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HOME > Expert Assessments > East Pacific Hurricane Outlook
 
NOAA 2016 Eastern Pacific Hurricane Season Outlook

Issued: 27 May 2016

Realtime monitoring of tropical East Pacific conditions
Realtime monitoring of tropical Atlantic conditions


The 2016 eastern Pacific hurricane season outlook is an official product of the National Oceanic and Atmospheric Administration (NOAA) Climate Prediction Center (CPC), and is produced in collaboration with scientists from the NOAA National Hurricane Center (NHC). The eastern Pacific hurricane region covers the eastern North Pacific Ocean east of 140°W north of the equator.

Interpretation of NOAA's eastern Pacific hurricane season outlook
This outlook is general guide to the expected overall activity during the upcoming hurricane season. It is not a seasonal hurricane landfall forecast, and it does not imply levels of activity for any particular location.

Preparedness
Hurricane disasters can occur whether the season is active or relatively quiet. It only takes one hurricane (or even a tropical storm) to cause a disaster. Therefore, residents, businesses, and government agencies of coastal and near-coastal regions are urged to prepare for every hurricane season regardless of this, or any other, seasonal outlook. NOAA, the Federal Emergency Management Agency (FEMA), the NHC, the Small Business Administration, and the American Red Cross all provide important hurricane preparedness information on their web sites.

NOAA does not make seasonal hurricane landfall predictions
NOAA does not make seasonal hurricane landfall predictions. Hurricane landfalls are largely determined by the weather patterns in place as the hurricane approaches, which are only predictable when the storm is several days of making landfall.

Nature of this Outlook and the "likely" ranges of activity
This outlook is probabilistic, meaning the stated "likely" ranges of activity have a certain likelihood of occurring. The seasonal activity is expected to fall within these ranges in 7 out of 10 seasons with similar conditions and uncertainties to those expected this year. They do not represent the total possible range of activity seen in past similar years.

This outlook is based on predictions of large-scale climate factors and conditions known to strongly influence seasonal eastern Pacific hurricane activity, along with climate model forecasts. The outlook also takes into account uncertainties inherent in such climate outlooks.

Sources of uncertainty in this seasonal outlook

  1. This year, it is difficult to assess whether the low-activity era for the eastern Pacific has ended.
  2. Predicting El Niño and La Niña (also called ENSO) impacts is an ongoing scientific challenge facing climate scientists today. Such forecasts made during the spring generally have limited skill.
  3. Many combinations of named storms and hurricanes can occur for the same general set of climate conditions. For example, one cannot know with certainty whether a given climate signal will be associated with several short-lived storms or fewer longer-lived storms with greater intensity.
  4. Weather patterns that are unpredictable on seasonal time scales can sometimes develop and last for weeks or months, possibly affecting seasonal hurricane activity.

2016 Eastern Pacific Hurricane Outlook Summary

a. Predicted Activity

NOAA's 2016 Eastern Pacific Hurricane Season Outlook indicates that a near-normal hurricane season is most likely. The outlook calls for a 40% chance of a near-normal season, a 30% chance of an above-normal season, and a 30% chance of a below-normal season. See NOAA definitions of above, near-, and below- normal seasons. The eastern Pacific hurricane region covers the eastern North Pacific Ocean east of 140°W north of the equator.

This is a more challenging hurricane outlook than most because it is difficult to determine whether there will be reinforcing or competing climate influences on tropical storm development. The outlook calls for a 70% probability for each of the following ranges of activity during the 2016 hurricane season:

  • 13-20 named storms,
  • 6-11 hurricanes,
  • 3-6 major hurricanes,
  • Accumulated Cyclone Energy (ACE) range of 70%-140% of the median.

The seasonal activity is expected to fall within these ranges in 70% of seasons with similar climate conditions and uncertainties to those expected this year. These ranges do not represent the total possible ranges of activity seen in past similar years. These expected ranges are centered near the 1981-2010 seasonal averages of 15 named storms, 8 hurricanes, and 4 major hurricanes.

There will be no further updates to this outlook.

b. Reasoning Behind the outlook

NOAA's eastern Pacific hurricane season outlook is based on predictions of the main climate factors known to influence seasonal hurricane activity, along with model predictions of regional and global atmospheric and oceanic conditions.

One climate phenomenon that influences the hurricane season strength is the El Niño / La Niña cycle (also called ENSO, the El Niño / Southern Oscillation). The current El Niño is dissipating. According to the latest outlook from the Climate prediction Center , La Niña is expected to develop and strengthen during the hurricane season . There is currently about a 70% chance of La Niña during the peak months (July-September-JAS) of the hurricane season. La Niña suppresses tropical storms and hurricanes over the eastern Pacific by increasing the vertical wind shear and by causing anomalous sinking motion in the atmosphere. One uncertainty for this outlook is the rate at which La Niña will develop and intensify.

Other climate factors that influence the eastern Pacific hurricane season are related to the global patterns of sea surface temperature (SST) anomalies. There is uncertainty as to whether the SST patterns (right) that have been associated with increased hurricane activity in the eastern Pacific during the last two seasons will again appear this season, or whether the SST patterns will be less conducive as was observed during the Pacific low-activity era of 1995-2013..

Because of this combination of uncertainties, the outlook reflects three general scenarios.

  • Scenario 1- competing factors: Near-normal or above-normal season most likely if La Niña is weaker and the global SST patterns of the last two active seasons are present.
  • Scenario 2- competing factors: Near-normal season most likely if La Niña is stronger and the global SST patterns of the last two active seasons are again present this year.
  • Scenario 3-re-inforcing factors: Near-normal or below-normal season most likely if La Niña develops and the global SST patterns observed during the 1995-2013 low-activity era for eastern Pacific hurricanes re-emerge.

Preparedness for Tropical Storm and Hurricane Landfalls:

It only takes one storm hitting an area to cause a disaster, regardless of the overall activity. Therefore, residents, businesses, and government agencies of coastal and near-coastal regions are urged to prepare every hurricane season regardless of this, or any other, seasonal outlook.

Predicting where and when hurricanes will strike is related to daily weather patterns, which are not reliably predictable weeks or months in advance. Therefore, it is currently not possible to accurately predict the number or intensity of landfalling hurricanes at these extended ranges, or whether a particular locality will be impacted by a hurricane this season.

DISCUSSION

1. Expected 2016 Activity

NOAA's 2016 eastern Pacific Hurricane Season Outlook indicates that a near-normal hurricane season is most likely (40% chance), with a 30% chance of an above-normal season and a 30% chance of a below-normal season. See NOAA definitions of above-, near-, and below-normal seasons.

An important measure of the total seasonal activity is NOAA's Accumulated Cyclone Energy (ACE) index , which accounts for the combined intensity and duration of named storms and hurricanes during the season. This outlook indicates a 70% chance that the 2016 seasonal ACE range will be 70%-140% of the median. An ACE value of 80%-115% of the median indicates a near-normal season. Values above this range reflect an above-normal season and values below this range reflect a below-normal season.

The 2016 eastern Pacific hurricane season is predicted to produce (with 70% probability for each range) 13-20 named storms, of which 6-11 are expected to become hurricanes, and 3-6 are expected to become major hurricanes. These ranges are centered near the official NHC 1981-2010 seasonal averages of 15 named storms, 8 hurricanes, and 4 major hurricanes.

Predicting the location, number, timing, and strength of hurricanes landfalls is ultimately related to the daily weather patterns including genesis locations and steering patterns, which are not predictable weeks or months in advance. As a result, it is currently not possible to reliably predict the number or intensity of landfalling hurricanes at these extended ranges, or whether a given locality will be impacted by a hurricane this season. Therefore, NOAA does not make an official seasonal hurricane landfall outlook.

2. Science behind the 2016 Outlook

NOAA's eastern Pacific hurricane season outlooks are based on predictions of the main climate factors known to influence the seasonal hurricane activity. They also takes into account dynamical model predictions from the NOAA's Climate Forecast System (CFS), NOAA Geophysical Fluid Dynamics Lab (GFDL) model HI-FLOR, the European Centre for Medium Range Weather Forecasting (ECMWF), and the EUROpean Seasonal to Inter-annual Prediction (EUROSIP), along with ENSO (El Niño / Southern Oscillation) forecasts from statistical and other dynamical models contained in the suite of Niño 3.4 SST forecasts compiled by the IRI (International Research Institute for Climate and Society) and the NOAA Climate Prediction Center.

a. Possible La Niña

El Niño is currently dissipating . The recent sub-surface temperature anomalies show that the El Niño-related warming is now confined to the upper 30m of the central and east-central equatorial Pacific Ocean. Also seen is an extensive area of below-average SSTs at depth extending across most of the equatorial Pacific, with those cool anomalies reaching the surface in the eastern Pacific. If the trade winds strengthen in the next few months, the resulting upwelling will bring enough colder water to the surface to produce La Niña. A similar scenario was observed during May-August 1998 in association with the rapid demise of the 1997-98 El Niño. That El Niño was followed by a significant La Niña during the 1998 hurricane season.

The Climate Prediction Center currently indicates about a 70% chance of La Niña during the peak months July-September (JAS) of the hurricane season. Based on the suite of ENSO forecasts issued by the IRI, the average of the dynamical models predicts La Niña to develop during June-August, and to approach moderate strength (defined by average SST anomalies in the Nino 3.4 region between -1.5°C and -0.5°C) by the end of the hurricane season.

The ensemble mean forecast from the CFS high-resolution model predicts a strong La Niña to develop during July (defined by average SST anomalies in the Nino 3.4 region dropping below -1.5°C), and to continue through the remainder of the hurricane season. In contrast, the CFS lower-resolution (T-128) ensemble mean forecast calls for a moderate-strength La Niña during JAS.

La Niña favors a weaker hurricane season by producing stronger vertical wind shear and anomalous sinking motion in the atmosphere across the eastern Pacific hurricane basin. However, the overall hurricane season strength depends not only on La Niña, but also on the global patterns of SST anomalies.

b. Global SST anomalies

The strength of the eastern Pacific hurricane season is also related to the global patterns of SST anomalies that occur on multi-decadal time scales. One such pattern is called the Atlantic Multi-Decadal Oscillation (AMO), and another is called the Pacific Decadal Oscillation (PDO). Since these climate patterns can last for decades, they are associated with strong multi-decadal fluctuations in hurricane activity. In contrast, ENSO contributes to inter-annual variations in hurricane activity.

During 1995-2013, the eastern Pacific hurricane seasons were generally below normal (called a low-activity era) while the Atlantic basin was experiencing a high-activity era. This dipole pattern in activity between the two hurricane basins was associated with the warm phase of the AMO (Left). This signal is indicated by above-average SSTs across the high latitudes and tropical latitudes of the North Atlantic, with the tropical Atlantic being anomalously warm compared to the remainder of the global Tropics.

In contrast, during the last two hurricane seasons (2014-2015) SSTs across the high latitudes of the North Atlantic have been below average and the tropical Atlantic SST anomalies have been near or colder than the departures for the remainder of the global Tropics. These conditions typify the cool phase of the AMO, and have been associated with reduced hurricane activity in the Atlantic basin and enhanced hurricane activity in the eastern Pacific It is unclear whether these recent changes in the AMO will be short-lived, or whether they reflect a multi-decadal time-scale change in the AMO phase which historically lasts 25-40 years.

Another aspect of the global SST anomaly pattern that differs between 1995-2013 and 2014-2015 is its projection onto the PDO. During 1995-2013, the SST anomalies indicated a horseshoe-shaped pattern above-average SSTs (blue arc) in the western Pacific and cooler SSTs in the eastern North Pacific (blue line). This pattern projects onto the negative phase of the PDO and also has some resemblance to La Niña. In contrast, during 2014-15, a horseshoe-shaped pattern of below-average SSTs was observed in the western Pacific and warmer SSTs were present in the eastern North Pacific. This more recent SST anomaly pattern (Right) resembles the positive phase of the PDO and is more typical of El Niño.

Mixed climate conditions are indicated by recent forecasts from the CFS high-resolution model. This model predicts that the tropical Atlantic will be colder than the remainder of the global Tropics again this hurricane season, suggesting a more active eastern Pacific hurricane season. The CFS is also predicting above average SSTs and weaker vertical wind shear across the eastern Pacific hurricane region, which could possibly offset the suppressing influence of La Niña, if it develops.

Because of the variability in the global SST anomaly patterns over the past few years, combined with model predictions of global SST anomalies which have limited skill this far in advance of the peak months of the hurricane season, it is difficult to assess whether there will be reinforcing or competing climate factors during the 2016 hurricane season. The outlook reflects three general scenarios.

  • Scenario 1- competing factors: Near-normal or above-normal season most likely if La Niña is weaker and the global SST patterns of the last two active seasons are again present.
  • Scenario 2- competing factors: Near-normal season most likely if La Niña is stronger and the global SST patterns of the last two active seasons are again present this year.
  • Scenario 3-re-inforcing factors: Near-normal or below-normal season most likely if La Niña develops and the global SST patterns observed during the 1995-2013 low-activity era for eastern Pacific hurricanes re-emerge.

NOAA FORECASTERS

Climate Prediction Center
Dr. Gerald Bell, Meteorologist, Gerry.Bell@noaa.gov
Dr. Jae Schemm, Meteorologist, Jae.Schemm@noaa.gov

National Hurricane Center
Eric Blake, Hurricane Specialist, Eric.S.Blake@noaa.gov
Todd Kimberlain, Hurricane Specialist, Todd.Kimberlain@noaa.gov

Dr. Christopher Landsea, Meteorologist, Chris.Landsea@noaa.gov


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Page Author: Climate Prediction Center Internet Team
Page last modified: May 27, 2015
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