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Hurricane Lane Forecast Discussion Number 10

2018-08-17 10:34:19| National Hurricane Center (East Pacific)

Issued at 200 AM PDT Fri Aug 17 2018 844 WTPZ44 KNHC 170834 TCDEP4 Hurricane Lane Discussion Number 10 NWS National Hurricane Center Miami FL EP142018 200 AM PDT Fri Aug 17 2018 Lane continues to gradually strengthen. Recent microwave images show a well-defined low-level eye, but this feature is not yet apparent in geostationary satellite images. The latest satellite images show an organized central dense overcast, but convection has decreased in the outer bands. An average of the Dvorak estimates from TAFB and SAB yields an initial intensity of 70 kt. The environmental factors suggest that continued steady or rapid strengthening is likely during the next couple of days. However, there could be some intrusions of dry air that might interrupt the rate of strengthening. Nonetheless, it seems likely that Lane will become a major hurricane within the next couple of days. By the end of the forecast period, the environment looks a little less ideal with drier air and an increase in shear likely causing slow weakening. The NHC intensity forecast is largely an update of the previous one, and it remains at the high end of the model guidance. After wobbling to the north late yesterday, Lane has resumed a more westward motion at 14 kt. The hurricane is expected to move westward to west-northwestward during the next several days as it continues to be steered by a subtropical ridge to its north. There is some north-south spread amongst the models with the UKMET on the southern side of the guidance and the GFS and HWRF on the northern side. This spread appears to be associated with how much influence a mid- to upper-level low off the Baja California coast has on Lane's steering flow. The NHC track forecast lies near the middle of the guidance envelope, favoring the various consensus models, and is slightly to the left of the previous forecast track. Lane is expected to cross into the Central Pacific basin in 36 to 48 hours. The initial 34-kt and 50-kt wind radii have been adjusted outward based on a 0544 UTC ASCAT-B pass. FORECAST POSITIONS AND MAX WINDS INIT 17/0900Z 11.4N 131.4W 70 KT 80 MPH 12H 17/1800Z 11.8N 133.6W 80 KT 90 MPH 24H 18/0600Z 12.2N 136.6W 95 KT 110 MPH 36H 18/1800Z 12.7N 139.4W 105 KT 120 MPH 48H 19/0600Z 13.4N 141.9W 110 KT 125 MPH 72H 20/0600Z 14.5N 146.5W 105 KT 120 MPH 96H 21/0600Z 15.0N 150.7W 100 KT 115 MPH 120H 22/0600Z 15.5N 155.3W 90 KT 105 MPH $$ Forecaster Cangialosi

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Tropical Storm Ernesto Forecast Discussion Number 9

2018-08-17 10:32:52| National Hurricane Center (Atlantic)

Issued at 500 AM AST Fri Aug 17 2018 924 WTNT45 KNHC 170832 TCDAT5 Tropical Storm Ernesto Discussion Number 9 NWS National Hurricane Center Miami FL AL052018 500 AM AST Fri Aug 17 2018 Ernesto is maintaining its strength and status as a tropical storm despite being over very cool 21 deg C waters. Deep convection remains well organized in a curved band that wraps across the eastern half of the circulation. The system is likely benefiting from a moist and unstable airmass, which seems to be the reason why Ernesto has held onto tropical storm status longer than expected. The initial wind speed is again held at 40 kt, using a blend of the latest satellite intensity estimates. The convective organization is not expected to last much longer as Ernesto is tracking over steadily colder waters and will also be moving into an environment of higher shear. These hostile environmental conditions should cause the system to lose its tropical characteristics within the next 24 hours, when the cyclone is forecast to be over SSTs of around 15 deg C. The post-tropical low is expected to gradually decay before it merges with a frontal zone near the United Kingdom in about 48 hours. Ernesto is now well embedded in fast mid-latitude flow, and the latest initial motion estimate is northeastward at 22 kt. An even faster northeastward to east-northeastward motion is expected until the system merges with the frontal zone. The models remain tightly clustered, and the NHC track forecast lies near the middle of the guidance envelope. FORECAST POSITIONS AND MAX WINDS INIT 17/0900Z 45.6N 36.4W 40 KT 45 MPH 12H 17/1800Z 47.8N 31.4W 40 KT 45 MPH 24H 18/0600Z 50.4N 23.2W 40 KT 45 MPH...POST-TROPICAL 36H 18/1800Z 52.5N 14.5W 35 KT 40 MPH...POST-TROP/EXTRATROP 48H 19/0600Z...DISSIPATED $$ Forecaster Cangialosi

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Hurricane Lane Forecast Discussion Number 9

2018-08-17 04:43:25| National Hurricane Center (East Pacific)

Issued at 800 PM PDT Thu Aug 16 2018 827 WTPZ44 KNHC 170243 TCDEP4 Hurricane Lane Discussion Number 9 NWS National Hurricane Center Miami FL EP142018 800 PM PDT Thu Aug 16 2018 Visible, infrared, and microwave satellite imagery indicate that Lane's overall cloud pattern has continued to improve, with several spiral bands and a more symmetrical outflow pattern having developed. Although the inner-core convection has deteriorated somewhat until just recently due to the entrainment of dry air, microwave images indicate that a well-defined inner-core and low-level eye feature has formed. Satellite intensity estimates at 0000 UTC ranged form T4.0/65 kt from TAFB and SAB to 55 kt and 59 kt from UW-CIMSS ADT and SATCON, respectively, which supported an intensity of 60 kt at that time. Since then, however, a nearly closed ring of cold-topped convection has developed near the center, so the intensity is set at 65 kt at the advisory time. Lanes has made a sharp jog toward the west-northwest during the past 6 hours, but this believed to be a short-term wobble due to the convection having recently wrapped around the north side of the low-level center. A return to a general westward motion of 280/13 kt is expected to resume shortly. The latest model guidance remains in good agreement on Lane continuing move between westward and west-northwestward direction for the next 3-4 days, followed by a turn back toward the west on day 5 as the stout subtropical ridge to the north strengthens to the east and northeast of the Hawaiian Islands and as a broad upper-level trough north of Hawaii gradually lifts out toward the northeast. The new NHC forecast track has been shifted a little to the right or north of the previous advisory track, primarily due to the more northward initial position, and closely follows the HCCA and TVCN/TVCE track consensus models. Now that a small well-defined inner core and partial eye feature have developed with a radius of maximum winds of 15-20 nmi, Lane is poised to rapidly intensity shortly, and sustain that trend for the next 36 hour so owing to the very low vertical-wind-shear and warm-SST regime that the cyclone will be moving through. Although brief intrusions of dry air may result in some flirtations in the intensity, the general trend should be for Lane to strengthen at a rate of at least 30 kt per 24 hours for the next 36-48 hours. After that, the intensity will be modulated by inner-core/eyewall fluctuations that can not be forecast accurately that far in advance. By days 4 and 5, however, a slow weakening trend is expected due to a gradual increase in southwesterly vertical wind shear. Overall, though, the new NHC intensity forecast is a little above the previous intensity forecast, and is above all of the intensity guidance. A good analog that was used for Lane's forecast was recent Hurricane Hector, which exhibited similar inner-core and outflow characteristics, and moved through similar environmental and oceanic conditions. FORECAST POSITIONS AND MAX WINDS INIT 17/0300Z 11.2N 129.8W 65 KT 75 MPH 12H 17/1200Z 11.5N 131.9W 75 KT 85 MPH 24H 18/0000Z 12.0N 134.9W 90 KT 105 MPH 36H 18/1200Z 12.5N 137.7W 105 KT 120 MPH 48H 19/0000Z 13.1N 140.3W 110 KT 125 MPH 72H 20/0000Z 14.4N 145.0W 110 KT 125 MPH 96H 21/0000Z 15.2N 149.2W 105 KT 120 MPH 120H 22/0000Z 15.6N 153.7W 95 KT 110 MPH $$ Forecaster Stewart

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Tropical Storm Ernesto Forecast Discussion Number 8

2018-08-17 04:37:48| National Hurricane Center (Atlantic)

Issued at 1100 PM AST Thu Aug 16 2018 866 WTNT45 KNHC 170237 TCDAT5 Tropical Storm Ernesto Discussion Number 8 NWS National Hurricane Center Miami FL AL052018 1100 PM AST Thu Aug 16 2018 Convection associated with Ernesto has increased in both coverage and intensity since the last advisory, with a large convective band wrapping about three-quarters of the way around the system. However, recent scatterometer data suggests that this has not yet resulted in strengthening, with winds of 35-40 kt observed about 80 n mi southeast of the center. Based mainly on the scatterometer data, the initial intensity remains 40 kt. While Ernesto is in a warm moist air mass to the east of a mid-latitude cyclone near Newfoundland, the forecast track quickly takes it over sea surface temperatures that will decrease to near 15C in 24 h. This should lead to the dissipation of the convection and to Ernesto becoming a post-tropical cyclone. In 36-48 h, the post-tropical cyclone should merge with a frontal zone, with the resulting extratropical low dissipating between 48-72 h. Overall, the new intensity forecast is nudged slightly downward from the previous forecast, as the guidance no longer shows significant strengthening. Given the increased convection, though, some short-lived strengthening could occur in the next 12 h. In addition, the current trends have led to the time of Ernesto becoming post-tropical being moved back 12 h. The initial motion is now 055/19. The cyclone should accelerate further while moving northeastward to east-northeastward within the mid-latitude westerlies over the next day or two. The dynamical model guidance remains tightly clustered and, as with the previous advisory, little change was made to the track forecast. On the forecast track, Ernesto or its remnants should approach Ireland and the United Kingdom in about 48 h. FORECAST POSITIONS AND MAX WINDS INIT 17/0300Z 44.1N 38.9W 40 KT 45 MPH 12H 17/1200Z 46.1N 34.8W 40 KT 45 MPH 24H 18/0000Z 48.9N 27.7W 40 KT 45 MPH...POST-TROPICAL 36H 18/1200Z 51.2N 19.5W 40 KT 45 MPH...POST-TROP/EXTRATROP 48H 19/0000Z 53.2N 12.1W 35 KT 40 MPH...POST-TROP/EXTRATROP 72H 20/0000Z...DISSIPATED $$ Forecaster Beven

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Tropical Storm Lane Forecast Discussion Number 8

2018-08-16 22:36:19| National Hurricane Center (East Pacific)

Issued at 200 PM PDT Thu Aug 16 2018 648 WTPZ44 KNHC 162036 TCDEP4 Tropical Storm Lane Discussion Number 8 NWS National Hurricane Center Miami FL EP142018 200 PM PDT Thu Aug 16 2018 Satellite images indicate that Lane is trying to form a ragged eye, with an interesting mid-level mesocyclone rotating counterclockwise around the northern side of the circulation. While Dvorak estimates from TAFB/SAB indicate Lane is already a hurricane, values from microwave data are a bit lower, and the cyclone only recently started to potentially form an eye. The initial wind speed is set to 60 kt, close to the latest CIMSS SATCON figure. Further intensification is expected, and given the warm waters, low shear and moderate mid-level humidity, rapid intensification is a distinct possibility. The new NHC forecast is basically an update from the previous one, on the high side of the guidance, and could be conservative. The initial motion estimate continues at 275/11. The synoptic pattern is well defined with a subtropical ridge persisting to the north. While the ridge could weaken somewhat in a few days, a west or west-northwestward track is anticipated throughout the forecast period. The spread in the guidance has decreased somewhat since the last advisory, and the newest model consensus has basically come in right on top of the last NHC forecast. Thus the new NHC track prediction is nearly unchanged, staying close to a blend of the dynamical model consensus and the corrected-consensus aids. FORECAST POSITIONS AND MAX WINDS INIT 16/2100Z 10.6N 128.6W 60 KT 70 MPH 12H 17/0600Z 10.9N 130.6W 70 KT 80 MPH 24H 17/1800Z 11.4N 133.4W 85 KT 100 MPH 36H 18/0600Z 11.9N 136.2W 95 KT 110 MPH 48H 18/1800Z 12.5N 139.1W 105 KT 120 MPH 72H 19/1800Z 13.8N 143.9W 105 KT 120 MPH 96H 20/1800Z 14.8N 148.2W 100 KT 115 MPH 120H 21/1800Z 15.3N 152.5W 90 KT 105 MPH $$ Forecaster Blake

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