JUGO and THE STORM on the Adriatic (Winds)

[vc_row][vc_column][vc_column_text]Jugo is a warm and humid south-easterly wind blowing from south-south-east (S-SE) to east-south-east (E-SE). It is typically accompanied by rain as well as storms. It blows along the whole Adriatic coast, and is the strongest in the southern part causing the largest waves in the Adriatic Sea. During the summer time jugo blows with the speed of 4-5Bf (16-20kn) while in winter it can reach the speed up to 7-8Bf (27-40kn). Jugo is stronger on the open sea. Along the coast, however it becomes stronger primarily in the channels between the islands and on some sheltered sides of the islands, where it is, due to the formation of the surface, channeled. Jugo blows throughout the whole year, in the northern Adriatic more often from March to June, and in the southern Adriatic during the autumn and winter months. In the autumn and winter, it is a warm wind, in spring it is relatively cold, and in the summer it is steaming. Jugo usually lasts 2-3 days in the summer and up to 3 weeks in winter. It is characterized by long waves.   Jugo usually begins blowing early in the morning after a quiet and cool night. Initially, it grows slightly but rapidly. Along with the wind grows also the cloudiness with the occasional rains. Just before and after the rain, the wind strengthens, while it is less strong during the rain itself. After the jugo dies away the wind usually changes the direction following the wind rose; firstly comes OSTRO or AUSTRO (Cro: OŠTRO) followed by LIBECCIO (Cro: LEBIĆ). OSTRO is a southerly wind that appears if the weather clears up first in the SW, while LEBIČ is the wind commonly set from the W. Such a change of weather in the summertime can suddenly cause a STORM with strong gusts of wind and downpours. The first gust is ephemeral but strongest. Since the cold front is usually 70-80 km wide, the storm may last for several hours with gusts of wind and showers.    

PREDICTING JUGO WIND:

  1. reduced visibility
  2. the appearance of mist (indistinct or foggy horizon)
  3. gradual fall of barometric pressure
  4. the rise of the relative humidity (dew on the deck of the vessel in clear weather) and temperature
  5. clouds prevail in the northwestern (NW) and northern (N) skies
  6. clear weather in the south-east (SE)
  7. CIRRUS clouds (high, translucent, feathery) move from the west (W)
  8. ALTOSTRATUS clouds (lower, guests, torn) move from the south (S) or south-east (SE) the appearance of swells from the direction of the SE
  9. the appearance of swells from the direction of the SE
   

CYCLONIC (“dark” or “black”) JUGO

The Cyclone region is approaching the Adriatic from SW to NW
  1. dense and low cloudines
  2. heavily undulated sea
  3. heavily undulated sea
  4. showers of rain
  5. rapid and sudden fall of barometric pressure
  6. the rapid fall of the barometric pressure causes a faster passage of the cyclone and thus the shorter period of jugo
  7.  The persistent cyclone over the Gulf of Genoa results in an extended period of jugo

The Cyclone region is approaching the Adriatic from SW to NW

  1. dense and low cloudines
  2. heavily undulated sea
  3. heavily undulated sea
  4. showers of rain
  5. rapid and sudden fall of barometric pressure
  6. the rapid fall of the barometric pressure causes a faster passage of the cyclone and thus the shorter period of jugo
  7.  The persistent cyclone over the Gulf of Genoa results in an extended period of jugo
        CYCLONE LOCATED NORTH FROM OUR LOCATION: Firstly we can see the appearance of the mist on the SW horizon. The mist quickly turns to become a black storm cloud. In only a few minutes we may be surprised by a sudden storm with the power of 6Bf or even more. Due to the crosswise waves, caused by the wind veering from jugo to LEBIĆ, the sea becomes unfavorable, unpleasant or even hazardous for navigation. Marinas on the Adriatic Sea are normally well protected against jugo but become uncomfortable when LEBIĆ begins to blow. Therefore it is advisable to reanchor the vessel in time. The weather will change only when the wind changes from the southwest (SW – LEBIČ) to the west (W – PONENT / GARBIN) and then to the northwest (NW – MAESTRAL). The storm occurs in the following way:
  1. after the rainfall jugo weakens and LEBIĆ starts to blow
  2. sky to the south has cleared up
  3. by carefully observing the Western (W) and the Northwest (NW) horizon we can notice the approaching storm cloud
  4. firstly we can notice a formation of a foggy curtain which is low with a defined lower line and can cover the whole W horizon from S to N for several hours. This “curtain” is a cold font. The cold air from the hinterland aggressively and rapidly pushes warm air upwards and causes dynamic weather changes resulting in strong winds, thunderstorms and heavy rain.
  5. afterwards we can see the appearance of a storm cloud (KOMULONIMBUS) in the western and north-western horizon in the form of ANVIL without cracks and completely black due to heavy rain
  6. the storm cloud appears like a wall and grows rapidly. Transparent, feathery clouds similar to CIRUS are spreading from its peak
  7. as far as this huge storm cloud has even the smallest crack or does not have any unevenly shaped cirruses on its top, there will be no storm, even if the storm cloud is completely black
    CYCLONE LOCATED DIRECTLY ABOVE OUR LOCATION: when the cyclone passes above us, clouds come in the exact order; from high transparent clouds to low dens and rain clouds. In this case, the sun sets in these clouds, which we at the time cannot see yet, since they are still below the horizon. It appears like the sun sets into the darkness. The clear signs that JUGO will begin to blow early in the morning are the following:
  1. as the clouds are approaching the wind is getting stronger and the barometric pressure falls
  2. it starts raining and the wind weakens
  3. the rain ceases and the wind rises again, which lasts about 10-20 hours
  4. the bright area appearing between the dark clouds everywhere on the horizon is a clear sign that we are in the center of the cyclone
  5. in this case, we must pay particular attention to the NW horizon, as the storm cloud of the COMULONIMBUS usually start to become stronger there
  6. when the cloud reaches the zenith, the wind turns momentarily 180 degrees from the south-east (SE) to the northwest (NW) and causes the strongest storm on the Adriatic known as ŠKONTRADURA. If we cannot see the end of the storm cloud, we can expect a severe storm is expected. If we see at least one end, the storm will be mild
  7. the time from the first sign of the storm to its arrival is usually one hour
  8. the storm may take several hours and during this time the cyclone will move to the east. This will cause TRAMONTANA and then BORA.
    CYCLONE LOCATED SOUTH FROM OUR LOCATION: when the cyclone passes south from where we are currently located, the appearance of jugo is expected. In the case that that the cyclone moves towards SE, jugo will suddenly turn into bora. This bora can be very violent and brings a sharp fall in temperature. When the jugo has weakened the barometric pressure starts to rise again. After a few hours or overnight the weather becomes clearer. In this condition, we can bind to the shore, as there is no time to expect bad weather from the west.    

ANTYCICLONIC (»clear« or »white«) JUGO

 

It results from a deep low extend of air pressure stationed above NW or N Europe and the high pressure sector above the eastern portion of the Mediterranean or the Balkan peninsula:

  1. most common in spring and autumn periods
  2. clear sky or moderate cloudy weather
  3.  little if any precipitation
  4. after a few days cirrocumulus or altocumulus types of clouds may appear from the NW.
Anticyclonic jugo arises due to the effect of the anti-cyclone in the east (E) or south-east (SE) of the Adriatic and the cyclone above the north-west (NE) of Europe:
  1. clear sky
  2. the appearance of “mackerel sky” (CIRROCUMULUS AND in ALTOCUMULUS)
  3. through the lower layer of the troposphere and in the wind moving direction appear NIMBOSTRATUS clouds
  4. the appearance of moderate jugo
  5. no precipitation or just a slight rainfall
  6. gloomy atmosphere, steamy air, diffuse reflection of light
  7. anticyclonic bora is usually of a long duration and causes bigger waves
 

NAVIGATION

Navigation against the direction of the wind (i.e. N-S direction) can be due to the high waves hazardous and dangerous since high waves and strong winds can be a very strong obstacle. For this reason, it is wise to choose a slightly longer route between the inland islands near the coast.   Picture source: portaloko.hr[/vc_column_text][/vc_column][/vc_row]