CPAC: LANE - Post-Tropical

[cycloneye]

Hurricane Lane Discussion Number 16
NWS National Hurricane Center Miami FL EP142018
200 PM PDT Sat Aug 18 2018

Lane remains an impressive hurricane in geostationary satellite
imagery. The distinct 15 nmi-wide eye is surrounded by a ring
of convection with clouds tops around -65 to -70C. The clouds
tops have warmed slightly but the subjective and objective Dvorak
Current Intensity (CI) numbers are unchanged so the initial
intensity is maintained at 120 kt for this advisory.

The hurricane continues moving west-northwestward at about 13 kt.
A large subtropical ridge to the north of Lane should keep the
hurricane on a west-northwestward to westward heading during the
next 24 hours. After that time, the ridge is forecast to build
westward which is expected to take Lane on a more westward course
between 36 and 72 hours. By day 4, Lane will be approaching the
western portion of the ridge which should result in a turn back
toward the west-northwest. The lastest iterations of the UKMET
and GFS models have shifted southward but remain along the northern
side of the guidance envelope. Meanwhile, the ECMWF remains along
the southern side of the guidance and also depicts a much faster
forward speed. The updated NHC track forecast has been adjusted
slightly southward to be near the latest consensus aids.

The intensity forecast reasoning is unchanged from the previous
advisory. Lane will be moving over SSTs of 27-28 degrees Celsius
throughout the forecast period, but some west to northwesterly
vertical shear is expected to affect the hurricane. As a result,
gradually weakening is indicated in the official forecast over the
next few days. A more significant increase in shear late in the
forecast period could result in a faster rate of weakening at days
4 and 5. The NHC intensity forecast is near the upper-end of the
guidance during the first 24 to 48 hours, and then is closest to
the HFIP corrected consensus later in the period.

Lane will move into the Central Pacific Basin very soon and this is
last NHC advisory on this system. Future information on Lane can be
found in advisories issued by the Central Pacific Hurricane Center
beginning at 5 PM HST (0300 UTC), under AWIPS header HFOTCPCP2, WMO
header WTPA32 PHFO, and on the web at http://www.prh.noaa.gov/cphc .


FORECAST POSITIONS AND MAX WINDS

INIT 18/2100Z 12.5N 139.7W 120 KT 140 MPH
12H 19/0600Z 12.9N 141.4W 115 KT 130 MPH
24H 19/1800Z 13.4N 143.6W 110 KT 125 MPH
36H 20/0600Z 13.7N 145.6W 105 KT 120 MPH
48H 20/1800Z 13.9N 147.5W 100 KT 115 MPH
72H 21/1800Z 14.1N 151.1W 95 KT 110 MPH
96H 22/1800Z 14.8N 154.7W 70 KT 80 MPH
120H 23/1800Z 15.9N 158.2W 60 KT 70 MPH

$$
Forecaster Brown/Latto

[Kingarabian]

The forecast looks a bit tricky now since Lane will be walking a fine line and could run into moderate shear. Considering its non annular structure, it'll also be more susceptible to dry air intrusion:

[NDG]

Because it continues to initialize Lane as a 997mb TS and keeps it as a TS through 60 hours.

When ridging is strong to the north and there's a deep easterly flow from the low levels to the mid levels it does not matter much how strong the storm is. IMO.
In the past I have seen many people dismiss the forecast track of a model because it does not initiate the correct strength of a storm but it ends up being correct.
The difference in this matter between the two models is that the GFS forecasts Lane to move slower and forecasts the mid level ridge to weaken at the 5 day range while the Euro does the opposite.

I understand that the Euro does not always initialize the storm correct and that usually does not affect its track solution, but it's not just initializing the storm wrong. It's also keeping the storm weak for an extended period of time (up to 60 hours) and then starts to strengthen to it later. The UKMET is handling Lane's intensity much better, and also keeps a stronger Lane than the Euro and thus shows considerably more poleward motion.

Per the latest NHC forecast and discussion they are not putting much stock on the UKMET and GFS.

[ncapps]

Lane looks so small and compact. Wonder how much moisture it draws up as it approaches Hawaii.

[Kingarabian]

Lane looks so small and compact. Wonder how much moisture it draws up as it approaches Hawaii.

If it takes the NHC's track, I don't see much impact from rainfall for Hawaii.

[Kingarabian]

When ridging is strong to the north and there's a deep easterly flow from the low levels to the mid levels it does not matter much how strong the storm is. IMO.
In the past I have seen many people dismiss the forecast track of a model because it does not initiate the correct strength of a storm but it ends up being correct.
The difference in this matter between the two models is that the GFS forecasts Lane to move slower and forecasts the mid level ridge to weaken at the 5 day range while the Euro does the opposite.

I understand that the Euro does not always initialize the storm correct and that usually does not affect its track solution, but it's not just initializing the storm wrong. It's also keeping the storm weak for an extended period of time (up to 60 hours) and then starts to strengthen to it later. The UKMET is handling Lane's intensity much better, and also keeps a stronger Lane than the Euro and thus shows considerably more poleward motion.

Per the latest NHC forecast and discussion they are not putting much stock on the UKMET and GFS.

Yes, very good to see.

[Kingarabian]

Doubt it's 120kts at the moment. Eye has cooled and its CDO showing some breaks. Looks like it's either undergoing an ERC or has taken a gulp of dry air:

[Alyono]

looks to be hitting the shear already. Only takes 10-15 kts to really damage an intense hurricnae

[Chris90]

Looks like it might be starting an EWRC. The next good microwave pass should confirm. Appearance on satellite though suggests EWRC to me. If environmental conditions start to deteriorate, EWRC might not succeed and it'll be what knocks him down a couple categories. It's looking like my 130kts forecast was too bullish, yet again...
Time for me to take a page out of the NHC playbook and be more conservative.

[Kingarabian]

looks to be hitting the shear already. Only takes 10-15 kts to really damage an intense hurricnae

Looks like it's dry air and a long overdue ERC to me since it's spitting out outflow boundaries in the last couple of frames.



But dry air, an ERC, with some shear on top could really knock it out.

[Kingarabian]

A bit faster on the 18z GFS, looks like it's on track to miss Hawaii:



Nevermind:



Hopefully the 00z GFS run moves Lane faster and does not allow that trough to catch it while any of the islands are north of it.

In the meanwhile we can monitor Lane's strength. The weaker it becomes the less likely its motion will be slow and poleward.

[ncapps]

A bit faster on the 18z GFS, looks like it's on track to miss Hawaii:



Nevermind:



Hopefully the 00z GFS run moves Lane faster and does not allow that trough to catch it while any of the islands are north of it.

Really making things difficult for the CPAC I imagine. Hopefully its off its rocker, it's been the slowest of any model for days now, so I think it is.

[Kingarabian]

A bit faster on the 18z GFS, looks like it's on track to miss Hawaii:

[img]https://i.imgur.com/bLPeAXv.gif[img]

Nevermind:

[img]https://i.imgur.com/Dz3Q3ms.png[img]

Hopefully the 00z GFS run moves Lane faster and does not allow that trough to catch it while any of the islands are north of it.

Really making things difficult for the CPAC I imagine. Hopefully its off its rocker, it's been the slowest of any model for days now, so I think it is.

The GFS, UKMET, and Navy are slower because they keep a much stronger vort.

But this solution of the GFS now stalling it south of Kauai and Oahu for more than 24 hours will flood us out:

[ncapps]

A bit faster on the 18z GFS, looks like it's on track to miss Hawaii:

[img]https://i.imgur.com/bLPeAXv.gif[img]

Nevermind:

[img]https://i.imgur.com/Dz3Q3ms.png[img]

Hopefully the 00z GFS run moves Lane faster and does not allow that trough to catch it while any of the islands are north of it.

Really making things difficult for the CPAC I imagine. Hopefully its off its rocker, it's been the slowest of any model for days now, so I think it is.

The GFS, UKMET, and Navy are slower because they keep a much stronger vort.

But this solution of the GFS now stalling it south of Kauai and Oahu for more than 24 hours will flood us out:

Kauai doesn't need that. I really pray its wrong. I think it is. More inclined to believe HMON/HWRF/Euro. The HMON/HWRF have the intensity modeled nicely, but keep Lane moving on a quick pace, similar to Euro (intensity aside)

[Alyono]

I do think what we've seen today is shear. The outflow is somewhat restricted on the SW side

It would not surprise me if this weakens to a TS by early Tuesday like HWRF/HMON say

[Alyono]

now, as we head into Tuesday, the shear may then decrease somewhat, so this may have a chance to recover. However, GFS is far too strong due to paramaterized convection. That allows he vortex to be shear resistant, artifically

[Alyono]

TIME (HR) 0 6 12 18 24 36 48 60 72 84 96 108 120
V (KT) NO LAND 120 117 109 103 97 88 80 74 71 70 64 62 62
V (KT) LAND 120 117 109 103 97 88 80 74 71 70 64 62 62
V (KT) LGEM 120 116 109 102 96 87 82 78 74 71 65 60 55
Storm Type TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP

SHEAR (KT) 12 15 14 14 10 12 11 9 10 13 13 14 16
SHEAR ADJ (KT) 2 2 1 0 -3 -4 -3 2 4 9 6 3 -2
SHEAR DIR 268 261 269 261 272 267 299 294 283 281 267 252 253
SST (C) 27.6 27.7 27.7 27.6 27.6 27.7 27.7 27.5 27.5 27.6 27.6 27.4 27.3
POT. INT. (KT) 141 142 142 141 140 141 141 139 138 139 139 138 136
200 MB T (C) -53.6 -53.3 -53.4 -53.3 -53.4 -53.3 -53.5 -53.1 -53.4 -53.2 -53.4 -53.0 -53.2
200 MB VXT (C) 0.1 0.1 0.2 0.2 0.2 0.1 0.0 0.1 0.1 0.1 0.1 0.1 0.1
TH_E DEV (C) 7 8 8 8 7 8 8 8 8 9 8 8 7
700-500 MB RH 63 61 60 59 60 58 53 51 53 59 64 69 69
MODEL VTX (KT) 18 18 15 16 17 19 20 21 21 23 21 21 23
850 MB ENV VOR -1 -3 0 4 16 31 32 38 40 43 33 47 43
200 MB DIV 51 57 41 27 14 16 36 19 50 60 36 52 60
700-850 TADV -4 -4 -4 -3 -1 1 2 0 4 2 2 4 1
LAND (KM) 1873 1742 1611 1493 1376 1178 974 807 681 554 449 385 410
LAT (DEG N) 12.4 12.7 13.0 13.3 13.5 13.9 14.2 14.4 14.5 14.7 15.0 15.5 16.0
LONG(DEG W) 138.9 140.1 141.3 142.4 143.5 145.4 147.5 149.4 151.1 152.8 154.5 156.3 158.0
STM SPEED (KT) 13 12 12 11 10 10 10 9 8 8 8 9 8
HEAT CONTENT 10 11 13 21 22 18 19 19 18 21 33 22 19

the shear we current have is more than enough to severely damage an intense hurricane

[Kingarabian]

TIME (HR) 0 6 12 18 24 36 48 60 72 84 96 108 120
V (KT) NO LAND 120 117 109 103 97 88 80 74 71 70 64 62 62
V (KT) LAND 120 117 109 103 97 88 80 74 71 70 64 62 62
V (KT) LGEM 120 116 109 102 96 87 82 78 74 71 65 60 55
Storm Type TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP

SHEAR (KT) 12 15 14 14 10 12 11 9 10 13 13 14 16
SHEAR ADJ (KT) 2 2 1 0 -3 -4 -3 2 4 9 6 3 -2
SHEAR DIR 268 261 269 261 272 267 299 294 283 281 267 252 253
SST (C) 27.6 27.7 27.7 27.6 27.6 27.7 27.7 27.5 27.5 27.6 27.6 27.4 27.3
POT. INT. (KT) 141 142 142 141 140 141 141 139 138 139 139 138 136
200 MB T (C) -53.6 -53.3 -53.4 -53.3 -53.4 -53.3 -53.5 -53.1 -53.4 -53.2 -53.4 -53.0 -53.2
200 MB VXT (C) 0.1 0.1 0.2 0.2 0.2 0.1 0.0 0.1 0.1 0.1 0.1 0.1 0.1
TH_E DEV (C) 7 8 8 8 7 8 8 8 8 9 8 8 7
700-500 MB RH 63 61 60 59 60 58 53 51 53 59 64 69 69
MODEL VTX (KT) 18 18 15 16 17 19 20 21 21 23 21 21 23
850 MB ENV VOR -1 -3 0 4 16 31 32 38 40 43 33 47 43
200 MB DIV 51 57 41 27 14 16 36 19 50 60 36 52 60
700-850 TADV -4 -4 -4 -3 -1 1 2 0 4 2 2 4 1
LAND (KM) 1873 1742 1611 1493 1376 1178 974 807 681 554 449 385 410
LAT (DEG N) 12.4 12.7 13.0 13.3 13.5 13.9 14.2 14.4 14.5 14.7 15.0 15.5 16.0
LONG(DEG W) 138.9 140.1 141.3 142.4 143.5 145.4 147.5 149.4 151.1 152.8 154.5 156.3 158.0
STM SPEED (KT) 13 12 12 11 10 10 10 9 8 8 8 9 8
HEAT CONTENT 10 11 13 21 22 18 19 19 18 21 33 22 19

the shear we current have is more than enough to severely damage an intense hurricane

If it's going to weaken I still expect it to maintain Cat. 2 strength considering its progress so far and sufficient SST's. But to see a 999mb TS like the Euro is showing, shear needs to be closer to 20-25kts.

Actually, the GFS keeping this near 970mb for most of its duration while it treks towards Hawaii is not completely bonkers.

A general rule of thumb is that the shear must be 20 knots or less for intensification to occur. Most instances of rapid intensification of hurricanes occur when the wind shear is 10 knots or less. However, large and powerful hurricanes can be resistant to shear values as high as 40 knots, as demonstrated by Hurricane Wilma

https://www.wunderground.com/education/shear.asp

[Alyono]

TIME (HR) 0 6 12 18 24 36 48 60 72 84 96 108 120
V (KT) NO LAND 120 117 109 103 97 88 80 74 71 70 64 62 62
V (KT) LAND 120 117 109 103 97 88 80 74 71 70 64 62 62
V (KT) LGEM 120 116 109 102 96 87 82 78 74 71 65 60 55
Storm Type TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP

SHEAR (KT) 12 15 14 14 10 12 11 9 10 13 13 14 16
SHEAR ADJ (KT) 2 2 1 0 -3 -4 -3 2 4 9 6 3 -2
SHEAR DIR 268 261 269 261 272 267 299 294 283 281 267 252 253
SST (C) 27.6 27.7 27.7 27.6 27.6 27.7 27.7 27.5 27.5 27.6 27.6 27.4 27.3
POT. INT. (KT) 141 142 142 141 140 141 141 139 138 139 139 138 136
200 MB T (C) -53.6 -53.3 -53.4 -53.3 -53.4 -53.3 -53.5 -53.1 -53.4 -53.2 -53.4 -53.0 -53.2
200 MB VXT (C) 0.1 0.1 0.2 0.2 0.2 0.1 0.0 0.1 0.1 0.1 0.1 0.1 0.1
TH_E DEV (C) 7 8 8 8 7 8 8 8 8 9 8 8 7
700-500 MB RH 63 61 60 59 60 58 53 51 53 59 64 69 69
MODEL VTX (KT) 18 18 15 16 17 19 20 21 21 23 21 21 23
850 MB ENV VOR -1 -3 0 4 16 31 32 38 40 43 33 47 43
200 MB DIV 51 57 41 27 14 16 36 19 50 60 36 52 60
700-850 TADV -4 -4 -4 -3 -1 1 2 0 4 2 2 4 1
LAND (KM) 1873 1742 1611 1493 1376 1178 974 807 681 554 449 385 410
LAT (DEG N) 12.4 12.7 13.0 13.3 13.5 13.9 14.2 14.4 14.5 14.7 15.0 15.5 16.0
LONG(DEG W) 138.9 140.1 141.3 142.4 143.5 145.4 147.5 149.4 151.1 152.8 154.5 156.3 158.0
STM SPEED (KT) 13 12 12 11 10 10 10 9 8 8 8 9 8
HEAT CONTENT 10 11 13 21 22 18 19 19 18 21 33 22 19

the shear we current have is more than enough to severely damage an intense hurricane

If it's going to weaken I still expect it to maintain Cat. 2 strength considering its progress so far and sufficient SST's. But to see a 999mb TS like the Euro is showing, shear needs to be closer to 20-25kts.

Actually, the GFS keeping this near 970mb for most of its duration while it treks towards Hawaii is not completely bonkers.

A general rule of thumb is that the shear must be 20 knots or less for intensification to occur. Most instances of rapid intensification of hurricanes occur when the wind shear is 10 knots or less. However, large and powerful hurricanes can be resistant to shear values as high as 40 knots, as demonstrated by Hurricane Wilma

https://www.wunderground.com/education/shear.asp

I've seen some statistical studies that have shown that large, intense hurricanes are the most susceptible to wind shear. Weak vorticies may be the most likely to intensify. Something I've also noticed in the hurricane models as well

Wilma was not sheared as it approached Florida. The strong upper winds were only confined to the north part of the vortex. Thus, the outflow was enhanced

[ncapps]

Dry air being ingested from NW Side?