EPAC: HILDA - Post-Tropical

[Yellow Evan]

This is a hurricane.

[Kingarabian]

[url]https://cdn.discordapp.com/attachments/733552978572869632/871151533130121266/20210731.png[url]

This is a hurricane.

Pretty sure it's a Cat.2 hurricane at least with that intense eastern eyewall.

[Yellow Evan]

18z GFS now has this absorbing 91E instead.

[MGC]

I think Hilda will become a hurricane. Outflow is only restricted on the eastern side of the storm. Hilda reminds me of my first hurricane. Hilda in 1964 passed to my west....MGC

[aspen]

https://cdn.discordapp.com/attachments/733552978572869632/871151533130121266/20210731.png

This is a hurricane.

Now the question is: will the eye ever clear out and give Hilda the look of a true hurricane, or will shear tear it apart before it has the chance?

[Yellow Evan]

https://cdn.discordapp.com/attachments/733552978572869632/871151533130121266/20210731.png

This is a hurricane.

Now the question is: will the eye ever clear out and give Hilda the look of a true hurricane, or will shear tear it apart before it has the chance?

It won’t ever clear an eye not that I ever expected to.

[Kingarabian]

Yeah needs much colder cloud tops in its western quads for the eye to fully clear out so this can become a major.

[Yellow Evan]

FWIW DT is T4.5 here with OW embedded in DG.

[Category5Kaiju]

 https://twitter.com/cyclonicwx/status/1421576484951629824




Ooof

[Subtrop]

EP, 08, 2021080100, , BEST, 0, 142N, 1183W, 75, 985, HU, 34, NEQ, 70, 80, 50, 70, 1010, 150, 20, 0, 0, E, 0, , 0, 0, HILDA, D, 0, , 0, 0, 0, 0, genesis-num, 011,
EP, 08, 2021080100, , BEST, 0, 142N, 1183W, 75, 985, HU, 50, NEQ, 40, 40, 30, 40, 1010, 150, 20, 0, 0, E, 0, , 0, 0, HILDA, D, 0, , 0, 0, 0, 0, genesis-num, 011,
EP, 08, 2021080100, , BEST, 0, 142N, 1183W, 75, 985, HU, 64, NEQ, 20, 20, 0, 20, 1010, 150, 20, 0, 0, E, 0, , 0, 0, HILDA, D, 0, , 0, 0, 0, 0, genesis-num, 011,

[Yellow Evan]

TXPZ29 KNES 312358
TCSENP

A. 08E (HILDA)

B. 31/2330Z

C. 14.1N

D. 118.4W

E. ONE/GOES-W

F. T4.5/4.5

G. IR/EIR/VIS/AMSR2

H. REMARKS...AN OW EYE THAT IS SURROUNDED BY AND EMBEDDED IN MG COLD
OVERCAST MAKES THE DT EQUAL TO 4.5. THE MET AND PT AGREE AND ARE ALSO
EQUAL TO 4.5 BASED ON A RAPID DEVELOPMENT TREND OVER THE PAST 24 HOURS. A
MID LEVEL EYE FEATURE WAS OBSERVED IN THE 89 GHZ 2055Z AMSR2 MI PASS. THE
FT IS BASED ON DT.

I. ADDL POSITIONS

31/2055Z 14.0N 118.0W AMSR2


...SAMBUCCI

[Yellow Evan]

NHC is Dvorak-hugging here. This most likely hasn't changed much in intensity today due to the shear and was probably slightly underestimating Hilda earlier and is overestimating Hilda now. Sure the eye has warmed but the storm looked more healthy earlier.

[Yellow Evan]

* GFS version *
* EAST PACIFIC 2021 SHIPS INTENSITY FORECAST *
* IR SAT DATA AVAILABLE, OHC AVAILABLE *
* HILDA EP082021 08/01/21 00 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 81 84 86 88 87 83 76 71 64 56 47 37 27 21 16 N/A
V (KT) LAND 75 81 84 86 88 87 83 76 71 64 56 47 37 27 21 16 N/A
V (KT) LGEM 75 81 83 84 84 84 80 74 65 57 51 44 38 32 27 23 19
Storm Type TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP

SHEAR (KT) 19 15 14 13 14 17 22 13 5 4 3 7 13 17 14 19 20
SHEAR ADJ (KT) -4 -4 -2 -4 -5 -4 -4 -5 -5 -3 -2 -3 -1 -2 -1 -1 0
SHEAR DIR 74 77 71 61 77 69 65 61 97 342 334 303 278 299 308 288 260
SST (C) 26.9 26.7 26.8 27.1 27.3 26.9 26.5 25.6 25.1 25.0 24.2 23.7 22.5 22.5 22.7 23.1 23.7
POT. INT. (KT) 133 131 131 134 136 131 128 119 113 112 104 100 87 86 89 94 101
200 MB T (C) -52.3 -52.7 -52.9 -52.7 -52.2 -52.7 -52.0 -52.5 -52.0 -52.4 -52.1 -52.4 -52.1 -52.4 -52.1 -52.3 -52.0
200 MB VXT (C) 0.2 0.2 0.4 0.3 0.2 0.5 0.4 0.4 0.3 0.5 0.3 0.3 0.2 0.3 0.0 0.0 0.0
TH_E DEV (C) 3 3 3 2 2 2 2 1 0 0 0 0 0 0 0 0 1
700-500 MB RH 79 76 76 75 75 75 70 72 73 68 66 66 65 69 71 67 58
MODEL VTX (KT) 19 19 17 16 18 19 21 21 22 21 19 16 13 10 LOST LOST LOST
850 MB ENV VOR 32 47 48 52 63 88 85 78 71 65 54 54 46 37 22 19 19
200 MB DIV 111 86 72 71 91 106 110 56 55 50 68 56 63 49 17 7 25
700-850 TADV -3 -10 -13 -10 -4 -2 -3 -9 -5 -11 -8 -10 -15 -13 5 4 5
LAND (KM) 1303 1353 1394 1420 1450 1521 1566 1609 1665 1737 1836 1972 2090 1903 1748 1535 1279
LAT (DEG N) 14.2 14.5 14.7 15.0 15.2 15.7 16.3 17.3 18.2 18.9 19.5 20.1 20.6 xx.x xx.x xx.x xx.x
LONG(DEG W) 118.3 119.3 120.2 121.0 121.7 123.2 124.3 125.8 127.5 129.0 130.6 132.5 134.8 xxx.x xxx.x xxx.x xxx.x
STM SPEED (KT) 11 10 9 8 8 7 7 9 9 8 9 11 10 8 9 11 14
HEAT CONTENT 2 1 2 3 6 5 3 0 0 0 0 0 0 0 0 0 0

FORECAST TRACK FROM OFCI INITIAL HEADING/SPEED (DEG/KT):285/ 11 CX,CY: -10/ 3
T-12 MAX WIND: 55 PRESSURE OF STEERING LEVEL (MB): 495 (MEAN=587)
GOES IR BRIGHTNESS TEMP. STD DEV. 50-200 KM RAD: 5.3 (MEAN=14.5)
% GOES IR PIXELS WITH T < -20 C 50-200 KM RAD: 100.0 (MEAN=65.0)
PRELIM RI PROB (DV .GE. 35 KT IN 36 HR): 26.6

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. -2. -3. -4. -4.
SST POTENTIAL 0. 0. 0. 0. -1. -5. -8. -12. -15. -18. -21. -25. -29. -33. -36. -40.
VERTICAL SHEAR MAG -1. -3. -4. -5. -6. -7. -6. -3. -1. 1. 2. 2. 1. 0. -0. -1.
VERTICAL SHEAR ADJ 0. 1. 1. 2. 3. 3. 3. 2. 1. 1. 0. 0. 0. 0. 1. 1.
VERTICAL SHEAR DIR 1. 1. 2. 3. 5. 6. 7. 7. 6. 5. 4. 4. 3. 2. 2. 1.
PERSISTENCE 4. 7. 7. 7. 5. 3. 2. 0. 0. 0. -0. -0. -1. -1. -0. -0.
200/250 MB TEMP. -0. -0. -0. -1. -1. -1. -2. -2. -2. -2. -2. -1. -1. -1. -1. -1.
THETA_E EXCESS -0. -1. -2. -2. -4. -6. -7. -9. -10. -12. -12. -13. -14. -14. -16. -19.
700-500 MB RH 0. 0. 0. 1. 1. 1. 1. 1. 1. 1. 1. 1. 2. 2. 3. 4.
MODEL VTX TENDENCY 0. -1. -1. -0. 1. 3. 3. 4. 3. 0. -4. -7. -9. -8. -8. -7.
850 MB ENV VORTICITY 0. 0. 0. 0. 0. -0. -0. -1. -1. -1. -1. -1. -1. -1. -1. -1.
200 MB DIVERGENCE 0. 0. 1. 1. 1. 2. 3. 4. 4. 4. 4. 3. 2. 1. -0. -1.
850-700 T ADVEC 0. 0. 0. 0. 0. -0. -0. -0. -0. -0. -0. -1. -1. -2. -2. -2.
ZONAL STORM MOTION 0. 0. 0. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 0. 0. -0.
STEERING LEVEL PRES -0. -0. -1. -1. -1. -1. -1. -1. -2. -2. -2. -2. -1. -1. -1. -0.
DAYS FROM CLIM. PEAK 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 1.
GOES PREDICTORS 1. 2. 3. 3. 3. 3. 3. 3. 3. 3. 3. 3. 3. 2. 2. 1.
OCEAN HEAT CONTENT -0. -0. -0. -0. -0. -1. -1. -1. -0. -0. 0. 1. 2. 3. 4. 6.
RI POTENTIAL 1. 1. 2. 4. 5. 5. 2. 1. -0. -1. -2. -2. -2. -2. -2. -2.
------------------------------------------------------------------------------
TOTAL CHANGE 6. 9. 11. 13. 12. 8. 1. -4. -11. -19. -28. -38. -48. -54. -59. -63.

CURRENT MAX WIND (KT): 75. LAT, LON: 14.2 118.3

** 2021 E. Pacific RI INDEX EP082021 HILDA 08/01/21 00 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) : 58.0 40.5 to 149.3 0.16 1.3
12 HR PERSISTENCE (KT) : 20.0 -22.0 to 44.0 0.64 5.8
D200 (10**7s-1) : 86.2 -33.0 to 159.5 0.62 4.5
850-200 MB SHEAR (KT) : 14.9 19.6 to 1.3 0.25 1.8
MAXIMUM WIND (KT) : 75.0 22.5 to 132.0 0.77 4.2
STD DEV OF IR BR TEMP : 5.3 37.8 to 2.1 0.91 4.5
BL DRY-AIR FLUX (W/M2) : 197.6 800.8 to -82.5 0.68 -3.8
HEAT CONTENT (KJ/CM2) : 2.8 2.7 to 106.7 0.00 0.0
%area of TPW <45 mm upshear : 0.0 56.6 to 0.0 1.00 1.6
2nd PC OF IR BR TEMP : -0.5 2.2 to -2.3 0.59 0.5

SHIPS Prob RI for 20kt/ 12hr RI threshold= 19% is 3.0 times climatological mean ( 6.3%)
SHIPS Prob RI for 25kt/ 24hr RI threshold= 25% is 2.0 times climatological mean (12.5%)
SHIPS Prob RI for 30kt/ 24hr RI threshold= 20% is 2.4 times climatological mean ( 8.6%)
SHIPS Prob RI for 35kt/ 24hr RI threshold= 19% is 3.1 times climatological mean ( 6.2%)
SHIPS Prob RI for 40kt/ 24hr RI threshold= 12% is 2.8 times climatological mean ( 4.2%)
SHIPS Prob RI for 45kt/ 36hr RI threshold= 15% is 2.3 times climatological mean ( 6.7%)
SHIPS Prob RI for 55kt/ 48hr RI threshold= 0% is 0.0 times climatological mean ( 5.9%)
SHIPS Prob RI for 65kt/ 72hr RI threshold= 0% is 0.0 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: 18.7% 24.6% 20.4% 19.4% 11.8% 15.3% 0.0% 0.0%
Logistic: 22.1% 30.7% 13.7% 8.8% 12.2% 2.0% 0.4% 0.2%
Bayesian: 3.5% 0.7% 0.3% 0.2% 0.2% 0.0% 0.0% 0.0%
Consensus: 14.8% 18.7% 11.5% 9.5% 8.1% 5.8% 0.1% 0.1%
DTOPS: 42.0% 37.0% 31.0% 23.0% 19.0% 5.0% 0.0% 0.0%

## ANNULAR HURRICANE INDEX (AHI) EP082021 HILDA 08/01/21 00 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) ##

[Yellow Evan]

Welp.

[aspen]

https://cdn.discordapp.com/attachments/733552978572869632/871201024382222346/image0.png

Welp.

That didn’t last long. Now time for an agonizing death over the next 3 days.

[Sciencerocks]

[cycloneye]

Hurricane Hilda Discussion Number 6
NWS National Hurricane Center Miami FL EP082021
800 PM PDT Sat Jul 31 2021

Hilda has resumed strengthening during the past several hours,
including the short-lived appearance of an eye in the central
dense overcast. Recent 37-GHz microwave imagery confirms an eye
is developing, but indicates that the eyewall is not yet closed on
the northeastern side of the eye. Satellite intensity estimates
from TAFB and SAB are 77 kt, while the CIMSS satellite consensus is
near 80 kt. Based on these data, the initial intensity is increased
to a possibly conservative 75 kt.

Although Hilda is experiencing some easterly vertical shear,
conditions are generally conducive for strengthening during the
next 24 h, and the early part of the intensity forecast has been
adjusted upward based mainly on current trends. After that
time, decreasing moisture and decreasing sea surface temperatures
along the forecast track should cause steady weakening. The latter
part of the intensity forecast has only minor changes from the
previous forecast and follows the trend of the intensity guidance.

The initial motion is now a little slower at 285/9. The
subtropical ridge to the north should steer Hilda generally
west-northwestward for the next several days, with a more
northwestward motion around 96 h as the cyclone passes south of a
weakness in the ridge. Overall, the guidance envelope has shifted a
little northward since the previous advisory, and the new forecast
track is also adjusted northward. It should be noted, though, that
the global models continue to show the possibility of erratic motion
due to Hilda interacting with TD-9E to the west and the weaker, but
larger, low pressure area to the east. The most drastic example of
this is in the Canadian model, which shows Hilda taking a
significant turn to the south before resuming a northward motion.


FORECAST POSITIONS AND MAX WINDS

INIT 01/0300Z 14.3N 118.7W 75 KT 85 MPH
12H 01/1200Z 14.7N 120.0W 85 KT 100 MPH
24H 02/0000Z 15.2N 121.7W 90 KT 105 MPH
36H 02/1200Z 15.8N 123.1W 85 KT 100 MPH
48H 03/0000Z 16.4N 124.2W 80 KT 90 MPH
60H 03/1200Z 17.2N 125.4W 75 KT 85 MPH
72H 04/0000Z 18.3N 126.8W 65 KT 75 MPH
96H 05/0000Z 20.0N 130.5W 50 KT 60 MPH
120H 06/0000Z 20.5N 134.0W 40 KT 45 MPH

$$
Forecaster Beven

[Yellow Evan]

“75 knots”

[Chris90]

I don't doubt that Hilda was 75kts earlier with the more impressive microwave presentation, but she's come down fairly quickly since then.

The way the conditions have been flipping in the EPAC this year has been kind of fun to watch. The fluid dynamics of the atmosphere have really been showing just how fast they can change. Felicia's utter collapse was fun to watch and now Hilda is providing a rollercoaster of entertainment.

[cycloneye]

Hurricane Hilda Discussion Number 7
NWS National Hurricane Center Miami FL EP082021
200 AM PDT Sun Aug 01 2021

Hilda's strengthening last evening was short lived. Infrared and
water vapor imagery show high-level clouds from a weather
disturbance to the east impinging on the eastern side of Hilda's
circulation, suggestive of moderate easterly shear. In fact,
85-GHz SSMIS data from 0241 UTC shows that the microwave
presentation has degraded significantly, with most of the deep
convection displaced to the west of the low-level center. Hilda's
initial intensity is being held at 75 kt based on Dvorak CI numbers
of 4.5 from TAFB and SAB, although that estimate could be generous.

Hilda continues to move west-northwestward, or 285/9 kt, to the
south of a subtropical ridge which is expected to build westward
over the Pacific during the next few days. Despite the placement
of this ridge, the dynamical models indicate that Hilda is likely
to have some degree of binary interaction with the disturbance to
its east and thus take on a northwestward heading on days 2 and 3.
After the interaction, the ridge should then cause Hilda to turn
back toward the west-northwest and then west by days 4 and 5.
While there are some model outliers, the spread among the guidance
has actually decreased over the past 24 hours. The updated NHC
track forecast is not too different from the previous forecast,
except that it is a little slower to account for recent model
trends.

The moderate easterly shear affecting Hilda is unlikely to abate
much during the next couple of days, especially as the distance
between the hurricane and the disturbance to the east decreases.
Still, Hilda will remain over relatively warm waters during that
period, and the models suggest that the hurricane will either
maintain its current intensity or strengthen slightly through 48
hours. Hilda is then expected to move over waters colder than 26
degrees Celsius, causing a steady weakening trend through the end
of the forecast period. The new NHC intensity forecast is a little
lower than the previous forecast to account for the current
structure of the cyclone and the latest model solutions, although
the forecast intensities are not as low as what is shown by the
HCCA and IVCN consensus aids.


FORECAST POSITIONS AND MAX WINDS

INIT 01/0900Z 14.5N 119.6W 75 KT 85 MPH
12H 01/1800Z 14.8N 120.8W 80 KT 90 MPH
24H 02/0600Z 15.3N 122.1W 80 KT 90 MPH
36H 02/1800Z 15.9N 123.3W 80 KT 90 MPH
48H 03/0600Z 16.7N 124.3W 75 KT 85 MPH
60H 03/1800Z 17.6N 125.4W 65 KT 75 MPH
72H 04/0600Z 18.7N 126.9W 55 KT 65 MPH
96H 05/0600Z 20.1N 130.9W 45 KT 50 MPH
120H 06/0600Z 20.7N 135.3W 35 KT 40 MPH

$$
Forecaster Berg