost a day, due to the dry stable air combined with strong tropospheric vertical shear. As the system is not expected to undergo extratropical transition, without deep convection gradual weakening is anticipated until dissipation in about four days. The official intensity forecast is a blend of the IVCN intensity consensus scheme along with the GFS and ECMWF global model guidance. This new forecast indicates a reduction from the previous advisory, and in fact, Joyce could become a post-tropical cyclone soon if deep convection does not reappear shortly.

Joyce is moving toward the southwest at about 5 kt, as it is situated slightly to the west of an upper-level low. In a couple days, a new short wave trough will dive equatorward west of Joyce and begin advecting Joyce toward the northeast. The new NHC track forecast is a bit to the left (southwest) of the previous advisory and is based upon a blend of the HWRF hurricane model and the GFS and ECMWF global models.

FORECAST POSITIONS AND MAX WINDS

INIT  13/2100Z 33.6N  44.2W   35 KT  40 MPH - Tropical Storm (SW Santa Cruz das Flores, Azores)
 12H  14/0600Z 33.1N  44.6W   35 KT  40 MPH - Tropical Storm (SW Santa Cruz das Flores, Azores)
 24H  14/1800Z 32.3N  44.7W   35 KT  40 MPH - Tropical Storm (SW Santa Cruz das Flores, Azores)
 36H  15/0600Z 32.4N  44.0W   35 KT  40 MPH - Tropical Storm (SW Santa Cruz das Flores, Azores)
 48H  15/1800Z 33.2N  43.1W   30 KT  35 MPH - Tropical Storm (SW Santa Cruz das Flores, Azores)
 72H  16/1800Z 36.0N  39.5W   25 KT  30 MPH - Tropical Storm (SW Santa Cruz das Flores, Azores)
 96H  17/1800Z...DISSIPATED

NWS National Hurricane Center Miami FL 1100 AM AST Thu Sep 13 2018

Tropical Storm Joyce’s  satellite presentation is less than impressive this morning, with the low-level center exposed to the northwest of a small patch of deep convection. The initial intensity is set to 35 kt based on the latest subtropical classification of ST2.5 from TAFB a 1208Z ASCAT-B overpass that showed 30-35 kt winds north and northeast of the center. Cyclone phase space diagrams still show Joyce with a shallow-to-moderate warm core, and the system remains a subtropical storm for now.

Little change in intensity is expected during the next few days, as Joyce will continue to be affected by strong westerly-to- southwesterly vertical wind shear. The new NHC forecast is a little below the intensity consensus given the weakening trend seen in the global models. Dissipation is shown at 96 hours, but it wouldn’t be surprising if Joyce becomes a post-tropical cyclone before that.

The initial motion estimate is 245/05. Joyce is currently situated a little to the west of an upper-level low, which is currently steering the system southwestward and southward, and that should continue for the next day or so. Then, Joyce should begin to accelerate northeastward ahead of an approaching mid-level trough. The new NHC track forecast follows the trend of the latest guidance, and is a little to the west of the previous one through 36 hours. The official forecast is close to the latest HCCA and TVCA consensus aids.

FORECAST POSITIONS AND MAX WINDS

INIT  13/1500Z 33.7N  43.7W   35 KT  40 MPH - Tropical Storm (SW Santa Cruz das Flores, Azores)
 12H  14/0000Z 33.1N  44.1W   35 KT  40 MPH - Tropical Storm (SW Santa Cruz das Flores, Azores)
 24H  14/1200Z 32.2N  44.4W   40 KT  45 MPH - Tropical Storm (SW Santa Cruz das Flores, Azores)
 36H  15/0000Z 31.9N  44.0W   40 KT  45 MPH - Tropical Storm (SW Santa Cruz das Flores, Azores)
 48H  15/1200Z 32.5N  42.6W   40 KT  45 MPH - Tropical Storm (SW Santa Cruz das Flores, Azores)
 72H  16/1200Z 35.5N  38.5W   35 KT  40 MPH - Tropical Storm (SW Santa Cruz das Flores, Azores)
 96H  17/1200Z...DISSIPATED

NWS National Hurricane Center Miami FL 500 AM AST Thu Sep 13 2018

Joyce is still co-located with an upper-level low, and the most recent TAFB intensity classification was still a subtropical type. Furthermore, there has been no discernible increase of convection near the center of the cyclone, and cloud tops have actually warmed over the past few hours. Therefore, Joyce is still classified as subtropical for this advisory. Since the cyclone hasn’t changed much in organization, the initial intensity has been held at 40 kt based on the TAFB subtropical intensity estimate, but this is still possibly generous.

Joyce’s struggle to maintain deep convection bodes poorly for its intensification prospects, considering that the shear is forecast by the global models to increase considerably over the next few days. SHIPS, LGEM, and the global models continue to show Joyce changing little in strength over the next few days until the system dissipates by early next week. The HWRF and HMON models are still outliers in showing substantial intensification, but even these models aren’t quite as aggressive in strengthening Joyce as they were previously. The NHC forecast continues to favor the statistical guidance and is just below the intensity consensus at most forecast hours because it is frankly hard to believe that Joyce will become a hurricane in 48 h based on its current appearance.

Joyce is still moving slowly southwestward with an initial motion of 220/5 kt. The global models remain in fairly good agreement that Joyce will move slowly southwestward for the next day or so as the storm remains in light steering flow. A turn toward the south will likely occur as Helene approaches from the southeast, followed by a quick turn northeastward once the larger tropical cyclone passes by. Joyce should then accelerate quickly northeastward ahead of a mid-latitude trough before dissipating southwest of the Azores. Little change was made to the official track forecast which is near the middle of the various consensus aids.

FORECAST POSITIONS AND MAX WINDS

INIT  13/0900Z 33.8N  43.1W   40 KT  45 MPH - Tropical Storm (SW Santa Cruz das Flores, Azores)
 12H  13/1800Z 33.3N  43.8W   40 KT  45 MPH - Tropical Storm (SW Santa Cruz das Flores, Azores)
 24H  14/0600Z 32.6N  44.2W   45 KT  50 MPH - Tropical Storm (SW Santa Cruz das Flores, Azores)
 36H  14/1800Z 32.0N  44.0W   45 KT  50 MPH - Tropical Storm (SW Santa Cruz das Flores, Azores)
 48H  15/0600Z 32.1N  43.2W   45 KT  50 MPH - Tropical Storm (SW Santa Cruz das Flores, Azores)
 72H  16/0600Z 34.6N  39.4W   40 KT  45 MPH - Tropical Storm (SW Santa Cruz das Flores, Azores)
 96H  17/0600Z 37.0N  32.5W   40 KT  45 MPH- Tropical Storm (SW Santa Cruz das Flores, Azores)
120H  18/0600Z...DISSIPATED

NWS National Hurricane Center Miami FL 800 AM EDT Wed Sep 12 2018

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

The National Hurricane Center is issuing advisories on Hurricane Florence, located over the western Atlantic Ocean, on Hurricane Helene, located over the eastern Atlantic, and on Tropical Storm Isaac, located several hundred miles east of the Lesser Antilles.

1. Cloudiness and showers associated with a trough of low pressure over the south-central Gulf of Mexico have decreased since yesterday and the Air Force reconnaissance plane scheduled to investigate the system for today will likely be cancelled. However, upper-level winds are forecast to become a little more conducive for development, and a tropical depression could still form Thursday or Friday before the system reaches the western Gulf Coast. Regardless of development, heavy rainfall and gusty winds are expected across portions of northeastern Mexico, Texas, and Louisiana late this week, and interests there should monitor the progress of this system. * Formation chance through 48 hours…medium…60 percent. * Formation chance through 5 days…medium…60 percent.

2. A non-tropical area of low pressure located several hundred miles west-southwest of the Azores is producing a large area of showers and thunderstorms and gale-force winds. This system could gradually acquire tropical or subtropical characteristics during the next couple of days while it meanders over the northeastern Atlantic Ocean, and before it becomes absorbed by a larger trough of low pressure. For more information, see High Seas Forecasts issued by the National Weather Service. * Formation chance through 48 hours…medium…40 percent. * Formation chance through 5 days…medium…50 percent.

NWS National Hurricane Center Miami FL 200 PM EDT Tue Sep 11 2018

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

The National Hurricane Center is issuing advisories on Hurricane Florence, located over the west-central Atlantic Ocean, on Hurricane Helene, located over the eastern Atlantic, and on Tropical Storm Isaac, located several hundred miles east of the Lesser Antilles.

1. Satellite images and surface observations indicate that the area of disturbed weather located over the extreme northwestern Caribbean Sea and the southeastern Gulf of Mexico is gradually becoming better organized. Ship reports indicate that this system is producing strong gusty winds over the Yucatan Channel. Upper-level winds are forecast to become more conducive for development, and a tropical depression is likely to form by Thursday night while the disturbance moves across the western Gulf of Mexico. If necessary, an Air Force Reconnaissance plane will investigate the system tomorrow. Interests across northeastern Mexico and the coasts of Texas and Louisiana should monitor the progress of this system. Regardless of development, heavy rainfall and gusty winds are expected to continue over western Cuba and portions of the northeastern Yucatan Peninsula today. * Formation chance through 48 hours…medium…50 percent. * Formation chance through 5 days…high...70 percent.

2. A non-tropical area of low pressure is forecast to form along a trough of low pressure located over the northeastern Atlantic Ocean. Environmental conditions are conducive for some development, and a tropical or subtropical depression could form by the end of the week while the low meanders over the northeastern Atlantic Ocean. * Formation chance through 48 hours…low…20 percent. * Formation chance through 5 days…medium…50 percent.

NWS National Hurricane Center Miami FL 800 AM EDT Tue Sep 11 2018

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

The National Hurricane Center is issuing advisories on Hurricane Florence, located over the west-central Atlantic Ocean, on Hurricane Helene, located over the eastern Atlantic, and on Tropical Storm Isaac, located over the central tropical Atlantic.

1. A large area of disturbed weather over the extreme northwestern Caribbean Sea and the southeastern Gulf of Mexico is a associated with a surface trough interacting with an upper-level low. Although this activity is showing signs of organization, there are no signs of a surface circulation. Limited development is anticipated today, but upper-level winds are forecast to become more conducive, and a tropical depression could form on Thursday or Friday while the disturbance moves across the western Gulf of Mexico. Interests across northeastern Mexico and the coasts of Texas and Louisiana should monitor the progress of this system. Regardless of development, heavy rainfall and gusty winds are likely over western Cuba and portions of the northeastern Yucatan Peninsula today. * Formation chance through 48 hours…low…30 percent.
* Formation chance through 5 days…medium...60 percent.

2. A non-tropical area of low pressure is forecast to form along a trough of low pressure located over the northeastern Atlantic Ocean. Environmental conditions are conducive for some development, and a tropical or subtropical depression could form by the end of the week while the low meanders over the northeastern Atlantic Ocean. * Formation chance through 48 hours…low…10 percent. * Formation chance through 5 days…medium…50 percent.

NWS National Hurricane Center Miami FL 200 PM EDT Mon Sep 10 2018

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

The National Hurricane Center is issuing advisories on Hurricane Florence, located over the west-central Atlantic Ocean, on Hurricane Helene, located over the eastern Atlantic, and on Hurricane Isaac, located over the central tropical Atlantic.

1. Showers and thunderstorms over the northwestern Caribbean Sea and western Cuba, associated with a surface trough, are showing some signs of organization. This system is forecast to move slowly northwestward near the Yucatan Peninsula on Tuesday with limited development. Upper-level winds are forecast to become more conducive for development on Wednesday when the system moves over the southern Gulf of Mexico, and a tropical depression could form on Thursday or Friday while the disturbance moves across the western Gulf of Mexico. Interests across northeastern Mexico and the coast of Texas and Louisiana should monitor the progress of this system. Regardless of development, heavy rainfall and gusty winds are likely over western Cuba through Tuesday. * Formation chance through 48 hours…low…30 percent. * Formation chance through 5 days…medium…50 percent.

2. A non-tropical area of low pressure is forecast to form in the northeastern Atlantic Ocean several hundred miles west-southwest of the Azores in about two days. Environmental conditions are conducive for some development, and a tropical or subtropical depression could form by the end of the week while the low moves erratically over the northeastern Atlantic Ocean. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…medium…50 percent.

NWS National Hurricane Center Miami FL 800 AM EDT Mon Sep 10 2018

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

The National Hurricane Center is issuing advisories on Hurricane Florence, located over the west-central Atlantic Ocean, on Hurricane Helene, located over the eastern Atlantic, and on Hurricane Isaac, located over the central tropical Atlantic.

1. Disorganized showers and thunderstorms over the northwestern Caribbean Sea and western Cuba are associated with a weak surface trough. The disturbance is forecast to move slowly northwestward across the northwestern Caribbean Sea and the Yucatan Peninsula over the next couple of days with only slow development expected during that time. However, upper-level winds are forecast to become more conducive, and a tropical depression could form late this week when the system moves across the western Gulf of Mexico. * Formation chance through 48 hours…low…10 percent. * Formation chance through 5 days…medium...40 percent.

2. A non-tropical area of low pressure is forecast to form in the northeastern Atlantic Ocean several hundred miles west-southwest of the Azores in about two days. Some slow tropical or subtropical development is possible by the end of the week while the low moves southwestward. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…medium...40 percent.

NWS National Hurricane Center Miami FL 200 PM EDT Sun Sep 9 2018

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

The National Hurricane Center is issuing advisories on recently upgraded Hurricane Florence, located over the west-central Atlantic Ocean, on Tropical Storm Helene, located just southwest of the Cabo Verde Islands, and on Tropical Storm Isaac, located over the eastern Atlantic.

The combination of an upper-level trough and a tropical wave over the northwestern Caribbean Sea is producing a large area of disorganized showers and thunderstorms between Cuba and Honduras. Upper-level winds could become somewhat more conducive for some development when the system moves into the Gulf of Mexico in a couple of days while the system moves slowly west-northwestward or northwestward. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…low…20 percent.

A non-tropical area of low pressure is forecast to form in the northeastern Atlantic Ocean several hundred miles west-southwest of the Azores in two or three days. Some slow tropical or subtropical development is possible by the middle of the week while the low moves southwestward. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…low…30 percent.

NWS National Hurricane Center Miami FL 800 AM EDT Sun Sep 9 2018

For the North Atlantic…Caribbean Sea and the Gulf of Mexico: The National Hurricane Center is issuing advisories on Tropical Storm Florence, located over the west-central Atlantic Ocean, on Tropical Storm Helene, located just south of the Cabo Verde Islands, and on Tropical Storm Isaac, located over the eastern Atlantic.

1. A non-tropical area of low pressure is forecast to form in the northeastern Atlantic Ocean several hundred miles west-southwest of the Azores in a few days. Some slow tropical or subtropical development is possible by the middle of the week while the low meanders. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…low…30 percent.

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

NWS National Hurricane Center Miami FL 800 PM EDT Fri Sep 7 2018 

For the North Atlantic…Caribbean Sea and the Gulf of Mexico: The National Hurricane Center is issuing advisories on Tropical Storm Florence, located over the central Atlantic Ocean, on Tropical Depression Eight and Tropical Depression Nine both located in the eastern Atlantic. The Weather Prediction Center is issuing advisories on Tropical Depression Gordon, located over Arkansas.

1. A large area of cloudiness and showers centered a few hundred miles west of Bermuda are associated with a trough of low pressure. Development of this system, if any, should be slow to occur during the next couple of days before environmental conditions become unfavorable. This system is expected to move little during the next few days. * Formation chance through 48 hours…low…10 percent. * Formation chance through 5 days…low…20 percent.

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Recent Tropical Storms

Video: Hurricane Florence, with Helene, Issac and Joyce

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