CPAC: CALVIN - Post-Tropical - Discussion

[Yellow Evan]

Hanging on as it benefits from DMax. Eye is WMG again but SSTs of 25C have kept it shallow.

[Sciencerocks]

[cycloneye]

Hurricane Calvin Discussion Number 17
NWS National Hurricane Center Miami FL EP032023
1100 AM HST Sat Jul 15 2023

The satellite appearance of Calvin has shown some ill effects today
from cooler SSTs and some drier air in its surrounding environment.
A 1512 UTC SSMIS 89 GHz passive microwave image of the hurricane
showed the eyewall was open to the east, where a dry slot was noted
earlier wrapping around that portion of the circulation. Since then,
the eye has become a bit warmer and more pronounced in infrared
satellite imagery, and some deeper inner-core convection has wrapped
around the center. The latest objective and subjective satellite
intensity estimates range from 77-90 kt. Based on a blend of these
data and recent satellite trends, the initial intensity is held at
85 kt for this advisory.

Weakening is expected during the next few days as the cyclone moves
into a drier and more stable air mass over sub-26C SSTs. In fact,
model-simulated satellite imagery from the GFS and ECMWF suggest
Calvin could lose most, or briefly all, of its convection once it
enters the central Pacific basin. However, the underlying SSTs
become slightly warmer between 48-96 h while the deep-layer shear
diagnosed by the global models is low to moderate. Therefore, it
seems that Calvin could regenerate new bursts of convection on its
approach to Hawaii, which is shown by the global and hurricane
models. Therefore, the NHC forecast keeps Calvin a tropical cyclone
through 96 h. Regardless of its status, the cyclone appears likely
to maintain some tropical-storm-force winds in the northern portion
of its circulation as it approaches Hawaii. The global model fields
suggest the system will be close to opening into a trough by or
shortly after day 5.

The long-term motion of Calvin is westward at 280/14 kt. A westward
to west-northwestward motion will continue through the forecast
period as the cyclone is steered by a mid-level ridge entrenched
over the eastern Pacific. Calvin is forecast to cross 140W and enter
the central Pacific basin on Monday morning and approach the
Hawaiian Islands on Tuesday into early Wednesday. The various track
models continue to bring Calvin near or over the Big Island of
Hawaii, but exactly where it will track relative to the island is
still unclear given the cross-track spread noted at day 3 and
beyond. The updated NHC forecast has been adjusted slightly faster
than the previous one, but otherwise very little change was made.


KEY MESSAGES:

1. Calvin is forecast to move across the central Pacific Ocean and
approach the Hawaiian Islands early next week. It is too early to
determine the exact location and magnitude of potential impacts
given uncertainties in the track, intensity, and structure of Calvin
as it approaches the islands. Interests in Hawaii should closely
monitor the latest forecast updates.


FORECAST POSITIONS AND MAX WINDS

INIT 15/2100Z 15.0N 130.4W 85 KT 100 MPH
12H 16/0600Z 15.6N 132.7W 75 KT 85 MPH
24H 16/1800Z 16.3N 135.8W 65 KT 75 MPH
36H 17/0600Z 16.8N 139.0W 55 KT 65 MPH
48H 17/1800Z 17.3N 142.5W 50 KT 60 MPH
60H 18/0600Z 17.7N 146.2W 45 KT 50 MPH
72H 18/1800Z 18.3N 149.9W 40 KT 45 MPH
96H 19/1800Z 19.4N 156.8W 35 KT 40 MPH
120H 20/1800Z 20.5N 164.0W 30 KT 35 MPH...POST-TROP/REMNT LOW

$$
Forecaster Reinhart

[Yellow Evan]

[Astromanía]

Not bad considering the cool waters

[Sciencerocks]

[Yellow Evan]

Hanging on still. Might look decent for one more D Max.

[Yellow Evan]

TXPZ28 KNES 160021
TCSENP

A. 03E (CALVIN)

B. 16/0000Z

C. 15.1N

D. 131.2W

E. ONE/GOES-E

F. T5.0/5.0

G. IR/EIR/VIS

H. REMARKS...SYSTEM CHARACTERIZED BY A OW EYE SURROUNDED BY LG AND
EMBEDDED IN LG FOR A DT=5.0 MET AND PT AGREE. THE FT IS BASED ON THE DT.

I. ADDL POSITIONS

NIL


...FISHER

[Yellow Evan]

EP, 03, 2023071600, , BEST, 0, 152N, 1312W, 85, 975, HU, 64, NEQ, 20, 15, 15, 20, 1009, 180, 15, 0, 0, E, 0, , 0, 0, CALVIN, D, 0, , 0, 0, 0, 0, genesis-num, 007,

[Yellow Evan]

[Kingarabian]

It's doing pretty good. Real test is the next 24 hours.

[Kingarabian]

If it hangs on tomorrow then it could rival Iselle 2014 for strongest landfall out of the east.

[Kingarabian]

Solid T5.0 for the past 12 hours.

[cycloneye]

Hurricane Calvin Discussion Number 18
NWS National Hurricane Center Miami FL EP032023
500 PM HST Sat Jul 15 2023

During the past several hours, the satellite cloud pattern of
Calvin has been unsteady, with the eye coming and going and the
eyewall cloud top temperatures fluctuating. Overall, though, there
has been little change in the organization and the various
satellite intensity estimates. Based on this, the initial
intensity is again held at 85 kt, which is close to the CIMMS
satellite consensus estimate.

Calvin is currently over 25C sea surface temperatures, and it should
be over 24C water in about 24 h. This should cause weakening during
the next 24-36 h. After that time, the sea surface temperatures
start to increase under the forecast track, although they are
expected to stay below 26C until the system passes near Hawaii.
During this period, the vertical wind shear is forecast to be light
to moderate. The consensus of the guidance during this time is
that Calvin will continue to weaken while producing intermittent
bursts of convection, and that is the basis for keeping it a
tropical storm. Regardless of how much convection is present, it
appears likely that Calvin will maintain tropical-storm-force winds
as it passes near the Big Island of Hawaii. After 96 h, stronger
shear should cause the cyclone to degenerate to a remnant low
pressure area or trough.

The initial motion is now 285/15 kt. As in the previous forecast,
a westward to west-northwestward motion will continue through the
forecast period as the cyclone is steered by a mid-level ridge
entrenched over the eastern Pacific. On the forecast track, Calvin
is forecast to cross 140W and enter the central Pacific basin on
Monday morning and approach the Hawaiian Islands on Tuesday into
early Wednesday. There remains some cross-track spread in the
models, so while the new forecast track calls for Calvin to pass
close to the Big Island of Hawaii it remains unclear exactly how it
will track relative to the island. The new forecast track has only
minor adjustments from the previous track.


KEY MESSAGES:

1. Calvin is forecast to move across the central Pacific Ocean and
approach the Hawaiian Islands early next week. It is too early to
determine the exact location and magnitude of potential impacts
given uncertainties in the track, intensity, and structure of Calvin
as it approaches the islands. Interests in Hawaii should closely
monitor the latest forecast updates.


FORECAST POSITIONS AND MAX WINDS

INIT 16/0300Z 15.4N 132.0W 85 KT 100 MPH
12H 16/1200Z 16.0N 134.3W 75 KT 85 MPH
24H 17/0000Z 16.6N 137.6W 65 KT 75 MPH
36H 17/1200Z 17.1N 140.9W 55 KT 65 MPH
48H 18/0000Z 17.4N 144.4W 50 KT 60 MPH
60H 18/1200Z 17.9N 148.0W 45 KT 50 MPH
72H 19/0000Z 18.4N 151.6W 40 KT 45 MPH
96H 20/0000Z 19.5N 158.5W 35 KT 40 MPH
120H 21/0000Z 20.5N 165.5W 25 KT 30 MPH...POST-TROP/REMNT LOW

$$
Forecaster Beven

[Sciencerocks]

[cycloneye]

Hurricane Calvin Discussion Number 19
NWS National Hurricane Center Miami FL EP032023
1100 PM HST Sat Jul 15 2023

The cloud pattern and overall organization of Calvin has been
deteriorating this evening. The eye and eyewall are unraveling and
opening up on the western side. Dry air entrainment and cool water
temperatures are also causing the convective banding to diminish
with cloud tops warming and the inner core dissipating. Subjective
Dvorak estimates, as well as CIMMS ADT and AiDT estimates, have come
down with this advisory ranging from 55 kt to 78 kt. Based on these
data, the initial intensity is lowered to 70 kt.

Calvin is currently moving over cooler SSTs near 25C and will
continue to be over even cooler water temps the next 24-36 hours.
Calvin is also moving into a drier mid-level airmass and a more
stable environment. Given the current satellite trends and the
environment Calvin is beginning to encounter, weakening is forecast
for the remainder of the period. However, the system is still likely
to continue to have bursts of convection as it approaches the
Hawaiian Islands in a few days. Regardless of how much convection
is present, it appears likely that Calvin will maintain tropical
storm force winds as it passes near the Big Island of Hawaii. After
it passes Hawaii, stronger shear should cause the cyclone to
degenerate to a remnant low pressure area or trough.

The initial motion is estimated to be 285/15 kt. A westward to
west-northwestward motion will continue through the forecast period
as the cyclone remains steered by a mid-level ridge over the eastern
Pacific. On the forecast track, Calvin is forecast to cross 140W and
enter the central Pacific basin Sunday night or early Monday
morning and approach the Hawaiian Islands on Tuesday into early
Wednesday. There remains some cross-track spread in the models, so
while the new forecast track calls for Calvin to pass close to the
Big Island of Hawaii it remains unclear exactly how it will track
relative to the island. The new forecast track has only minor
adjustments from the previous track.


KEY MESSAGES:

1. Calvin is forecast to move across the central Pacific Ocean and
approach the Hawaiian Islands within the next few days. Interests in
Hawaii should closely monitor the latest forecast updates and a
Tropical Storm Watch could be issued for portions of the main
Hawaiian Islands late Sunday.


FORECAST POSITIONS AND MAX WINDS

INIT 16/0900Z 15.7N 133.4W 70 KT 80 MPH
12H 16/1800Z 16.2N 135.8W 60 KT 70 MPH
24H 17/0600Z 16.7N 139.1W 50 KT 60 MPH
36H 17/1800Z 17.2N 142.6W 45 KT 50 MPH
48H 18/0600Z 17.6N 146.1W 40 KT 45 MPH
60H 18/1800Z 18.2N 149.6W 40 KT 45 MPH
72H 19/0600Z 18.6N 153.2W 35 KT 40 MPH
96H 20/0600Z 19.9N 160.0W 30 KT 35 MPH
120H 21/0600Z 20.3N 166.2W 25 KT 30 MPH...POST-TROP/REMNT LOW

$$
Forecaster Kelly/Cangialosi

[Kingarabian]

It's losing convection really fast. Overall structure looks great though.

[Sciencerocks]

[cycloneye]

Tropical Storm Calvin Discussion Number 20...Corrected
NWS National Hurricane Center Miami FL EP032023
500 AM HST Sun Jul 16 2023

Corrected timing in the key messages

The cloud pattern of Calvin has further deteriorated this morning.
The center is now exposed, and cloud tops have warmed over much of
the circulation with only a small area of moderate to deep
convection noted to the east of the center. The objective and
subjective satellite intensity estimates continue to quickly
decline, with a blend of the recent data suggesting that Calvin is
no longer a hurricane. Based on these data and its poor satellite
structure, the initial intensity is lowered to 60 kt.

The track forecast remains straightforward. Calvin is expected to
keep moving generally westward for the next several days as it is
steered by a well-established ridge over the eastern Pacific. This
motion will bring the cyclone into the central Pacific basin (west
of 140W) tonight or early Monday morning. Calvin is forecast to
approach the Hawaiian Islands on Tuesday and pass near or over the
Big Island of Hawaii early Wednesday. The track guidance remains in
good agreement on this overall scenario, although the details of its
track near Hawaii are still uncertain given the average amount of
cross-track spread in the guidance. The latest NHC forecast is
slightly faster and has been nudged slightly northward at 60-96 h,
but still lies near the center of the guidance envelope and close to
the HCCA and TVCE aids.

Calvin will move over 24 deg C waters and into a drier, more stable
environment during the next couple of days. Therefore, continued
weakening is anticipated, and the system could struggle to produce
convection on its trek into the central Pacific basin. As Calvin
moves closer to Hawaii, model-simulated satellite imagery suggests
it could produce some renewed bursts of convection to the north of
its center. This forecast keeps Calvin as a tropical cyclone through
72 h, although it could become post-tropical sooner if convection
collapses for an extended period. Regardless, there is good support
from both the global and hurricane models that Calvin will maintain
some tropical-storm-force winds (mainly to the north of its center)
as it nears Hawaii. With strong deep-layer southwesterly shear
expected in 96-120 h, this forecast shows Calvin opening into a
trough and dissipating by day 5.


KEY MESSAGES:

1. Calvin is forecast to move across the central Pacific Ocean and
approach the Hawaiian Islands during the next few days. A Tropical
Storm Watch could be issued for portions of the main Hawaiian
Islands later today, and interests in Hawaii should closely monitor
the latest forecast updates.


FORECAST POSITIONS AND MAX WINDS

INIT 16/1500Z 16.0N 134.8W 60 KT 70 MPH
12H 17/0000Z 16.4N 137.3W 55 KT 65 MPH
24H 17/1200Z 17.0N 140.6W 45 KT 50 MPH
36H 18/0000Z 17.5N 144.2W 45 KT 50 MPH
48H 18/1200Z 17.9N 147.9W 40 KT 45 MPH
60H 19/0000Z 18.6N 151.6W 40 KT 45 MPH
72H 19/1200Z 19.2N 155.0W 35 KT 40 MPH
96H 20/1200Z 20.1N 161.8W 30 KT 35 MPH...POST-TROP/REMNT LOW
120H 21/1200Z...DISSIPATED

$$
Forecaster Reinhart

[Sciencerocks]