EPAC: FLOSSIE - Remnants

[Kingarabian]

HWRF and HMON have dropped their intensities Flossie.

[Kingarabian]

Convection has quickly built back over what was once a well exposed center:


Lets see if this presists.

[NDG]

Convection has quickly built back over what was once a well exposed center:
https://i.imgur.com/9BHT53P.gif

Lets see if this presists.

It keeps leaving the convection behind once again, isn't it moving kind of fast for being over the EPAC?

[Kingarabian]

Convection has quickly built back over what was once a well exposed center:
https://i.imgur.com/9BHT53P.gif

Lets see if this presists.

It keeps leaving the convection behind once again, isn't it moving kind of fast for being over the EPAC?

The high has been pretty strong. But yeah pretty abnormal.

[Yellow Evan]

This should still bounce back when upper conditions improve. This isn't over by any means.

[Kingarabian]

Models now recurve this safely east of the islands except for HWRF, HMON, and COAMPS.

[cycloneye]

Tropical Storm Flossie Discussion Number 18
NWS National Hurricane Center Miami FL EP072019
1100 AM HST Thu Aug 01 2019

Again there has been little change in the structure of Flossie
during the past several hours. There are ongoing bursts of
convection near the low-level center, and the overall cloud pattern
has a very asymmetric look due to the impact of 15-20 kt of
northwesterly vertical wind shear. A recent ASCAT overpass showed
several 45-50 kt wind vectors near the center, and based on a
combination of these data and other satellite intensity estimates
the initial intensity will remain 55 kt.

The storm has turned a little to the right with the initial motion
now 290/16. Other than that, there is little change to the track
forecast philosophy. The subtropical tropical ridge to the north
should keep Flossie moving generally west-northwestward for the
next 72 h as indicated by the tightly clustered track guidance. The
guidance spread increases after that, with the regional models
(HWRF, HMON, COAMPS-TC) continuing to take Flossie more westward
toward Hawaii and the global models remaining in good agreement on
Flossie turning northward to the northeast of Hawaii ahead of a mid-
to upper-level trough. The new NHC track forecast continues to
follow the global model scenario, and the new forecast lies a little
north of the previous forecast due mainly to the initial position
and motion.

Flossie is expected to experience moderate shear during the first 72
h of the forecast period, and the shear is likely to increase after
that time. The intensity guidance responds to this by showing a
gradual weakening, and the new NHC forecast, which is an update of
the previous forecast, follows the overall trend of the guidance.

It is worth noting that the confidence in the 5-day forecast
position of Flossie is still low, and the average error of track and
intensity forecasts at that range is about 200 miles and 20 mph,
respectively. In addition, hazards associated with tropical storms
extend well away from the center of circulation. Users should
therefore consult local forecasts from the National Weather Service
Forecast Office in Honolulu, Hawaii, at www.weather.gov/hfo for
information specific to the Hawaiian Islands.


FORECAST POSITIONS AND MAX WINDS

INIT 01/2100Z 16.0N 133.2W 55 KT 65 MPH
12H 02/0600Z 16.6N 135.6W 55 KT 65 MPH
24H 02/1800Z 17.2N 138.5W 55 KT 65 MPH
36H 03/0600Z 17.9N 141.4W 50 KT 60 MPH
48H 03/1800Z 18.5N 144.1W 50 KT 60 MPH
72H 04/1800Z 19.3N 149.0W 40 KT 45 MPH
96H 05/1800Z 21.0N 153.5W 35 KT 40 MPH
120H 06/1800Z 25.0N 155.5W 35 KT 40 MPH

$$
Forecaster Beven

[Kingarabian]

Tropical Storm Flossie Discussion Number 18
NWS National Hurricane Center Miami FL EP072019
1100 AM HST Thu Aug 01 2019

Again there has been little change in the structure of Flossie
during the past several hours. There are ongoing bursts of
convection near the low-level center, and the overall cloud pattern
has a very asymmetric look due to the impact of 15-20 kt of
northwesterly vertical wind shear. A recent ASCAT overpass showed
several 45-50 kt wind vectors near the center, and based on a
combination of these data and other satellite intensity estimates
the initial intensity will remain 55 kt.

The storm has turned a little to the right with the initial motion
now 290/16. Other than that, there is little change to the track
forecast philosophy. The subtropical tropical ridge to the north
should keep Flossie moving generally west-northwestward for the
next 72 h as indicated by the tightly clustered track guidance. The
guidance spread increases after that, with the regional models
(HWRF, HMON, COAMPS-TC) continuing to take Flossie more westward
toward Hawaii and the global models remaining in good agreement on
Flossie turning northward to the northeast of Hawaii ahead of a mid-
to upper-level trough. The new NHC track forecast continues to
follow the global model scenario, and the new forecast lies a little
north of the previous forecast due mainly to the initial position
and motion.

Flossie is expected to experience moderate shear during the first 72
h of the forecast period, and the shear is likely to increase after
that time. The intensity guidance responds to this by showing a
gradual weakening, and the new NHC forecast, which is an update of
the previous forecast, follows the overall trend of the guidance.

It is worth noting that the confidence in the 5-day forecast
position of Flossie is still low, and the average error of track and
intensity forecasts at that range is about 200 miles and 20 mph,
respectively. In addition, hazards associated with tropical storms
extend well away from the center of circulation. Users should
therefore consult local forecasts from the National Weather Service
Forecast Office in Honolulu, Hawaii, at www.weather.gov/hfo for
information specific to the Hawaiian Islands.


FORECAST POSITIONS AND MAX WINDS

INIT 01/2100Z 16.0N 133.2W 55 KT 65 MPH
12H 02/0600Z 16.6N 135.6W 55 KT 65 MPH
24H 02/1800Z 17.2N 138.5W 55 KT 65 MPH
36H 03/0600Z 17.9N 141.4W 50 KT 60 MPH
48H 03/1800Z 18.5N 144.1W 50 KT 60 MPH
72H 04/1800Z 19.3N 149.0W 40 KT 45 MPH
96H 05/1800Z 21.0N 153.5W 35 KT 40 MPH
120H 06/1800Z 25.0N 155.5W 35 KT 40 MPH

$$
Forecaster Beven

[Kingarabian]

UW - CIMSS
ADVANCED DVORAK TECHNIQUE
ADT-Version 9.0
Tropical Cyclone Intensity Algorithm

----- Current Analysis -----
Date : 01 AUG 2019 Time : 203000 UTC
Lat : 15:57:56 N Lon : 133:03:55 W


CI# /Pressure/ Vmax
3.8 / 988.3mb/ 61.0kt


Final T# Adj T# Raw T#
3.5 4.0 4.1

[cycloneye]

Tropical Storm Flossie Discussion Number 19
NWS National Hurricane Center Miami FL EP072019
500 PM HST Thu Aug 01 2019

Somewhat surprisingly, Flossie has become better organized this
evening. Satellite images indicate that deep convection has become
more circular near the center, although the convection is still
favoring the eastern semicircle. Microwave data also show that
a low-level eye feature is present again, so the initial wind speed
is raised to 60 kt, which is in good agreement with the CIMSS
satellite consensus. The storm has a reasonable chance to become a
hurricane again overnight since shear is forecast to stay about the
same in the diurnal convective maximum period, in addition to the
cyclone moving over a warmer SST ridge during that time. This
strengthening window should be short-lived with increasing
northwesterly shear in all of the model guidance, along with more
marginal water temperatures. Thus the new forecast is raised from
the previous one in the short-term, then basically matches the last
advisory after 36 hours and lies close to the model consensus.

Flossie continues to move west-northwestward or 285/16. A large
subtropical ridge to the north is forecast to keep the storm moving
in the same general direction for the next few days, with some
reduction in forward speed over the weekend. Thereafter, Flossie
reaches the southwestern periphery of the subtropical ridge, and
is anticipated to turn northwestward on Monday and northward on
Tuesday. The model spread is similar to the previous cycle, but it
is notable that the regional hurricane models (HWRF, HMON,
COAMPS-TC) have shifted somewhat to the northeast on this cycle,
closer to the previous NHC prediction and model consensus.
Therefore, very little change is made to the last NHC track
forecast, except that it is faster, since the models have had a
tough time keeping up with the speed of Flossie.

It is worth noting that the confidence in the 4-day forecast
position of Flossie is still low, and the average error of track and
intensity forecasts at that range is about 150 miles and 20 mph,
respectively. In addition, hazards associated with tropical storms
extend well away from the center of circulation. Users should
therefore consult local forecasts from the National Weather Service
Forecast Office in Honolulu, Hawaii, at www.weather.gov/hfo for
information specific to the Hawaiian Islands.


FORECAST POSITIONS AND MAX WINDS

INIT 02/0300Z 16.4N 134.8W 60 KT 70 MPH
12H 02/1200Z 16.9N 137.2W 65 KT 75 MPH
24H 03/0000Z 17.5N 140.2W 60 KT 70 MPH
36H 03/1200Z 18.1N 143.0W 55 KT 65 MPH
48H 04/0000Z 18.7N 145.7W 50 KT 60 MPH
72H 05/0000Z 19.7N 150.6W 40 KT 45 MPH
96H 06/0000Z 22.5N 154.5W 35 KT 40 MPH
120H 07/0000Z 27.5N 155.5W 30 KT 35 MPH

$$
Forecaster Blake

[cycloneye]

Tropical Storm Flossie Discussion Number 28
NWS Central Pacific Hurricane Center Honolulu HI EP072019
1100 PM HST Sat Aug 03 2019

Flossie's satellite presentation is typical of a sheared tropical
cyclone, with deep convection removed from the low level
circulation center (LLCC). In this case, westerly vertical wind
shear around 25 kt is keeping the convection displaced east of the
LLCC, which remains obscured by mid- and high-level clouds. The
initial intensity has been maintained at 40 kt for this advisory, as
the satellite appearance has changed little since an earlier ASCAT
pass indicating winds close to 40 kt, entirely in the northern
semicircle. This is higher than the Dvorak intensity estimates that
range from 1.0/25 kt to 2.5/35 kt from HFO/SAB/PGTW, but close to
UW-CIMSS SATCON.

Flossie is tracking almost due west this evening, with an initial
motion estimate of 280/11 kt. A low- to mid-level ridge north of
Flossie has been supporting this motion for the past couple of
days, and forecast models are now indicating that this ridge will
remain stronger than originally anticipated in the short term.
Track guidance has once again shifted to the left in response, and
the official forecast follows suit, building on a trend that started
about 24 hours ago.

HWRF/HMON and CTCI have been on the left side of the guidance
envelope for several runs, taking Flossie very close to, or over,
portions of the Hawaiian Islands Monday and Tuesday - albeit as a
weak tropical cyclone. Other reliable models are now indicating a
similar scenario, and the updated official forecast brings the
center of Flossie over waters just east of the Hawaiian Islands as
a tropical depression. Given recent trends and average forecast
error, a Tropical Storm Watch may be required for portions of the
Hawaiian Islands on Sunday. The updated track forecast closely
follows the ECMWF guidance, and indicates a turn toward the
northwest after 48 hours as Flossie finally rounds the ridge, and
gets wrapped in the flow around a persistent deep-layer trough
northwest of Hawaii.

The gradual spin down of Flossie is expected to continue as it
draws closer to the Hawaiian Islands, despite SSTs gradually warming
to near 27C. Vertical wind shear is expected to increase to over 30
kt after 24 hours, leading to steady weakening, and eventually
dissipation. The intensity forecast is mainly an update of the
prior forecast, and is close to the trends indicated by both the
statistical and dynamical guidance.


FORECAST POSITIONS AND MAX WINDS

INIT 04/0900Z 19.1N 146.7W 40 KT 45 MPH
12H 04/1800Z 19.3N 148.4W 35 KT 40 MPH
24H 05/0600Z 19.4N 150.8W 35 KT 40 MPH
36H 05/1800Z 19.9N 153.5W 30 KT 35 MPH
48H 06/0600Z 21.0N 155.9W 30 KT 35 MPH
72H 07/0600Z 22.9N 159.8W 25 KT 30 MPH...POST-TROP/REMNT LOW
96H 08/0600Z...DISSIPATED

$$
Forecaster Birchard

[CyclonicFury]

Once again, the ECMWF was way too strong with Flossie in the long range. It seems like global models always underestimate the unfavorable conditions east of Hawaii.

[cycloneye]

Tropical Depression Flossie Discussion Number 31
NWS Central Pacific Hurricane Center Honolulu HI EP072019
500 PM HST Sun Aug 04 2019

Deep convection in the northeast quadrant of Flossie collapsed
around 1800 UTC due to westerly vertical wind shear in excess of 20
kt. Since then, the low-level circulation center (LLCC) has been
completely exposed, and isolated convection has been displaced
over 175 nm to the east. Subjective Dvorak current intensity
estimates ranged from a 1.5/25 kt from SAB to 2.0/30 kt from JTWC to
2.5/35 kt from HFO, while data T numbers were all lower. Based on
these inputs and the absence of central convection for more than six
hours, the initial intensity is lowered to 30 kt, and Flossie is now
a tropical depression.

The exposed LLCC of the depression is moving toward the west (270
degrees) at 11 kt. The continued westward motion, which will persist
into Monday, gives increased confidence that the weakening system is
becoming shallow and under a greater steering influence from the
low- to mid-level ridge to the north. As the ridge weakens, Flossie
is forecast to turn toward the west-northwest late Monday and remain
on that motion near or over the main Hawaiian Islands until
dissipation. The forecast track is nudged slightly south from the
prior advisory and remains close to the ECMWF and HWRF near the
middle of the guidance envelope.

Flossie will gradually spin down over the next couple of days. An
upper-level trough northwest of Hawaii will remain in place during
this time, maintaining strong west-southwest winds aloft. As Flossie
moves westward under these strong upper-level winds, vertical wind
shear will increase to 30 to 40 kt tonight and Monday, causing
the depression to slowly weaken as it moves near or over the
Hawaiian Islands. The forecast is in line with the dynamical and
statistical guidance but keeps Flossie slightly stronger than nearly
all guidance in the next 12 to 24 hours.

Interests in the main Hawaiian Islands should refer to products
issued by the National Weather Service in Honolulu for information
on flooding and surf impacts from Tropical Depression Flossie.


FORECAST POSITIONS AND MAX WINDS

INIT 05/0300Z 18.9N 149.8W 30 KT 35 MPH
12H 05/1200Z 19.1N 151.8W 30 KT 35 MPH
24H 06/0000Z 19.8N 154.4W 30 KT 35 MPH
36H 06/1200Z 20.8N 156.7W 25 KT 30 MPH...POST-TROP/REMNT LOW
48H 07/0000Z 21.8N 158.3W 25 KT 30 MPH...POST-TROP/REMNT LOW
72H 08/0000Z...DISSIPATED

$$
Forecaster Wroe

[cycloneye]

Post-Tropical Cyclone Flossie Discussion Number 35
NWS Central Pacific Hurricane Center Honolulu HI EP072019
500 PM HST Mon Aug 05 2019

Vigorous deep convection has been persistent through much of the day
to the northeast of the cloud system center, which has become
significantly elongated and poorly defined by several outflow
boundaries. Recent analyses of satellite cloud drift winds suggest
that the highly elongated cloud system center is lacking westerly
winds that define a closed area of low pressure, and subjective
Dvorak current intensity estimates were 25 kt from HFO and SAB,
while JTWC deemed the system too weak to classify. Given these
inputs and the presence of continued vertical wind shear of more
than 30 kt, Flossie will be designated a post-tropical remnant low.
The intensity will remain 30 kt, since an ASCAT-C pass earlier in
the day detected winds this strong within the deep convection. While
the cloud system center could arguably be a trough, a mean center
location gives an initial motion of 300/10 kt.

Under relentless vertical wind shear, the remnant low will continue
to degenerate as it passes near the main Hawaiian Islands. The
westerly vertical wind shear will be maintained by a deep
upper-level trough parked northwest of the Hawaiian Islands. This
upper trough is also eroding the low- to mid-level ridge that is
steering Flossie. As a result, the remnant low will gradually turn
toward the northwest tonight, then shift toward the north-northwest
until dissipation on Wednesday. The track forecast was nudged to the
right from the prior advisory and is near TVCN. All guidance shows
weakening or little change in intensity until dissipation.

This is the last advisory on Flossie. Additional information on this
system can be found in the High Seas Forecasts issued by the
National Weather Service in Honolulu under AWIPS header HFOHSFNP and
WMO header FZPN40 PHFO. Interests in the main Hawaiian Islands
should refer to products issued by the National Weather Service in
Honolulu for information on flooding and surf impacts.


FORECAST POSITIONS AND MAX WINDS

INIT 06/0300Z 20.8N 154.6W 30 KT 35 MPH...POST-TROPICAL
12H 06/1200Z 22.1N 155.8W 30 KT 35 MPH...POST-TROP/REMNT LOW
24H 07/0000Z 24.0N 156.8W 30 KT 35 MPH...POST-TROP/REMNT LOW
36H 07/1200Z 26.0N 157.4W 30 KT 35 MPH...POST-TROP/REMNT LOW
48H 08/0000Z...DISSIPATED

$$
Forecaster Wroe

[Hurricane Jed]

Should have been discontinued hours ago