Occluded fronts. An occluded front forms when a cold front reaches a warm front, forcing all the warm air to rise to higher altitudes and the cold air is stratified near the ground. At our latitudes, over the Atlantic, cyclonic areas form continuously, these are fed by the Azores anticyclone and the Polar anticyclone.
Pikachu - Raichu. Eevee - Jolteon. As of the IV generation, only two Pokemon will evolve if exposed to a Thunder Stone: Pikachu into Raichu and Eevee into Jolteon. Despite the number of Electric-type Pokemon, only these two require a Thunder Stone to evolve. pikachu- evolves into raichu. eevee- evolves into jolteon.
Return the Sapphire and Ruby to Celio on One Island witch is the Side quest you must do, and beat the upgraded Elite Four. Once you have attained these purposes then you can head to the Cerulean Cave and test your luck at catching one of the most powerful Pokemon in the game.