GDP is reported at a seasonally adjusted annual rate (SAAR). Therefore, a 30% Q2 decline is around a 7% decline from Q1 (SA).
From Merrill Lynch: CIO
We are tracking -5.2% qoq saar for 1Q GDP and expect a -30% qoq saar plunge in 2Q. [SAAR May 15 estimate]
From the NY Fed: Nowcasting Report
The New York Fed Staff Nowcast stands at –31.1% for 2020:Q2. [EST: May 15, 2020]
From the Atlanta Fed: GDPNow
The GDPNow model estimate for real GDP growth (seasonally adjusted annual rate) in the second quarter of 2020 is -42.8 percent on May 15, 2020, down from -34.9 percent on May 8.