The Barakaat and blessings that Allah swt sends in the month of Ramadan, start to trickle in the month of Shabaan. Imam Rabbani Mujaddid Alf-e-Sani Ra has explained this in his Maktubat using the example of the Sunrise. The Sunrise is that moment when the rays of sunlight come on the horizon, but there is period in the morning during which the sky is light but the Sun is not yet visible. Just like that before the month of Ramadan appears, the barakaat and the fuyuzaat of Ramadan Start to flood the sky, especially during the last 15 days of the month of Shabaan.