786 WTNT41 KNHC 070241 TCDAT1 Tropical Storm Wanda Discussion Number 29 NWS National Hurricane Center Miami FL AL212021 300 AM GMT Sun Nov 07 2021 Wanda has continued to weaken tonight. Only small bursts of convection have occurred during the past several hours, and Wanda's low-level center is starting to move away from the ongoing convection in its southeastern quadrant. A 2220 UTC ASCAT-A pass revealed a small area of 30-kt winds in this portion of the cyclone, but the infrared cloud top temperatures have cooled in this area since that data was collected. The initial intensity is lowered to 35 kt for this advisory, which lies on the higher end of the most recent satellite estimates. Wanda is beginning to move faster toward the northeast, and its initial motion is estimated to be 050/12 kt. The cyclone will continue to accelerate northeastward over the next day or so within the strengthening, deep-layer southwesterly flow associated with a deepening mid-latitude low pressure system over the northern Atlantic. The track guidance remains tightly clustered, and the latest NHC track forecast is virtually unchanged from the previous advisory. Environmental conditions are forecast to become increasingly unfavorable for any further tropical development of Wanda. As the cyclone races northeastward, it will encounter decreasing SSTs and increasing deep-layer southerly shear within a dry mid-level environment. Thus, Wanda's convective structure is unlikely to improve over the next 24 h. The intensity guidance suggests the peak winds could increase slightly later today, but this is most likely a product of the system's increasing forward speed and its merger with an approaching front. Thus, the official NHC intensity forecast has been lowered from the previous one. Wanda is still forecast to merge with the front and become extratropical tonight, then dissipate over the northeastern Atlantic on Monday. FORECAST POSITIONS AND MAX WINDS INIT 07/0300Z 37.8N 36.8W 35 KT 40 MPH 12H 07/1200Z 39.8N 34.1W 35 KT 40 MPH 24H 08/0000Z 44.4N 28.3W 40 KT 45 MPH...POST-TROP/EXTRATROP 36H 08/1200Z 48.9N 21.5W 35 KT 40 MPH...POST-TROP/EXTRATROP 48H 09/0000Z...DISSIPATED $$ Forecaster Reinhart
This graphic shows an approximate representation of coastal areas under a hurricane warning (red), hurricane watch (pink), tropical storm warning (blue) and tropical storm watch (yellow). The orange circle indicates the current position of the center of the tropical cyclone. The black line, when selected, and dots show the National Hurricane Center (NHC) forecast track of the center at the times indicated. The dot indicating the forecast center location will be black if the cyclone is forecast to be tropical and will be white with a black outline if the cyclone is forecast to be extratropical. If only an L is displayed, then the system is forecast to be a remnant low. The letter inside the dot indicates the NHC’s forecast intensity for that time:
D: Tropical Depression – wind speed less than 39 MPH S: Tropical Storm – wind speed between 39 MPH and 73 MPH H: Hurricane – wind speed between 74 MPH and 110 MPH M: Major Hurricane – wind speed greater than 110 MPH
NHC tropical cyclone forecast tracks can be in error. This forecast uncertainty is conveyed by the track forecast “cone”, the solid white and stippled white areas in the graphic. The solid white area depicts the track forecast uncertainty for days 1-3 of the forecast, while the stippled area depicts the uncertainty on days 4-5. Historical data indicate that the entire 5-day path of the center of the tropical cyclone will remain within the cone about 60-70% of the time. To form the cone, a set of imaginary circles are placed along the forecast track at the 12, 24, 36, 48, 72, 96, and 120 h positions, where the size of each circle is set so that it encloses 67% of the previous five years official forecast errors. The cone is then formed by smoothly connecting the area swept out by the set of circles.
It is also important to realize that a tropical cyclone is not a point. Their effects can span many hundreds of miles from the center. The area experiencing hurricane force (one-minute average wind speeds of at least 74 mph) and tropical storm force (one-minute average wind speeds of 39-73 mph) winds can extend well beyond the white areas shown enclosing the most likely track area of the center. The distribution of hurricane and tropical storm force winds in this tropical cyclone can be seen in the Wind History graphic linked above.
Considering the combined forecast uncertainties in track, intensity, and size, the chances that any particular location will experience winds of 34 kt (tropical storm force), 50 kt, or 64 kt (hurricane force) from this tropical cyclone are presented in tabular form for selected locations and forecast positions. This information is also presented in graphical form for the 34 kt, 50 kt, and 64 kt thresholds.
112 WTNT41 KNHC 062034 TCDAT1 Tropical Storm Wanda Discussion Number 28 NWS National Hurricane Center Miami FL AL212021 900 PM GMT Sat Nov 06 2021 Convection associated with Wanda has decreased during the past several hours, with only a small convective cluster occurring just east of the center. In addition, scatterometer data received since the last advisory suggests that the maximum winds have decreased to near 40 kt. That will be the initial intensity for this advisory. Wanda is starting its long-anticipated northeastward turn, with the initial motion now 090/3 kt. Developing deep-layer southwesterly flow on the southeast side of a large mid-latitude low pressure area should cause the cyclone to accelerate northeastward during the next 12 h, with a fast northeastward motion continuing until Wanda dissipates between 36-48 h. The track guidance is in good agreement, and the new track forecast lies near the various consensus models. Despite the recent weakening, the intensity guidance still forecasts some intensification during the next 12-24 h, possibly due to increased upper-level divergence over the cyclone caused by the mid-latitude low or the upcoming significant increase in forward speed. The new intensity forecast will continue to call for Wanda to strengthen for 24 h, although given current trends it would not be surprising if it did not. The cyclone is expected to merge with a cold front between 24-36 h, and the forecast follows the the global model guidance in calling for the circulation to dissipate by 48 h. FORECAST POSITIONS AND MAX WINDS INIT 06/2100Z 37.0N 37.8W 40 KT 45 MPH 12H 07/0600Z 38.5N 35.7W 45 KT 50 MPH 24H 07/1800Z 42.2N 30.9W 50 KT 60 MPH 36H 08/0600Z 47.4N 23.8W 45 KT 50 MPH...POST-TROP/EXTRATROP 48H 08/1800Z...DISSIPATED $$ Forecaster Beven
This graphic shows an approximate representation of coastal areas under a hurricane warning (red), hurricane watch (pink), tropical storm warning (blue) and tropical storm watch (yellow). The orange circle indicates the current position of the center of the tropical cyclone. The black line, when selected, and dots show the National Hurricane Center (NHC) forecast track of the center at the times indicated. The dot indicating the forecast center location will be black if the cyclone is forecast to be tropical and will be white with a black outline if the cyclone is forecast to be extratropical. If only an L is displayed, then the system is forecast to be a remnant low. The letter inside the dot indicates the NHC’s forecast intensity for that time:
D: Tropical Depression – wind speed less than 39 MPH S: Tropical Storm – wind speed between 39 MPH and 73 MPH H: Hurricane – wind speed between 74 MPH and 110 MPH M: Major Hurricane – wind speed greater than 110 MPH
NHC tropical cyclone forecast tracks can be in error. This forecast uncertainty is conveyed by the track forecast “cone”, the solid white and stippled white areas in the graphic. The solid white area depicts the track forecast uncertainty for days 1-3 of the forecast, while the stippled area depicts the uncertainty on days 4-5. Historical data indicate that the entire 5-day path of the center of the tropical cyclone will remain within the cone about 60-70% of the time. To form the cone, a set of imaginary circles are placed along the forecast track at the 12, 24, 36, 48, 72, 96, and 120 h positions, where the size of each circle is set so that it encloses 67% of the previous five years official forecast errors. The cone is then formed by smoothly connecting the area swept out by the set of circles.
It is also important to realize that a tropical cyclone is not a point. Their effects can span many hundreds of miles from the center. The area experiencing hurricane force (one-minute average wind speeds of at least 74 mph) and tropical storm force (one-minute average wind speeds of 39-73 mph) winds can extend well beyond the white areas shown enclosing the most likely track area of the center. The distribution of hurricane and tropical storm force winds in this tropical cyclone can be seen in the Wind History graphic linked above.
Considering the combined forecast uncertainties in track, intensity, and size, the chances that any particular location will experience winds of 34 kt (tropical storm force), 50 kt, or 64 kt (hurricane force) from this tropical cyclone are presented in tabular form for selected locations and forecast positions. This information is also presented in graphical form for the 34 kt, 50 kt, and 64 kt thresholds.
201 WTNT41 KNHC 061442 TCDAT1 Tropical Storm Wanda Discussion Number 27 NWS National Hurricane Center Miami FL AL212021 300 PM GMT Sat Nov 06 2021 The structure of Wanda has changed little since the last advisory, with a band of convection near the center in the northern semicircle and more isolated convective cells elsewhere near the center. The various objective and subjective satellite intensity estimates range from 30-47 kt. Given the spread and the unchanged structure, the initial intensity is held at 45 kt. The initial motion is 180/5 kt. Satellite imagery shows a large mid-latitude low pressure system approaching Wanda from the west and northwest, which should cause the tropical cyclone to turn northeastward during the next 12 h. After that, Wanda is expected to accelerate toward the northeast. The current guidance is in good agreement on the direction of motion, although it is a little slower than the previous guidance. The new forecast track is similar to, but slightly slower than, the previous forecast. Increasing upper-level divergence associated with the mid-latitude low should allow Wanda to strengthen slightly during the next 24 h. Afterwards, the cyclone is expected to merge with a cold front and become an extratropical low. The global models subsequently forecast this low to weaken to a trough by 60 h, and the new intensity forecast shows dissipation at that time. Otherwise, there are only minor adjustments to the previous intensity forecast. FORECAST POSITIONS AND MAX WINDS INIT 06/1500Z 37.0N 38.2W 45 KT 50 MPH 12H 07/0000Z 37.6N 36.8W 45 KT 50 MPH 24H 07/1200Z 40.5N 33.0W 50 KT 60 MPH 36H 08/0000Z 45.3N 26.7W 50 KT 60 MPH...POST-TROP/EXTRATROP 48H 08/1200Z 50.6N 18.1W 45 KT 50 MPH...POST-TROP/EXTRATROP 60H 09/0000Z...DISSIPATED $$ Forecaster Beven
This graphic shows an approximate representation of coastal areas under a hurricane warning (red), hurricane watch (pink), tropical storm warning (blue) and tropical storm watch (yellow). The orange circle indicates the current position of the center of the tropical cyclone. The black line, when selected, and dots show the National Hurricane Center (NHC) forecast track of the center at the times indicated. The dot indicating the forecast center location will be black if the cyclone is forecast to be tropical and will be white with a black outline if the cyclone is forecast to be extratropical. If only an L is displayed, then the system is forecast to be a remnant low. The letter inside the dot indicates the NHC’s forecast intensity for that time:
D: Tropical Depression – wind speed less than 39 MPH S: Tropical Storm – wind speed between 39 MPH and 73 MPH H: Hurricane – wind speed between 74 MPH and 110 MPH M: Major Hurricane – wind speed greater than 110 MPH
NHC tropical cyclone forecast tracks can be in error. This forecast uncertainty is conveyed by the track forecast “cone”, the solid white and stippled white areas in the graphic. The solid white area depicts the track forecast uncertainty for days 1-3 of the forecast, while the stippled area depicts the uncertainty on days 4-5. Historical data indicate that the entire 5-day path of the center of the tropical cyclone will remain within the cone about 60-70% of the time. To form the cone, a set of imaginary circles are placed along the forecast track at the 12, 24, 36, 48, 72, 96, and 120 h positions, where the size of each circle is set so that it encloses 67% of the previous five years official forecast errors. The cone is then formed by smoothly connecting the area swept out by the set of circles.
It is also important to realize that a tropical cyclone is not a point. Their effects can span many hundreds of miles from the center. The area experiencing hurricane force (one-minute average wind speeds of at least 74 mph) and tropical storm force (one-minute average wind speeds of 39-73 mph) winds can extend well beyond the white areas shown enclosing the most likely track area of the center. The distribution of hurricane and tropical storm force winds in this tropical cyclone can be seen in the Wind History graphic linked above.
Considering the combined forecast uncertainties in track, intensity, and size, the chances that any particular location will experience winds of 34 kt (tropical storm force), 50 kt, or 64 kt (hurricane force) from this tropical cyclone are presented in tabular form for selected locations and forecast positions. This information is also presented in graphical form for the 34 kt, 50 kt, and 64 kt thresholds.
000 WTNT41 KNHC 060845 TCDAT1 Tropical Storm Wanda Discussion Number 26 NWS National Hurricane Center Miami FL AL212021 900 AM GMT Sat Nov 06 2021 Wanda's convective structure has continued to evolve this morning, with two earlier bands situated east and west of the well-defined center now having consolidated into a solid band of convection with cloud tops of -50C to -57C wrapping around the eastern semicircle. The initial intensity remains 45 kt for this advisory based on continuity with earlier 40-45 kt ASCAT data and the recently improved convective structure. The initial motion estimate is southward or 180/04 kt. Wanda is expected to slow down further this morning and then turn sharply northeastward this afternoon as a narrow mid-/upper-level shortwave ridge passes to the north of the cyclone. A strong deep-layer trough and associated frontal system are then forecast to approach Wanda from the west by tonight, causing the cyclone to accelerate northeastward on Sunday and Monday. The front is forecast to catch up with Wanda in the 36-48-h period, resulting in extratropical transition before the system is absorbed by a large, deepening extratropical cyclone over the northern Atlantic early next week. The latest NHC model guidance is in excellent agreement on this developing forecast track scenario, and the official forecast track lies very near the the middle of the tightly packed simple- and corrected-consensus guidance envelope. Wanda's is now over what will be the warmest water for the remainder of the cyclone's lifetime. The deep-layer shear is forecast to remain around 10-15 kt for the next 24 h or so, while colder aloft overspreads the cyclone, creating a little more instability. This combination of positive environmental factors should continue to produce deep convection near Wanda's center, possibly resulting in some slight strengthening before the system becomes an extratropical cyclone. The new NHC intensity forecast is basically identical to the previous advisory, and closely follows a blend of the various intensity consensus models. FORECAST POSITIONS AND MAX WINDS INIT 06/0900Z 37.4N 38.3W 45 KT 50 MPH 12H 06/1800Z 37.5N 37.7W 45 KT 50 MPH 24H 07/0600Z 39.4N 35.0W 45 KT 50 MPH 36H 07/1800Z 43.6N 29.5W 50 KT 60 MPH 48H 08/0600Z 48.7N 22.2W 50 KT 60 MPH...POST-TROP/EXTRATROP 60H 08/1800Z 54.2N 12.8W 40 KT 45 MPH...POST-TROP/EXTRATROP 72H 09/0600Z...DISSIPATED $$ Forecaster Stewart
This graphic shows an approximate representation of coastal areas under a hurricane warning (red), hurricane watch (pink), tropical storm warning (blue) and tropical storm watch (yellow). The orange circle indicates the current position of the center of the tropical cyclone. The black line, when selected, and dots show the National Hurricane Center (NHC) forecast track of the center at the times indicated. The dot indicating the forecast center location will be black if the cyclone is forecast to be tropical and will be white with a black outline if the cyclone is forecast to be extratropical. If only an L is displayed, then the system is forecast to be a remnant low. The letter inside the dot indicates the NHC’s forecast intensity for that time:
D: Tropical Depression – wind speed less than 39 MPH S: Tropical Storm – wind speed between 39 MPH and 73 MPH H: Hurricane – wind speed between 74 MPH and 110 MPH M: Major Hurricane – wind speed greater than 110 MPH
NHC tropical cyclone forecast tracks can be in error. This forecast uncertainty is conveyed by the track forecast “cone”, the solid white and stippled white areas in the graphic. The solid white area depicts the track forecast uncertainty for days 1-3 of the forecast, while the stippled area depicts the uncertainty on days 4-5. Historical data indicate that the entire 5-day path of the center of the tropical cyclone will remain within the cone about 60-70% of the time. To form the cone, a set of imaginary circles are placed along the forecast track at the 12, 24, 36, 48, 72, 96, and 120 h positions, where the size of each circle is set so that it encloses 67% of the previous five years official forecast errors. The cone is then formed by smoothly connecting the area swept out by the set of circles.
It is also important to realize that a tropical cyclone is not a point. Their effects can span many hundreds of miles from the center. The area experiencing hurricane force (one-minute average wind speeds of at least 74 mph) and tropical storm force (one-minute average wind speeds of 39-73 mph) winds can extend well beyond the white areas shown enclosing the most likely track area of the center. The distribution of hurricane and tropical storm force winds in this tropical cyclone can be seen in the Wind History graphic linked above.
Considering the combined forecast uncertainties in track, intensity, and size, the chances that any particular location will experience winds of 34 kt (tropical storm force), 50 kt, or 64 kt (hurricane force) from this tropical cyclone are presented in tabular form for selected locations and forecast positions. This information is also presented in graphical form for the 34 kt, 50 kt, and 64 kt thresholds.
000 WTNT41 KNHC 060239 TCDAT1 Tropical Storm Wanda Discussion Number 25 NWS National Hurricane Center Miami FL AL212021 300 AM GMT Sat Nov 06 2021 A dry mid-level environment appears to be hindering Wanda's convective organization tonight. While infrared cloud top temperatures have warmed within the eastern semicircle, a more recent burst of moderately deep convection has been noted in the northwestern quadrant of Wanda. A timely ASCAT-B pass just before 0000 UTC revealed a broad swath of 40- to 45-kt winds within Wanda's western semicircle. Based on these data, the initial intensity is held at 45 kt for this advisory. A narrow mid-level ridge to the north and west of Wanda is steering the cyclone southward. Its estimated motion is 185/8 kt, although Wanda has been moving more south-southwestward over the past several hours. The storm is expected to briefly slow down and meander over the central Atlantic this morning as the steering flow collapses. Then, increasing deep-layer southwesterly flow ahead of an approaching mid- to upper-level trough located near Atlantic Canada is forecast to cause Wanda to accelerate northeastward through early next week. The global models indicate that Wanda is likely to merge with a baroclinic zone by Sunday night, then become absorbed by a deepening extratropical cyclone over the northern Atlantic early next week. The latest track guidance is in good agreement, but it has trended faster with Wanda's forward motion ahead of the trough, which will likely expedite its extratropical transition. Some along-track adjustments were made to the official NHC forecast, which now shows Wanda becoming extratropical in 48 h and becoming absorbed at 72 h. Wanda's southward motion will bring the cyclone over slightly warmer (22 deg C) SSTs today, and cold air aloft could result in enough stability for Wanda to generate some more convection while the deep-layer shear diminishes to less than 10 kt. But the dry environment in which Wanda is embedded will continue to make it difficult for the storm's organization to improve very much, as suggested by the latest GFS and ECMWF-model simulated satellite imagery. The latest NHC intensity forecast allows for just a bit of strengthening this weekend, in good agreement with the IVCN/HCCA consensus aids. By late Sunday and Monday, the aforementioned upper-level trough will bring strong south-southwesterly shear over Wanda while the cyclone moves over plummeting SSTs in the North Atlantic. Baroclinic processes and a fast forward motion could allow Wanda to briefly maintain its intensity, but a weakening trend should commence on Monday before the cyclone is absorbed. FORECAST POSITIONS AND MAX WINDS INIT 06/0300Z 38.0N 38.1W 45 KT 50 MPH 12H 06/1200Z 37.6N 38.0W 45 KT 50 MPH 24H 07/0000Z 38.4N 36.5W 45 KT 50 MPH 36H 07/1200Z 41.9N 32.4W 50 KT 60 MPH 48H 08/0000Z 47.4N 25.6W 50 KT 60 MPH...POST-TROP/EXTRATROP 60H 08/1200Z 54.0N 17.0W 40 KT 45 MPH...POST-TROP/EXTRATROP 72H 09/0000Z...ABSORBED $$ Forecaster Reinhart
This graphic shows an approximate representation of coastal areas under a hurricane warning (red), hurricane watch (pink), tropical storm warning (blue) and tropical storm watch (yellow). The orange circle indicates the current position of the center of the tropical cyclone. The black line, when selected, and dots show the National Hurricane Center (NHC) forecast track of the center at the times indicated. The dot indicating the forecast center location will be black if the cyclone is forecast to be tropical and will be white with a black outline if the cyclone is forecast to be extratropical. If only an L is displayed, then the system is forecast to be a remnant low. The letter inside the dot indicates the NHC’s forecast intensity for that time:
D: Tropical Depression – wind speed less than 39 MPH S: Tropical Storm – wind speed between 39 MPH and 73 MPH H: Hurricane – wind speed between 74 MPH and 110 MPH M: Major Hurricane – wind speed greater than 110 MPH
NHC tropical cyclone forecast tracks can be in error. This forecast uncertainty is conveyed by the track forecast “cone”, the solid white and stippled white areas in the graphic. The solid white area depicts the track forecast uncertainty for days 1-3 of the forecast, while the stippled area depicts the uncertainty on days 4-5. Historical data indicate that the entire 5-day path of the center of the tropical cyclone will remain within the cone about 60-70% of the time. To form the cone, a set of imaginary circles are placed along the forecast track at the 12, 24, 36, 48, 72, 96, and 120 h positions, where the size of each circle is set so that it encloses 67% of the previous five years official forecast errors. The cone is then formed by smoothly connecting the area swept out by the set of circles.
It is also important to realize that a tropical cyclone is not a point. Their effects can span many hundreds of miles from the center. The area experiencing hurricane force (one-minute average wind speeds of at least 74 mph) and tropical storm force (one-minute average wind speeds of 39-73 mph) winds can extend well beyond the white areas shown enclosing the most likely track area of the center. The distribution of hurricane and tropical storm force winds in this tropical cyclone can be seen in the Wind History graphic linked above.
Considering the combined forecast uncertainties in track, intensity, and size, the chances that any particular location will experience winds of 34 kt (tropical storm force), 50 kt, or 64 kt (hurricane force) from this tropical cyclone are presented in tabular form for selected locations and forecast positions. This information is also presented in graphical form for the 34 kt, 50 kt, and 64 kt thresholds.
