EPAC: FLOSSIE - Remnants

[cycloneye]

First forecast to go major.

Tropical Storm Flossie Discussion Number 7
NWS National Hurricane Center Miami FL EP072019
500 PM HST Mon Jul 29 2019

Flossie's satellite appearance in visible, infrared, and microwave
channels has steadily improved since the previous advisory,
including the development of a small CDO feature. However, nearly
identical to Hurricane Erick this time last night, Flossie's
low-level center has migrated southward toward the strongest
convection and is positioned just north of the coldest cloud tops.
Similarly, Flossie is being affected by occasional intrusions of dry
air and some northerly mid-level wind shear that is undercutting the
otherwise favorable upper-level outflow pattern. The initial
intensity of 55 kt is based on a blend of satellite estimates of
T3.5/55 kt from TAFB, T3.0/45 kt from SAB, and T3.9/63 kt and 60 kt
from UW-CIMMS ADT and SATCON, respectively.

The initial motion estimate is westward or 270/15 kt. Despite the
recent west-southwestward jog -- deja vu Erick last night -- the
models are in excellent agreement that Flossie will move westward
for the next 24 hours along the southern periphery of a deep-layer
subtropical ridge, followed by a turn toward the west-northwest on
Wednesday, with that motion continuing through the remainder of the
forecast period. The new official forecast track is south of and
slightly faster than the previous advisory track, mainly due to the
more southerly initial position, and lies between the tightly
clustered consensus models and the more southerly ECMWF model.

If not for dry air mid-level occasionally wrapping into the
hurricane's inner core, Flossie would be poised to rapidly intensify
as per the lastest SHIPS model Rapid Intensification Index (RII).
However, similar to Hurricane Erick, the best course of action is to
just show steady strengthening until a more persistent RI signal
becomes evident. Thus, Flossie is forecast to gradually intensify
into a category 3 hurricane by 72 hours, followed by a near-steady
state condition thereafter due to Flossie moving across cooler
water, which is bounded by the 26C and 26.5C SST isotherms. The
official intensity forecast is very similar to the previous
advisory, and is close to a blend of the NOAA HCCA and the Florida
State Superensemble consensus models.

FORECAST POSITIONS AND MAX WINDS

INIT 30/0300Z 12.3N 117.8W 55 KT 65 MPH
12H 30/1200Z 12.4N 119.9W 65 KT 75 MPH
24H 31/0000Z 12.8N 122.4W 75 KT 85 MPH
36H 31/1200Z 13.3N 125.0W 85 KT 100 MPH
48H 01/0000Z 14.1N 127.6W 95 KT 110 MPH
72H 02/0000Z 15.9N 133.5W 100 KT 115 MPH
96H 03/0000Z 17.4N 139.2W 100 KT 115 MPH
120H 04/0000Z 18.5N 144.4W 90 KT 105 MPH

$$
Forecaster Stewart

[Yellow Evan]

[Kingarabian]

Looking at the 00z Euro I'm like "wow still bearish"...



... till I saw how terrible it looks on IR imagery:

[cycloneye]

Tropical Storm Flossie Discussion Number 8
NWS National Hurricane Center Miami FL EP072019
1100 PM HST Mon Jul 29 2019

Flossie's overall appearance has not changed much over the past
several hours. There continues to be some dry air evident over the
northern semicircle that is entraining into the storm's circulation
and the SHIPS guidance also suggests there is about 10 kt of
northerly shear across the system. This has resulted in most of the
deep convection being confined to the southern semicircle for
much of tonight. The initial intensity remains 55 kt, which is in
agreement with the latest subjective satellite intensity estimates
from both TAFB and SAB.

The motion over the past 12 hours has been just south of due west,
or 265/15 kt. A turn to the west to west-northwest is expected by
later today or tonight and this general motion is expected to
continue for the remainder of the forecast period as Flossie is
steered by a broad mid-level ridge to its north. The track guidance
remains tightly clustered, and the official NHC forecast track is
very close to the previous one.

Recently, deep convection has been trying to wrap around the
northeastern portion of the circulation. If this trend were to
continue, then strengthening would likely resume in the near term.
There is about a 48-hour window remaining for Flossie to
significantly intensify in a fairly favorable environment. The
lastest SHIPS model Rapid Intensification Index (RII) shows a
greater than 50 percent chance for Flossie to intensify by 25 kt
over a 24 hour period. However, Flossie will need to consolidate its
inner core soon if this rapid strengthening is to occur. The
official NHC forecast calls for steady strengthening through much of
today, followed by a 24 hour period of more rapid strengthening that
would make Flossie a category 3 hurricane in 48 hours. After 48
hours, increasing shear and marginal SSTs are expected to cause a
weakening trend to begin. The official intensity forecast is close
to the previous forecast as well as the NOAA corrected consensus,
HCCA, and the Florida State Superensemble consensus models.

FORECAST POSITIONS AND MAX WINDS

INIT 30/0900Z 12.2N 119.3W 55 KT 65 MPH
12H 30/1800Z 12.3N 121.3W 65 KT 75 MPH
24H 31/0600Z 12.8N 123.9W 80 KT 90 MPH
36H 31/1800Z 13.6N 126.5W 90 KT 105 MPH
48H 01/0600Z 14.3N 129.1W 100 KT 115 MPH
72H 02/0600Z 16.1N 134.8W 95 KT 110 MPH
96H 03/0600Z 17.5N 140.5W 90 KT 105 MPH
120H 04/0600Z 18.5N 145.5W 80 KT 90 MPH

$$
Forecaster Latto/Pasch

[Kingarabian]

Its important to note that the HWRF/HMON at hour 120, continue to show Flossie at the same point as the Euro and GFS, but as a potent major hurricane instead of a weakening tropical storm.

[Chris90]

Flossie has improved quite a bit over the past few hours. CDO has blossomed quite nicely and is a nice circular ball of deep convection. I would anticipate future microwave images to show bands wrapping around the northern semi-circle forming an eyewall. Up until now this storm has been weighted to the southern portions of the circulation. Let's see if she can change that today.

[cycloneye]

SAB up to 4.0.


A. 07E (FLOSSIE)

B. 30/1200Z

C. 12.3N

D. 119.6W

E. THREE/GOES-W

F. T4.0/4.0/D1.5/24HRS

G. IR/EIR/SWIR/AMSR2

H. REMARKS...SYSTEM IS CHARACTERIZED BY A CENTRAL COLD COVER (CCC)
WHICH DOES NOT ALLOW FOR A DT. MET AND PT = 4.0. FT BASED ON MET.

I. ADDL POSITIONS

30/0940Z 12.1N 118.9W AMSR2


...KIBLER

[cycloneye]

Location: 12.1°N 119.9°W
Maximum Winds: 60 kt Gusts: nan kt
Minimum Central Pressure: 999 mb
Environmental Pressure: 1010 mb
Radius of Circulation: 180 NM
Radius of Maximum Wind: 30 NM

[Yellow Evan]

[Yellow Evan]

* EAST PACIFIC 2019 SHIPS INTENSITY FORECAST *
* IR SAT DATA AVAILABLE, OHC AVAILABLE *
* FLOSSIE EP072019 07/30/19 12 UTC *

TIME (HR) 0 6 12 18 24 36 48 60 72 84 96 108 120
V (KT) NO LAND 60 64 70 74 77 82 81 77 73 66 59 54 49
V (KT) LAND 60 64 70 74 77 82 81 77 73 66 59 54 49
V (KT) LGEM 60 63 66 69 71 74 75 74 71 65 57 50 45
Storm Type TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP

SHEAR (KT) 6 10 9 11 18 16 25 14 11 13 18 17 23
SHEAR ADJ (KT) 0 4 7 5 -1 1 -3 3 5 4 4 4 2
SHEAR DIR 349 339 347 337 337 356 359 354 330 304 312 289 294
SST (C) 28.2 28.5 28.9 28.9 28.5 28.2 27.8 26.6 27.3 26.4 26.0 26.6 26.2
POT. INT. (KT) 148 151 155 155 151 148 144 132 139 129 124 130 126
200 MB T (C) -52.8 -52.7 -52.1 -52.5 -52.9 -52.3 -52.6 -51.9 -52.3 -51.9 -52.2 -52.3 -52.7
200 MB VXT (C) 0.0 0.1 0.2 0.3 0.5 0.5 0.6 0.4 0.3 0.4 0.4 0.2 0.2
TH_E DEV (C) 6 6 6 5 5 5 5 5 4 4 3 4 4
700-500 MB RH 71 69 68 71 70 65 61 56 54 55 56 57 57
MODEL VTX (KT) 19 18 20 21 20 22 23 23 24 23 22 21 21
850 MB ENV VOR 20 12 10 24 25 30 19 8 21 13 17 24 29
200 MB DIV 69 72 105 110 74 32 5 -2 10 16 -19 11 -12
700-850 TADV -8 -13 -13 -13 -11 -12 -13 -3 2 3 2 0 0
LAND (KM) 1594 1680 1756 1809 1871 2025 2160 2317 1988 1680 1394 1124 857
LAT (DEG N) 12.1 12.2 12.3 12.7 13.1 13.8 14.6 15.6 16.3 17.0 17.7 18.2 18.6
LONG(DEG W) 119.9 121.2 122.5 123.8 125.1 127.7 130.3 133.2 136.3 139.1 141.7 144.2 146.7
STM SPEED (KT) 13 13 13 13 13 13 14 15 14 13 13 12 12
HEAT CONTENT 20 30 38 29 20 19 17 4 29 2 0 9 1

FORECAST TRACK FROM OFCI INITIAL HEADING/SPEED (DEG/KT):270/ 14 CX,CY: -13/ 0
T-12 MAX WIND: 55 PRESSURE OF STEERING LEVEL (MB): 612 (MEAN=587)
GOES IR BRIGHTNESS TEMP. STD DEV. 50-200 KM RAD: 6.2 (MEAN=14.5)
% GOES IR PIXELS WITH T < -20 C 50-200 KM RAD: 99.0 (MEAN=65.0)
PRELIM RI PROB (DV .GE. 35 KT IN 36 HR): 39.9

INDIVIDUAL CONTRIBUTIONS TO INTENSITY CHANGE
6 12 18 24 36 48 60 72 84 96 108 120
----------------------------------------------------------
SAMPLE MEAN CHANGE 0. 0. 1. 1. 1. 2. 1. 1. 1. 0. -1. -1.
SST POTENTIAL 1. 2. 3. 4. 5. 5. 5. 5. 4. 3. 3. 2.
VERTICAL SHEAR MAG 0. 0. 0. -1. -2. -3. -4. -3. -2. -3. -3. -5.
VERTICAL SHEAR ADJ 0. -1. -1. -1. -1. -1. -1. -1. -1. 0. 0. 0.
VERTICAL SHEAR DIR 0. 0. 0. -1. -1. -1. -1. -1. -2. -3. -3. -3.
PERSISTENCE 1. 1. 1. 1. 1. 1. 0. 0. 0. 0. 0. 0.
200/250 MB TEMP. 0. 0. 0. 0. -1. -1. -1. 0. 0. 0. 0. 0.
THETA_E EXCESS 0. 0. 0. 0. -1. -2. -2. -3. -3. -4. -5. -5.
700-500 MB RH 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.
MODEL VTX TENDENCY 0. 1. 1. 1. 3. 4. 5. 7. 6. 5. 3. 2.
850 MB ENV VORTICITY 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.
200 MB DIVERGENCE 0. 0. 1. 1. 1. 1. 1. 0. 0. -1. -1. -1.
850-700 T ADVEC 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.
ZONAL STORM MOTION 0. 0. 1. 1. 2. 2. 3. 2. 2. 2. 2. 2.
STEERING LEVEL PRES 0. 0. 0. 0. 0. 1. 1. 1. 1. 1. 1. 1.
DAYS FROM CLIM. PEAK 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.
GOES PREDICTORS 1. 2. 3. 3. 3. 3. 3. 3. 3. 2. 3. 3.
OCEAN HEAT CONTENT 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.
RI POTENTIAL 1. 3. 5. 7. 10. 9. 5. 1. -1. -3. -5. -5.
----------------------------------------------------------
TOTAL CHANGE 4. 10. 14. 17. 22. 21. 17. 13. 6. -1. -6. -11.

CURRENT MAX WIND (KT): 60. LAT, LON: 12.1 119.9

** 2019 E. Pacific RI INDEX EP072019 FLOSSIE 07/30/19 12 UTC **
(SHIPS-RII PREDICTOR TABLE for 30 KT OR MORE MAXIMUM WIND INCREASE IN NEXT 24-h)

Predictor Value RI Predictor Range Scaled Value(0-1) % Contribution
POT = MPI-VMAX (KT) : 91.7 40.5 to 149.3 0.47 4.3
12 HR PERSISTENCE (KT) : 5.0 -22.0 to 44.0 0.41 5.5
850-200 MB SHEAR (KT) : 10.8 19.6 to 1.6 0.49 5.5
D200 (10**7s-1) : 86.0 -33.0 to 156.2 0.63 5.6
MAXIMUM WIND (KT) : 60.0 22.5 to 132.0 0.97 8.5
HEAT CONTENT (KJ/CM2) : 27.4 2.7 to 106.7 0.24 1.7
STD DEV OF IR BR TEMP : 6.2 37.8 to 2.1 0.89 6.9
BL DRY-AIR FLUX (W/M2) : 211.6 800.8 to -82.5 0.67 0.0
2nd PC OF IR BR TEMP : -0.6 2.2 to -1.9 0.67 0.6
%area of TPW <45 mm upshear : 0.0 62.3 to 0.0 1.00 -0.3

SHIPS Prob RI for 20kt/ 12hr RI threshold= 27% is 4.4 times climatological mean ( 6.1%)
SHIPS Prob RI for 25kt/ 24hr RI threshold= 56% is 4.5 times climatological mean (12.5%)
SHIPS Prob RI for 30kt/ 24hr RI threshold= 38% is 4.5 times climatological mean ( 8.4%)
SHIPS Prob RI for 35kt/ 24hr RI threshold= 29% is 4.9 times climatological mean ( 6.0%)
SHIPS Prob RI for 40kt/ 24hr RI threshold= 20% is 5.1 times climatological mean ( 4.0%)
SHIPS Prob RI for 45kt/ 36hr RI threshold= 23% is 3.6 times climatological mean ( 6.5%)
SHIPS Prob RI for 55kt/ 48hr RI threshold= 18% is 3.1 times climatological mean ( 5.9%)
SHIPS Prob RI for 65kt/ 72hr RI threshold= 6% is 1.3 times climatological mean ( 4.8%)

Matrix of RI probabilities
------------------------------------------------------------------------------
RI (kt / h) | 20/12 | 25/24 | 30/24 | 35/24 | 40/24 | 45/36 | 55/48 |65/72
------------------------------------------------------------------------------
SHIPS-RII: 27.1% 56.1% 38.1% 29.3% 20.5% 23.3% 18.0% 6.2%
Logistic: 24.9% 38.5% 23.5% 18.0% 4.6% 4.3% 0.8% 0.4%
Bayesian: 26.0% 38.7% 23.8% 14.6% 2.3% 3.4% 0.7% 0.0%
Consensus: 26.0% 44.4% 28.5% 20.6% 9.1% 10.3% 6.5% 2.2%
DTOPS: 15.0% 29.0% 15.0% 12.0% 12.0% 17.0% 3.0% 1.0%

## ANNULAR HURRICANE INDEX (AHI) EP072019 FLOSSIE 07/30/19 12 UTC ##
## STORM NOT ANNULAR, SCREENING STEP FAILED, NPASS=4 NFAIL=3 ##
## AHI= 0 (AHI OF 100 IS BEST FIT TO ANN. STRUC., 1 IS MARGINAL, 0 IS NOT ANNULAR) ##

[cycloneye]

Tropical Storm Flossie Discussion Number 9
NWS National Hurricane Center Miami FL EP072019
500 AM HST Tue Jul 30 2019

Convection associated with Flossie increased overnight, and the
cyclone's cloud-top pattern has become more symmetric. However, AMSR
data from about 6 hours ago indicated that most of the deep
convection was limited to the southern semicircle of the cyclone,
indicative of northerly shear, and an SSMIS pass at 1213 appeared to
confirm that this is still the case. The latest Dvorak intensity
estimates from TAFB and SAB are 55 kt and 65 kt, respectively, so
the initial intensity of Flossie has been increased to 60 kt, as a
compromise of those two assessments.

Overall, there is little change in the track or intensity forecast
reasoning. Flossie is moving westward on the south side of a broad
mid-level ridge that extends across most of the eastern Pacific.
All of the guidance indicates that Flossie will move generally
west-northwestward for the next 5 days, and the model spread is low.
Very little changes were made to the NHC track forecast which is
near the various multi-model consensus aids, and confidence in the
track forecast is high.

Conversely, there is low confidence in the intensity forecast.
Flossie appears to have about 36 to 48 hours in a marginally
conducive environment to intensify, and the HWRF even explicitly
forecasts that rapid intensification could occur. An increase in
northerly shear in about 48 h could then inhibit further
intensification, however the GFS and ECMWF suggest that the shear
could decrease again by the end of the forecast period. The spread
in the intensity guidance is very high, particularly beyond 48 h,
with the dynamical models generally higher than the statistical
guidance. No major changes were made to the intensity forecast,
which is near HCCA and FSSE at all forecast hours, however larger
changes could be required in future advisories given the high
uncertainty in the forecast.

FORECAST POSITIONS AND MAX WINDS

INIT 30/1500Z 12.2N 120.5W 60 KT 70 MPH
12H 31/0000Z 12.5N 122.5W 70 KT 80 MPH
24H 31/1200Z 13.1N 125.0W 85 KT 100 MPH
36H 01/0000Z 13.8N 127.6W 90 KT 105 MPH
48H 01/1200Z 14.6N 130.3W 95 KT 110 MPH
72H 02/1200Z 16.1N 136.0W 90 KT 105 MPH
96H 03/1200Z 17.3N 141.7W 90 KT 105 MPH
120H 04/1200Z 18.5N 147.0W 80 KT 90 MPH

$$
Forecaster Zelinsky

[Kingarabian]

I feel for the NHC on this one. Flossie is really taking its time in getting its act together and model forecasts from the GFS and Euro dont make much sense. That being said, it still has quite a bit of time on its side. Just like how we were losing hope in Erick and it eventually came through, it's best to believe that Flossie will do the same.

06z HWRF:

[Kingarabian]

Its IR appearence does in fact look a lot better.



We'll see if it can keep it up.

[wxman57]

Its important to note that the HWRF/HMON at hour 120, continue to show Flossie at the same point as the Euro and GFS, but as a potent major hurricane instead of a weakening tropical storm.

I think the HWRF & HMON are way too strong with Flossie. HWRF intensity forecasts tend to be way off, and HMON is not a good model at all. It may well either barely be a TS when it reaches the islands or it may weaken to a depression east of the islands. I think the NHC will be reducing the predicted intensity in future advisories.

[Yellow Evan]

Its important to note that the HWRF/HMON at hour 120, continue to show Flossie at the same point as the Euro and GFS, but as a potent major hurricane instead of a weakening tropical storm.

I think the HWRF & HMON are way too strong with Flossie. HWRF intensity forecasts tend to be way off, and HMON is not a good model at all. It may well either barely be a TS when it reaches the islands or it may weaken to a depression east of the islands. I think the NHC will be reducing the predicted intensity in future advisories.

Honestly HWRF and HMON and the dynamics more so than the statistical models in general have enough credibility with these type of straight runners in terms of correctly weakening them slowly instead of briskly these past 5 years over 26-27C waters in low shear environments that it merits taking seriously. In this case, I’m not shear how low the shear will be, however. Taking the SHIPS output at 12z literally, I don’t think the shear, while expected to kick in somewhat tomorrow morning, will be enough to totally weaken it, and it’s possible it won’t do much to prevent the usual fluctuations in intensity from 85 to 125 knots that these storms usually undergo.

[cycloneye]

Finnally a Hurricane.

Location: 12.2°N 120.7°W
Maximum Winds: 65 kt Gusts: nan kt
Minimum Central Pressure: 995 mb
Environmental Pressure: 1010 mb
Radius of Circulation: 180 NM
Radius of Maximum Wind: 20 NM

[Kingarabian]

Its important to note that the HWRF/HMON at hour 120, continue to show Flossie at the same point as the Euro and GFS, but as a potent major hurricane instead of a weakening tropical storm.

I think the HWRF & HMON are way too strong with Flossie. HWRF intensity forecasts tend to be way off, and HMON is not a good model at all. It may well either barely be a TS when it reaches the islands or it may weaken to a depression east of the islands. I think the NHC will be reducing the predicted intensity in future advisories.

Honestly HWRF and HMON and the dynamics more so than the statistical models in general have enough credibility with these type of straight runners in terms of correctly weakening them slowly instead of briskly these past 5 years over 26-27C waters in low shear environments that it merits taking seriously. In this case, I’m not shear how low the shear will be, however. Taking the SHIPS output at 12z literally, I don’t think the shear, while expected to kick in somewhat tomorrow morning, will be enough to totally weaken it, and it’s possible it won’t do much to prevent the usual fluctuations in intensity from 85 to 125 knots that these storms usually undergo.

The GFS and Euro may have the right idea that Flossie will be weakening as soon as it crosses 150W.
However, Evan has a point here in that the HWRF/HMON have been solid in this region. It could be by luck, and that because both hurricane models are always bullish and because systems in this area between the EPAC and CPAC tend to always over perform, that the HWRF/HMON end up verifying. The question is: what happens if Flossie enters 145W-150W near 960mb and 100kt winds instead of 995mb and 40-50kt winds?

[Kingarabian]

EPS mean continues to be centered on a Hawaii hit. Fortunately still a lot of time for the track to change.

[cycloneye]

Hurricane Flossie Discussion Number 10
NWS National Hurricane Center Miami FL EP072019
1100 AM HST Tue Jul 30 2019

Deep convection associated with Flossie has been increasing in both
intensity and coverage during the past several hours, and the
cyclone now consists of a well-organized central dense overcast
with some broken outer bands. The Dvorak classifications from TAFB
and SAB are now both 4.0/65 kt and, based on this data, Flossie has
been upgraded to a 65-kt hurricane.

Flossie is moving westward at about 12 kt steered by a mid-level
ridge that is situated to the north of the tropical cyclone. This
ridge is expected to be the primary steering feature during the
next several days, and it should cause Flossie to move westward to
west-northwestward at about the same forward speed through the
weekend. The models are tightly clustered, and only small
changes were made to the previous NHC track forecast. This
forecast lies near the consensus aids, which usually have the
lowest track errors.

The cyclone is expected to be in generally favorable environmental
conditions to strengthen during the next day or so. After that
time, however, the sea surface temperatures beneath the hurricane
gradually decrease and the wind shear is expected to increase a
little. A combination of these factors should end the strengthening
trend and induce a slow weakening by the weekend. The NHC intensity
forecast is a tad lower than the previous one, but it lies near the
high end of the model guidance, in best agreement with the HCCA and
IVDR consensus aids.


FORECAST POSITIONS AND MAX WINDS

INIT 30/2100Z 12.3N 121.3W 65 KT 75 MPH
12H 31/0600Z 12.7N 123.2W 75 KT 85 MPH
24H 31/1800Z 13.4N 125.6W 85 KT 100 MPH
36H 01/0600Z 14.2N 128.3W 90 KT 105 MPH
48H 01/1800Z 15.0N 130.9W 90 KT 105 MPH
72H 02/1800Z 16.3N 136.7W 90 KT 105 MPH
96H 03/1800Z 17.3N 142.0W 85 KT 100 MPH
120H 04/1800Z 18.1N 147.3W 75 KT 85 MPH

$$
Forecaster Cangialosi

[Kingarabian]

I think the NHC intensity forecast is too low.

Flossie continues to have very cold cloud tops over its CDO. It's probably reforming its core. I think Flossie could undergo a couple more core reconstructions and still have a good chance at becoming a major hurricane.