what exactly goes on in front of a front?

[CaptainChris87]

If for example, I see a prog chart and a warm front is over us right now what should I be expecting on the ground? or stationary, occluded, I know for cold fronts squall line thudnerstorms are a possibility, what else could be going on, on the ground?

[JDP]

I have a page that my aviation meteorology teacher gave us that shows everything during a cold front and a warm front that I'll try and figure out how to display a link to it. when I don't have class but it's not getting done in the next couple hours.

[surreal1221]

Okay. . . here we go. Bear with me, I do this stuff for a living so if I say anything that you don't understand - just let me know and I'll try my best to break it down in a easier way to understand.

Warm fronts: Depending on your relative position in relation to the warm frontal boundary you can expect a varying degree of weather types. If you are south of the boundary, your winds will traditionally be out of the SE-S out ahead of the approaching Cold front with fair skies, and cumuliform cloud development associated with the approaching cold front - and winds north of the boundary will be out of the ESE-NE associated with the pressure gradient related to the SFC Parent Low center. Warm fronts have a gentle slow, as the warm air rises up and over the cooler ahead that is north of the boundary, this gentle rising slow provides just enough lift to provide stratiform (stratus, nimbo-stratus, alto-stratus, etc) types of cloud cover. Also, if you are north of the boundary, you can expect stratiform precipitation with the possibility for isold convection (embedded convection [thunderstorms]). But for the most part, precipitation will be in the stratiform variant (-RA/-DZ, etc.). Also, the potential for fog and mist is at an increased possibility thanks to the increased atmospheric stability that a warm front provides (the shallow sloping of the front and warm air overiding cooler air (Warm over cold air is a stable environment, as warm air wants to raise as it is less dense, and colder air is more dense and sinks - hence no significant interaction of the differing air types).

So over all, north of a warm front expect marginal CIGs with -RA/-DZ and BR or FG, as well as low clouds (stratus) the closer to the boundary that you are.



Cold fronts are a much different animal. Cold fronts, with a much sharper slope as cold air is dropped onto the warmer SFC environment (Cold over Warm, the sinking cold air clashes with the raising warm air, hence the unstable environment). This unstable environment gives way to cumuliform cloud types (cumulus, towering cumulus, CBs, etc). Winds ahead of the boundary will traditionally be out of the SE-WSW depending on the positon of the parent SFC Low center.

Precipitation types will be cumuliform, meaning showery. Expect -SHRA/-TSRA, etc, and FG and BR are not frequent occurances in the warm sector out ahead of a cold front. Low cigs will predominately be isold to the frontal boundary itself and prompt cloud clearing will occur after the front passes.

But here is another one, there are two types of cold fronts. Active and inactive. Actives fronts have the weather associated with the front behind the boundary, and inactive fronts have the weather associated with the front at and ahead the actual SFC boundary due to a much steeper slope and increased lifting associated with its fast speed. Either way, cloud, and precip types, remain cumuliform - but one can expect a slight increase in stratiform cloud cover with active boundaries due to the increased subsidence associated with the trailing High pressure and upper level subsidence with the transitory High height center.



If you have any questions. . . just let me know. I'll gladly go over ANY weather questions you have.

[CaptainChris87]

thank you so much, now I can bookmark this page for future references

[surreal1221]

Anytime!