Glossary and Acronyms: M

MAX:

Weather radar product derived from volumetric exploration. Maximum raindrops echos are projected on an horizontal plan and on two vertical plans which are directed west-east and north-south.

McIDAS:

Man computer Interactive Data Access System. Suite of sophisticated software packages that perform a wide variety of functions with satellite imagery, observational reports, numerical forecasts, and other geophysical data. Those functions include displaying, analyzing, interpreting, acquiring and managing the data. In existence since 1973, MacIDAS was developed at the SSEC (Space Science and Engineering Center) of the University of Wisconsin-Madison.

Medium-range forecast:

MET :

Model Expected T-Number. (Dvorak technique) The MET is determined by using the 24-old T-number and the past amount of intensity change of the storm.

METOP :

Meteorological Operational Polar Satellite (EUMETSAT)

Meridian :

(track) : a track in the south to north direction or vice versa. A meridional flow is wind in a meridional direction.

Mesoscale :

dimensions of an atmospheric layer which ranges from a few kilometres to some tens of kilometres horizontally and, vertically, from the ground to the top of the friction layer.

METAR :

Code for an aviation routine weather report.

Meteor :

Phenomenon observed in the atmosphere or on the surface of the Earth, which consists of a suspension, a precipitation, or a deposit of aqueous or non-aqueous liquid or solid particles, or a phenomenon of the nature of an optical or electrical manifestation.

Meteorological equator:

MJO :

Madden-Julian Oscillation Intra-seasonal oscillation discovered by Madden and Julian (1971-1972).

Moccana :

MOdele Climatologique de Cyclones par ANAlogues. Climatological numerical forecasting Model of cyclones, based on analogues, developed by the Cyclone Research Unit of La Reunion Island.

Moderate tropical storm:

MODIS :

MODerate resolution Imaging Spectroradiometer. Spectroradiometer on board the satellites Terra and Aqua for the observation of Earth.

Monsoon :

A term whose roots are from the Arabic for "season", it is a seasonal wind reversal. The monsoon has inflow to a surface heat low and an offshore flow from high pressure during the winter when the land cools relative to the ocean. The Indian monsoon is the most prominent but it has been recognized that that monsoon region extends from Southeast Asia to West Africa. The summer monsoon is a vital source of moisture; its arrival, duration, and amount of precipitation modulates the economies of these regions.

Monsoon depression:

• a broad extension, with a diameter of the outermost closed isobare of the order of 1000 km;
• deep convective clusters generally poorly organised, but forming rather often an elongated band of convection in the eastern semi-circle of the cloud circulation;
• a wind field at low levels and at the surface which shows weak winds in the centre (with a diameter of 150 to 200 km), usually partially surrounded by a band of stronger winds (near gale to gale force winds), with a very asymmetrical structure;
• no clearly defined cloud system center.

Monsoon trough:

Mid altitude :

(trough, ridge) : around the 5000 m or the 500 hPa altitude.

MSG :

MSLP :

MSW :

MWS :