Page History

...

The Singular Vector(SV) technique seeks perturbations for wind, temperature and pressure that will maximize their impact on a 48 hour forecast as measured by the total energy over the hemisphere outside the tropics.  This maximization does not mean that SVs only intensify weather systems; just as often they weaken or displace them.  A special (tropical) version of the SV is created for use in the tropics to deal with uncertainties in the moisture processes typical of low latitudes, in particular of tropical cyclones.  These tropical SVs may also influence forecasts of extratropical extra-tropical developments, (e.g. when tropical cyclones enter mid-latitudes some days into the forecast and interact with the baroclinic developments in the westerlies).

...