Review of the 2014/15 Tropical Cyclone Season Review of the 2014/15 Tropical Cyclone Season in the Southwest Pacific Ocean Basinin the Southwest Pacific Ocean Basin

VUW SeminarVUW SeminarWellington, NZ; 27-August-2015Wellington, NZ; 27-August-2015

Howard J. Diamond, PhDHoward J. Diamond, PhDAdjunct Research Associate, Victoria University of WellingtonAdjunct Research Associate, Victoria University of Wellington, ,

School of Geography, Environment and Earth SciencesSchool of Geography, Environment and Earth Scienceshoward.diamond@vuw.ac.nz

Up Close View of TC Pam [from NASA] TC Marcia

AgendaAgenda Outlook Prior to the SeasonOutlook Prior to the Season

Summary of Activity & Some Unique Seasonal FeaturesSummary of Activity & Some Unique Seasonal Features

Tropical Cyclone PamTropical Cyclone Pam ImpactsImpacts Climatological ConditionsClimatological Conditions

Sub-Tropical Storm “Katie” in late April/early May; and Sub-Tropical Storm “Katie” in late April/early May; and Late Season TC Raquel – Straddling Season Line Late Season TC Raquel – Straddling Season Line between June 30/July 1between June 30/July 1

SummarySummary

SW Pacific BasinMain Development Area

Extent of SW Pacific TC Region

No RSMC Responsibility

World Meteorological Organization’s Tropical Cyclone Programme – Regional Specialised Meteorological Centres (RSMC)

Average annual profile of tropical cyclone longitude crossings for the Southern Hemisphere (Natural Break at 135º East) – Kuleshov, 2006

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30ºE 50ºE 70ºE 90ºE 110ºE 130ºE 150ºE 170ºE 170ºW 150ºW 130ºW 110ºW

Longitude

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Historical Climatology

135º East – Gulf of Carpentaria

Australian Region Southwest Pacific Region

35º E 135º E 160º E 110º W

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160º E – Boundary of Monitoring Centres

TC Outlook Issued by NIWA – October 2014 Based on Coupled ENSO Index Analog Seasons (Gergis and Fowler,

2005)

C Climatology based on Period from 1981-2010

NIWA Outlook Highlights and Results• Six analog TC seasons: 1978/79; 1979/80; 1980/81; 1990/91;

2001/02; and 2012/13 – typified as ENSO-neutral to weak El Niño seasons

• 8-12 named TCs expected [11 named TCs]

• One Cat 5 TC expected [2 Aussie Cat 5 TCs – Marcia and Pam] – Furthermore, Pam was a Saffir-Simpson Cat 5 TC

• Chances of 2 or more TCs passing near Vanuatu

• Reduced activity for early part of season (Nov-Jan) [From Nov-Jan there were only 2 named storms, but 8 Invests or TDs]

• More active late part of the season (Feb-Apr) [From Feb-Apr there were 6 named storms, and 4 Invests or TDs]

• Outside of season (May-Jun) [2 named storms*, and 3 Invests or TDs]

* One – a sub-tropical storm well east of the normal basin.

Geographic Grouping TC FrequencyVanuatu 3.9New Caledonia 3.4Fiji 3.3Tonga 2.7Wallis and Futuna 2.4Niue 2.2Solomon Islands 2.2Samoa 2.0Tuvalu 1.8Southern Cook Islands 1.7Gulf of Carpentaria 1.5Papua New Guinea 1.5Tokelau 1.2New Zealand 1.1Austral Islands 1.0Northern Cook Islands 1.0Society Islands 0.9French Polynesia 0.7Tuamotu 0.4Pitcairn Island 0.3Western Kiribati 0.2Marquesas 0.1Eastern Kiribati 0.0

1970-2010 Full Season Climatological Distribution of TCs 1970-2010 Full Season Climatological Distribution of TCs per SPEArTC Datasetper SPEArTC Dataset

Coupled ENSO Index (CEI)• The CEI is an index used to jointly indicate ocean and atmosphere

conditions associated with ENSO (Gergis and Fowler, 2005).

• The primary components of the CEI are the Southern Oscillation Index (SOI) and the Niño3.4 (N3.4) index

• Each of these indices is smoothed (as explained in Gergis and Fowler, 2005) and minimum threshold values indicate whether the atmosphere (SOI) or ocean (N3.4) indicates if an ENSO phase is present.

• When both indices indicate the same ENSO state, the ocean-atmosphere system is considered to be well-coupled (either a NIÑO or NIÑA style event).

• When only the N3.4 index or SOI indicates ENSO is present, a N3.4 NIÑO/N3.4NIÑA or SOI NIÑO/SOI NIÑA style of event is suggested, respectively.

Verification of TC Outlook Issued by NIWA

Preliminary TC Tracks – 25 Total Tracks11 Named Storms plus 1 Sub-Tropical Storm

TC Category Wind Speeds (knots)

Tropical Depression < 34

Category 1 34-47

Category 2 48-63

Category 3* 64-84

Category 4* 85-106

Category 5* > 106

* Considered Major -

TC Storm Intensities

Period Total # of TCs Total # of Major TCs

Total # of Category 5 TCs

1970-1990 298 (56%) 83 (27.9% of total) 4 (19%)

1991-2010 234 (44%) 86 (36.8% of total) 17 (81%)

Australian TC Intensity Scale http://www.bom.gov.au/cyclone/about/intensity.shtml

The increased proportion of major TCs over the past 20 years is statistically significant with a t-test score of p > .005 (19 degrees of freedom)

The Story of TC Pam

• Early on 13-March, the JTWC determined Pam reached its peak one-minute sustained winds of 270 km/h (146 knots) as it neared Vanuatu.

• Several hours later, the TC began to curve towards the south-southeast, allowing Pam to pass just east of Efate in Vanuatu. At that time, the Fiji Met Service (FMS) estimated Pam as having record-breaking 250 km/h (135 knots) ten-minute sustained winds.

• The storm's winds gradually slowed afterwards as Pam tracked west of Tafea. However, the FMS indicated that the cyclone's pressure dropped further to a minimum of 896 hPa on 14-March, making Pam the second most intense TC in the South Pacific basin after Cyclone Zoe in 2002. MJO maxed out at 4.6 on 16-March

• This intensity was short-lived, however, as Pam's central pressure began rising shortly thereafter as the storm accelerated southeastward. Pam weakened to Category 4 intensity on 15-March after maintaining Category 5 intensity for 36 hours.

• Shortly after, the storm's eye faded away and Pam's low level circulation became displaced from its associated thunderstorms, signaling a rapid weakening phase. Later on 15-March advisories were discontinued and Pam entered a phase of extratropical transition affecting northeastern New Zealand. The system moved eastwards, and eventually dissipated over the waters of the South Pacific by 23-March.

Highlights

TC Pam’s Power in Stripping Vegetation from Tanna Island in Vanuatu

Landsat Before Landsat After

Aerial View Before Aerial View After

Sea Surface Temperature (SST) Anomalies for March 2015 [NOAA OISST Data; + indicates genesis position of TC Pam]

Blue – Negative; Red - Positive

Vorticity Anomalies on the Day of Cyclogenesis for TC Pam (+) [ERA-40 1ºx1º Data]

Blue – Negative; Red - Positive

Wind Shear & 700-hPa Wind Anomalies on the Day of Cyclogenesis for TC Pam (+) [ERA-40 1ºx1º Data]

Blue – Negative; Red - Positive

Mean Sea Level Pressure (MSLP) Anomalies Across the Track of TC Pam (+)[ERA-40 1ºx1º Data]

Blue – Negative; Red - Positive

Geopotential Height (GPH) Anomalies Across the Track of TC Pam (+) [ERA-40 1ºx1º Data]

Blue – Negative; Red - Positive

Phenomenon (2014-15) Nov Dec Jan Feb Mar Apr May Jun

Southern Ocean Oscillation - SOI -1.0 -0.6 -0.7 0.0 -1.0 -0.2 -1.2 -1.1

Southern Annular Mode – SAM 0.35 2.45 1.35 4.92 0.88 2.03 0.41 2.41

Madden-Julian Oscillation - MJO 1.29 1.36 1.58 0.89 2.40 1.04 0.67 1.90

Teleconnections and TCs

Case #1-rSAM/-SOI

Case #2-rSAM/+SOI

Case #3+rSAM/-SOI

Case #4+rSAM/+SOI

West Indian

East Indian

West Maritime

East Maritime

West Pacific

Central Pacific

Western Hemisphere

Africa

MJO - Combined EOF analysis using OLR, 850-hPa zonal wind & 200-hPa zonal wind as input.850-hPa Velocity Potential (NOAA/CPC)

Wheeler and Hendon, 2004

MJO and TCs

• An exceptionally strong MJO, and an equatorial Rossby (ER) wave (red).

• The MJO was a bit fast, so it was borderline MJO/Kelvin wave.

• Westerly winds extremely strong at the dateline

• Referred to an event that was “biblical” in proportion

Birth of Twins on 10-March-2015: Pam (SH) and Bavi (NH)

Birth of Twins Satellite MTSAT Imagery [11-March-2015]

A Second Set of Twins [30-June-2015]

Typhoon Chan-Hom

TC Raquel

• The second set was Chan-Hom and Raquel, which are right on top of each other around June 30 near 150E.

• The set up was very similar, though less of an Equatorial Rossby wave signal.

• This particular MJO was associated with eleven TCs spanning from Ashobaa in the Arabian Sea to Claudette in the Atlantic.

• TC Raquel formed near the Solomon Islands, and was the first named TC to exist in the South Pacific Ocean during July on record, while it was the third TC on record in the Australian region.

Sub-Tropical Storm “Katie” from 29-April to 5-May

• Outside of any RSMC (just off Chilean coast)

• To be documented in a Nature paper to be entitled “A Pacific Basin Sub-Tropical Cyclone off the Chilean Coast”

• Analyzed by Steve Young from the Australian Severe Weather Web Site; and Brenden Moses from NOAA

Sub-Tropical Storm “Katie” (+ - Genesis)

[NOAA OISST Data; + indicates genesis position of TC Pam]Blue – Negative; Red - Positive

Summary• Active TC season that had a very good seasonal outlook prior to the season

• Two Australian Category 5 TCs – Marcia and Pam; with Pam being a Category 5 TC on the Saffir-Simpson Scale – most powerful TC since Zoe in 2002

• Two twin cyclone events as a result of strong westerly waves in March (Pam/Bavi) and in June (Raquel/Chan-Hom)

• Latest time for a named storm (Raquel) in the SW Pacific Basin (30-June)

• Unique Sub-Tropical storm (“Katie”) outside of any

• The 2015/16 could be off to an early start• TC 01P formed in early August 2015• Last big El Niño season in 1997/98 had 2 TCs in October 1997• Seasonal Outlook will be due out by mid-October 2015 and it will be interesting to see what

is in store

• My thanks and recognition to Steve Young at the Australian Severe Weather site at http://www.australiasevereweather.com/; Matthew Ford at NZ Metservice, and the BoM for data that allowed me to do the preliminary TC tracks here. Still awaiting official best tracks data from both RSMCs Nadi and Wellington.

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Thank You - Any Questions??

Keeling CO2 Observatory at Mauna Loa

Thank you

Damage from TC Heta in 2004