Hurricanes Blanca and Andres Set Records For Early-Season Northeast Pacific Activity

Hurricane Blanca put on a furious display of rapid intensification this week, going from a tropical storm with 70 mph winds on Tuesday morning to a Category 4 storm with 135 mph winds on Wednesday morning--a remarkable 65 mph increase in winds in 24 hours, an intensification rate that is rarely seen. Blanca topped out at 140 mph winds on Wednesday afternoon, making it the fourth strongest Northeast Pacific hurricane for so early in the year. It has been a remarkable run of early-season activity for the region, since just two days before that Hurricane Andres topped out as a Category 4 storm with 145 mph winds, becoming the second strongest Northeast Pacific hurricane for so early in the year. Only six Northeast Pacific major hurricanes have occurred prior to June 5 since accurate satellite records began in 1971, and two of them were this year:

1) Hurricane Amanda, 2014: 155 mph winds on May 25
2) Hurricane Andres, 2015: 145 mph winds on June 1
2) Hurricane Adolph, 2001: 145 mph winds on May 29
4) Hurricane Blanca, 2015: 140 mph winds on June 3
5) Hurricane Alma, 2002: 115 mph winds on May 30
6) Hurricane Bud, 2012: 115 mph winds on May 25


Figure 1. VIIRS infrared image of Hurricane Blanca taken at 3:58 pm EDT June 3, 2015. At the time, Blanca was at peak strength, with top winds of 140 mph. Image credit: Dan Lindsey, NOAA/RAMMB/CIRA.


Figure 2. The eye of Hurricane Andres as seen at dawn on June 1, 2015 from the International Space Station. At the time, Andres was a Category 4 storm with 140 mph winds. Image credit: Terry Virts.

Blanca became a hurricane on June 2, setting a record for the earliest appearance of the season's second hurricane, beating the previous record set by Hurricane Boris of 1990 on June 5. Blanca also set a record for the earliest appearance of the season's second major hurricane on June 3. This is the second year in a row that the Eastern Pacific has set a record for the earliest appearance of the season's second major hurricane. The previous record was set June 12, 2014 (Hurricane Christina.) Only one other season besides 2015 has had the first two storms of the season intensify into major hurricanes--1995, when the year kicked off with Hurricane Adolph and Hurricane Barbara. The second major hurricane of the season typically doesn't form until August 19, and an entire season typically has only four major hurricanes (using stats from 1981-2010.) The record is eight major hurricanes in a season, accomplished most recently in 2014 (with a ninth storm, Genevieve, becoming a major hurricane after it crossed over into the Central Pacific.)

Forecast for Blanca
Hurricane Blanca performed its rapid intensification feat while parked for three days over an ocean hot spot, with warm waters of at least 26°C (79°F) that extended to a depth of about 100 meters (328 feet.) However, the storm sat too long in one place, and the powerful winds of the storm were finally able to churn up cooler waters from the depths on Thursday morning, causing Blanca to weaken to a Category 2 storm with 110 mph winds (though an eyewall replacement cycle also may have contributed to the weakening.) Satellite loops show that a portion of the eyewall collapsed, and the cloud tops have warmed, indicating that the heavy thunderstorms of the hurricane have weaker updrafts and no longer extend as high into the sky. The storm began a slow motion to the northwest at 3 mph on Thursday morning, though, and this motion will carry the storm away from the cold spot it created, and should allow Blanca to re-intensify. By Friday, the hurricane should be at Category 2 strength, but is unlikely to have enough time to become a Category 4 or 5 storm before hitting cooler waters and a drier surrounding air mass on Saturday. An Air Force hurricane hunter aircraft is scheduled to investigate Blanca on Friday afternoon. Blanca will pose a heavy rainfall threat to Mexico's Baja Peninsula beginning on Sunday.

The earliest Category 5 storm in the Northeast Pacific was Hurricane Ava of 1973, which peaked at 160 mph winds on June 6, 1973. The earliest Category 5 storm in the Atlantic occurred on July 16, 2005, when Hurricane Emily attained sustained winds of 160 mph.


Figure 3. The total heat content of the ocean at 2 am EDT June 4, 2015 showed that Hurricane Blanca has been sitting over a "hot spot" for heat energy over the past three days. For hurricanes with intensities less than 90 mph in favorable environmental conditions for intensification (vertical wind shear less than 15 kt, mid-level relative humidity >50 %, and warm SSTs >28.5°C), values of ocean heat content greater than 50 kJ/cm^2 (yellow colors) have been shown to promote greater rates of intensification. Image credit: NOAA/CIRA/RAMMB.

NOAA and CONAGUA predict an active Northeast Pacific hurricane season
Andres and Blanca are merely the opening salvos of what is likely to be a very busy Northeast Pacific hurricane season. Averaged over the entire Northeast Pacific, sea surface temperatures are running 1°C (1.8°F) above average, which is an unusually high amount of extra heat energy available for storms to take advantage of. NOAA's pre-season prediction for the Eastern Pacific hurricane season, issued on May 27, calls for 15 - 22 named storms, 7 - 12 hurricanes, 5 - 8 major hurricanes, and an ACE index 110% - 190% of the median. The mid-point of these ranges gives us a forecast for 18.5 named storms, 9.5 hurricanes, and 6.5 major hurricanes, with an ACE index 150% of average. CONAGUA, the Mexican meteorological service, is predicting 19 named storms, 8 hurricanes, and 4 intense hurricanes. The 1981 - 2010 averages are 15 named storms, 8 hurricanes, and 4 major hurricanes.

Wunderblogging hurricane expert Steve Gregory will begin issuing regular Atlantic hurricane updates twice per week, beginning Thursday, June 4.

Jeff Masters