CPAC: IONA - Tropical Storm - Discussion

[Yellow Evan]

Looking at the satellite loop, 65 knots could be a smidge generous. Whatever computer figures the ADT agrees with me.




UW - CIMSS
ADVANCED DVORAK TECHNIQUE
ADT-Version 9.1
Tropical Cyclone Intensity Algorithm

----- Current Analysis -----
Date : 28 JUL 2025 Time : 144021 UTC
Lat : 10:41:59 N Lon : 150:03:02 W


CI# /Pressure/ Vmax
2.7 /1007.8mb/ 39.0kt

I disagree. CBs have been wrapping around efficiently all morning, indicative of a core, microwave has had a low-level core since yesterday, and upper level outflow is well established. Unless shear gets to it, we’re probably on track for a bonafide major atp.

[Kingarabian]

Agree this is a hurricane. Looks like it will attempt to clear an eye out soon.

[Hurricane2022]

 https://x.com/TropicScope/status/1949885103452369224

[ElectricStorm]

12z HWRF/HMON/HAFS-A and B all now showing this becoming a major in the 105-115kt range. With the current structure that would not be all that surprising at all

[Hurricane2022]

Fun fact: "The name Iona was used for the first time this season, replacing Iwa, which was retired after the 1982 season." Source - Wikipedia.

[cycloneye]

New Peak intensity is 95kt

Hurricane Iona Discussion Number 7
NWS Central Pacific Hurricane Center Honolulu HI CP012025
Issued by NWS National Hurricane Center Miami FL
1100 AM HST Mon Jul 28 2025

After rapidly strengthening overnight, the cloud pattern and
overall structure of Iona has changed little during the past 6
hours. A fairly symmetric Central Dense Overcast is seen over the
center in geostationary satellite imagery, but there has been no
recent microwave data to examine the inner core structure. The
latest subjective satellite intensity estimates are T4.0/65 kt
from SAB, and T3.5/55 kt from both PHFO and JTWC. Objective
estimates remain lower, although it is possible that the small size
of the cyclone is making it difficult for those techniques to
capture the true intensity. The initial intensity for this advisory
will remain 65 kt, in line with the higher subjective estimate from
SAB.

Iona is located within a low-shear environment and over sea surface
temperatures of around 28C. Those conditions favor strengthening,
however some nearby dry mid-level air may have been entrained in
the circulation which likely caused the recent pause in
intensification. Given the favorable upper-air pattern and warm
sea surface temperatures, additional strengthening appears likely.
The regional hurricane models are more aggressive this cycle and
indicate that Iona could be near or at major hurricane strength in
a day or so. As a result, the lastest official forecast calls
for rapid strengthening during the next 24 hours and the peak
intensity is raised slightly from the previous advisory. Around
midweek, slightly lower SSTs and an increase in vertical
wind shear are expected to cause gradual weakening through the
remainder of the forecast period. The updated NHC intensity
forecast is close to the regional models through 24 hours, and then
follows the latest multi-model (IVCN) consensus aid after that time.

Iona is moving westward or 270 degrees at 9 kt. The storm is
forecast to move along the southern portion of a subtropical ridge
that is well established over the central Pacific. This steering
pattern should take the storm westward during the next day or so,
followed by a faster west-northwestward motion after midweek. The
updated track forecast is once again near the center of the model
envelope, close to the various consensus aids. Confidence remains
high that Iona will stay well south of the Hawaiian Islands.


FORECAST POSITIONS AND MAX WINDS

INIT 28/2100Z 10.6N 151.0W 65 KT 75 MPH
12H 29/0600Z 10.6N 152.6W 80 KT 90 MPH
24H 29/1800Z 10.6N 155.0W 95 KT 110 MPH
36H 30/0600Z 10.7N 157.7W 90 KT 105 MPH
48H 30/1800Z 10.9N 161.0W 80 KT 90 MPH
60H 31/0600Z 11.2N 164.5W 65 KT 75 MPH
72H 31/1800Z 11.7N 168.1W 55 KT 65 MPH
96H 01/1800Z 12.9N 175.2W 45 KT 50 MPH
120H 02/1800Z 14.7N 178.5E 40 KT 45 MPH

$$
Forecaster Brown

[ScottNAtlanta]

Forgive me if anyone has talked about this already, but look at the spin NE of the hurricane. It looks like Iona had a baby. It's got plenty of rotation...don't know how long it will last though

[cycloneye]

Forgive me if anyone has talked about this already, but look at the spin NE of the hurricane. It looks like Iona had a baby. It's got plenty of rotation...don't know how long it will last though

That is Tropical Storm Keli.

[ScottNAtlanta]

Forgive me if anyone has talked about this already, but look at the spin NE of the hurricane. It looks like Iona had a baby. It's got plenty of rotation...don't know how long it will last though

That is Tropical Storm Keli.

When it rains it pours in CPAC it seems

[Yellow Evan]

VHT curling southward. Pressure will tank at a faster rate once a full wrap of B or colder cloud tops occurs.

[DorkyMcDorkface]

HMON is the most bullish of the guidance, peaking this at C4 intensity in a mere 18 hours! Honestly given the rate in which this is intensifying it is very much possible.

[Hurricane2022]

HMON is the most bullish of the guidance, peaking this at C4 intensity in a mere 18 hours! Honestly given the rate in which this is intensifying it is very much possible.

https://i.imgur.com/A4eKzNl.png

Yeah. Look at this burst!

[cycloneye]

CP, 01, 2025072900, , BEST, 0, 109N, 1516W, 70, 985, HU

[Yellow Evan]

Here we go.

[Yellow Evan]

TXPN26 KNES 290016
TCSCNP

A. 01C (IONA)

B. 28/2330Z

C. 10.9N

D. 151.5W

E. THREE/GOES-W

F. T4.0/4.0

G. IR/EIR/VIS/GMI

H. REMARKS...LLCC EMBEDDED IN MG YIELDS A DT OF 4.0. THE MET AND PT
ARE 4.0 BASED ON A 24HR RAPID DEVELOPING TREND. THE FT IS BASED ON THE
MET BECAUSE THE CLOUD FEATURES ARE NOT CLEAR CUT.

I. ADDL POSITIONS

28/2214Z 10.9N 151.3W GMI


...GATLING

[Yellow Evan]

We don't have a ton of time here. GFS and ECMWF start picking up the shear as early as tonight and a small, rapidly intensifying cyclone can be vulnerable to even a slight increase in shear.

[cycloneye]

 https://x.com/VortixWx/status/1949999181591884128

[sasha_B]

JTWC has this on the latest satellite bulletin:

F. T4.5/4.5/D2.0/24HRS STT: D0.5/03HRS

G. IR/EIR/VIS/MSI

H. REMARKS: 15A/PBO TIGHTLY CURVED BNDG/ANMTN. LG EYE SURROUNDED BY
LG YIELDS AN E# OF 5.0. SUBTRACTED 0.5 EYE ADJUSTMENT FOR B TO
YIELD A DT OF 4.5. MET YIELDS 4.0. PT YIELDS 4.5. DBO DT.

...and ADT estimates are climbing towards T4.5 as well. 70 kts could be somewhat conservative & the improvement in satellite presentation over the past several hours is notable.

[StormWeather]

JTWC has this on the latest satellite bulletin:

F. T4.5/4.5/D2.0/24HRS STT: D0.5/03HRS

G. IR/EIR/VIS/MSI

H. REMARKS: 15A/PBO TIGHTLY CURVED BNDG/ANMTN. LG EYE SURROUNDED BY
LG YIELDS AN E# OF 5.0. SUBTRACTED 0.5 EYE ADJUSTMENT FOR B TO
YIELD A DT OF 4.5. MET YIELDS 4.0. PT YIELDS 4.5. DBO DT.

...and ADT estimates are climbing towards T4.5 as well. 70 kts could be somewhat conservative & the improvement in satellite presentation over the past several hours is notable.

Infrared satellite shows that the convection has wrapped around the eye (which is starting to appear in infrared), I can’t do Dvorak (I’m no expert) but I would hazard a guess to say this is probably 75-80 kts now at best, with my highest estimate going for 90 kts.

[WaveBreaking]

CDO is much more circular than it was a few hours ago and a new VHT is firing in the E eyewall