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تجزیه و تحلیل وضعیت جوی در سال زراعی 93-94 /فصل دوم( دي- بهمن-اسفند)

وضعیت
موضوع بسته شده است.

Amir Mohsen

متخصص بخش هواشناسی
[h=2]Occluded frontsAn occluded front is symbolized on a weather map as a line with both semicircles and triangles. They are often coloured purple.
occluded_front1.gif

These are slightly more complex than cold or warm fronts. The word 'occluded' means 'hidden' and an occlusion occurs when the cold front 'catches up' with the warm front. The warm air is then lifted up from the surface, and therefore 'hidden'. An occlusion can be thought of as having the characteristics of both warm and cold fronts.
Figure-9-Occluded-front%28image%29.jpg
Cross-section through an occluded front​
 

Amir Mohsen

متخصص بخش هواشناسی
warm-front.gif


cold-front.gif



occluded-front.gif





خوب ما در طول فعالیت این سیستم در مناطق مختلف کشور با انواع جبهه هایی که در بالا ذکر شده مواجه هستیم. مثلا الان در خوزستان جبهه سرد حاکم شده و نشانه اونهم ظهور ابرهای همرفتی و رعد و برق هست
 

Amir Mohsen

متخصص بخش هواشناسی
wave-cyclone.gif




  • [h=3]Wave Cyclones In mid-latitudes, the weather commonly reflects the movement of a large low-pressure air mass that moves from west to east. The polar front theory is a simplified model of how some extratropical/mid-latitude cyclones develop. The polar front is the stationary boundary between the Polar and Ferrel circulation cells near 60° latitude. Air from the north gets deflected westward by the Coriolis effect, while air from the south gets deflected eastward. Air starts to circulate counterclockwise around a center, creating a mid-latitude cyclone or wave cyclone. Wave cyclones can also form along other stationary front.
Stages of a wave cyclone:
  • initially two air masses shear past each other along a stationary front. This sets up a cyclonic wind shear.
  • under the right conditions, an indentation, or "wave" develops along the front
  • a warm front develops on the leading side, a faster-moving cold front develops on the trailing side of a developing low-pressure center
  • the indentation becomes more pronounced, and air circulates in a counterclockwise path (it becomes a cyclone). The low pressure near the center intensifies
  • the faster cold front starts to occlude the warm front, from the center outward. The weather is most severe where the occlusion occurs
  • the cyclone feeds on 1) the transfer of potential energy of sinking cold air into kinetic energy and 2) on the release of latent heat by rising warm air
  • when occlusion is complete, the cyclone dissipates. This happens when the triple point where the three fronts (cold, warm, occluded) meet are too far away from the center to feed the cyclone.
 

felan123

New member
امیدوارم همه جا ایران بارش بیش از حد داشته باشه چون الان همه جا خشکی هست و انقدر هوا گرمه که نمیتونه یه برف درست بیاد
سمنان از 1500 متر سفید پوش شده و بقیه به شکل بارون و این هم خدا شکر
 

Ahmad7777

New member
اینقدر ماسه و نمک ریختن که برف نمیشینه!


هرکی واسه بار اول گردنه تیوان رو ببینه فکر میکنه جاده خاکیه.:سوت:

آقا امیرمحسن نظر شما درمورد امشب مشهد و فردا چطوره؟؟ما فقط منتظریم برف 15 سانتی یکشنبه مشهد رو تایید کنید استاد.
:گل::گل:
 

Amir Mohsen

متخصص بخش هواشناسی
OCCLUSION: WARM CONVEYOR BELT TYPE - WEATHER EVENTS
by ZAMG


Parameter Description
Precipitation
  • Broad precipitation bands (5-50 km wide) are found within and ahead of the surface front. Maximum precipitation close to the Occlusion point (in contrast to Occlusion: Cold Conveyor Belt Type).
  • At the rear part of the cloud spiral showers and thunder, even hail.
Temperature
  • Seasonal dependence: rising temperatures in wintertime, cool conditions in the summer.
Wind (incl. gusts)
  • Moderate to strong winds. The most intense wind on the outer edge of the cloud spiral.
Other relevant information
  • Generally, Occlusions are connected with multi-level cloudiness. Therefore the weather activities are highly variable.

21 April 1998/18.00 UTC - Meteosat IR image; weather events (green: rain and showers, blue: drizzle, cyan: snow, purple: freezing rain, red: thunderstorm with precipitation, orange: hail, black: no actual precipitation or thunderstorm with precipitation)
okwesk1k.gif

okwe1k.gif

 

Amir Mohsen

متخصص بخش هواشناسی
OCCLUSION: COLD CONVEYOR BELT TYPE - WEATHER EVENTS
by ZAMG


Parameter Description
Precipitation
  • Intensive precipitation within and especially ahead of the Occlusion point.
  • Rainbands typically oriented parallel to the occluded front (5-10 km wide).
Temperature
  • Rising temperature associated with the passage of the secondary Occlusion.
Wind (incl. gusts)
  • Strong winds circulating around secondary vortex, veering of the wind associated with the passage of the secondary Occlusion.
Other relevant information
  • rear part of cloud spiral close to Occlusion point, possibly situated to the left exit region of a jet streak, is predestined for convective development due to potentially unstable troposphere.

28 March 1997/12.00 UTC - Meteosat IR image; weather events (green: rain and showers, blue: drizzle, cyan: snow, purple: freezing rain, red: thunderstorm with precipitation, orange: hail, black: no actual rain or thunderstorm with precipitation)
ccwesk1k.gif

ccwe1k.gif



 

ali.doosti

کاربر ويژه
بالای10 م.م بارید و باز صاف شد...ابر خفنی بود...قطره هاش قدر گیلاس بود!الآن مجددا ابری شده...کاش همه جا باریده باشه و فقط بخشی از شهرو باتوجه به ماهیتش پوشش نده که چیزی ثبت بشه.
 

Amir Mohsen

متخصص بخش هواشناسی
OCCLUSION: WARM CONVEYOR BELT TYPE - CLOUD STRUCTURE IN SATELLITE IMAGES
by ZAMG

As already mentioned in the general remarks, the cloud band of the Occlusion described in this chapter is the result of a classical Wave development (see Wave) represented by a growing multilayered cloud spiral.
oksask1k.gif


For a fully developed stage the following points can be summarized:
  • The IR, WV and VIS images show a cyclonically curved synoptic scale cloud spiral, which is because of its genesis connected with the cloud band of the Cold and the Warm Front.
  • In the VIS image the cloud spiral is white indicating cloudiness with high albedo.
  • In the IR image the grey shades can vary between grey and white with the brightest tops in the transition area between the cloud band of the Cold Front and the Occlusion, where the point of Occlusion can be found. Often grey shades are becoming continously darker downstream towards the centre of the spiral. This is due to the already descending conveyor belts within the mid- and upper levels of the troposphere (see Meteorological physical background). In most cases the cloud tops of the cloud spiral are characterized by a structured appearance.
  • The WV image is characterized by high pixel values (white) within the frontal cloudiness. The rear cloud edge of the cloud spiral is characterized by a sharp gradient from white to black, caused by dry descending air within the relative stream of the dry intrusion (see Meteorological physical background).
  • Convective cells and even Cb Cloudiness might be embedded within the area of the rear cloud edge of the cloud spiral. This is a preferred area for Cb development, because of a potential unstable stratification of the troposphere caused by the different relative streams (see Meteorological physical background and Weather events).
oksask2k.gif


19 February 1998/00.00 UTC - Meteosat IR image
19 February 1998/00.00 UTC - Meteosat WV image
oksa1k.gif

oksa2k.gif

oksa3k.gif

oksa4k.gif

19 February 1998/06.00 UTC - Meteosat IR image
19 February 1998/06.00 UTC - Meteosat WV image

At 00.00 UTC a well-developed Wave stage can be observed south of Iceland at approximately 61N/22W with distinct dry air (Black Stripe in the WV image) being involved in the circulation.
At 06.00 UTC an intensification of both the cloud spiral as well as the dry intrusion can be noticed. The cellular structure immediately south of Iceland at approximately 62N/17W indicates a potentially unstable stratification within the troposphere.
19 February 1998/12.00 UTC - Meteosat IR image
19 February 1998/12.00 UTC - Meteosat WV image
oksa5k.gif

oksa6k.gif

oksa7k.gif


19 February 1998/12.00 UTC - Meteosat VIS image


At 12.00 UTC this process has further developed where a lot of typical features can be observed: a bright cloud spiral in all three channels, a structured appearance in all three channels, decreasing cloud tops to the centre of the spiral south to south-east of Iceland from approximately 62N/18W to approximately 64N/14W, an intensive (dry) black area in the WV image - this area, which is slightly superimposed on the bright area in the VIS image, is restricting the height of the cloud tops.
A stripe of more cellular structured cloudiness extending from Iceland above the Norwegian Sea at approximately 65N/05W is easily detectable in the IR and WV image.​
 

felan123

New member
خیلی جالب فکر کنم کویر بارشش بیشتر از سمنان باشه خخخخ چجوری رطوبت به اونجا رفته نمیدونم
 

Amir Mohsen

متخصص بخش هواشناسی
امیر محسن عزیز

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