How rarely does this occur?

August 7, 2014
1330.17z
UNISYS Goes West Water Vapor Satellite (click here for 12 hour loop)

Hawaii has never received a dual storm system in it's history.

Hawaii (click here) braced for its first direct hurricane hit in 22 years Thursday as Iselle headed toward the Big Island with a second storm on its tails. Bottled water and supplies were in high demand at stores ahead of the Category 1 storm’s expected impact on Thursday night. “It’s a fairly potent hurricane by Hawaiian standards,” Weather Channel meteorologist Kevin Roth said. Heavy rains totaling 5 to 8 inches, winds gusting up to 80 mph and flooding were expected, before Iselle was set to weaken to a tropical storm by the time it hit Honolulu at about 9 a.m. local time (3 p.m. ET) on Friday. Tropical storm warnings were issued for Oahu, Kauai and Maui, and a flash flood warning was in effect for the entire island chain....

This is NOAA's Satellite (click here)

This is a NOAA satellite from the Central Pacific that visualizes the larger circulation system west of Hawaii. I haven't found it documented anywhere in the east or west Pacific records to date.

This is it in the West Central Pacific satellite image. It is on the right side of the image. It dwarfs the two hurricanes now in route to Hawaii.

Here it is:

The track of Genevieve was just south of Hawaii. I would have been shocked if it wasn't documented somewhere.

Date: 25 JUL-07 AUG 2014
Hurricane-4 GENEVIEVE
ADV  LAT    LON      TIME     WIND  PR  STAT
  1  12.20 -134.00 07/25/06Z   35     - TROPICAL STORM
  2  12.30 -135.00 07/25/12Z   40     - TROPICAL STORM
  3  12.20 -135.80 07/25/18Z   40     - TROPICAL STORM
  4  12.10 -135.90 07/26/00Z   40     - TROPICAL STORM
  5  12.10 -136.40 07/26/06Z   35     - TROPICAL STORM
  6  12.20 -136.80 07/26/12Z   30     - TROPICAL DEPRESSION
  7  12.40 -137.50 07/26/18Z   30     - TROPICAL DEPRESSION
  8  12.50 -138.80 07/27/00Z   30     - TROPICAL DEPRESSION...

 ...37  11.90 -174.60 08/06/06Z   50     - TROPICAL STORM
 38  12.80 -176.80 08/06/05Z   65   990 HURRICANE-1
 39  13.50 -178.40 08/06/11Z   75   980 HURRICANE-1
 40  14.10 -179.70 08/07/03Z  120     - HURRICANE-4
 41  14.50  179.80 08/07/06Z  130     - HURRICANE-4
+12  15.50  177.70 08/07/18Z  145     - HURRICANE-5
+24  17.20  176.00 08/08/06Z  140     - HURRICANE-5
+36  19.50  175.30 08/08/18Z  130     - HURRICANE-4
+48  22.10  175.10 08/09/06Z  120     - HURRICANE-4
+72  26.60  173.90 08/10/06Z   95     - HURRICANE-2