000
WTPZ43 KNHC 270842
TCDEP3
Tropical Storm Hernan Discussion Number 5
NWS National Hurricane Center Miami FL EP132020
300 AM MDT Thu Aug 27 2020
Although Hernan is a sheared tropical cyclone, another strong burst
of deep convection with cloud tops of -83C to -86C has developed
near and south through west of the center. An 0401Z ASCAT-A
scatterometer pass revealed several 38-40 kt surface wind vectors of
south through southwest of the center, so the initial intensity has
been increased to 40 kt, which is supported by a recent UW-CIMSS
SATCON estimate of 40 kt.
The initial motion is estimate is 355/04 kt. Hernan is expected to
remain caught within a large-scale, eastern North Pacific cyclonic
gyre during the next few days, which will result in Hernan moving
counter-clockwise around the eastern and northern periphery of the
gyre. The cyclone will continue to move slowly northward this
morning, followed by a turn toward the northwest by Thursday
afternoon, with a west-northwestward motion expected on Friday. By
Saturday, Hernan is forecast to degenerate into a remnant low
pressure system, and possibly even dissipate and merge with Tropical
Storm Iselle when the two systems are west-southwest of Baja
California. The new NHC track is a very similar to the previous
advisory track, and lies close to a blend of the simple track
consensus models TVCE and GFEX, and the NOAA-HCCA
corrected-consensus model.
Hernan will remain in a moderate-to-strong easterly vertical wind
shear regime for the next three days, which is expected to prevent
any significant strengthening from occurring despite the cyclone
being over warm waters and within a moist mid-level environment.
By 60 hours, Hernan is forecast to degenerate into a remnant low,
and possibly merge with Tropical Storm Iselle in 72-96 hours. The
official intensity forecast is similar to the IVCN intensity
consensus model.
FORECAST POSITIONS AND MAX WINDS
INIT 27/0900Z 18.6N 106.0W 40 KT 45 MPH
12H 27/1800Z 19.5N 106.2W 40 KT 45 MPH
24H 28/0600Z 20.7N 107.3W 40 KT 45 MPH
36H 28/1800Z 21.9N 108.8W 35 KT 40 MPH
48H 29/0600Z 22.7N 110.8W 30 KT 35 MPH
60H 29/1800Z 22.7N 112.9W 30 KT 35 MPH...POST-TROP/REMNT LOW
72H 30/0600Z 22.4N 114.2W 25 KT 30 MPH...POST-TROP/REMNT LOW
96H 31/0600Z...DISSIPATED
$$
Forecaster Stewart
WTPZ43 KNHC 270842
TCDEP3
Tropical Storm Hernan Discussion Number 5
NWS National Hurricane Center Miami FL EP132020
300 AM MDT Thu Aug 27 2020
Although Hernan is a sheared tropical cyclone, another strong burst
of deep convection with cloud tops of -83C to -86C has developed
near and south through west of the center. An 0401Z ASCAT-A
scatterometer pass revealed several 38-40 kt surface wind vectors of
south through southwest of the center, so the initial intensity has
been increased to 40 kt, which is supported by a recent UW-CIMSS
SATCON estimate of 40 kt.
The initial motion is estimate is 355/04 kt. Hernan is expected to
remain caught within a large-scale, eastern North Pacific cyclonic
gyre during the next few days, which will result in Hernan moving
counter-clockwise around the eastern and northern periphery of the
gyre. The cyclone will continue to move slowly northward this
morning, followed by a turn toward the northwest by Thursday
afternoon, with a west-northwestward motion expected on Friday. By
Saturday, Hernan is forecast to degenerate into a remnant low
pressure system, and possibly even dissipate and merge with Tropical
Storm Iselle when the two systems are west-southwest of Baja
California. The new NHC track is a very similar to the previous
advisory track, and lies close to a blend of the simple track
consensus models TVCE and GFEX, and the NOAA-HCCA
corrected-consensus model.
Hernan will remain in a moderate-to-strong easterly vertical wind
shear regime for the next three days, which is expected to prevent
any significant strengthening from occurring despite the cyclone
being over warm waters and within a moist mid-level environment.
By 60 hours, Hernan is forecast to degenerate into a remnant low,
and possibly merge with Tropical Storm Iselle in 72-96 hours. The
official intensity forecast is similar to the IVCN intensity
consensus model.
FORECAST POSITIONS AND MAX WINDS
INIT 27/0900Z 18.6N 106.0W 40 KT 45 MPH
12H 27/1800Z 19.5N 106.2W 40 KT 45 MPH
24H 28/0600Z 20.7N 107.3W 40 KT 45 MPH
36H 28/1800Z 21.9N 108.8W 35 KT 40 MPH
48H 29/0600Z 22.7N 110.8W 30 KT 35 MPH
60H 29/1800Z 22.7N 112.9W 30 KT 35 MPH...POST-TROP/REMNT LOW
72H 30/0600Z 22.4N 114.2W 25 KT 30 MPH...POST-TROP/REMNT LOW
96H 31/0600Z...DISSIPATED
$$
Forecaster Stewart