CPAC: LINDA - Post-Tropical

[Sciencerocks]

[ScottNAtlanta]

Per microwave imagery, NHC, and visible imagery, Felicia was an actual annular hurricane (resembled one a bit more than Linda tbh) and behaved like one. Remains to be seen if Linda will behave like a true annular hurricane the way Felicia did.

I went back and looked and saw no official (or unofficial) documentation on Felicia being annular. It had a 10 mile eye which is rather small for an annular storm and it weakened pretty rapidly. The NHC did, however, say this one was annular.

https://i.imgur.com/ZZNbLLy_d.webp?maxwidth=640&shape=thumb&fidelity=medium

In the last section
https://twitter.com/pppapin/status/1416346221225017347?lang=en
Pappin from the NHC.

https://twitter.com/webberweather/status/1416355362349801477?lang=en
US Government met.

I stand corrected. I read through the discussions (since I haven't had time before today), and did indeed see that. I dont follow a lot on twitter so I did not see those and really didn't follow the Felicia thread. You are correct, and I apologize for doubting you.
That doesn't make this one any less amazing though. For anyone else interesting in geeking out over annular hurricanes

https://rammb.cira.colostate.edu/resour ... _Knaff.pdf

[Yellow Evan]

TXPZ23 KNES 171758
TCSENP

A. 12E (LINDA)

B. 17/1730Z

C. 17.6N

D. 127.8W

E. ONE/GOES-W

F. T5.0/5.0

G. IR/EIR/VIS

H. REMARKS...SYSTEM HAS A WMG EYE TEMP, SURROUNDED BY LG RING TEMP,
AND IS EMBEDDED IN MG RESULTING IN AN EYE PATTERN DT OF 5.0. THE 24 HR
TREND IS STEADY. MET IS 4.5 AND PT IS 5.0. FT IS BASED ON DT.

I. ADDL POSITIONS

NIL


...PATEL

[Sciencerocks]

[cycloneye]

Hurricane Linda Discussion Number 31
NWS National Hurricane Center Miami FL EP122021
1100 AM HST Tue Aug 17 2021

Linda still has annular characteristics with a large circular
eye evident in satellite images and a ring of deep convection
surrounding that feature. Visible satellite images show
mesovorticies rotating around in the hurricane's eye. The Dvorak
classifications have nudged back up this cycle and range from 75 to
90 kt. Based on these estimates, the initial intensity is raised
a little to 80 kt.

Linda has moved over slightly warmer waters during the past few
hours and is now hugging the 26 deg C isotherm. Annular hurricanes
like Linda typically hold their intensity or weaken at a slower pace
over cool waters than what is climatological, and it appears that
Linda is accomplishing that. Nonetheless, a combination of cool SSTs
and drier air should eventually cause a slow weakening trend during
the next several days. The models suggest that an increase in
southerly shear is likely toward the end of the forecast period, and
that could assist in the storm becoming post-tropical by then. The
NHC intensity forecast remains near the high end of the guidance in
the short term and then falls in line with the majority of the
guidance from days 3-5.

Linda is moving due westward at 270/9 kt. The track forecast
reasoning is unchanged. A mid-level ridge is expected to remain
anchored to the north of Linda, which should keep the storm on a
westward to west-northwestward track during the next several days.
The models have trended a little faster this cycle, and the NHC
track forecast has followed suit. Based on this prediction, Linda
is expected to cross into the Central Pacific basin in 48-60 h and
be located to the north or northeast of the Hawaiian Islands late
this weekend and early next week.


FORECAST POSITIONS AND MAX WINDS

INIT 17/2100Z 17.6N 128.3W 80 KT 90 MPH
12H 18/0600Z 18.1N 129.9W 80 KT 90 MPH
24H 18/1800Z 18.7N 132.4W 75 KT 85 MPH
36H 19/0600Z 19.6N 135.2W 65 KT 75 MPH
48H 19/1800Z 20.4N 138.0W 55 KT 65 MPH
60H 20/0600Z 21.0N 141.0W 45 KT 50 MPH
72H 20/1800Z 21.5N 143.9W 40 KT 45 MPH
96H 21/1800Z 22.1N 148.6W 35 KT 40 MPH...POST-TROPICAL
120H 22/1800Z 22.6N 152.8W 35 KT 40 MPH...POST-TROPICAL

$$
Forecaster Cangialosi

[Kingarabian]

12z guidance majoirty still supporting some sort of Hawaii landfall. Would be weak and probably nothing more than a rain event. Only the NCEP/GFS based guidance is taking this north of Hawaii.

[Kingarabian]

6 hour old SSMIS F-17 pass:


1 hour old GMI pass:


Looks like it's deepening again.

[Nimbus]

12z guidance majoirty still supporting some sort of Hawaii landfall. Would be weak and probably nothing more than a rain event. Only the NCEP/GFS based guidance is taking this north of Hawaii.

35 knots of wind at Hilo with some upslope rain?

[Yellow Evan]

Krispy Kreme Donuts has now opened in the middle of the Pacific.

[Kingarabian]

12z guidance majoirty still supporting some sort of Hawaii landfall. Would be weak and probably nothing more than a rain event. Only the NCEP/GFS based guidance is taking this north of Hawaii.

35 knots of wind at Hilo with some upslope rain?

Depends on the wind direction at the time. If the southerly/south westerly winds near Hawaii are strong at the time then it'll probably keep all the weather off shore if this doesn't make a direct landfall.

They key thing now is how strong this can remain before it makes any Hawaii approach. But more importantly what is the track philosophy in the next 72 hours. Are the models showing this reaching Hawaii because it's expected to be super weak and shallow and ends up being caught in the low level flow or is it because there's a stronger ridge now being modeled.

[Kingarabian]

Round of applause for ATMS. It finally resolved a systems core properly.

[Kingarabian]

AMSR2 pass:

[Yellow Evan]

As someone moving to Hawaii for graduate school at the University of Hawaii this weekend, interesting to possibly be getting some TC impacts very fast. But for now still a believer in a northward track with effects mostly being enhanced trades but it's clearly not going to successfully recurve like originally shown. Wind shear will sharply increase due to an upper trough near 145W and while SST's will be increasing by then, it won't be enough.

[Yellow Evan]

----- Current Analysis -----
Date : 17 AUG 2021 Time : 222031 UTC
Lat : 17:52:12 N Lon : 128:36:36 W


CI# /Pressure/ Vmax
4.9 / 971.6mb/ 87.4kt


Final T# Adj T# Raw T#
4.6 5.1 5.1

Estimated radius of max. wind based on IR : 37 km

Center Temp : +16.5C Cloud Region Temp : -58.4C

Scene Type : LARGE EYE

[Kingarabian]

As someone moving to Hawaii for graduate school at the University of Hawaii this weekend, interesting to possibly be getting some TC impacts very fast. But for now still a believer in a northward track with effects mostly being enhanced trades but it's clearly not going to successfully recurve like originally shown. Wind shear will sharply increase due to an upper trough near 145W and while SST's will be increasing by then, it won't be enough.

Welcome!

[Kingarabian]

Big jump in the raw numbers:

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

----- Current Analysis -----
Date : 17 AUG 2021 Time : 232031 UTC
Lat : 17:51:36 N Lon : 128:46:47 W


CI# /Pressure/ Vmax
5.0 / 969.7mb/ 90.0kt


Final T# Adj T# Raw T#
5.0 5.8 5.8

Estimated radius of max. wind based on IR : 32 km

Center Temp : +16.3C Cloud Region Temp : -61.7C

Scene Type : EYE

Subtropical Adjustment : OFF

Extratropical Adjustment : OFF

Positioning Method : ARCHER POSITIONING

Ocean Basin : EAST PACIFIC
Dvorak CI > MSLP Conversion Used : CKZ Method

Tno/CI Rules : Constraint Limits : NO LIMIT
Weakening Flag : OFF
Rapid Dissipation Flag : OFF

[Kingarabian]

[Kingarabian]

SAB has a major hurricane again:

TXPZ23 KNES 180014
TCSENP

A. 12E (LINDA)

B. 17/2330Z

C. 17.7N

D. 128.9W

E. ONE/GOES-W

F. T5.5/5.5

G. IR/EIR

H. REMARKS...WMG EYE SURROUNDED AND EMBEDDED IN LG RESULTS IN A DT OF
5.5 AFTER AN EYE ADJUSTMENT OF 0.5 WAS MADE. THE MET AND PT ARE EQUAL
TO 5.0 BASED ON A SLOW DEVELOPMENT TREND OVER THE PAST 24 HOURS. FT IS
BASED ON DT.

I. ADDL POSITIONS

NIL


...COVERDALE

[Yellow Evan]

I’d expect TAFB to follow. I’d hold it down a little lower because the eye is large and not as circle than before but this is clearly re-intensifying.

[Yellow Evan]

* GFS version *
* EAST PACIFIC 2021 SHIPS INTENSITY FORECAST *
* IR SAT DATA AVAILABLE, OHC AVAILABLE *
* LINDA EP122021 08/18/21 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 90 93 92 89 85 73 61 53 47 44 44 42 40 39 38 33 31
V (KT) LAND 90 93 92 89 85 73 61 53 47 44 44 42 40 39 38 33 31
V (KT) LGEM 90 92 90 86 80 66 55 49 45 42 40 38 36 34 31 29 27
Storm Type TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP

SHEAR (KT) 5 6 4 5 3 3 3 8 8 14 15 19 19 20 22 32 29
SHEAR ADJ (KT) 0 0 0 0 4 0 2 0 2 2 3 4 6 3 3 -5 -1
SHEAR DIR 140 170 220 293 349 230 206 255 258 246 225 229 209 225 237 258 261
SST (C) 26.8 26.4 26.0 25.7 25.0 24.3 23.9 24.2 24.6 24.9 25.7 26.1 26.8 26.4 26.3 26.8 26.5
POT. INT. (KT) 132 128 124 122 115 107 103 106 110 112 120 124 132 128 127 131 128
200 MB T (C) -52.3 -52.2 -52.4 -52.5 -52.2 -52.2 -52.1 -52.3 -52.4 -52.8 -52.9 -53.2 -53.6 -53.9 -54.2 -54.4 -54.5
200 MB VXT (C) 0.5 0.5 0.6 0.9 1.0 1.1 0.9 0.9 0.7 1.0 0.7 0.5 0.0 0.3 0.2 -0.1 0.2
TH_E DEV (C) 5 4 4 3 3 2 2 3 3 4 4 5 6 6 7 7 7
700-500 MB RH 40 40 40 39 40 39 36 34 31 32 34 32 31 30 33 38 39
MODEL VTX (KT) 21 21 21 20 20 18 15 14 14 13 14 13 13 12 12 10 9
850 MB ENV VOR 48 54 52 49 45 47 37 32 40 23 21 12 3 -3 -18 -25 -31
200 MB DIV 1 -8 -8 -17 -10 -8 -14 7 -6 8 -11 7 -7 9 -11 10 -32
700-850 TADV 1 0 -3 -6 -3 0 -2 -1 2 3 5 6 1 0 2 0 1
LAND (KM) 1814 1887 1964 2062 2165 1892 1590 1273 1013 782 591 434 291 210 135 166 296
LAT (DEG N) 17.8 18.1 18.3 18.7 19.1 20.0 20.6 21.2 21.6 21.9 22.1 22.4 22.7 xx.x xx.x xx.x xx.x
LONG(DEG W) 129.0 130.1 131.2 132.6 134.0 136.7 139.6 142.7 145.3 147.7 149.8 151.9 154.1 xxx.x xxx.x xxx.x xxx.x
STM SPEED (KT) 10 11 12 14 14 14 14 13 12 11 10 10 10 11 10 9 8
HEAT CONTENT 2 1 0 0 0 0 0 0 0 0 0 0 4 3 1 5 4

FORECAST TRACK FROM OFCI INITIAL HEADING/SPEED (DEG/KT):280/ 10 CX,CY: -9/ 2
T-12 MAX WIND: 75 PRESSURE OF STEERING LEVEL (MB): 500 (MEAN=587)
GOES IR BRIGHTNESS TEMP. STD DEV. 50-200 KM RAD: 9.0 (MEAN=14.5)
% GOES IR PIXELS WITH T < -20 C 50-200 KM RAD: 96.0 (MEAN=65.0)
PRELIM RI PROB (DV .GE. 35 KT IN 36 HR): 1.5

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 -1. -2. -3. -5. -11. -18. -25. -30. -35. -38. -40. -41. -42. -44. -46. -48.
VERTICAL SHEAR MAG -0. 0. 0. 1. 3. 5. 7. 8. 8. 7. 5. 4. 2. -1. -3. -5.
VERTICAL SHEAR ADJ 0. 0. 0. -0. -1. -1. -1. -0. -0. -0. -0. -0. -0. -0. -0. -0.
VERTICAL SHEAR DIR -0. -0. -1. -1. -1. -2. -2. -2. -1. -1. -1. -1. -0. -0. 0. 0.
PERSISTENCE 4. 5. 5. 5. 3. 2. 0. -1. -1. -1. -1. -2. -2. -2. -1. -1.
200/250 MB TEMP. -0. -0. -0. -0. 0. 1. 2. 4. 5. 6. 7. 7. 6. 6. 5. 5.
THETA_E EXCESS -0. -0. -1. -1. -3. -4. -5. -6. -7. -7. -7. -7. -6. -6. -6. -6.
700-500 MB RH -0. -0. -1. -1. -2. -2. -2. -2. -3. -3. -3. -4. -4. -5. -7. -9.
MODEL VTX TENDENCY -0. -0. -1. -1. -2. -5. -8. -10. -11. -10. -10. -10. -10. -9. -10. -9.
850 MB ENV VORTICITY 0. 0. 0. 0. 0. -0. -0. -0. -0. -0. -0. -0. -0. 0. 0. 0.
200 MB DIVERGENCE -0. -0. -1. -1. -1. -2. -3. -4. -5. -5. -5. -4. -2. -1. 0. 2.
850-700 T ADVEC -0. -0. 0. 0. 0. -0. -0. -0. 0. 0. 0. 0. 0. 0. 1. 1.
ZONAL STORM MOTION 0. 0. 0. 0. 1. 1. 1. 1. 1. 1. 1. 0. 0. 0. 0. -0.
STEERING LEVEL PRES -0. -0. -0. -1. -1. -1. -1. -1. -1. -2. -2. -2. -1. -1. -1. -0.
DAYS FROM CLIM. PEAK 0. 0. 0. 0. 0. 1. 1. 1. 2. 2. 2. 3. 3. 4. 4. 5.
GOES PREDICTORS 1. 1. 1. 1. 1. 2. 2. 2. 2. 2. 3. 3. 3. 3. 2. 3.
OCEAN HEAT CONTENT -0. -0. -0. -0. -0. -1. -2. -1. -1. -0. 0. 1. 2. 3. 4. 6.
RI POTENTIAL -0. -1. -1. -2. -4. -4. -3. -1. 1. 2. 3. 4. 4. 4. 4. 4.
------------------------------------------------------------------------------
TOTAL CHANGE 3. 2. -1. -5. -17. -29. -37. -42. -46. -46. -48. -50. -51. -52. -57. -59.

CURRENT MAX WIND (KT): 90. LAT, LON: 17.8 129.0

** 2021 E. Pacific RI INDEX EP122021 LINDA 08/18/21 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) : 34.1 40.5 to 149.3 0.00 0.0
12 HR PERSISTENCE (KT) : 15.0 -22.0 to 44.0 0.56 999.0
D200 (10**7s-1) : -8.4 -33.0 to 159.5 0.13 999.0
850-200 MB SHEAR (KT) : 4.8 19.6 to 1.3 0.81 999.0
MAXIMUM WIND (KT) : 90.0 22.5 to 132.0 0.57 999.0
STD DEV OF IR BR TEMP : 9.0 37.8 to 2.1 0.81 999.0
BL DRY-AIR FLUX (W/M2) : 838.0 800.8 to -82.5 0.00 0.0
HEAT CONTENT (KJ/CM2) : 0.6 2.7 to 106.7 0.00 0.0
%area of TPW <45 mm upshear : 27.7 56.6 to 0.0 0.51 999.0
2nd PC OF IR BR TEMP : 0.2 2.2 to -2.3 0.44 999.0

SHIPS Prob RI for 20kt/ 12hr RI threshold= 14% is 2.2 times climatological mean ( 6.3%)
SHIPS Prob RI for 25kt/ 24hr RI threshold= 0% is 0.0 times climatological mean (12.5%)
SHIPS Prob RI for 30kt/ 24hr RI threshold= 0% is 0.0 times climatological mean ( 8.6%)
SHIPS Prob RI for 35kt/ 24hr RI threshold= 0% is 0.0 times climatological mean ( 6.2%)
SHIPS Prob RI for 40kt/ 24hr RI threshold= 0% is 0.0 times climatological mean ( 4.2%)
SHIPS Prob RI for 45kt/ 36hr RI threshold= 0% is 0.0 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: 13.8% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0%
Logistic: 2.0% 0.5% 2.1% 0.2% 0.6% 0.0% 0.0% 0.0%
Bayesian: 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0%
Consensus: 5.3% 0.2% 0.7% 0.1% 0.2% 0.0% 0.0% 0.0%
DTOPS: 10.0% 2.0% 1.0% 2.0% 2.0% 0.0% 0.0% 0.0%

## ANNULAR HURRICANE INDEX (AHI) EP122021 LINDA 08/18/21 00 UTC ##
## PASSED SCREENING STEP, MIGHT BE ANNULAR, CALCULATE AHI FROM DISCRIMINANT ANALYSIS ##
## AHI= 89 (AHI OF 100 IS BEST FIT TO ANN. STRUC., 1 IS MARGINAL, 0 IS NOT ANNULAR) ##