Nostradamus (1503-1566) was a famous seer who was known for his predictions. To call someone who makes predictions a “Nostradamus” is similar to calling a smart person an “Einstein.”
 
Someone who makes foolish or poor predictions (such as predicting stock winners or sports winners or political winners) is sometimes called a “Nostradumbass” (Nostradamus + dumbass). The nickname “Nostradumbass” has been used since at least the 1990s.
 
   
Wikipedia: Nostradamus
Michel de Nostredame (depending on the source, 14 or 21 December 1503 – 2 July 1566), usually Latinised as Nostradamus, was a French apothecary and reputed seer who published collections of prophecies that have since become famous worldwide. He is best known for his book Les Propheties, the first edition of which appeared in 1555. Since the publication of this book, which has rarely been out of print since his death, Nostradamus has attracted a following that, along with much of the popular press, credits him with predicting many major world events.
 
Most academic sources maintain that the associations made between world events and Nostradamus’s quatrains are largely the result of misinterpretations or mistranslations (sometimes deliberate) or else are so tenuous as to render them useless as evidence of any genuine predictive power. Nevertheless, occasional commentators have successfully used a process of free interpretation and determined ‘twisting’ of his words to predict an apparently imminent event. In 1867, three years before it happened, for example, Le Pelletier did so to anticipate either the triumph or the defeat of Napoleon III in a war that, in the event, begged to be identified as the Franco-Prussian war, while admitting that he could not specify either which or when.
       
Salon
WEDNESDAY, MAR 18, 1998 04:00 PM EDT
ESPN: The Magazine kicks sand in SI: The Swimsuit Issue’s face
ESPN’s glammy print startup courts young sports fans who don’t want their fathers’ breasts.
JAMES PONIEWOZIK
(...)
It’s a fine line between Nostradamus and Nostradumbass, as several of our more excitable media outlets discovered over Asteroid 1997 XF11′s not quite 24 hours of infamy.
 
Urban Dictionary
Nostradumbass
Referring to Nostradamus who, in ancient times did much predicting of the future.
Nostradumbass would be someone who thinks they can predict the future, but is too much of a dumbass to get it right.
Him: I predict that the sky will fall tomorrow!
Her: Whatever, Nostradumbass!
by queenoftheknownuniverse October 15, 2003
 
OCLC WorldCat record
The Life and Times of Nostradumbass.
Author: Christophe, Bernard
Publisher: Xlibris Corp 2012.
Edition/Format:   Book : English
 
Not Quite Noahpinion
Wednesday, July 10, 2013
How to be a Nostradumbass
Author: Noah Smith
...or, in case you’re me, a “Noahstradumbass”.

Here’s a quick guide for making easy (“dumbass”) predictions that are nearly guaranteed to be borne out by events, thus making you look like a sage. The key is to make non-time-sensitive predictions of things that are very likely to happen at some point in the infinite future.
 
For example: “The S&P 500 will eventually hit 6,000.”
   
MMA Mania
UFC Fight Night 32 predictions, preview and analysis
By Jesse Holland  @Jesse_Holland on Nov 8 2013, 11:03a
(...)
Nostradumbass predicts: The whole purpose of taking TRT is so that older fighters can stay competitive against the younger guys.