Atlanta Fed's nowcast of Q1 GDP (0.6%) was really close to preliminary estimate announced today by BEA (0.5%). Atlanta's was much closer than the New York Fed's nowcast (0.8%). The question is which of the two nowcasts will be closer to the final estimate, after revisions (available in late June).
Gavyn Davies and Juan Antolín-Díaz explain why these two nowcasts can differ so much from each other, and from their own nowcast at Fulcrum Asset Management. The Atlanta Fed's approach consists of "bean counting," i.e. they mimick the way the BEA calculates GDP by aggregating monthly data as they are released. The New York Fed's and Fulcrum's methodologies are both dynamic factor models, which extract a "common factor" from multiple time series (not only those used by BEA to estimate GDP). This underlying growth can then be scaled to match certain properties of the GDP time series (as the New York Fed does), or not be scaled (which is the approach they prefer at Fulcrum).