Weather_Systems_I-v3

Weather_Systems_I-v3 - Geog 166: weather systems Prof....

Info iconThis preview shows pages 1–9. Sign up to view the full content.

View Full Document Right Arrow Icon
Geog 166: weather systems Prof. Leila M. V. Carvalho
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
objectives The weather analysis will be focused first on the formation and evolution of extratropical cyclones We will discuss a case-study that caused strong winds and heavy precipitation to parts of the central United States It was unusually intense but typifies many features of winter storms in middle and high latitudes
Background image of page 2
Plotting conventions synoptic charts
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Extratropical cyclones: case study example: November 1998 500hPa chart for 00UTC Polar Vortex is split into two regional cyclonic features (Russia and Northern Canada) Two ridges separate the two troughs Solid red lines denote axes of ridges and dashed red lines are axes of troughs Typical distance between two troughs : 50o of longitude or ~ 4000km
Background image of page 4
500hPa charts (contours 60m intervals (dKm) and relative vorticity (blue shading 10-4s-1). Right sea level pressure 4hPa interval and 1000-500hPa thickness (colors) q Baroclinic waves travel ~ 10m/s: wintertime climatological wind at 700Pa (steering level) q Successive ridges (or troughs typically ass at a fixed point on Earth at roughly 4 days (but it can be sometimes 1 or 2 days apart depending on the steering flow) q Baroclinic waves tend to be stronger over the oceans (as we have seen many times) but they can develop over land Frontal surfaces
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
q Note the intensification of the Low pressure system and how it “splits off the westerly to form a CUTOFF LOW (ISOLATED MINIMUM OF GEOPOTENTIAL HEIGHT FIELD) q That implies the existence of a closed cyclonic circulation q Note the tightening of the contours that imply the intensification of the winds around the low Note the intensification of the low pressure at the surface Amplification of the wave
Background image of page 6
q The surface low is the EXTRATROPICAL CYCLONE q Note that pressure gradients increase with time showing the intensification of the low as the cold air moves southward and the warm air moves northward q In the beginning the surface Low is eastward of the trough but as the 500hPa and low level cyclone amplify they come into vertical alignment Advection of temperature, amplification of the wave and the extratropical cyclone
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Vorticity analysis y u x v - = ζ indicates cyclonic vorticity related to the horizontal wind shear (u varies rapidly with y and v varies rapidly with x) these maxima move eastward 9 hours later Surface Low pressure system drops from 998 hPa at 00UTC to 978 hPa at 18UTC (bottom) to 968 at 00UTC (not shown) Nov 11=> 30hPa in 24h!!! 3x more rapid than the typical cyclone
Background image of page 8
Image of page 9
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 39

Weather_Systems_I-v3 - Geog 166: weather systems Prof....

This preview shows document pages 1 - 9. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online