EPAC: GENEVIEVE - Post-Tropical

[aspen]

EPac storms seem to be addicted to dry air this year

Seems like Genevieve is doing a decent job at mixing it out. She just needs a solid eyewall, and then a major will be on its way.

Agreed. Still wasn't expecting even a brief hiccup due to dry air though. Very high ceiling nonetheless

You can tell this has insane potential just by looking at how quickly it became a hurricane (TD to 65 kt in just 24 hours) and its killer outflow pattern. This has been rapidly intensifying and is primed to continue doing so once it’s done hiccuping.

[StruThiO]

Seems like Genevieve is doing a decent job at mixing it out. She just needs a solid eyewall, and then a major will be on its way.

Agreed. Still wasn't expecting even a brief hiccup due to dry air though. Very high ceiling nonetheless

You can tell this has insane potential just by looking at how quickly it became a hurricane (TD to 65 kt in just 24 hours) and its killer outflow pattern. This has been rapidly intensifying and is primed to continue doing so once it’s done hiccuping.

Yeah it's what a real storm looks like. Wonder how it'll compare at peak intensity to its previous namesake from 2014

[Kingarabian]

EPac storms seem to be addicted to dry air this year

Where is it coming from? All the way from Africa? Wouldn't it then also be an issue for the expected Atlantic cyclones?

Cold EPAC waters in the subtropics is the primary source. More prevalent this year due to oncoming La Nina.

[zeehag]

as she gets more gorgeous i get more cautious... i remember patricia all too well.. she is awesome to watch as long as i know she isnot coming to get me and other sailboat residents who sail west coast mexico.

[Kingarabian]

Most recent frames show the dry air almost completely mixed out:

[Kingarabian]

This system has the potential to be a strong one. GMI shows strong eyewall convection present even though it's disrupted by dry air and not wrapped around.

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

----- Current Analysis -----
Date : 17 AUG 2020 Time : 192020 UTC
Lat : 14:51:51 N Lon : 104:02:54 W


CI# /Pressure/ Vmax
4.7 / 975.0mb/ 82.2kt


Final T# Adj T# Raw T#
4.4 4.6 5.0

Center Temp : -37.0C Cloud Region Temp : -64.0C

Scene Type : EMBEDDED CENTER CLOUD REGION

[Yellow Evan]

EP, 12, 2020081718, , BEST, 0, 150N, 1039W, 75, 985, HU, 34, NEQ, 120, 120, 60, 100, 1010, 150, 20, 0, 0, E, 0, , 0, 0, GENEVIEVE, D, 0, , 0, 0, 0, 0, genesis-num, 020,
EP, 12, 2020081718, , BEST, 0, 150N, 1039W, 75, 985, HU, 50, NEQ, 50, 50, 30, 40, 1010, 150, 20, 0, 0, E, 0, , 0, 0, GENEVIEVE, D, 0, , 0, 0, 0, 0, genesis-num, 020,
EP, 12, 2020081718, , BEST, 0, 150N, 1039W, 75, 985, HU, 64, NEQ, 20, 20, 0, 20, 1010, 150, 20, 0, 0, E, 0, , 0, 0, GENEVIEVE, D, 0, , 0, 0, 0, 0, genesis-num, 020,

[Yellow Evan]

* GFS version *
* EAST PACIFIC 2020 SHIPS INTENSITY FORECAST *
* IR SAT DATA AVAILABLE, OHC AVAILABLE *
* GENEVIEVE EP122020 08/17/20 18 UTC *

TIME (HR) 0 6 12 18 24 36 48 60 72 84 96 108 120 132 144 156 168
V (KT) NO LAND 75 85 94 105 112 119 123 115 104 92 79 68 57 47 37 28 20
V (KT) LAND 75 85 94 105 112 119 123 115 104 92 79 68 57 47 37 28 20
V (KT) LGEM 75 85 95 104 110 120 120 108 97 85 67 53 42 33 27 22 18
Storm Type TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP EXTP EXTP

SHEAR (KT) 3 5 4 3 9 4 5 4 8 12 14 15 9 18 18 19 26
SHEAR ADJ (KT) 2 -2 -3 -6 -6 -3 -2 1 4 4 5 5 8 4 10 4 0
SHEAR DIR 55 96 106 161 174 222 231 107 174 152 171 173 209 187 199 203 210
SST (C) 30.4 30.2 29.9 29.4 29.2 29.1 27.9 26.9 26.7 25.5 23.6 23.6 22.0 21.5 21.1 20.7 20.1
POT. INT. (KT) 171 169 166 160 157 155 142 132 130 117 98 98 82 76 71 66 60
200 MB T (C) -52.3 -52.1 -52.7 -52.8 -52.3 -52.1 -51.5 -51.2 -50.6 -50.1 -50.0 -49.8 -50.1 -49.8 -49.6 -49.8 -50.0
200 MB VXT (C) 0.1 0.3 0.4 0.5 0.4 0.5 0.5 0.8 0.8 0.9 1.3 1.1 1.2 0.9 0.9 0.7 0.6
TH_E DEV (C) 7 8 7 7 8 7 7 6 5 4 3 2 0 0 0 0 0
700-500 MB RH 78 79 77 77 75 74 70 61 57 56 57 54 53 47 44 37 36
MODEL VTX (KT) 21 23 22 25 27 25 30 29 28 27 26 24 21 19 16 13 12
850 MB ENV VOR 21 25 26 37 45 66 70 75 61 63 49 41 46 47 59 56 21
200 MB DIV 107 129 127 124 100 102 87 61 25 13 -9 5 11 -4 17 -8 1
700-850 TADV -18 -8 -9 -2 0 -1 -5 -11 -3 -5 -2 0 0 7 2 4 0
LAND (KM) 353 344 350 350 380 378 255 227 216 271 292 332 503 590 625 572 535
LAT (DEG N) 15.0 15.8 16.6 17.4 18.2 19.5 20.8 22.0 23.2 24.2 25.2 26.3 27.4 xx.x xx.x xx.x xx.x
LONG(DEG W) 103.9 105.2 106.6 107.6 108.5 110.0 111.0 112.0 113.5 114.9 116.2 117.9 120.1 xxx.x xxx.x xxx.x xxx.x
STM SPEED (KT) 16 15 14 12 11 9 8 8 8 8 9 10 10 8 7 6 6
HEAT CONTENT 38 30 29 25 16 18 8 1 1 0 0 0 0 0 0 0 0

FORECAST TRACK FROM OFCI INITIAL HEADING/SPEED (DEG/KT):305/ 17 CX,CY: -13/ 10
T-12 MAX WIND: 55 PRESSURE OF STEERING LEVEL (MB): 494 (MEAN=587)
GOES IR BRIGHTNESS TEMP. STD DEV. 50-200 KM RAD: 7.0 (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): 64.8

INDIVIDUAL CONTRIBUTIONS TO INTENSITY CHANGE
6 12 18 24 36 48 60 72 84 96 108 120 132 144 156 168
------------------------------------------------------------------------------
SAMPLE MEAN CHANGE 0. 0. 1. 1. 1. 2. 1. 1. 0. -0. -1. -2. -3. -4. -4. -5.
SST POTENTIAL 1. 2. 4. 4. 4. 2. -1. -3. -6. -9. -12. -15. -19. -24. -29. -34.
VERTICAL SHEAR MAG 0. 1. 2. 2. 3. 4. 6. 7. 7. 6. 5. 5. 3. 1. -1. -3.
VERTICAL SHEAR ADJ 0. 0. 1. 1. 2. 2. 2. 1. 0. 0. -0. 0. 0. 0. -0. -0.
VERTICAL SHEAR DIR 0. 1. 1. 1. 0. 0. -0. -1. -1. -1. -1. -1. -1. -0. 0. 0.
PERSISTENCE 4. 7. 7. 7. 5. 3. 2. 0. 0. 0. -0. -0. -0. -0. 0. 1.
200/250 MB TEMP. -0. -0. -0. -1. -1. -1. -1. -0. 0. 1. 2. 3. 4. 4. 6. 6.
THETA_E EXCESS 0. 0. 0. 1. 1. 1. 1. 1. 0. -1. -2. -3. -4. -5. -7. -8.
700-500 MB RH 0. 0. 0. 1. 1. 1. 1. 1. 1. 1. 1. 0. 0. 0. 0. -0.
MODEL VTX TENDENCY 0. 0. 3. 4. 3. 8. 10. 10. 8. 6. 3. -0. -3. -5. -8. -8.
850 MB ENV VORTICITY -0. -0. 0. 0. 0. -0. -0. -1. -1. -1. -1. -1. -1. -1. -1. -0.
200 MB DIVERGENCE 0. 1. 1. 2. 2. 3. 4. 5. 4. 3. 3. 2. 1. 0. 0. 0.
850-700 T ADVEC 0. 0. 0. 0. 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. 1. 1. 1. -0.
STEERING LEVEL PRES -0. -0. -1. -1. -1. -1. -1. -1. -1. -2. -2. -2. -1. -1. -1. -0.
DAYS FROM CLIM. PEAK 0. 0. 0. 0. 0. 0. 1. 1. 2. 2. 3. 3. 3. 4. 4. 5.
GOES PREDICTORS 1. 2. 2. 2. 2. 2. 2. 2. 2. 2. 3. 3. 3. 3. 2. 2.
OCEAN HEAT CONTENT -0. 0. 0. 0. 0. 0. -0. -0. -0. -0. -0. 0. 0. 1. 2. 3.
RI POTENTIAL 2. 5. 8. 12. 19. 18. 11. 3. -2. -6. -10. -11. -12. -12. -12. -12.
------------------------------------------------------------------------------
TOTAL CHANGE 10. 19. 30. 37. 44. 48. 40. 29. 17. 4. -7. -18. -28. -38. -47. -55.

CURRENT MAX WIND (KT): 75. LAT, LON: 15.0 103.9

** 2020 E. Pacific RI INDEX EP122020 GENEVIEVE 08/17/20 18 UTC **
(SHIPS-RII PREDICTOR TABLE for 30 KT OR MOREMAXIMUM WIND INCREASE IN NEXT 24-h)

Predictor Value RI Predictor Range Scaled Value(0-1) % Contribution
POT = MPI-VMAX (KT) : 89.6 40.5 to 149.3 0.45 10.4
12 HR PERSISTENCE (KT) : 20.0 -22.0 to 44.0 0.64 17.4
850-200 MB SHEAR (KT) : 4.7 19.6 to 1.4 0.82 17.4
D200 (10**7s-1) : 117.4 -33.0 to 160.6 0.78 17.0
MAXIMUM WIND (KT) : 75.0 22.5 to 132.0 0.77 12.6
STD DEV OF IR BR TEMP : 7.0 37.8 to 2.1 0.86 11.7
HEAT CONTENT (KJ/CM2) : 27.6 2.7 to 106.7 0.24 3.1
BL DRY-AIR FLUX (W/M2) : 106.2 800.8 to -82.5 0.79 -13.4
%area of TPW <45 mm upshear : 0.0 56.6 to 0.0 1.00 5.7
2nd PC OF IR BR TEMP : 0.1 2.2 to -1.9 0.52 0.8

SHIPS Prob RI for 20kt/ 12hr RI threshold= 85% is 13.5 times climatological mean ( 6.3%)
SHIPS Prob RI for 25kt/ 24hr RI threshold= 86% is 6.8 times climatological mean (12.6%)
SHIPS Prob RI for 30kt/ 24hr RI threshold= 83% is 9.6 times climatological mean ( 8.6%)
SHIPS Prob RI for 35kt/ 24hr RI threshold= 76% is 12.3 times climatological mean ( 6.2%)
SHIPS Prob RI for 40kt/ 24hr RI threshold= 62% is 14.8 times climatological mean ( 4.2%)
SHIPS Prob RI for 45kt/ 36hr RI threshold= 57% is 8.5 times climatological mean ( 6.7%)
SHIPS Prob RI for 55kt/ 48hr RI threshold= 33% is 5.6 times climatological mean ( 5.9%)
SHIPS Prob RI for 65kt/ 72hr RI threshold= 11% is 2.3 times climatological mean ( 4.7%)

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: 85.0% 85.9% 82.8% 76.3% 62.1% 56.6% 32.8% 10.9%
Logistic: 72.2% 77.6% 73.0% 65.0% 56.2% 53.2% 14.8% 0.9%
Bayesian: 81.2% 87.8% 94.0% 92.0% 80.1% 52.0% 1.7% 0.0%
Consensus: 79.5% 83.8% 83.3% 77.8% 66.2% 53.9% 16.4% 3.9%
DTOPS: 77.0% 78.0% 77.0% 62.0% 52.0% 47.0% 17.0% 0.0%

## ANNULAR HURRICANE INDEX (AHI) EP122020 GENEVIEVE 08/17/20 18 UTC ##
## STORM NOT ANNULAR, SCREENING STEP FAILED, NPASS=3 NFAIL=4 ##
## AHI= 0 (AHI OF 100 IS BEST FIT TO ANN. STRUC., 1 IS MARGINAL, 0 IS NOT ANNULAR) ##

[aspen]

Dry air has almost been fully mixed out. Now Genevieve needs to start producing some deep convection, but since it’s close to Dmin, that could take a bit.

[Kingarabian]

Dry air has almost been fully mixed out. Now Genevieve needs to start producing some deep convection, but since it’s close to Dmin, that could take a bit.

I believe DMIN and DMAX affect developing TC's much more compared to hurricanes.

[cycloneye]

Hurricane Genevieve Discussion Number 6
NWS National Hurricane Center Miami FL EP122020
400 PM CDT Mon Aug 17 2020

Genevieve has continued to rapidly strengthen today, and has been
undergoing RI since its formation yesterday morning. One-minute
GOES-16 satellite imagery and an earlier GMI microwave overpass has
revealed very impressive banding features, along with evidence of a
small low-level eye feature. Since the time of that microwave data,
banding has continued to increase near the center, and it appears
that a banding-type eye may be forming. The various satellite
intensity estimates range from 70-80 kt, so the initial wind speed
has been raised to 75 kt.

Genevieve remains within a very favorable oceanic and atmospheric
environment, and the intensity guidance suggests that rapid
strengthening is likely to continue for another day or so. The
SHIPS Rapid Intensification Index again shows a greater than 80-
percent chance of a 30 kt increase in wind speed over the next 24
hours and about a 60-percent chance of a 40 kt increase over that
time period. The NHC intensity forecast continues to call for rapid
strengthening and shows Genevieve reaching category 4 strength by
late Tuesday. This is in line with the latest SHIPS and HFIP
corrected consensus models. After 48 h, the hurricane will be
moving over slightly cooler waters and weaken should begin, with a
faster rate of weakening expected on days 4 and 5.

The hurricane has moved a bit right of track since yesterday, but
the longer term motion is west-northwestward at 16 kt. A strong
ridge of high pressure over the western United States should
continued to steer Genevieve west-northwestward for another 24
hours. After that time, a slower northwestward motion should
commence. There is a bit more spread in the dynamical model
guidance with the GFS, its ensemble mean, and the HWRF having
shifted slightly eastward. However, the consensus aids have not
changed much, and the NHC track is similar to the previous advisory,
near the middle of the guidance envelope.

Recent ASCAT data showed that the tropical-storm-force wind field
was a little larger than previously estimated over the eastern
semicircle of the storm. The initial and forecast wind radii have
been adjusted outward accordingly.

Key Messages:

1. There is an increasing risk of tropical-storm-force winds over
the southern portion of the Baja California peninsula beginning
Wednesday afternoon and continuing into Thursday as Genevieve passes
near or southwest of the southern tip of Baja California, and a
Tropical Storm Watch has been issued for a portion of this area.

2. Large swells generated by Genevieve are affecting portions of the
coast of southern Mexico and will spread northward along the coast
of Mexico to the Baja California peninsula by Wednesday.


FORECAST POSITIONS AND MAX WINDS

INIT 17/2100Z 15.5N 104.6W 75 KT 85 MPH
12H 18/0600Z 16.6N 106.6W 95 KT 110 MPH
24H 18/1800Z 18.0N 108.5W 110 KT 125 MPH
36H 19/0600Z 19.3N 109.8W 120 KT 140 MPH
48H 19/1800Z 20.6N 110.8W 115 KT 130 MPH
60H 20/0600Z 21.6N 111.6W 105 KT 120 MPH
72H 20/1800Z 22.8N 113.1W 90 KT 105 MPH
96H 21/1800Z 24.8N 116.0W 60 KT 70 MPH
120H 22/1800Z 27.2N 119.7W 45 KT 50 MPH

$$
Forecaster Brown

[Kingarabian]

Warm spot is more and more prevalent but there's still dry air issues.

[aspen]

https://i.imgur.com/HRYXBmS.png

Warm spot is more and more prevalent but there's still dry air issues.

Looks like a tiny core is trying to form. I hope Genevieve can stop snacking on dry air like nearly everything else before it.

[Kingarabian]

https://i.imgur.com/HRYXBmS.png

Warm spot is more and more prevalent but there's still dry air issues.

Looks like a tiny core is trying to form. I hope Genevieve can stop snacking on dry air like nearly everything else before it.

The core is there. I think its been there since the past 12 hours. The eyewall needs to get stronger and hold long enough for the eye to clear. It does look like it's trying to accomplish that based on this recent AMSR2 pass. If it does within the next 6 hours, we will have a major hurricane.

[Yellow Evan]

By comparison since this is the most similar storm to Genevieve, this is what Marie looked like right before bombing out at 3z on August 24:

[Kingarabian]

Looks like the eye is clearing out:

[SouthDadeFish]

I think the wild card with the short term intensity trend is the potential for an ERC. Microwave and geostationary imagery suggest that may be beginning now. Regardless, the TC is really starting to wrap up on visible now.

[Yellow Evan]

I'll add the usual caveat that an ERC would be quite unusual for a Cat 1.

[Kingarabian]

:uarrow: I'll add the usual caveat that an ERC would be quite unusual for a Cat 1.

Think we seen it with Douglas as well, earlier this season. I think this just proves that Douglas and this were stronger than advertised at the time of the ERC process.

[aspen]

:uarrow: I'll add the usual caveat that an ERC would be quite unusual for a Cat 1.

Think we seen it with Douglas as well, earlier this season. I think this just proves that Douglas and this were stronger than advertised at the time of the ERC process.

I think this is probably a Cat 2 right now (85-90 kt), but what could be the main culprit for an EWRC is the outer banding that was left during the dry air intrusion. Also, this current eyewall is tiny, and tiny eyes usually fall to EWRCs.