CPAC: LINDA - Post-Tropical

[Sciencerocks]

[Yellow Evan]

Convection getting thin to its west. I think this weakening again.

[Yellow Evan]

TXPZ23 KNES 161818
TCSENP

A. 12E (LINDA)

B. 16/1730Z

C. 17.7N

D. 124.0W

E. ONE/GOES-W

F. T4.5/5.5

G. IR/EIR/VIS

H. REMARKS...SYSTEM HAS A WMG EYE TEMP SURROUNDED BY A MG RING TEMP
AND IS EMBEDDED IN DG RESULTING TO AN EYE PATTERN DT OF 4.5. THE ONCE
COLD CONVECTIVE RING AROUND THE EYE IS NOW COLLAPSING ON EIR IMAGERY AND
WARMING. THE 24 HR DEVELOPING TREND RESULTS IN WEAKENING SLOWLY. MET IS
5.0 AND PT IS 4.5. FT IS BASED ON DT.

I. ADDL POSITIONS

NIL


...PATEL

[Sciencerocks]

[cycloneye]

Hurricane Linda Discussion Number 27
NWS National Hurricane Center Miami FL EP122021
1100 AM HST Mon Aug 16 2021

Linda still has a very striking appearance on visible satellite
imagery, with a well-defined large eye, and multiple eyewall
mesovorticies rotating about the mean center. However, the ring of
cold cloud tops associated with the eyewall has become just a touch
more ragged over the last few hours, and an earlier SSMIS microwave
pass at 1518 UTC showed a break in the singular eyewall on the south
side. The 1800 UTC Dvorak CI numbers were steady from SAB and TAFB,
but the data-T numbers have decreased a bit from earlier today. In
addition, the latest UW-CIMSS ADT intensity estimate was down to
T4.8/85-kt. Therefore, Linda is estimated to be a bit weaker this
advisory, with maximum sustained winds near 85-kt.

The initial motion is beginning to turn a bit more westward, now at
260/8 kt. A well-established mid-level ridge north of Linda is
expected to build in gradually to the northeast, allowing the storm
to begin gaining latitude starting tomorrow. This west-northwest
track is then expected to continue through the forecast period. The
latest NHC track forecast is very close to the previous one, and is
closest to the GEFX consensus, which is a simple blend of the most
recent GFS and ECMWF forecasts.

As discussed in previous advisories, Linda is expected to remain in
a low deep-layer vertical-wind-shear environment (below 10 kt) for
the next 4-5 days. Thus, Linda's intensity forecast is expected to
be driven by a combination of thermodynamic factors and the
cyclone's stable annular inner-core structure. While sea-surface
temperatures (SSTs) are only between 25-26 C under the hurricane
right now, the forecast track takes Linda back over slightly warmer
SSTs in the 12-36 h period, and this could delay weakening in the
short-term. The NHC intensity forecast continues to be above much of
the intensity guidance, showing little change in intensity over the
next 24-36 hours. In fact, when Linda moves over slightly warmer
SSTs tomorrow, it would not be surprising to see a bit of
restrengthening, assuming nearby dry-air does not disrupt the stable
eyewall structure. However by 48 hours, SSTs decrease below 26 C in
earnest and Linda is expected to begin a pronounced weakening trend.
Towards the end of the forecast, Linda should become devoid of deep
convection as indicated by the latest GFS and ECMWF IR brightness
temperature forecast, and Linda is expected to become a
post-tropical gale by Friday.


FORECAST POSITIONS AND MAX WINDS

INIT 16/2100Z 17.7N 124.6W 85 KT 100 MPH
12H 17/0600Z 17.6N 125.9W 85 KT 100 MPH
24H 17/1800Z 17.7N 127.7W 85 KT 100 MPH
36H 18/0600Z 18.2N 129.8W 85 KT 100 MPH
48H 18/1800Z 19.0N 132.2W 75 KT 85 MPH
60H 19/0600Z 19.9N 134.8W 60 KT 70 MPH
72H 19/1800Z 20.7N 137.5W 50 KT 60 MPH
96H 20/1800Z 22.0N 142.6W 40 KT 45 MPH...POST-TROPICAL
120H 21/1800Z 23.0N 146.8W 35 KT 40 MPH...POST-TROPICAL

$$
Forecaster Papin/Brown

[Blown Away]

What is going on to allow that eye to be so big? That’s awesome.

[Yellow Evan]

Cloud tops re-cooling and becoming more symmetrical. T5.0 but almost T5.5 again with WMG nearly embedded in LG.

[Yellow Evan]

TXPZ23 KNES 170006
TCSENP

A. 12E (LINDA)

B. 16/2330Z

C. 17.7N

D. 125.0W

E. ONE/GOES-W

F. T4.5/5.5

G. IR/EIR

H. REMARKS...WMG EYE SURROUNDED AND EMBEDDED IN MG RESULTS IN A DT OF
4.5. THE MET AND PT ARE ALSO 4.5 BASED ON A SLOW WEAKENING TREND OVER
THE PAST 24 HOURS. FT IS BASED ON DT.

I. ADDL POSITIONS

NIL


...COVERDALE

[Sciencerocks]

[Yellow Evan]

This is getting really shallow. Might have a chance to deepen again tomorrow over warmer waters but for now we seem to be in a slow weakening phase.

[cycloneye]

Hurricane Linda Discussion Number 28
NWS National Hurricane Center Miami FL EP122021
500 PM HST Mon Aug 16 2021

This evening's conventional satellite images indicate that the
cloud pattern hasn't changed that much during the past 6 hours. If
anything, the eyewall cloud top temperatures continue to gradually
warm, however, the convective MG (-51 to -53C) ring is showing less
erosion in the west quadrant as noted earlier. A blend of the
objective and subjective satellite intensity estimates supports
maintaining 85 kt for this advisory.

Finally, Linda has begun moving over cooler 25C waters, so we could
see some weakening overnight. NOAA's daily Real-Time Global Sea
Surface temperature analysis, however, reveals a marginally warm
pool of water just to the west of the hurricane. Consequently,
little change in strength, or possibly some restrengthening could
occur on Tuesday. Toward the end of the week, Linda is forecast to
traverse even cooler oceanic temperatures which should induce a
more rapid weakening as the cyclone crosses into the central
Pacific. The NHC forecast follows the statistical SHIPS intensity
model through 60 hours, then stays close to the IVCN consensus aid.

Linda is embedded in the deep easterly flow provided by high
pressure located over the northeast Pacific, and the initial motion
is 265/8 kt. The hurricane should be bending back to the right
(west-northwestward) around early Wednesday as the aforementioned
ridge builds to the northeast, behind a mid- to upper-level trough
approaching the U.S. west coast and the Baja California peninsula.
Global and regional models are in agreement that Linda should
continue moving toward the west-northwest through day 5, and the
official forecast follows suit. The track forecast is near the
middle of the guidance envelope, and is in best agreement with the
TVCN multi-model consensus.


FORECAST POSITIONS AND MAX WINDS

INIT 17/0300Z 17.7N 125.4W 85 KT 100 MPH
12H 17/1200Z 17.7N 126.7W 85 KT 100 MPH
24H 18/0000Z 17.9N 128.7W 80 KT 90 MPH
36H 18/1200Z 18.6N 130.9W 80 KT 90 MPH
48H 19/0000Z 19.4N 133.5W 70 KT 80 MPH
60H 19/1200Z 20.3N 136.2W 60 KT 70 MPH
72H 20/0000Z 21.1N 139.0W 50 KT 60 MPH
96H 21/0000Z 22.1N 144.2W 40 KT 45 MPH...POST-TROPICAL
120H 22/0000Z 22.9N 148.1W 35 KT 40 MPH...POST-TROPICAL

$$
Forecaster Roberts

[cheezyWXguy]

Linda’s slow downward trend has been fascinating to watch. The cdo has shrunk so much while the eye has remained stable, to the point that it’s basically just an eyewall at this point.

[Yellow Evan]

TXPZ23 KNES 170608
TCSENP

A. 12E (LINDA)

B. 17/0530Z

C. 17.6N

D. 125.9W

E. ONE/GOES-W

F. T4.0/4.5

G. IR/EIR

H. REMARKS...WMG EYE SURROUNDED BY MG AND EMBEDDED IN OW RESULTS IN A
DT OF 4.0. THE MET AND PT ARE 4.5 BASED ON A WEAKENING TREND OVER THE
PAST 24 HOURS. FT IS BASED ON DT.

I. ADDL POSITIONS

NIL


...COVERDALE

[Kingarabian]

Almost the entire 00z model suite showing Linda or its remnants reaching Hawaii.

[Kingarabian]

Refuses to drop its annular status.

[Yellow Evan]

Almost has a LG ring again.

[cycloneye]

Hurricane Linda Discussion Number 29
NWS National Hurricane Center Miami FL EP122021
1100 PM HST Mon Aug 16 2021

Linda has weakened, tonight. The eyewall has warmed during the past
6 hours, particularly in the west semicircle, and the convective
ring has also decreased significantly in coverage, but still
completely surrounds the 38 n mi diameter eye. The various
subjective and objective satellite intensity estimates have all
decreased, and a blend of these data yields an initial intensity of
80 kt for this advisory. It's worth noting that Linda appears to be
losing its annular cloud pattern which now consists of spiral
banding features showing up in all quadrants.

As research has proven in the past, tropical cyclones that are
characterized by an annular cloud pattern usually weaken more slowly
than at a climatological rate in the eastern Pacific. Despite
currently moving over sub-26C waters, the low shear surrounding
environment could still offset the negative contribution of
gradually decreasing sea surface temperatures, at least for the next
12 hours. As I mentioned in the previous discussion, Linda may
still have an outside chance of restrengthening some, or leveling
off again, while the cyclone moves back over marginally warmer
water. Beyond this short term period, Linda is forecast to move
over much colder waters which should induce a faster weakening as
the cyclone crosses into the central Pacific. Global models
generally agree that Linda will lose organized deep convection in 4
days and become a post-tropical gale, and this is indicated in the
official forecast.

The initial motion estimate is 265/9 kt. There is no significant
change to the previous forecast track or reasoning. Linda should
continue moving westward for the next 12 hours or so, followed by a
west-northwestward motion while the hurricane moves around the
southwest periphery of a mid-tropospheric high located over the
northeastern Pacific. The new NHC forecast track is essentially
just an extension of the previous one and is based primarily on the
better performing TVCN and HCCA consensus guidance.

A 0614 UTC METOP-B scatterometer pass indicated that Linda's wind
radii had contracted in all quadrants, and adjustments were made,
accordingly.


FORECAST POSITIONS AND MAX WINDS

INIT 17/0900Z 17.6N 126.4W 80 KT 90 MPH
12H 17/1800Z 17.7N 127.8W 80 KT 90 MPH
24H 18/0600Z 18.1N 129.8W 75 KT 85 MPH
36H 18/1800Z 18.8N 132.2W 70 KT 80 MPH
48H 19/0600Z 19.8N 134.9W 65 KT 75 MPH
60H 19/1800Z 20.7N 137.7W 60 KT 70 MPH
72H 20/0600Z 21.3N 140.5W 50 KT 60 MPH
96H 21/0600Z 22.1N 145.8W 40 KT 45 MPH...POST-TROPICAL
120H 22/0600Z 22.7N 149.9W 35 KT 40 MPH...POST-TROPICAL

$$
Forecaster Roberts

[tolakram]

All alone, and GOES-W acting up again, but this is a unique sight.

[Yellow Evan]

TXPZ23 KNES 171213
TCSENP

A. 12E (LINDA)

B. 17/1130Z

C. 17.5N

D. 126.9W

E. ONE/GOES-W

F. T4.0/4.5

G. IR/EIR/SWIR

H. REMARKS...SYSTEM HAS A WMG EYE TEMP SURROUNDED BY A MG GRAY RING TEMP
AND IS EMBEDDED IN OW RESULTING IN AN EYE PATTERN DT OF 4.0. THE 24 HR
DEVELOPING TREND RESULTS IN WEAKENING. MET IS 4.5 AND PT IS 4.0. FT IS
BASED ON DT.

I. ADDL POSITIONS

NIL


...PATEL

[cycloneye]

Hurricane Linda Discussion Number 30
NWS National Hurricane Center Miami FL EP122021
500 AM HST Tue Aug 17 2021

Linda has not changed much during the past several hours. The
system still has characteristics of an annular hurricane with a
large circular eye (a little more than 30 n mi in diameter) and a
ring of deep convection completely surrounding that feature. The
convection in the eyewall appears a little less symmetric than it
was a few hours ago, however. A blend of the latest Dvorak
estimates from TAFB, SAB, and automated values from CIMSS at the
University of Wisconsin support nudging the intensity down to 75 kt.

Even though Linda is over cool 25-26 deg C waters, research has
proven that tropical cyclones that are characterized by an annular
cloud pattern usually weaken more slowly than the climatological
rate in the eastern Pacific, and we expect Linda to be in that
category during the next day or so. Nonetheless, a combination of
cool SSTs and drier air should induce a slow weakening trend. 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 lies
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 nearly due westward at 265/9 kt. The track
forecast reasoning appears fairly straightforward. 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 are tightly clustered, and
only small changes were made to the previous track forecast. Based
on this prediction, Linda is expected to cross into the Central
Pacific basin in 60-72 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 17/1500Z 17.5N 127.4W 75 KT 85 MPH
12H 18/0000Z 17.8N 128.8W 75 KT 85 MPH
24H 18/1200Z 18.3N 131.0W 70 KT 80 MPH
36H 19/0000Z 19.1N 133.7W 65 KT 75 MPH
48H 19/1200Z 20.1N 136.5W 60 KT 70 MPH
60H 20/0000Z 20.8N 139.4W 50 KT 60 MPH
72H 20/1200Z 21.3N 142.1W 40 KT 45 MPH
96H 21/1200Z 22.0N 147.3W 35 KT 40 MPH...POST-TROPICAL
120H 22/1200Z 22.5N 151.4W 35 KT 40 MPH...POST-TROPICAL

$$
Forecaster Cangialosi