WORLD METEOROLOGICAL ORGANIZATION
_________________________
TCM-8/Doc. 4.2 (1)
(23.X.2015)
___________
EIGHTH TROPICAL CYCLONE RSMCs/TCWCs
TECHNICAL COORDINATION MEETING
ITEM 4.2
MIAMI, FLORIDA USA
2 TO 6 NOVEMBER 2015
ENGLISH ONLY
RECENT AND CURRENT ACTIVITIES OF THE RSMC LA REUNION
(Submitted by RSMC La Réunion)
TCM-8/Doc. 4.2 (1), p. 2
Review of recent (2012-2015) main activities and achievements
at RSMC La Reunion
I-
Introduction
4.2(1).1
The Direction of Météo-France in La Réunion has been formally designated as
the Regional Specialized Meteorological Centre (RSMC) - Tropical Cyclones for the SouthWest Indian Ocean during the 45th session of WMO/Executive Council (Geneva, June
1993), with effect on 1 July 1993.
4.2(1).1.2
The area of responsibility of the RSMC includes the tropical and subtropical
areas of the South-West Indian Ocean from the Equator to 40°S and west of 90°E to Africa
(therefore including the Mozambique Channel).
4.2(1).1.3
The primary mission of the RSMC/La Réunion is to provide appropriate
guidance information (analyses, forecasts, prognostic reasoning,...) to the 15 Members of the
AR I Tropical Cyclone Committee (Botswana, Comoros, France, Kenya, Lesotho,
Madagascar, Malawi, Mauritius, Mozambique, Namibia, Seychelles, South Africa, Swaziland,
Tanzania, Zimbabwe) for all the tropical disturbances occurring within its area of
responsibility. However, beyond this fundamental operational function, the RSMC has the
role to become the regional focal centre for all the other activities conducted in the field of
tropical cyclones such as, for instance, Training and Research/Development.
4.2(1)1.4
In addition to its responsibilities as an RSMC, Météo-France La Réunion has
numerous other national and international responsibilities. Within the GTS, it is a hub in the
regional telecommunication network. In the framework of GMDSS, it has the responsibility of
preparing marine forecasts and warnings for extensive portions of the METAREA VII-OI and
METAREA VIII-S areas. Furthermore, with the role of assisting the MWO's of the whole
region in the preparation of SIGMET messages for tropical cyclones, ICAO has designated
RSMC/La Réunion as its Regional Tropical Cyclone Advisory Centre.
4.2(1).1.5
Météo-France La Réunion takes also an active part in the International Buoys
Programme in the Indian Ocean (IBPIO) and in the RAMA Programme (instrumented moored
buoys network deployed in the near-equatorial Indian Ocean), implementing pressure
recorders and regularly organizing the deployment in tropical or polar areas of drifters from
ships calling at La Réunion.
4.2(1).1.6
RSMC La Reunion issues different types of bulletins: Marine Warnings,
« RSMC » Technical Bulletins, ICAO Advisories, « BUFR » bulletins, « best-track » bulletins,
and a daily bulletin about convective activity in the South-West Indian Ocean that includes a
diagnosis and prognosis of cyclogenesis for the next five days.
The « RSMC Bulletins » are the most complete advisories. They provide, in particular,
position and intensity forecasts with prognostic reasoning for the coming 120 hours (5 days
forecast).
Bulletins
Marine Warnings
Headings
English
French
Dissemination time
WTIO20, 22, 24, GTS 00, 06, 12, 18 UTC
26
WTIO21
Same
TCM-8/Doc. 4.2 (1), p. 3
RSMC Bulletins
English
WTIO30
GTS
French
WTIO31
Same
ICAO Advisories
English
"BUFR" Bulletins
-
FKIO20
ATIO01
AFTN
GTS
GTS
00, 06, 12, 18 UTC
00, 06, 12, 18 UTC
00, 06, 12, 18 UTC
"Best-Track"
Bulletins
-
AXIO20
GTS
AWIO20
GTS
generally within one
month after the cyclone’s
demise
12 UTC
AWIO21
GTS
Tropical
outlook English
and
Cyclone French
information Bulletin
II-
00, 06, 12, 18 UTC
12 UTC
Operational activities
II-1. Tropical cyclone activities during past seasons
4.2(1).2.1
With an annual number of listed tropical storms or mature tropical cyclones of
respectively 10 (cyclone season 2012-2013) and 11 (seasons 2103-2014 and 2014-2015),
the tropical cyclone activity has been remarkably stable in the South-West Indian Ocean
basin during the past three cyclone seasons, with normal or slightly above average yearly
numbers of disturbed activity or cyclone days.
4.2(1).2.2
While the activity of cyclone season 2012-2013 was practically in perfect
accordance with the climatological norm, one element however departed from the norm,
namely the high number of cyclones that developed, since out of the ten tropical storms
which formed, seven of them evolved into mature tropical cyclones (of which three became
intense cyclones). A proportion that was remarkable, without being exceptional. Out of the
ten meteors, four of them had an influence on the inhabited lands, but only cyclone HARUNA
claimed a number of victims (in Madagascar). This season was one of the longest in
contemporary history since spreading over more than six months. It started not only very
early (before mid-October), but in a staggering way with the occurrence of an exceptional
storm : tropical cyclone ANAIS which became the first intense tropical cyclone observed in
October in the South Indian Ocean (and the second earliest mature cyclone on record in the
South-West Indian Ocean basin). That phenomenon was all the more out-of-norm as it was
eventually the most intense cyclone of the season, which was out of the ordinary for a
system that developed at the very beginning of the austral spring!
4.2(1).2.3
As for cyclone season 2013-2014, if it was associated with the development of
only 5 tropical cyclones, the intensity reached by all of them was quite remarkable since they
were all ranked at the minimum stage of intense tropical cyclone and two of them even
climaxed at the very intense tropical cyclone stage (10-min average wind above 115 kt in our
classification), an uncommon event, as one had to go back 20 years to find an equivalent,
with the great 1993-1994 season (which had even three very intense tropical cyclones
occurring). The other anomaly in 2013-2014, was to be found in the time distribution of those
tropical cyclones, since, oddly enough, none of those phenomena developed during the
usual heart of the season (e.g. between mid-January and mid-March), when there were only
four tropical storms observed. The hard core of the 2013-2014 seasons had actually taken
place earlier, as the month between mid-December and mid-January concentrated the bulk
of the disturbed activity, with half of the named systems, of which four were cyclones of
severe intensity. Only one cyclone could afterwards develop after mid-January, but what a
cyclone it was! As HELLEN, which evolved in the northern Mozambique Channel, will be
remembered as an exceptional cyclone, probably unique, all cyclone basins considered,
TCM-8/Doc. 4.2 (1), p. 4
associated with evolution rates of demented rapidity resulting in an unprecedented up and
down of intensity. Fortunately, this cyclone for history of cyclones did not have a too severe
influence on inhabited lands since sparing miraculously Madagascar in particular. In fact the
season was rather clement as a whole with no major impact recorded. The system that had
the most notable influence was cyclone BEJISA, but it was no longer at its maximum
intensity when it brushed past La Réunion Island.
4.2(1).2.4
The season 2014-2015 was almost a perfect replica of the previous one:
same number of phenomena and a cumulated number of days of significant disturbed activity
remaining virtually unchanged. The mimicry went even further, since they presented another
more uncommon analogy, namely both counting two very intense cyclones, a common
feature which was far from being banal considering the fact that such a multiple occurrence
is a rare event. An even more exceptional event is the occurrence of two very intense tropical
cyclones during the same month, which was actually the case during this season with the
development of cyclones BANSI and EUNICE in January (2015), last analogous event dating
back March 1994. But the most striking feature of the season, and which made it really
specific, was the quite unusual typology of the tracks followed by the different named
systems.
4.2(1).2.5
One witnessed a remarkable predominance of eastward or southeastward
oriented trajectories, in particular within the tropical domain. Those atypical trajectories
resulted from the abnormal meteorological situation that prevailed over the basin, especially
in January 2015, a month that cumulated by far the strongest disturbed activity (with no fewer
than five phenomena). That particular configuration of the tracks was a priori rather
favourable for the inhabited lands, more especially for the eastern coast of Madagascar,
which as a matter of fact was exempt of any impact of a storm (for the third consecutive year
– an exceptionally long quiescent period). Actually, only one meteor directly hit a territory,
namely tropical storm CHEDZA, which made landfall on the western coast of Madagascar.
4.2(1).2.6
But the almost non-existence of impact did not mean that the season was
completely merciful for the inhabitants of the region. Because CHEDZA alone claimed many
casualties and damage, not only in Madagascar, but also in Mozambique and above all in
Malawi, a country that was the most affected by the rains generated during the pre-genesis
phase of the system, with induced deadly floods, the worst that the South of the country had
ever undergone for 24 years.
II-2. Official track forecasts performances
4.2(1).2.2. After a 2012-2013 season associated with record low errors for the RSMC La
Reunion official track forecasts, raw performances have undergone some deterioration
during last two seasons resulting in a levelling off in the reducing trend of the 5-year running
means of the track forecast errors. But in spite of this seeming underwhelming impression,
which is in fact deceptive, the reality is that improvements keep on as witnessed by the skill
against persistence, which still shows a positive trend during the past two seasons (which
were much more difficult in terms of track forecasting, especially so for the season
2014-2015 which was associated with many atypical trajectories).
TCM-8/Doc. 4.2 (1), p. 5
Time-evolution of 5-year running means of RSMC official track forecasts errors since 1990
Main achievements since last TCM-7 meeting
III-1. Towards the introduction of a new LAM : AROME INDIAN
4.2(1).3.1
The dedicated high resolution Limited Area Model (LAM) called ALADINRéunion developed specifically for the RSMC, being run at Toulouse (where the supercomputer of Meteo-France is located) and first implemented in October 2006, will be stopped
in 2016 after 10 years of operations. Considering the fact that the different operational
models used at Météo-France and at the RSMC will benefit from significant upgrades in
2015, an increased horizontal resolution in particular (with ~10 km for the IFS model of the
European Centre and ~16 km for the French model ARPEGE), the added value of ALADIN
(with its ~8 km horizontal resolution and 70 vertical levels) will be much reduced.
4.2(1).3.2
As a result, it has been decided to replace the ALADIN model by a new high
resolution LAM called AROME Indian, a “tropical” version of the 2.5 km high resolution model
AROME already used in continental France since 2009. In fact this model will be run on five
different domains covering the different French Overseas Territories (French Guyana, the
Caribbean Islands, French Polynesia, New Caledonia and the Indian Ocean). The AROME
Indian one will serve as a prototype for all the other ones and will cover the largest domain
by far, thus benefiting from the greatest portion of the computation time allocated on the
Météo-France supercomputer. This huge computational effort was granted owing to the
RSMC responsibility of the Météo-France Centre in La Réunion. Despite that extended
domain, the area of responsibility of the RSMC will not be entirely covered, but almost all the
inhabited lands will be (except the main archipelago of Seychelles). Following the last
arbitration, the AROME Indian model will indeed have the following boundaries:
32.5 -67.8°East; 7.25 – 26°South (~ 3500 km x 2000 km), representing 1395 x 747 grid
points with 90 vertical levels. With its high resolution (of 2.5 km horizontally) convection will
be explicitly resolved (physical processes), while the orography will be much better
represented (in particular for a mountainous island like La Reunion).
TCM-8/Doc. 4.2 (1), p. 6
4.2(1).3.3
The operational implementation of the model is planned for the end of 2015,
but with a basic configuration for its first version, namely just a dynamical adaptation from the
IFS model (the global coupled model) with 4 runs/day and 30h to 48h forecasts. An upgrade
will thereafter take place in 2016, with the inclusion of a 1D ocean coupling (AROME Indian
thus becoming the first operational model of Météo-France coupled with an ocean model)
and an own 3DVAR assimilation (not guaranteed yet however for this second version).
First preliminary sensitivity experiments and case studies conducted by the Cyclone
Research Cell based at Météo-France La Réunion have demonstrated promising
improvements and even some impressive performances in terms of simulation of intensity
changes (including rapid intensification), structure changes, quantitative precipitation
forecasts.
III-2. Towards a new forecaster workstation: SYNOPSIS
4.2(1).3.2
After several years of development, a new workstation called SYNOPSIS will
replace in 2016 the current SYNERGIE workstation that has been used during past two
decades by all the Météo-France forecasters. Making use of all the modern technologies
(webservices in particular) this new workstation will benefit from improved tools and facilities
compared to SYNERGIE. A specific cyclone module will be developed in the next few
months, following the specifications provided by the forecasters of RSMC La Réunion, before
the operational deployment before cyclone season 2016-2017. Forecasters have already
been trained (in October 2015) on the usage of this new tool.
III-3. Participating to IWTC-VIII
4.2(1).3.3
Meteo-France La Reunion has actively participated to the eighth International
Workshop on Tropical Cyclones (IWTC-VIII) and to the third International Workshop on
Landfall processes (IWTCLP-III) held from 2 to 10 December 2014 in Jeju (South Korea).
Several people both from forecasting side and research side were involved in the events by
contributing to the different topics, including a topic chair and rapporteur and a participant to
the recommendation group.
III-4. Training activities
4.2(1).3.4
RSMC La Réunion has hosted and organized the 6th and 7th RA I Training
Courses on Tropical Cyclones and Public Weather Services (from 28 October to 5 November
2013, and from 14 – 25 September 2015), with the support of WMO for the forecasters of the
15 NMHSs of the RA I Tropical Cyclone Committee member states.
III-5. Continued implication in the RA I SWFDP project
4.2(1).3.5
Meteo-France and RSMC La Reunion are active partners of the Severe
Weather Forecasting Demonstration Project (SWFDP) that has been implemented with
WMO for southern African countries. Meteo-France involvement includes provision of all the
RSMC bulletins/products (for the tropical cyclone hazard) and the provision of a number of
NWP fields both from deterministic models (especially the ALADIN-Réunion Limited Area
Model) and from ensemble prediction with a variety of products like probabilities of exceeding
pre-defined thresholds of winds or rainfalls, etc…
III-6. Satellite re-analysis project (REDO-SAT)
4.2(1).3.6
RSMC La Réunion has started in 2011 a re-analysis project based on the
Dvorak re-analysis of past satellite imagery and additional use of other data that were not
available in real-time (like microwave imagery) for all tropical systems of the 1978-1998
period. This project, strongly supported by the last IWTCs and IBTrACS Workshop
TCM-8/Doc. 4.2 (1), p. 7
recommendations, has become feasible thanks to the disposal of the HURSAT database, an
archive of TC-dedicated satellite images developed by the NCDC (NOAA National Climate
Data Center – Asheville).
4.2(1).3.6.1 Via a treatment of the NetCDF format of the data, in-house visualization of the
geo-localized images on our Synergie workstations has been rendered possible, enabling the
use of all the facilities and tools of Synergie for re-analysis purpose.
The re-analysis project will last several years but just focusing first on most intense cyclones
it has yielded some preliminary results : while the increasing trend in terms of the number of
very intense tropical cyclones claimed by the current best-track database has been wiped out
by the re-analysis process and demonstrated to be a spurious trend just resulting from the
quasi systematic under-estimation of intensities in the past, it has confirmed some of the
results of the work endeavoured by Kossin et al. about the “poleward migration of the
location of tropical cyclone maximum intensity” (Nature 509, 349-352).
Tracks and locations of the very intense tropical cyclones in the SWIO (period 1979 to 2015)
III-7. Work on storm surge
4.2(1).3.7
Following tropical cyclone NARGIS which devastated Myanmar in May 2008
and the strong recommendation made by the ensuing 60th session of the WMO Executive
Council that Storm Surge Watch Schemes should be established in all cyclone basins and
that all Tropical Cyclone RSMCs should provide information on storm surges generated by
TCs, RSMC La Reunion has strongly committed itself to work on this topic since 2011 and
quite significant achievements have been obtained. Re-activating the Météo-France storm
surge model, an interface has been developed to enable the TC forecasters to get real-time
estimates of the maximum storm surge height that could result from a landfalling tropical
cyclone, taking into account the uncertainty on the predicted track, storm’s intensity, etc…On
13 February 2012 the RSMC had included for the first time a “deterministic” forecast of storm
surge in its technical bulletins before the landfall of TC Giovanna on the east coast of
Madagascar. Now it is possible to refine the simple deterministic forecast by including some
“realistic” uncertainty around the scenario of the official deterministic track and intensity
forecast issued by the RSMC.
4.2(1)3.7.1
Apart from that operational purpose, the databases with the some 3 millions
simulations that have been run have enabled to design an Atlas of storm surges for the
TCM-8/Doc. 4.2 (1), p. 8
South-West Indian Ocean covering all the coastal areas of the basin. This Atlas has been
graciously provided (in digital format) to all member states of the RA I Tropical cyclone
Committee (in October 2015). It could be used for multiple purposes, including risk mapping.
Interface enabling the display of the Atlas of storm surges of the South-West Indian Ocean cyclone
basin
Storm surge simulation for TC Giovanna
on 13 February 2012 at 18 utc.