EPAC: ROSA - Post-Tropical

[gfsperpendicular]

I don't think it'll be as strong, but this is a little similar to Patricia 2015

Not even close. The SSTs near Mexican coast was at record high during Patricia.

Obviously. Nothing will approach Patricia in terms of strength ... I hope

On another note, lots of convection with this one:

[Ntxw]

Yeah you will need 30C+ and near perfect low shear for something like Patricia. This is probably a cat 4 peak. Small shot at low end 5 if it overperforms.

[Yellow Evan]

Major model spread after day 3 or so. ECMWF slows this down as it interacts with a disturbance to the southwest while the GFS recurves this, bringing this to Baja California Norte. Been a longtime since we've had a real California threat. SST's drop off quickly due to the California Current once this gets past 20-21N but given it takes 36-48 hours for an EPAC major to spin down, that'd make a landfalling tropical cyclone in the northern portion of the Baja California Peninsula possible

[Kingarabian]

Beautiful developing EPAC hurricane. FV3-GFS had this coming super close to Socal as a weakening system a few days ago. Let's see what happens..

[Kingarabian]

Major model spread after day 3 or so. ECMWF slows this down as it interacts with a disturbance to the southwest while the GFS recurves this, bringing this to Baja California Norte. Been a longtime since we've had a real California threat. SST's drop off quickly due to the California Current once this gets past 20-21N but given it takes 36-48 hours for an EPAC major to spin down, that'd make a landfalling tropical cyclone in the northern portion of the Baja California Peninsula possible

When was the last *real* California threat? I can't recall any in recent memory.

[zeehag]

she is pretty, but no where near the beauty of patricia. she was wicked. i am still shaking off the wet from that one. hahahahaha

water of our coast is not as hot as it has been in past 3 to 4 years.. that long band of current off south america seems to have taken a toll on our water temp, thankfully. even soc is not as hot as has been for past few years. is a good thing. but we do miss the water..sssshhhhh...

[Yellow Evan]

Major model spread after day 3 or so. ECMWF slows this down as it interacts with a disturbance to the southwest while the GFS recurves this, bringing this to Baja California Norte. Been a longtime since we've had a real California threat. SST's drop off quickly due to the California Current once this gets past 20-21N but given it takes 36-48 hours for an EPAC major to spin down, that'd make a landfalling tropical cyclone in the northern portion of the Baja California Peninsula possible

When was the last *real* California threat? I can't recall any in recent memory.

https://en.wikipedia.org/wiki/Hurricane_Nora_(1997)

[Kingarabian]

[cycloneye]

Tropical Storm Rosa Discussion Number 3
NWS National Hurricane Center Miami FL EP202018
300 PM MDT Tue Sep 25 2018

Rosa has become better organized this afternoon. An earlier 1601
UTC GMI microwave image showed impressive banding features in the
south semicircle with a banding eye type feature wrapping three
quarters around the center of circulation. A blend of the Dvorak
intensity estimates from TAFB and SAB yield an initial intensity of
45 kt for this advisory.

Although there is some modest northeasterly shear impinging in the
northeast side of the cyclone, the SHIPS intensity guidance
indicate that this shear will diminish in 12 hours. Subsequently,
the SHIPS RI index and the DTOPS model indicate a relatively high
probability of rapid intensification in 24 hours. Accordingly, the
NHC forecast calls for Rosa to become a hurricane in 12 hours based
on these data. Further strengthening through the 72 hour period is
expected and is based on the IVCN multi-model intensity consensus.
Beyond day 3, gradual weakening is expected due to increasing shear
and slightly cooler waters.

The initial motion is estimated to be west-northwestward, or 290 at
8 kt, and this general motion is forecast to continue through the
next 3 days south of a mid-level ridge extending from northern
Mexico westward over the eastern Pacific. In response to a
mid-latitude trough approaching from the northwest, Rosa should turn
towards the northwest to north over the weekend. It is worth noting
that there is considerable along and cross-track spread in the track
guidance beyond day 3. Therefore, the official track forecast
follows the TVCN consensus, which lies in between the left and right
global model outlier clusters.


FORECAST POSITIONS AND MAX WINDS

INIT 25/2100Z 15.0N 108.9W 45 KT 50 MPH
12H 26/0600Z 15.4N 110.0W 65 KT 75 MPH
24H 26/1800Z 15.9N 111.5W 80 KT 90 MPH
36H 27/0600Z 16.3N 113.1W 95 KT 110 MPH
48H 27/1800Z 16.5N 114.8W 100 KT 115 MPH
72H 28/1800Z 17.3N 118.0W 110 KT 125 MPH
96H 29/1800Z 19.2N 120.0W 100 KT 115 MPH
120H 30/1800Z 21.7N 120.8W 80 KT 90 MPH

$$
Forecaster Ramos/Roberts

[EquusStorm]

Definitely a proto-eye in development. Really impressive organization speed.

[Abdullah]

The NHC says it'll be a Category 3.

That's something right there...

[Kingarabian]

Low level structure looks really good so far. Should be a hurricane soon.

[EquusStorm]

[CaliforniaResident]

Back in July, the SST in pockets of the Southern California coast were around 80F with widespread SST in the mid to upper 70s: now they dropped back down to normal (mostly upper 60s with a few pockets in the low 70s. Still a chance of getting some remnants if the track is right but would have been far more interesting if the abnormally warm SST sustained themselves into September.

[cycloneye]

Up to 55 kts on Best Track.

As of 00:00 UTC Sep 26, 2018:

Location: 15.0°N 109.3°W
Maximum Winds: 55 kt Gusts: N/A
Minimum Central Pressure: 997 mb
Environmental Pressure: 1008 mb
Radius of Circulation: 150 NM
Radius of Maximum Wind: 15 NM

[cycloneye]

Tropical Storm Rosa Discussion Number 4
NWS National Hurricane Center Miami FL EP202018
900 PM MDT Tue Sep 25 2018

Satellite imagery indicates that Rosa is still strengthening. The
tropical storm has impressive banding features that wrap
cyclonically from the northwest to northeast quadrant, though a dry
slot has recently been observed infringing on the storm's developing
inner-core. The most recent Dvorak intensity estimates from TAFB and
SAB are 55 kt, so the initial intensity has been raised to that
value.

All of the intensity guidance suggests that rapid intensification
(RI) is either already underway or imminent. SSMIS imagery from
around 2300 UTC appeared to confirm the onset of RI with the
development of a small low-level eye-like feature that has been
associated with rapid intensification in past tropical cyclones.
Although more recent imagery indicates this feature may have been
disrupted by the aforementioned dry slot, the models suggest that
this disruption may not last long. The NHC forecast therefore
continues to show RI, and now calls for Rosa to become a major
hurricane in about 36 h. Beyond that time, the hurricane is expected
to remain in a fairly favorable environment through Friday, however,
eyewall replacement cycles could limit the extent to which Rosa
intensifies once it nears major hurricane strength. By the weekend,
cooler SSTs and a drier surrounding environment should cause Rosa to
begin weakening. The NHC intensity forecast is similar to the
previous advisory, and is generally close to HCCA, especially beyond
48 h.

Rosa is moving steadily west-northwestward, or 285/8 kt. A mid-
level ridge to the north of Rosa should keep the cyclone on the
same general heading for the next several days. There is still some
large discrepancies between the global models on the strength of the
ridge for the next few days, resulting in differences in the forward
speed of Rosa during that time. By the end of the week, a large
mid-latitude trough is expected to create a weakness in the ridge,
allowing Rosa to turn northwestward, and possibly northward. The NHC
track forecast will continue to follow the TVCE and HCCA consensus
aids for this advisory.


FORECAST POSITIONS AND MAX WINDS

INIT 26/0300Z 15.1N 109.7W 55 KT 65 MPH
12H 26/1200Z 15.5N 110.9W 70 KT 80 MPH
24H 27/0000Z 16.0N 112.5W 85 KT 100 MPH
36H 27/1200Z 16.3N 114.1W 100 KT 115 MPH
48H 28/0000Z 16.6N 115.8W 105 KT 120 MPH
72H 29/0000Z 17.8N 119.0W 110 KT 125 MPH
96H 30/0000Z 20.0N 120.4W 90 KT 105 MPH
120H 01/0000Z 22.0N 121.0W 75 KT 85 MPH

$$
Forecaster Zelinsky

NNNN

[cycloneye]

Tropical Storm Rosa Discussion Number 5
NWS National Hurricane Center Miami FL EP202018
300 AM MDT Wed Sep 26 2018

After steadily intensifying yesterday, Rosa's strengthening trend
has temporarily paused. The tropical storm has a well-defined
curved band that wraps about three-quarters of the way around the
center. However, some dry air appears to be intruding into the core
from the northeastern quadrant, which could be the reason why Rosa
has stopped strengthening for now. The Dvorak classifications from
TAFB and SAB remain 3.5/55 kt, so the initial intensity is held at
that value. This wind speed is also close to the latest SATCON
estimate from CIMSS at the University of Wisconsin.

A strengthening trend is expected to resume soon, and it seems
likely that Rosa will rapidly intensify during the next couple of
days while it remains over warm SSTs and in an environment of low
wind shear of 10 kt or less. The NHC intensity forecast closely
follows the HCCA model, and brings Rosa to hurricane strength later
today and major hurricane strength on Thursday. Beyond a few days,
steady weakening is forecast due to cooler SSTs, dry and stable air,
and an increase in southwesterly wind shear.

The tropical storm is moving west-northwestward at 7 kt, steered by
a mid-level ridge to its north. A west to west-northwest motion at
about the same forward speed is expected for the next couple of days
as the pattern holds. After that time, the ridge is expected to
break down as a large, deep-layer low moves toward the U.S. west
coast. This change in the steering flow should cause Rosa to move
northwestward late Friday and Saturday and then northward late in
the weekend. The models have come into a little better agreement
this cycle, and a slight eastward shift has been made at 96- and
120-hours based on this guidance. This forecast lies fairly close
to the various consensus aids.

FORECAST POSITIONS AND MAX WINDS

INIT 26/0900Z 15.5N 110.4W 55 KT 65 MPH
12H 26/1800Z 15.9N 111.5W 70 KT 80 MPH
24H 27/0600Z 16.2N 113.2W 85 KT 100 MPH
36H 27/1800Z 16.5N 115.0W 100 KT 115 MPH
48H 28/0600Z 16.8N 116.7W 105 KT 120 MPH
72H 29/0600Z 18.3N 119.0W 105 KT 120 MPH
96H 30/0600Z 20.7N 120.3W 85 KT 100 MPH
120H 01/0600Z 23.0N 120.0W 65 KT 75 MPH

$$
Forecaster Cangialosi

[cycloneye]

 https://twitter.com/EricBlake12/status/1044946038392532992

[cycloneye]

Hurricane Rosa Discussion Number 6
NWS National Hurricane Center Miami FL EP202018
900 AM MDT Wed Sep 26 2018

Rosa is undergoing rapid intensification. Rosa's inner core has
quickly consolidated, indicated by a 1134 UTC SSMI/S image that
showed a solid mid-level ring with a strong well-developed banding
feature in the south semicircle. The lower frequency image from
the pass indicated a small break in the north portion, probably due
to the drier air and northeasterly shear that had been inhibiting
the cyclone's cloud pattern last night. Based on the conventional
and microwave imagery presentation, the initial intensity is raised
to 65 kt.

Rosa should continue on this fast strengthening trend during the
next 12 hours or so. Afterward, further intensification, at a
slower pace, is expected during the next couple of days. Through
the remaining portion of the forecast, gradual weakening is expected
as a result of decreasing sea surface temperatures, increasing
southwesterly vertical shear, and an invading stable, more drier,
marine layer air mass.

The initial motion is estimated to be west-northwestward, or 290/9
kt, within the easterly mid-tropospheric flow produced by a
ridge to the north of the hurricane. Around mid-period, the
large-scale models show a weakness developing the in the
aforementioned ridge in response to a mid-latitude trough
approaching the southwest U.S. and Baja California peninsula. As a
result of this synoptic pattern change, Rose should move
northwestward Saturday and then north-northwestward Sunday. The
large along and cross-track spread recognized in the guidance 24
hours ago has decreased significantly, increasing the forecast
confidence some beyond 48 hours. The NHC forecast is fairly close
to the previous one, and is based primarily on the multi-model
consensus.


FORECAST POSITIONS AND MAX WINDS

INIT 26/1500Z 16.1N 111.4W 65 KT 75 MPH
12H 27/0000Z 16.4N 112.7W 90 KT 105 MPH
24H 27/1200Z 16.6N 114.6W 100 KT 115 MPH
36H 28/0000Z 16.8N 116.2W 105 KT 120 MPH
48H 28/1200Z 17.3N 117.5W 110 KT 125 MPH
72H 29/1200Z 19.2N 119.5W 105 KT 120 MPH
96H 30/1200Z 22.0N 120.2W 85 KT 100 MPH
120H 01/1200Z 24.9N 119.0W 60 KT 70 MPH

$$
Forecaster Roberts

[Yellow Evan]

* EAST PACIFIC 2018 SHIPS INTENSITY FORECAST *
* IR SAT DATA AVAILABLE, OHC AVAILABLE *
* ROSA EP202018 09/26/18 18 UTC *

TIME (HR) 0 6 12 18 24 36 48 60 72 84 96 108 120
V (KT) NO LAND 70 76 82 88 94 102 109 108 103 98 89 75 57
V (KT) LAND 70 76 82 88 94 102 109 108 103 98 89 75 57
V (KT) LGEM 70 78 84 90 94 99 102 102 96 86 73 58 43
Storm Type TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP

SHEAR (KT) 10 9 10 9 5 6 1 4 5 11 15 27 29
SHEAR ADJ (KT) -2 0 0 0 0 0 0 -5 -3 0 0 6 -2
SHEAR DIR 47 52 46 32 16 356 41 322 236 220 210 218 232
SST (C) 28.9 28.8 28.8 28.7 28.6 28.4 28.1 27.6 26.9 26.1 24.8 23.8 23.4
POT. INT. (KT) 153 152 152 151 150 147 144 139 132 123 110 100 96
200 MB T (C) -52.3 -51.8 -51.9 -52.0 -51.8 -51.9 -51.3 -51.2 -51.0 -51.0 -51.0 -50.8 -51.5
200 MB VXT (C) 0.5 0.4 0.5 0.7 0.9 1.2 1.0 1.2 1.3 1.5 1.5 1.5 1.0
TH_E DEV (C) 9 9 8 7 6 6 5 4 3 2 1 1 1
700-500 MB RH 73 74 71 73 70 68 65 59 53 50 45 40 33
MODEL VTX (KT) 24 27 27 29 31 32 37 39 39 40 38 36 28
850 MB ENV VOR 45 48 55 66 68 63 60 73 63 75 72 61 30
200 MB DIV 37 40 35 34 45 58 49 45 30 49 19 20 31
700-850 TADV -2 -2 -3 -3 -2 -5 -3 -1 3 7 4 6 -1
LAND (KM) 744 753 775 820 873 951 967 960 931 864 732 579 398
LAT (DEG N) 16.4 16.6 16.8 16.9 16.9 17.2 17.9 18.8 20.1 21.5 23.0 24.4 25.9
LONG(DEG W) 111.7 112.7 113.6 114.5 115.4 116.8 118.0 119.0 119.8 120.1 120.0 119.4 118.4
STM SPEED (KT) 9 9 9 9 8 7 7 7 7 8 7 8 8
HEAT CONTENT 24 22 21 17 14 13 8 6 1 0 0 0 0

FORECAST TRACK FROM OFCI INITIAL HEADING/SPEED (DEG/KT):300/ 9 CX,CY: -7/ 5
T-12 MAX WIND: 55 PRESSURE OF STEERING LEVEL (MB): 576 (MEAN=584)
GOES IR BRIGHTNESS TEMP. STD DEV. 50-200 KM RAD: 12.0 (MEAN=14.5)
% GOES IR PIXELS WITH T < -20 C 50-200 KM RAD: 98.0 (MEAN=65.0)
PRELIM RI PROB (DV .GE. 55 KT IN 48 HR): 27.1

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. 1. 1. 0. -1. -1. -2. -3.
SST POTENTIAL 1. 2. 3. 4. 4. 3. 1. -1. -4. -6. -8. -10.
VERTICAL SHEAR MAG 0. -1. -1. 0. 1. 3. 5. 7. 7. 7. 4. 0.
VERTICAL SHEAR ADJ 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.
VERTICAL SHEAR DIR 0. 1. 1. 1. 1. 2. 1. 1. 0. 1. 1. 2.
PERSISTENCE 4. 5. 6. 6. 4. 3. 2. 1. 0. 0. 0. -1.
200/250 MB TEMP. 0. 0. 0. 0. -1. 0. 0. 1. 2. 3. 3. 4.
THETA_E EXCESS 0. 1. 1. 1. 1. 1. 0. -1. -2. -3. -4. -5.
700-500 MB RH 0. 0. 0. 1. 1. 1. 1. 1. 1. 0. 0. -1.
MODEL VTX TENDENCY 1. 2. 4. 6. 8. 13. 17. 20. 22. 21. 16. 6.
850 MB ENV VORTICITY 0. 0. 0. 0. 0. -1. -1. -1. -2. -2. -2. -2.
200 MB DIVERGENCE 0. 0. 0. 0. 0. 0. 0. 0. 1. 0. 0. 0.
850-700 T ADVEC 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 1. 1.
ZONAL STORM MOTION 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.
STEERING LEVEL PRES 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.
DAYS FROM CLIM. PEAK 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.
GOES PREDICTORS 1. 1. 1. 1. 1. 2. 2. 2. 2. 2. 2. 3.
OCEAN HEAT CONTENT 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.
RI POTENTIAL 0. 1. 3. 4. 8. 11. 8. 4. 1. -2. -4. -5.
----------------------------------------------------------
TOTAL CHANGE 6. 12. 18. 24. 32. 39. 38. 33. 28. 19. 5. -13.

CURRENT MAX WIND (KT): 70. LAT, LON: 16.4 111.7

** 2018 E. Pacific RI INDEX EP202018 ROSA 09/26/18 18 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) : 81.7 40.5 to 149.3 0.38 3.6
12 HR PERSISTENCE (KT) : 15.0 -22.0 to 44.0 0.56 6.3
850-200 MB SHEAR (KT) : 8.8 19.6 to 1.4 0.59 5.3
HEAT CONTENT (KJ/CM2) : 19.6 1.8 to 106.7 0.17 1.2
D200 (10**7s-1) : 38.2 -33.0 to 156.2 0.38 3.0
STD DEV OF IR BR TEMP : 12.0 37.8 to 2.1 0.72 4.7
MAXIMUM WIND (KT) : 70.0 22.5 to 132.0 0.83 5.2
BL DRY-AIR FLUX (W/M2) : 241.2 721.6 to -82.5 0.60 -3.3
%area of TPW <45 mm upshear : 0.0 62.3 to 0.0 1.00 0.7
2nd PC OF IR BR TEMP : -0.2 2.2 to -1.9 0.57 0.6

SHIPS Prob RI for 20kt/ 12hr RI threshold= 24% is 3.9 times climatological mean ( 6.1%)
SHIPS Prob RI for 25kt/ 24hr RI threshold= 28% is 2.3 times climatological mean (12.5%)
SHIPS Prob RI for 30kt/ 24hr RI threshold= 27% is 3.2 times climatological mean ( 8.4%)
SHIPS Prob RI for 35kt/ 24hr RI threshold= 20% is 3.3 times climatological mean ( 6.0%)
SHIPS Prob RI for 40kt/ 24hr RI threshold= 14% is 3.4 times climatological mean ( 4.0%)
SHIPS Prob RI for 45kt/ 36hr RI threshold= 21% is 3.2 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= 7% is 1.5 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: 23.9% 28.5% 27.2% 19.6% 13.8% 20.5% 18.3% 7.3%
Logistic: 16.8% 30.1% 16.0% 11.4% 6.6% 14.4% 8.7% 0.9%
Bayesian: 11.0% 42.5% 18.0% 9.2% 5.6% 7.5% 1.1% 0.0%
Consensus: 17.2% 33.7% 20.4% 13.4% 8.7% 14.1% 9.4% 2.7%
DTOPS: 21.0% 67.0% 61.0% 49.0% 39.0% 46.0% 6.0% 0.0%

## ANNULAR HURRICANE INDEX (AHI) EP202018 ROSA 09/26/18 18 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) ##

CONTRIBUTIONS TO ANNULAR INDEX