CPAC: LANE - Post-Tropical

[Blown Away]

Gusts to 160kt = 184 mph, WOW.

[Kingarabian]

WTPA42 PHFO 210857
TCDCP2

Hurricane Lane Discussion Number 26
NWS Central Pacific Hurricane Center Honolulu HI EP142018
1100 PM HST Mon Aug 20 2018


Lane has quite an impressive satellite signature this evening, with
a solid ring of very cold cloud tops surrounding a warming eye.
Aircraft from NOAA and the 53rd Weather Reconnaissance Squadron
have been flying through lane at 8 to 10 thousand feet respectively
this evening, and are confirming that Lane is a powerful hurricane
that has intensified since their last visit this morning. The
central pressure has dropped roughly 10 mb, peak SFMR winds were 140
kt with max flight level winds near 128 kt, and an eyewall
dropsonde recorded winds near 139 kt. Based on a blend of the
aircraft data, the initial intensity for this advisory is increased
to 130 kt, maintaining Lane as a powerful category 4 hurricane.

The initial motion for this advisory is 280/10 kt, with Lane
continuing to be steered by a mid-level ridge centered to the
north. Over the next couple of days, Lane is expected to reach the
western periphery of the ridge, allowing the cyclone to gain
latitude. Some increase in the clustering of the track model
guidance has occurred this cycle, with the ECMWF no longer on the
left hand side of the envelope. All of the reliable model guidance
now indicates that Lane will begin to make a gradual turn to the
west-northwest by Wednesday, with a gradual slowing in forward
speed. A more decided turn toward the northwest is expected
Thursday, with relatively slow-moving Lane now forecast to move
dangerously close to the main Hawaiian Islands. A turn toward the
west is expected in the later forecast periods, with forecast models
indicating a weakened Lane increasingly being steered by the
low-level trade wind flow. The updated track forecast lies between
the previous official forecast and the HCCA.

The weakening in the latter forecast periods appears to be related
to an increase in vertical wind shear, but it also appears that
forecast models are expecting interaction with island terrain to
interrupt the low-level wind flow into Lane. Water temperatures
along the forecast track will be sufficiently warm to support a
major hurricane, and thus any significant weakening before Lane
draws closer to the Hawaiian Islands will likely be due to shear.
With shear expected to be minimal in the short term, subtle
intensity fluctuations associated with inner-core dynamics will
likely lead to little overall change in intensity. The later
forecast periods anticipate an increase in shear as Lane will lie
between the ridge to the east and trough aloft to the northwest of
the main Hawaiian Islands, and the updated intensity forecast has
been nudged upward in the short term due to recent trends and
follows the previous official forecast in the latter forecast
periods, close to the IVCN consensus.

The uncertainty in the track forecast necessitates that interests in
the Hawaiian Islands continue to closely monitor Lane the next
couple of days. It is important to not focus on the exact forecast
track, as impacts from Lane extend well away from its center.


FORECAST POSITIONS AND MAX WINDS

INIT 21/0900Z 14.0N 151.2W 130 KT 150 MPH
12H 21/1800Z 14.3N 152.4W 130 KT 150 MPH
24H 22/0600Z 14.7N 153.9W 120 KT 140 MPH
36H 22/1800Z 15.4N 155.1W 115 KT 130 MPH
48H 23/0600Z 16.4N 156.0W 110 KT 125 MPH
72H 24/0600Z 18.9N 157.3W 95 KT 110 MPH
96H 25/0600Z 20.7N 159.0W 75 KT 85 MPH
120H 26/0600Z 21.0N 161.5W 60 KT 70 MPH

$$
Forecaster Birchard

That blend is closer to 136kts than 130kts...

[Blown Away]

Which model from the 00z suite showed this solution CPHC?

https://i.imgur.com/N1QPdxG.png

Are the siding with the Euro?

I suspect following TVCN consensus and leaning slightly to the Euro, I would.

[Chris90]

ESTIMATED MINIMUM CENTRAL PRESSURE 950 MB
EYE DIAMETER 15 NM
MAX SUSTAINED WINDS 130 KT WITH GUSTS TO 160 KT.

I take it that's a larger boost for gusts than normal due to the data.

I think that's about normal for a 130kt storm. In my opinion(which is amateur), they could have even gone a bit higher on the gusts considering there was another eyewall dropsonde that measured a peak gust of 176kts 21mb above the surface. It was not a thick layer of wind though. It measured 171kts directly after that 20mb above the surface, and the rest of the measurements were in the 120-130kt range the rest of the way down to the surface.

[Kingarabian]

I believe it's called "we don't want to believe that this will plow right into Hawaii" model. It's a mouthful I know, but I didn't name it.

Gulf states declare a state of emergency days in advance of a threat. Why hasn't Hawaii issued one yet? And the bend back to the west is to soon on this advisory forecast. They need to discredit the UKMET and CMC here, and go with what makes sense -- which is whatever that's close to the GFS. This forecast can still give people a potentially wrong sense of safety and that Lane will not affect them.

[NotoSans]

That blend is closer to 136kts than 130kts...

You need to apply the standard 0.9 adjustment factor to the flight-level wind speed before blending the data. In this case, the blend would yield an intensity estimate of 131 knots.

I understand the CPHC may be a bit conservative for this storm, but it should be noted that dropsonde winds are more representative of gusts rather than sustained winds, and SFMR winds may have a high bias as recon from the previous ATL season suggested. More often, the average winds over the lowest 150m (WL150) are used (after applying an adjustment factor of ~0.85) to derive an intensity estimate. In this case, the intensity estimate derived from WL150 would be around 132 knots. I would say either 130 or 135 knots would be a reasonable intensity estimate.

[Chris90]

WTPA42 PHFO 210857
TCDCP2

Hurricane Lane Discussion Number 26
NWS Central Pacific Hurricane Center Honolulu HI EP142018
1100 PM HST Mon Aug 20 2018


Lane has quite an impressive satellite signature this evening, with
a solid ring of very cold cloud tops surrounding a warming eye.
Aircraft from NOAA and the 53rd Weather Reconnaissance Squadron
have been flying through lane at 8 to 10 thousand feet respectively
this evening, and are confirming that Lane is a powerful hurricane
that has intensified since their last visit this morning. The
central pressure has dropped roughly 10 mb, peak SFMR winds were 140
kt with max flight level winds near 128 kt, and an eyewall
dropsonde recorded winds near 139 kt. Based on a blend of the
aircraft data, the initial intensity for this advisory is increased
to 130 kt, maintaining Lane as a powerful category 4 hurricane.

The initial motion for this advisory is 280/10 kt, with Lane
continuing to be steered by a mid-level ridge centered to the
north. Over the next couple of days, Lane is expected to reach the
western periphery of the ridge, allowing the cyclone to gain
latitude. Some increase in the clustering of the track model
guidance has occurred this cycle, with the ECMWF no longer on the
left hand side of the envelope. All of the reliable model guidance
now indicates that Lane will begin to make a gradual turn to the
west-northwest by Wednesday, with a gradual slowing in forward
speed. A more decided turn toward the northwest is expected
Thursday, with relatively slow-moving Lane now forecast to move
dangerously close to the main Hawaiian Islands. A turn toward the
west is expected in the later forecast periods, with forecast models
indicating a weakened Lane increasingly being steered by the
low-level trade wind flow. The updated track forecast lies between
the previous official forecast and the HCCA.

The weakening in the latter forecast periods appears to be related
to an increase in vertical wind shear, but it also appears that
forecast models are expecting interaction with island terrain to
interrupt the low-level wind flow into Lane. Water temperatures
along the forecast track will be sufficiently warm to support a
major hurricane, and thus any significant weakening before Lane
draws closer to the Hawaiian Islands will likely be due to shear.
With shear expected to be minimal in the short term, subtle
intensity fluctuations associated with inner-core dynamics will
likely lead to little overall change in intensity. The later
forecast periods anticipate an increase in shear as Lane will lie
between the ridge to the east and trough aloft to the northwest of
the main Hawaiian Islands, and the updated intensity forecast has
been nudged upward in the short term due to recent trends and
follows the previous official forecast in the latter forecast
periods, close to the IVCN consensus.

The uncertainty in the track forecast necessitates that interests in
the Hawaiian Islands continue to closely monitor Lane the next
couple of days. It is important to not focus on the exact forecast
track, as impacts from Lane extend well away from its center.


FORECAST POSITIONS AND MAX WINDS

INIT 21/0900Z 14.0N 151.2W 130 KT 150 MPH
12H 21/1800Z 14.3N 152.4W 130 KT 150 MPH
24H 22/0600Z 14.7N 153.9W 120 KT 140 MPH
36H 22/1800Z 15.4N 155.1W 115 KT 130 MPH
48H 23/0600Z 16.4N 156.0W 110 KT 125 MPH
72H 24/0600Z 18.9N 157.3W 95 KT 110 MPH
96H 25/0600Z 20.7N 159.0W 75 KT 85 MPH
120H 26/0600Z 21.0N 161.5W 60 KT 70 MPH

$$
Forecaster Birchard

That blend is closer to 136kts than 130kts...

They mention peak SFMR winds of 140kts, which I haven't seen yet. If there was 140kt readings, combined with the other data (specifically the dropsondes), I would say this is definitely a Cat 5. And at a pressure of 950mb...

Is it just me, or do these storms continue to produce higher winds at higher pressures? Matthew went Cat 5 in the low 940s, Irma was putting down 150-155kts at 929 mb, and now Lane. I'm feeling like a few years from now there's going to be a Cat 5 with a central pressure of 985mb.

[Kingarabian]

That blend is closer to 136kts than 130kts...

You need to apply the standard 0.9 adjustment factor to the flight-level wind speed before blending the data. In this case, the blend would yield an intensity estimate of 131 knots.

I understand the CPHC may be a bit conservative for this storm, but it should be noted that dropsonde winds are more representative of gusts rather than sustained winds, and SFMR winds may have a high bias as recon from the previous ATL season suggested. More often, the average winds over the lowest 150m (WL150) are used (after applying an adjustment factor of ~0.85) to derive an intensity estimate. In this case, the intensity estimate derived from WL150 would be around 132 knots. I would say either 130 or 135 knots would be a reasonable intensity estimate.

Makes sense now. Thanks for the explanation.

[AutoPenalti]

GFS 06z about to initialize.

[Kingarabian]

WTPA42 PHFO 210857
TCDCP2

Hurricane Lane Discussion Number 26
NWS Central Pacific Hurricane Center Honolulu HI EP142018
1100 PM HST Mon Aug 20 2018


Lane has quite an impressive satellite signature this evening, with
a solid ring of very cold cloud tops surrounding a warming eye.
Aircraft from NOAA and the 53rd Weather Reconnaissance Squadron
have been flying through lane at 8 to 10 thousand feet respectively
this evening, and are confirming that Lane is a powerful hurricane
that has intensified since their last visit this morning. The
central pressure has dropped roughly 10 mb, peak SFMR winds were 140
kt with max flight level winds near 128 kt, and an eyewall
dropsonde recorded winds near 139 kt. Based on a blend of the
aircraft data, the initial intensity for this advisory is increased
to 130 kt, maintaining Lane as a powerful category 4 hurricane.

The initial motion for this advisory is 280/10 kt, with Lane
continuing to be steered by a mid-level ridge centered to the
north. Over the next couple of days, Lane is expected to reach the
western periphery of the ridge, allowing the cyclone to gain
latitude. Some increase in the clustering of the track model
guidance has occurred this cycle, with the ECMWF no longer on the
left hand side of the envelope. All of the reliable model guidance
now indicates that Lane will begin to make a gradual turn to the
west-northwest by Wednesday, with a gradual slowing in forward
speed. A more decided turn toward the northwest is expected
Thursday, with relatively slow-moving Lane now forecast to move
dangerously close to the main Hawaiian Islands. A turn toward the
west is expected in the later forecast periods, with forecast models
indicating a weakened Lane increasingly being steered by the
low-level trade wind flow. The updated track forecast lies between
the previous official forecast and the HCCA.

The weakening in the latter forecast periods appears to be related
to an increase in vertical wind shear, but it also appears that
forecast models are expecting interaction with island terrain to
interrupt the low-level wind flow into Lane. Water temperatures
along the forecast track will be sufficiently warm to support a
major hurricane, and thus any significant weakening before Lane
draws closer to the Hawaiian Islands will likely be due to shear.
With shear expected to be minimal in the short term, subtle
intensity fluctuations associated with inner-core dynamics will
likely lead to little overall change in intensity. The later
forecast periods anticipate an increase in shear as Lane will lie
between the ridge to the east and trough aloft to the northwest of
the main Hawaiian Islands, and the updated intensity forecast has
been nudged upward in the short term due to recent trends and
follows the previous official forecast in the latter forecast
periods, close to the IVCN consensus.

The uncertainty in the track forecast necessitates that interests in
the Hawaiian Islands continue to closely monitor Lane the next
couple of days. It is important to not focus on the exact forecast
track, as impacts from Lane extend well away from its center.


FORECAST POSITIONS AND MAX WINDS

INIT 21/0900Z 14.0N 151.2W 130 KT 150 MPH
12H 21/1800Z 14.3N 152.4W 130 KT 150 MPH
24H 22/0600Z 14.7N 153.9W 120 KT 140 MPH
36H 22/1800Z 15.4N 155.1W 115 KT 130 MPH
48H 23/0600Z 16.4N 156.0W 110 KT 125 MPH
72H 24/0600Z 18.9N 157.3W 95 KT 110 MPH
96H 25/0600Z 20.7N 159.0W 75 KT 85 MPH
120H 26/0600Z 21.0N 161.5W 60 KT 70 MPH

$$
Forecaster Birchard

That blend is closer to 136kts than 130kts...

They mention peak SFMR winds of 140kts, which I haven't seen yet. If there was 140kt readings, combined with the other data (specifically the dropsondes), I would say this is definitely a Cat 5. And at a pressure of 950mb...

Is it just me, or do these storms continue to produce higher winds at higher pressures? Matthew went Cat 5 in the low 940s, Irma was putting down 150-155kts at 929 mb, and now Lane. I'm feeling like a few years from now there's going to be a Cat 5 with a central pressure of 985mb.

Think the higher than normal pressures is due to the systems being situated and intensifying under the presence of a ridge

[Kingarabian]

06z GFS initialized @ 971mb l0l.

[Kingarabian]

06z GFS landfall as a strong hurricane over the big island and then has it ripped apart:

[Kingarabian]

06z GFS looks completely off like 00z UKMET. Has a much weaker Lane initially (975mb instead of the actual pressure @ 950mb) which plays a large role in keeping Lane weaker than normal due to that artificial 25mb decrease.

[Blown Away]

06 GFS doesn’t look like a landfall on Big Island, just gets on the W side of island and disengrates then goes W as a shallow Low. Crazy.

[AutoPenalti]

Slide shift west from 0z.

[Kingarabian]

06 GFS doesn’t look like a landfall on Big Island, just gets on the W side of island and disengrates then goes W as a shallow Low. Crazy.

Yeah the data is filling in slowly.



Goes from a strong Cat.3/4 to a weak TS in less than 12 hours. Scientifically it doesn't make sense.

[Twisted-core]

https://imgur.com/qt4zeBS

NHC track is better, just on the outta gale radius. Heaps better than the centre, hope it holds true.

[Eric Webb]

06 GFS doesn’t look like a landfall on Big Island, just gets on the W side of island and disengrates then goes W as a shallow Low. Crazy.

Yeah the data is filling in slowly.



Goes from a strong Cat.3/4 to a weak TS in less than 12 hours. Scientifically it doesn't make sense.

It actually does, 13,000+ foot volcanoes will do that to a tropical cyclone, we've seen many storms in the Atlantic weaken as fast or faster going over comparatively shallower terrain in Cuba or Hispaniola.

[Kingarabian]

06 GFS doesn’t look like a landfall on Big Island, just gets on the W side of island and disengrates then goes W as a shallow Low. Crazy.

Yeah the data is filling in slowly.



Goes from a strong Cat.3/4 to a weak TS in less than 12 hours. Scientifically it doesn't make sense.

It actually does, 13,000+ foot volcanoes will do that to a tropical cyclone, we've seen many storms in the Atlantic weaken as fast or faster going over comparatively shallower terrain in Cuba or Hispaniola.

I understand that, but the center is not crossing over such terrain (it doesnt make landfall). It basically just degenerates as Blown Away said.

[Kingarabian]

Regardless of intensity and what happened to the system, the break in the ridge is there. The only way the models kept Hawaii safe from Lane, is by moving a shallow vort shift west. Now we watch to see if the advertised shear will actually be there or not.