WEATHER IN BULGARIA AND SOPOT


   
BULGARIA

    The weather in Bulgaria is influenced mostly by the Atlantic, European and Mediterranean climate zones resulting in four distinct seasons:

- white winter (January - February): Temperatures can drop to -15° C (it is warmer higher up in mountains than in flatlands and closed valleys); The snow cover is from January to the first half of February (from December to April at the north slopes of higher mountains).
   The country is invaded by cold Siberian anticyclonic air masses with prevailing N and NE winds with sunshine in high mountains above the strong ground inversions bellow. In the flatlands and especially in closed valleys the inversions may trap Stratus clouds and cause periods of 3-5 days without sunshine.
   The flying is best in higher mountains where naked trees and rocks produce thermals. Flatlands are also working and can be better choice when mountains are covered by low clods. Around the seacoast and 50 km inside the climate is influenced by the warmer in winter Black Sea - snow cover is for very few days and pilots reported 20-30 km XC flights from 200-300 high hills. Some sites may become better for soaring in winter because of the more stable and dense wind.
   Usually the begining of XC season starts after the first half of February.

- energetic spring (March-May): The weather is changeable because of fighting cold north and warm south air masses. The temperatures rise and can reach 20-30°C but still cold in the night. The snow is mostly in mountains but until March short snow revenges can surprise the lower valleys and flatlands.
   Sometimes the country is visited by weak cyclones from Turkish or Italian Mediterranean which can regenerate in the area and cause 3-4 days of rainy weather. The humidity is increased and when combined with the night ground inversions can obscure the closed valleys with stratus clouds.
   In March the prevailing winds are from the N quarter. Local falling gravity winds might be created by the snow covered mountains.
   The ground inversions are burning out in March and the snow covered mountains provide an excellent temperature gradient with 5-8 m/s strong thermals (often blue or with 2500 - 3000 m amsl high cloudbases). Forests are naked and also release thermals. April and first half of May may have days with strong south winds (no problem for Sopot) which create waves over the mountains and still have good temperature gradient (there were several flights of over 100 km in this conditions).
   From the second half of May until the first half of June the atmosphere becomes more unstable with bigger chances of Cumulo Nimbuses but still flyable before their development - usualy later in the afternoon. The most reliable XC flying periods are in March/April and April/May but generally the weather in spring is difficult to predict. At the beginning of May a pilot reached a record cloudbase of more than 4300 m amsl (it happened in Koniavo in south winds). The more unstable atmosphiere sometimes makes flatlands better choice for spring XC.
    The colder sea and much warmer land are producing strong sea breeze winds and good seacoast soaring conditions. In spring were also registered good convergences (between humid and cold sea breeze and humid and cold NW winds) along the seacoast when some coastal height gain records (1100 m amsl) were done.

- hot and dry summer (June-September) Most of the summer is influenced by the high pressure systems from Mediterranean and about every 2 weeks is refreshed by quick cold fronts from cyclones from NW Europe or by small local cyclones (mostly around the beginnings of June and September). This and the plenty of northern winds minimize the stable inversion days. Temperatures reach 35°C and nights are warm in flatlands and cool in mountain areas. In the beginning of June there might be more Cumulo Nimbuses but later they become less, isolated (mostly in mountain areas), weaker and slow growing (which allows use them quite confidently).
   High altitude flights (4000 m amsl) were made in slow growing Cu congestus clouds. Cloudbases are about 2500 m amsl but pilots registered over 4000 m amsl in mountain areas. The typical NW and NE winds in July and August bring cooler air aloft (thus good gradient and 3-6 m/s strong thermals) and most big flights and records were set then (including three flights of more than 200 km). Everything works good - mountains, their north slopes, flatlands.
Surprisingly sea breeze can be strong and persistent in August.

- autumn up and down (October - December) The weather in autumn is mostly influenced by the big cyclones and fronts from NW Europe and the warm south airmasses preceding them. The first longer periods of bad weather (up to 1 week) usualy come in October but even later in November there could be long periods (up to 2 weeks) of gypsi summer. The second half of November and beginning of December may be foggy and rainy. Strong inversions start to fill up the flatlands and closed valleys and good thermal days become rarer. The typical south winds in the autumn produce excellent wave conditions in mountain areas. Around sea coast, rivers and lakes fog may form.


   After the furthest parts of SW Europe, the climate of Bulgaria is one of the best in Europe and provides big variety of flying conditions (thermals, cross-country, waves, ridge and see breeze soaring). This combined with the various landscape (2-3000 m high mountains, hills, flatlands and seacoast) makes Bulgaria interesting for all year round flying.





SOPOT

   The weather in Sopot is not much different to the rest of Bulgaria. The bad weather and frontal systems usualy come from west and they reach Sopot a day later compared to west Bulgaria.

  The Rose Valley between Stara planina mountain and Sredna Gora mountain is more stable for thermals in the autumn and winter compared with E Bulgaria. In the rest of the time Sopot area usualy has the most and best thermals and XC conditions compared to rest of Bulgaria.

    Due to high mountain Sopot is well protected from NE and S-SW winds and it remained flyable even when the rest of Bulgaria is too windy. If the NW winds are less than 10-15 m/s (measured at Botev peak) then the local valley-mountain circulation can prevail the main wind and make Sopot flyable. If until 12-13 p.m. the N and NW wind at take off doesn't stop then it is unlikely to be flyable the whole day. If the NW wind is more than 5-7 m/s at the take off around 10-11 a.m. then it's better to go to Kliment or Plovdiv area.

    When trying long XC E or W along the mountain range then aware the possible falling winds at Beklemeto, Shipka, Tvarditza. In winter/spring these falling winds are stronger due to the colder snow covered mountains.

   The local Cb generators are Bogdan (in Sredna Gora), Vezhen and Botev peaks. After their full development the Bogdan Cb usually goes E along Sredna Gora, The Vezhen Cb can go SE in the valley or E toward Sopot, the Botev Cb can stay in one place or go E, W, S. Around Bania and Karnare it can be more safe from neighbouring Cb's but aware their gust fronts.