CPAC: LANE - Post-Tropical

[CyclonicFury]

Hope our Hawaii S2K members stay safe. Even if shear significantly Lane, heavy rainfall may be a major issue. The track and intensity forecast of Lane remains quite uncertain. Impacts, if they were to occur, will most likely be on Friday.

[TheAustinMan]

The reconnaissance aircraft delivered a dropsonde which documented a mean wind of 144 kt in the boundary layer below 500 gpm and 147 kt in the lowest 150 meters altitude before dropping into the ocean in the northwestern eyewall. Dropsonde values are instantaneous gusts, but given the layer averages I think we have pretty solid evidence of a Category 5 at this point.

A second dropsonde was also deployed in the northwestern eyewall which showed similar means of 146 kt and 145 kt in the lowest 150 gpm and 500 gpm, respectively.

[NotoSans]

The reconnaissance aircraft delivered a dropsonde which documented a mean wind of 144 kt in the boundary layer below 500 gpm and 147 kt in the lowest 150 meters altitude before dropping into the ocean in the northwestern eyewall. Dropsonde values are instantaneous gusts, but given the layer averages I think we have pretty solid evidence of a Category 5 at this point.

A second dropsonde was also deployed in the northwestern eyewall which showed similar means of 146 kt and 145 kt in the lowest 150 gpm and 500 gpm, respectively.

Need to apply an adjustment factor of ~0.85 to the WL150 winds. Unlikely that the two eyewall dropsondes hit the RMW (given the very tight core), thus surface winds estimates derived may not be representative of true intensity.

[Aric Dunn]

the last hour eyewall convection has expanded and deepened. this next recon pass should solidify the upgrade to Cat 5.

[Kingarabian]

the last hour eyewall convection has expanded and deepened. this next recon pass should solidify the upgrade to Cat 5.

Always a treat to get your input, Aric!

[Aric Dunn]

I suppose the increased deep convection is partially due the fact that it is moving over warmer water.

[AJC3]

If Oahu gets hit, where will recon fly from? Johnston is too far away. Only place I could think of is Christmas Island

Johnston makes the most sense. Christmas Island is in the AUS.

there is a Christmas Island south of Hawaii, in the Line Islands

Interesting...supposedly the airstrip at Johnston has been unmaintained for 15 years, and I don't know what facilities they would have there now to support even an emergency landing.

Can Bonriki (Christmas/Kiribati) service military aircraft? Because it's either that or...Midway, I guess? Better yet, C-130's have been able to safely land on a carrier....

[NotoSans]

Highest SFMR winds that were not auto-flagged was 136 knots in the SE quad. SFMR winds at the NW quad were consistently at the 140-knot range, but most of them had been flagged.

EDIT: 140 knots unflagged SFMR winds found in NW quad.

[NotoSans]

CPHC goes with 135 knots at 21Z based on previous recon data. Will see whether they will upgrade LANE to category 5 based on the latest pass.

ESTIMATED MINIMUM CENTRAL PRESSURE 941 MB
EYE DIAMETER 20 NM
MAX SUSTAINED WINDS 135 KT WITH GUSTS TO 165 KT.
64 KT....... 35NE 25SE 25SW 30NW.
50 KT....... 60NE 45SE 35SW 60NW.
34 KT.......110NE 95SE 60SW 120NW.
12 FT SEAS..210NE 150SE 150SW 210NW.
WINDS AND SEAS VARY GREATLY IN EACH QUADRANT. RADII IN NAUTICAL
MILES ARE THE LARGEST RADII EXPECTED ANYWHERE IN THAT QUADRANT.

[Camerooski]

A direct landfall on the Big Island is the best case scenario by far for Hawaii as a whole, would completely kill the system. My fear is a track offshore the big island and one that scrapes all the islands....

[Cunxi Huang]

205230 1415N 15313W 6956 02719 9597 +127 +127 025130 136 140 022 00

140 kt unflagged SFMR.

[supercane4867]

Racon has found conclusive evidence that Lane is a CAT5 storm. Stadium effect eye is becoming visible on satellite

IMO CPHC should do a special advisory to upgrade Lane to CAT5 in the next hour.

[Yellow Evan]

I can confidently say this is a Category 5 now.

[Kingarabian]

205230 1415N 15313W 6956 02719 9597 +127 +127 025130 136 140 022 00

140 kt unflagged SFMR.

They better upgrade it in the discussion

[cycloneye]

135 kts

Hurricane Lane Discussion Number 28
NWS Central Pacific Hurricane Center Honolulu HI EP142018
1100 AM HST Tue Aug 21 2018

Lane remains a powerful hurricane this morning, with a well-
developed warm eye completely surrounded by persistent cold cloud
tops. Morning visible satellite imagery also depicts a well-defined
eye. The Hurricane Hunter aircraft from the 53rd Weather
Reconnaissance Squadron is flying through Lane again this morning,
and confirms that the hurricane has intensified further since
their previous visit on Monday evening. The central pressure
has dropped around 10 mb during the past 12 hours, with the most
recent dropsonde in the eye finding 941 mb. Peak SFMR winds measured
so far have been 134 kt, and max flight level winds are 143 kt.
Subjective Dvorak current intensity estimates range from 6.5/127 kt
to 7.0/140 kt, with the latest ADT current intensity at 6.4/125 kt.
Based primarily on the aircraft data, the intial intensity for this
advisory is increased to 135 kt, which makes Lane a high-end
Category 4 hurricane.

Lane is moving a bit slower this morning and appears to have wobbled
slightly to the WNW during the last few hours, and the initial
motion for this advisory is 280/8 kt. Lane has been moving westward
to the south of a mid-level ridge during the past several days.
However, this will be changing soon, as Lane begins to round the
western periphery of this ridge and moves into an area of
relatively light steering flow. This is expected to allow the
cyclone to gain latitude as its forward speed diminishes. The
hurricane is forecast to turn gradually to the west-northwest
through tonight, then to the northwest Wednesday through Thursday,
as it moves between the mid-level ridge to the east and a developing
upper-level trough to the northwest of Hawaii. After this point, the
track and intensity forecasts remain highly uncertain, as the
majority of the reliable model guidance brings Lane very close to
the islands with potential interaction between Lane and the
mountainous terrain of the islands. This interaction combined with
increasing vertical wind shear leads to a weakened Lane being
steered to the west by the low-level trade wind flow. The new track
forecast has been nudged slightly to the north or closer to the
islands from 36 through 72 hours, into better agreement with the
multi-model consensus HCCA.

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 increasing wind shear. In the short-term through
the next 24 hours or so, shear is expected to remain light, and
expect only slow weakening as the cyclone moves over slightly
cooler SSTs and may be impacted by eyewall replacement cycles.
At 72 hours and beyond, the forecast anticipates a sharp increase
in shear as Lane moves closer to the large upper trough to the
northwest of the main Hawaiian Islands. The new intensity
forecast is close to the previous forecast, and although it
remains on the high end of the guidance envelope, it generally
follows the trends presented by the multi-model consensus IVCN and
HCCA.

In addition to continued storm penetrations by the Hurricane Hunters
of the 53rd Weather Reconnaissance Squadron, the NOAA G-IV will once
again be sampling the larger scale environment today to help with
initialization of the forecast models.


KEY MESSAGES:

1. Lane is forecast to move dangerously close to the main Hawaiian
Islands as a hurricane later this week, potentially bringing
damaging winds and life-threatening flash flooding from heavy
rainfall. As Lane is expected to be slow-moving as it nears the
islands, it will produce large and damaging surf. A Hurricane Watch
remains in effect for Hawaii and Maui counties, and additional
Tropical Storm or Hurricane Watches may be required this afternoon
or tonight.

2. It is much too early to confidently determine which, if any, of
the main Hawaiian Islands will be directly impacted by Lane. Even
if the center of Lane were to remain offshore, it is important to
remember that impacts from a hurricane can extend well away from
the center. Interests throughout Hawaii are urged to closely
monitor the progress of Lane during the next few days.


FORECAST POSITIONS AND MAX WINDS

INIT 21/2100Z 14.3N 153.2W 135 KT 155 MPH
12H 22/0600Z 14.7N 154.2W 130 KT 150 MPH
24H 22/1800Z 15.6N 155.3W 120 KT 140 MPH
36H 23/0600Z 16.6N 156.2W 110 KT 125 MPH
48H 23/1800Z 17.9N 156.9W 100 KT 115 MPH
72H 24/1800Z 20.6N 158.2W 80 KT 90 MPH
96H 25/1800Z 21.7N 160.5W 55 KT 65 MPH
120H 26/1800Z 21.5N 164.0W 40 KT 45 MPH

$$
Forecaster Jacobson

[cjrciadt]

https://goo.gl/images/YKGq1j

[Kazmit]

Why didn't they upgrade it? The evidence is clear.

[NotoSans]

Central pressure down to 935mb according to latest center dropsonde. Enough evidence for a category 5 upgrade.

[Kingarabian]

Why are they factoring Dvorak in the blend when recon is still in the plane?

[NotoSans]

Why didn't they upgrade it? The evidence is clear.

The advisory package was issued before the latest center pass showing 140-knot winds.