1. Introduction
While deep low "Klaus" has been approaching Northern Spain and Southwestern France on 24.01.09, meteorologists raised fears that a "Lothar"-like winter storm will threaten the countries with severe hurricane winds. Some people compare the arising storm with "Lothar" on 26.12.199, other ones compare it with "Martin" on 28.12.1999. The following analysis will illuminate that the similarity to "Lothar" has been much greater than to "Martin" since the "Martin" belonged to a classic "warm conveyor belt" (WCB) cyclogenesis type whereas "Klaus" seemed to be a "cold conveyor belt" (CCB) cyclone, as well "Lothar". CCB-representatives tend to stronger (small-scale) vortexing than the WCB's because they move on the cold side of the jetstream and come underneath intense lift which allow them to rapid pressure fall and rapid occlusion process. WCB's like "Martin" can obtain more energy from the warm (anticyclonic) side of the jet. Their frontal cloudiness is often deeper and more uniform than with the cold ones. Thus, WCB's reveal more (stable) stratiform cloudiness than CCB's which are generally dominated from deep-moist convection (more upper-level cold air and destabilization). As a result, the energy entering the low development stems from different scales and origins (sudden release of latent heat or gradually release by stratified lifting condensation).2. Analysis
Matthias Jaeneke (known as "Wetterfuchs" in the Wetterzentrale Forum) had already written an exhaustive analysis to "Lothar"http://www.wzforum.de/forum2/read.php?23,1437892,1438164#msg-143816 (in german, maybe you could translate it with the google translater).
I just will refer to the last image in his analysis where Jaeneke says:
[...]
Another concluding comment on the last WV-Image: As it can be seen easily, an ominous structure with dryslot approached from the Englisch Channel again. Simultanously, the wind had become stronger and temporarily, confusion arose whether the event would start another round. It had been only a short flare up and soon it had been clear that anything would happen (at least not this day because storm "Martin" gave some time to the French People).
[...]
Recently, I found an intriguing satellite imagery loop at this french website:
http://www.meteo.fr/la_une/tempetes.html (please scroll down)
I extracted four images from this loop and labelled them (as far as the copyright is concernced: the website coordinator allows the reproduction of the images for scientific purpose respectively for non-commercial purpose)
The last image from Jaeneke stems from 15 UTC, three hours after the following image:
"Lothar" unfolds its entire power and aesthetics in Central Europe. The occluded core region brushs past Southern Germany and yields the most severe hurricane-force winds in exceed of 200 km/h in the Black Forest. If you compare external structure of Lothar with Klaus, Lothar had extraordinarily deep (bright) cloudiness in the mature stage indicating vigorous quasi-geostrophic forcing (shear and curvature vorticity, respectively) throughout the whole atmosphere. "Klaus" never reached that degree of aesthetics as Lothar did. Subsequently, temporarily cloud free periods crossed Northern France and Belgium, but further upstream, "Lothar Successor" draws nearer (the German Weather Service, DWD, called it "trough line" misleadingly).
Supplementation
I remember exactly the second Christmas day. I've been at home in Lowern Franconia (between Frankfurt and Wuerzburg) and I looked at my barometer all the day which revealed a strong pressure fall. In the forenoon hours, the radio broadcasted about the hurricane-force winds in Paris causing a lot of damage there. At that time, I hadn't have internet, I hadn't known any weather maps and I had have to trust the broadcasts. During the noon hours, the wind intensified, with some gales, but not more than 80 km/hs. The core of Lothar nearly hit me. I still know that the clouds raced over the sky and within few hours, they came from different directions. From time to time, the sun has been shining, probably while the "eye" of the storm has been passing Franconia.
Then, the event has been over and the pressure strongly increased. However, in the evening hours my barometer showed a strong pressure fall and I didn't know why. The radio and tv said a "trough line" will cross our region during the night with strong winds but not as intense as with the storm before. In fact, hurricane-force winds could be observed and two bricks became loose just above my roof-light stampeding my a little bit...
Neither the radio nor the tv mentioned the second storm after Lothar evoking a kind of dissatisfaction because the event I experienced has been ignored. Later, meteorologists will talk about two storm events (not three as I think).
End of Supplementation
A few years ago, I found the following analysis in the ZAMG's manual of satellite synoptic meteorology
(they denote the second storm as a "comma")
In fact, the satellite image displays a cyclonic stucture at the entrance of the English Channel, with a short occlusion front to the southwest of Wales, a short warmfront part over the English Channcel, and a long cold front to the west. The NCEP reanalysis maps (source: www.wetterzentrale.de) indicate a weak wave in the area of interest (look at 850mb + temperature).
It should be noted that the reanalysis data are not "real" data which means that the core pressure of Lothar is underestimated (nearly 15mb). Anyway, the assumed trough line or comma emerges as individual wave. I would exclude a classic comma low because commas typically arise with strong curvature vorticity.
Six hours later, Lothar decays in Eastern Europe. The projected deep low "Martin" lies well upstream in the North Atlantics revealing the typical characteristics of a warm conveyor belt cyclogenesis type, with deep and compact high cloudiness highlighting the warm conveyor belt transporting moistwarm air masses with the jetstream. Situated between Lothar and Martin, Lothar Successor is reaching its mature stage with a clearly cyclonci structure and a back-bent occlusion, a short warmfront in Southern Germany respectively the Northern Alps as well as the cold front which is aligned nearly parallel to the flow.
Near midnight, Lothar Successor is at its culmination point. The occlusion process steps forward and tends to decay in upper-level heights within the core. The core crosses the regions which Lothar had spared with intense winds. Certainly, "Lothar Successor" has been weaker than Lothar, but in my opinion, Lothar Successor is an individual storm with a clear cyclonic structure. Meanwhile, Martin prances its cloudiness and the warm conveyor belt and the cloud head to the north merge into a uniform cloud mass.
Eighteen hours later, Lothar and Lothar Successor completey decayed. Martin is a full-developed intense low-pressure system with a broad dryslot over Western France. Martin seemed to be quite stratiform and the remains of the warm conveyor belt pass the Alpine Region.