Windspeed Posted September 7, 2018 Share Posted September 7, 2018 413 WTNT43 KNHC 072046 TCDAT3 Tropical Depression Eight Discussion Number 2 NWS National Hurricane Center Miami FL AL082018 500 PM AST Fri Sep 07 2018 Satellite data and surface observations indicate that the low pressure system located just west of the coast of Africa has developed into a tropical depression. Conventional satellite imagery shows a well-defined convective band has formed near the center, and microwave satellite imagery has hinted at the formation of an inner ring of convection. The initial intensity of 30 kt and the central pressure of 1002 mb are based on surface observations from ships and the west coast of Africa. The depression currently has good cirrus outflow in all directions. The initial motion is 275/9. During the next 3-4 days, the cyclone should move generally west-northwestward with an increase in forward speed on the south side of the subtropical ridge over the eastern Atlantic. Near the end of the forecast period, a developing mid- to upper-level trough over the central Atlantic is expected to weaken the ridge and allow the cyclone to turn northwestward with a decrease in forward speed. There is some spread in the guidance late in the period, with the UKMET and the Canadian models showing an earlier turn than the other models. The new forecast track, which is similar to the previous track, is in best agreement with the TVCN and HCCA consensus models. The depression is in an environment of light to moderate easterly vertical shear and over sea surface temperatures of 27-28C. This should allow at least steady strengthening, and rapid strengthening is possible based on the hints of the inner core in microwave imagery. This portion of the intensity forecast has been increased to the upper edge of the intensity guidance, with the cyclone forecast to become a tropical storm in 12 h or less and a hurricane between 48-72 h. After 72 h, the system should be over sea surface temperatures near 26C and encountering southwesterly vertical shear due to the aforementioned trough. This should cause at least a gradual weakening. FORECAST POSITIONS AND MAX WINDS INIT 07/2100Z 13.2N 18.6W 30 KT 35 MPH 12H 08/0600Z 13.5N 19.9W 35 KT 40 MPH 24H 08/1800Z 13.9N 21.9W 45 KT 50 MPH 36H 09/0600Z 14.4N 24.5W 55 KT 65 MPH 48H 09/1800Z 14.9N 27.5W 60 KT 70 MPH 72H 10/1800Z 16.5N 33.5W 70 KT 80 MPH 96H 11/1800Z 18.0N 38.5W 65 KT 75 MPH 120H 12/1800Z 20.5N 42.0W 60 KT 70 MPH $$ Forecaster Beven Link to comment Share on other sites More sharing options...
Windspeed Posted September 7, 2018 Author Share Posted September 7, 2018 TD8 is forecast to become a hurricane before moving into a more unfavorable upper-level environment over the MDR. Link to comment Share on other sites More sharing options...
yoda Posted September 8, 2018 Share Posted September 8, 2018 We have TS Helene BULLETIN Tropical Storm Helene Advisory Number 3 NWS National Hurricane Center Miami FL AL082018 1100 PM AST Fri Sep 07 2018 ...TROPICAL STORM HELENE FORMS BETWEEN THE COAST OF AFRICA AND THE CABO VERDE ISLANDS... ...EXPECTED TO BRING TROPICAL STORM CONDITIONS TO PORTIONS OF THE CABO VERDE ISLANDS SATURDAY NIGHT AND SUNDAY. SUMMARY OF 1100 PM AST...0300 UTC...INFORMATION ----------------------------------------------- LOCATION...13.6N 18.5W ABOUT 405 MI...650 KM E OF THE SOUTHERNMOST CABO VERDE ISLANDS MAXIMUM SUSTAINED WINDS...40 MPH...65 KM/H PRESENT MOVEMENT...W OR 280 DEGREES AT 12 MPH...19 KM/H MINIMUM CENTRAL PRESSURE...1002 MB...29.59 INCHES Link to comment Share on other sites More sharing options...
yoda Posted September 8, 2018 Share Posted September 8, 2018 Tropical Storm Helene Discussion Number 3 NWS National Hurricane Center Miami FL AL082018 1100 PM AST Fri Sep 07 2018 A very timely ASCAT pass indicated that the winds associated with the depression have increased to 35 kt, and also that the center was a little east of the location previously indicated. This is very common in systems during the formative stage. Based on the ASCAT data, the system has been upgraded to Tropical Storm Helene, the eighth named storm of the season. The satellite presentation has also improved during the past several hours, and now the cyclone has large cyclonically curved convective bands to the south of the center. The outflow is fair in all quadrants. Helene will be moving over warm waters and within an environment of light shear through the next 3 to 4 days, and most of the guidance responds to that environment by gradually strengthening the cyclone. The NHC forecast follows the trend of the intensity consensus, and brings Helene to hurricane intensity in about 3 days. Currently, Helene is embedded within a southwest monsoon-type flow, and is moving toward the west at about 9 or 10 knots. However, as the cyclone moves away from the African coast, it will become steered by the easterly flow around the subtropical ridge and should then increase in forward speed. Most of the track models are in extremely good agreement, at least for the next 3 days when the confidence in the forecast is high. At the long range, a mid-level trough is expected to develop over the central Atlantic, forcing the cyclone to turn more to the northwest and even north later on. The NHC forecast is in the middle of the guidance envelope and basically on top of the corrected consensus HCCA. FORECAST POSITIONS AND MAX WINDS INIT 08/0300Z 13.6N 18.5W 35 KT 40 MPH 12H 08/1200Z 13.8N 19.9W 35 KT 40 MPH 24H 09/0000Z 14.3N 22.3W 40 KT 45 MPH 36H 09/1200Z 14.8N 25.0W 50 KT 60 MPH 48H 10/0000Z 15.4N 28.0W 55 KT 65 MPH 72H 11/0000Z 17.0N 33.9W 65 KT 75 MPH 96H 12/0000Z 18.5N 39.0W 65 KT 75 MPH 120H 13/0000Z 20.5N 42.5W 60 KT 70 MPH $$ Forecaster Avila Link to comment Share on other sites More sharing options...
Windspeed Posted September 10, 2018 Author Share Posted September 10, 2018 Helene expected to become a major hurricane before lifting north into east-central Atlantic and weakening. 274 WTNT43 KNHC 101436 TCDAT3 Hurricane Helene Discussion Number 13 NWS National Hurricane Center Miami FL AL082018 1100 AM AST Mon Sep 10 2018 Helene's cloud pattern has become much better organized during the past few hours, with a clear 20 n mi wide eye seen in Meteosat infrared imagery, and a clear eye noted in a 1135 UTC AMSU overpass. A Dvorak classifications from TAFB and SAB were both T5.0/90 knots at 1200 UTC, and that is the initial intensity for this advisory. Helene will remain in an environment that should support some additional strengthening for the next 12 hours or so, with very low shear and SSTs of 27C or above. After that time, the SSTs cool quickly and the shear increases dramatically by 36 hours, which should induce steady weakening. Late in the period, the shear continues, and while SSTs increase the atmosphere dries out, and the intensity is held steady at day 5. The new NHC intensity forecast is above most of the guidance through 24 hours to account for the recent intensification of the storm, but then is close to or slightly above HCCA and IVCN. The initial motion estimate is 285/14. The subtropical ridge north of Helene will gradually weaken as an upper-level trough digs southward around 40W. This pattern will cause Helene to slow down and gradually recurve during the forecast period, with a faster northward motion expected at days 4 and 5 as Helene interacts with the aforementioned upper-level trough. While there is significant variability between the various global models in the exact evolution of the upper-level pattern, the track model guidance is in generally good agreement on this evolution, although the UKMET, its ensemble mean and the GEFS mean are notable outliers to the right. The new NHC track was not changed much from the previous one and lies near the middle of the guidance envelope and is close to HCCA. FORECAST POSITIONS AND MAX WINDS INIT 10/1500Z 14.6N 30.0W 90 KT 105 MPH 12H 11/0000Z 15.2N 32.0W 100 KT 115 MPH 24H 11/1200Z 15.9N 34.3W 100 KT 115 MPH 36H 12/0000Z 16.8N 36.1W 90 KT 105 MPH 48H 12/1200Z 18.0N 37.7W 75 KT 85 MPH 72H 13/1200Z 21.5N 39.5W 60 KT 70 MPH 96H 14/1200Z 27.0N 40.5W 50 KT 60 MPH 120H 15/1200Z 32.5N 40.5W 50 KT 60 MPH $$ Forecaster Brennan Link to comment Share on other sites More sharing options...
yoda Posted September 10, 2018 Share Posted September 10, 2018 Hurricane Helene Discussion Number 14 NWS National Hurricane Center Miami FL AL082018 500 PM AST Mon Sep 10 2018 Helene's cloud pattern continues to be well organized with a large eye of about 20 nm in diameter, surrounded by a ring of deep convection. The cyclone's circulation is large with numerous cyclonically curved convective bands, and the outflow is fair in all quadrants. Dvorak classifications have not changed much, and support an initial intensity of 90 kt. Helene has the opportunity to strengthen some during the next 24 hours or so, while the shear is low and the ocean is still relatively warm. After that time, both shear and SSTs will become less favorable and gradual weakening should then begin. The NHC intensity forecast is similar to the previous one, and follows closely the intensity consensus aids. Helene is moving toward the west-northwest or 290 degrees at 15 kt. Soon, the hurricane will encounter a mid-level trough which the most reliable global models are forming in the eastern Atlantic. This new flow pattern will force Helene to turn to the northwest and north ahead of the developing trough. Track models are quite consistent with this solution and the the spread of the guidance envelope is small through the forecast period. This increases the confidence in the Helene's northward turn, followed by recurvature over the eastern Atlantic. FORECAST POSITIONS AND MAX WINDS INIT 10/2100Z 14.9N 31.5W 90 KT 105 MPH 12H 11/0600Z 15.5N 33.3W 100 KT 115 MPH 24H 11/1800Z 16.4N 35.3W 100 KT 115 MPH 36H 12/0600Z 17.5N 37.0W 85 KT 100 MPH 48H 12/1800Z 19.0N 38.0W 75 KT 85 MPH 72H 13/1800Z 23.0N 39.5W 60 KT 70 MPH 96H 14/1800Z 28.5N 40.0W 50 KT 60 MPH 120H 15/1800Z 34.0N 37.0W 50 KT 60 MPH $$ Forecaster Avila Link to comment Share on other sites More sharing options...
NJwx85 Posted September 10, 2018 Share Posted September 10, 2018 Probably one of the ugliest IR presentations I've ever seen for a well organized, healthy cane. Link to comment Share on other sites More sharing options...
bugalou Posted September 10, 2018 Share Posted September 10, 2018 Looking to be a threat to the Azores in some capacity before all is said in done. It may be fun to watch the interaction with the disturbance around 35N as well if it pops. Link to comment Share on other sites More sharing options...
yoda Posted September 11, 2018 Share Posted September 11, 2018 Hurricane Helene Discussion Number 15 NWS National Hurricane Center Miami FL AL082018 1100 PM AST Mon Sep 10 2018 Helene remains a well organized hurricane with a fairly large 25 n mi diameter eye and ring of cold cloud tops surrounding that feature. There are a few dry slots beyond the inner core, however, which have prevented some of the Dvorak estimates from increasing this cycle. A blend of the latest subjective and objective satellite intensity estimates supports raising the initial intensity slightly to 95 kt. The hurricane has a limited amount of time to strengthen as the current environment of low wind shear and relatively warm SSTs will be changing soon. Helene is expected to cross the 26 deg C isotherm within 24 hours and it will enter an environment of increasing south-southwesterly shear just beyond that time period. These conditions should promote a steady weakening trend beginning late Tuesday. By the end of the forecast period, however, SSTs increase along the forecast track, and there could be some baroclinic enhancements to end the weakening trend and perhaps even cause some strengthening. This scenario is supported by the HWRF/HMON regional models and the GFS/ECMWF global models. The NHC intensity forecast is largely an update of the previous one, except it is slightly higher at the end of the period. The hurricane is gradually turning to the right, with the latest initial motion estimate being 295/13 kt. A large mid- to upper-level trough over the north Atlantic is expected to dig southward causing a significant weakness in the subtropical ridge. In response to this change in the steering pattern, Helene is forecast to gradually turn northward and then north-northeastward during the next several days. The track models are in fairly good agreement, and the NHC track forecast lies near the middle of the guidance envelope. This forecast is only a little to the right of the previous track. FORECAST POSITIONS AND MAX WINDS INIT 11/0300Z 15.5N 32.4W 95 KT 110 MPH 12H 11/1200Z 16.2N 34.0W 95 KT 110 MPH 24H 12/0000Z 17.2N 35.7W 85 KT 100 MPH 36H 12/1200Z 18.6N 37.2W 75 KT 85 MPH 48H 13/0000Z 20.1N 38.0W 65 KT 75 MPH 72H 14/0000Z 24.6N 39.0W 60 KT 70 MPH 96H 15/0000Z 30.0N 38.0W 50 KT 60 MPH 120H 16/0000Z 36.2N 34.0W 55 KT 65 MPH $$ Forecaster Cangialosi Link to comment Share on other sites More sharing options...
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