SIO: OLGA - Remnants

[Hurricane2022]

[Hurricane2022]

From JTWC's discussion

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: TROPICAL CYCLONE (TC) 21S HAS UNDERGONE EXTREME RAPID INTENSIFICATION (ERI) OVER THE PAST 24 HOURS, INCREASING 65 KNOTS FROM 55 KNOTS AT 061200Z TO THE INITIAL INTENSITY OF 120 KNOTS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY DEPICTS A SLIGHTLY OBLONG CONVECTIVE CORE SURROUNDING AN 8 NM EYE (FROM THE RCM-3 SAR PASS), WITH TROCHOIDAL MOTION EVIDENT OVER THE PAST 12 HOURS. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE EIR IMAGERY. AS A RESULT OF THE EXTENSIVE DRY AIR AROUND THE PERIPHERY OF THE SYSTEM, A 071039Z SSMIS 91 GHZ MICROWAVE IMAGE REVEALS A COMPACT CONVECTIVE CORE, WITH LIMITED SPIRAL BANDING OVER THE WESTERN QUADRANT. DUE TO THE SYSTEM'S COMPACT SIZE AND ROBUST POLEWARD OUTFLOW, TC OLGA HAS BEEN ABLE TO THRIVE AND COCOON ITSELF FROM THE INCREASING (25 TO 30 KNOTS) NORTHWESTERLY VERTICAL WIND SHEAR (VWS). HOWEVER, THE HIGH VWS HAS STARTED TO IMPINGE ON THE WESTERN EDGE OF THE SYSTEM, WITH A PRONOUNCED FLATTENING REVEALED IN THE EIR IMAGERY. ADDITIONALLY, DRY AIR IS ENTRAINING INTO THE NORTHEASTERN QUADRANT OF THE SYSTEM. THE INITIAL INTENSITY OF 120 KTS IS ASSESSED WITH HIGH CONFIDENCE BASED ON A FORTUITOUS 071032Z RCM-3 SAR PASS, INDICATING A MAXIMUM INTENSITY OF 122 KNOTS. THE INITIAL INTENSITY IS ASSESSED SLIGHTLY HIGHER THAN THE AGENCY DVORAK ESTIMATES OF T6.0 (115 KNOTS) BUT IS CLOSE TO THE RECENT ADT AND AIDT ESTIMATES.

[al78]

Another storm that has been massively underforecast by the JTWC.

[Hurricane2022]

Rapid Weakening is ongoing.

[cycloneye]

Severe Tropical Cyclone Olga, 11U, has begun its weakening phase. There is no
longer an eye visible in EIR satellite imagery and as such there decreasing
confidence in analysis position. This confidence is expected to diminish
further unless microwave sensor passes successfully capture the low level
centre.

Dvorak analysis: Recent EIR images give a DT of 5.0 based on an embedded centre
of black. MET is 4.5 with no adjustment. FT is set at 5.0 with CI held at 6.0
for initial weakening. Objective guidance (1-min average): ADT 127kn, AiDT
123kn, DPRINT 119kn, DMINT 107kn, SATCON 114kn.

Intensity is set to 90 knots (10-minute average) and is based on significant
weakening trend in recent satellite imagery.

Olga has transitioned into an environment that will favour weakening, with
vertical wind shear having increased to 19kn northerly (1200UTC analysis via
CIMSS). The shear is forecast to increase further as the system tracks further
to the southwest. With dry air present to the north of the system, it is
expected that the initial weakening that has occurred over the past 6 hours
will continue. Weakening is likely to be rapid due to the small size of Olga
(particularly the northern flank).

Olga has been moving towards the south-southwest. As Olga weakens, a low-level
ridge to the south will become the dominant steering influence and the system
will move southwest during Monday. In the longer term the remnant low is
expected to continue to move westward with gales in southern quadrants through
to Wednesday.

[cycloneye]

Severe Tropical Cyclone Olga, 11U, has shown strong signs of weakening over the
last 12 hours losing its round circular eye and becoming asymmetrical in its
cloud structures.

Dvorak analysis is based on embedded centre pattern with W background giving a
DT=5.0. MET is 4.0 on a W- 24-hr trend, adjusted to PT=4.5. FT is set at 4.5
with CI held at 5.6. Objective guidance (1-min average): ADT 107kn, AiDT 104kn,
DPRINT 92kn, DMINT 106kn, SATCON 82kn. Intensity is set to 80 knots (10-minute
average).

Olga has transitioned into an environment that will favour continued weakening,
due to increased vertical wind shear and dry air entrainment. The system is
expected to weaken below tropical cyclone category late on Tuesday, although
gales are likely to continue on the southern side till Wednesday.

Olga has been moving in a general southwards direction but is expected to
assume a more southwest movement as it weakens further. A low-level ridge to
the south will become the dominant steering influence in the coming days.

[cycloneye]

Tropical Cyclone Olga, 11U, has continued to show strong signs of weakening
over the last 18 to 24 hours. It had lost its round circular eye 12 hours ago
and deep convection had become almost non-existent, before renewed deep
convection developed near the centre in the last 3 hours.

Dvorak analysis is based on embedded centre pattern with MG background giving a
DT=4.0. MET is 4.0 on a W+ 24-hr trend, adjusted to PT=3.5. FT is set at 3.5
with CI held at 4.0. Objective guidance (1-min average): ADT 94kn, AiDT 93kn,
DPRINT 53kn, SATCON 83kn. Intensity is set to 80 knots (10-minute average).

Olga is continuing to weaken in an unfavourable environment with increased
vertical wind shear and dry air entrainment. The system is expected to weaken
below tropical cyclone category by late Tuesday, although gales are likely to
continue on the southern side till overnight Wednesday.

Olga has been moving in a general southwards direction but is expected to
assume a more southwest movement as it weakens further. A low-level ridge to
the south will become the dominant steering influence in the coming days.

[cycloneye]

Olga is gradually weakening in an unfavourable environment with strong
northwest vertical wind shear and dry air entrainment. Deep convection remains
confined to southern quadrants and exhibits little curvature, however in recent
hours has redeveloped closer to the centre.
Intensity is analysed at 45 knots (10 minute mean) based on earlier satellite
winds (scatterometry, SAR (RCM-2 at 2148UTC and RCM3 at 1039UTC)), consistent
with Dvorak and within range of objective guidance.
Dvorak analysis is based on a shear pattern with the LLCC <3/4 degree from deep
convection. DT=2.5. MET is 3.0 based on a 24 hour W trend. FT=2.5 and CI=3.0.
This lies within the broad envelope of objective guidance (all 1 min. mean):
SATCON 42kn, ADT 45kn, AiDT 41kn while DPRINT lower at 30kn.
Olga is expected to only slowly weaken with gales reducing to southern
quadrants overnight at which stage it will be de-classified as a tropical
cyclone. These southern quadrant gales are likely to continue until late
Wednesday, however. Some NWP guidance suggests an increase in winds south of
the centre overnight, likely reflecting some low-level NE/ESE
convergence-induced storm enhancement. For this reason the wind intensity of
45kn is retained through to Wednesday morning.
Olga is expected to assume a steady southwest track as it weakens, with a
low-level ridge to the south the dominant steering influence.

[cycloneye]

Bye.

Ex-Tropical Cyclone Olga is gradually weakening in an unfavourable environment
due to strong northwest vertical wind shear (25-30 knots from CIMSS) and dry
air entrainment. Deep convection is occurring only in sporadic bursts south of
the centre.

Olga has been de-classified as a tropical cyclone. Gales are now analysed in
southern quadrants only, based on extrapolating a weakening trend from the
09/1047 SAR pass, and consistent with deterministic NWP guidance. These
southern quadrant gales are likely to continue until late Wednesday, however.
Some NWP guidance suggests an increase in winds south of the centre overnight,
likely reflecting some low-level NE/ESE convergence-induced storm enhancement.

Ex-Olga is expected to continue a steady southwest track as it weakens further,
with a low-level ridge to the southeast being the dominant steering influence.