NOAA predicts a near-normal Atlantic hurricane season
NOAA forecasts a near-normal Atlantic hurricane season in 2012, in their May 24 outlook. They give a 50% chance of a near-normal season, a 25% chance of an above-normal season, and a 25% chance of a below-normal season. They predict a 70% chance that there will be 9 - 15 named storms, 4 - 8 hurricanes, and 1 - 3 major hurricanes, with an Accumulated Cyclone Energy (ACE) 65% - 140% of the median. If we take the midpoint of these numbers, NOAA is calling for 12 named storms, 6 hurricanes, 2 major hurricanes, and an ACE index 102% of normal. This is very close to the 1981 - 2010 average of 12 named storms, 6 hurricanes, and 3 major hurricanes. Hurricane seasons during the active hurricane period 1995 - 2011 have averaged 15 named storms, 8 hurricanes, and 4 major hurricanes, with an ACE index 153% of the median. Only five seasons since 1995 have not been above normal--including four El Niño years (1997, 2002, 2006, and 2009), and the neutral 2007 season.
Figure 1. The strongest Atlantic hurricane of 2011, Ophelia, as seen at 1:40 pm EDT October 1, 2011. At the time, Ophelia was a Category 3 hurricane with 120 mph winds. At 11 pm that night, Ophelia peaked at Category 4 strength with 140 mph winds. Image credit: NASA.
The forecasters cited the following main factors that will influence the coming season:
1) Near-average sea surface temperatures (SSTs) are expected in the hurricane Main Development Region (MDR), from the Caribbean to the coast of Africa between between 10°N and 20°N. SSTs in the MDR during April were near-average, and are expected to remain so during hurricane season, based on current observations, climatology, and long-range model forecasts.
2) We are in an active period of hurricane activity that began in 1995, thanks to a natural decades-long cycle in hurricane activity called the Atlantic Multidecadal Oscillation (AMO): "During 1995-2010, some key aspects of the tropical multi-decadal signal within the MDR have included reduced vertical wind shear and weaker easterly trade winds, below-average sea-level pressure, a configuration of the African easterly jet that is more conducive to hurricane development from tropical cloud systems (aka Easterly waves) moving off the African coast, and warmer than average SSTs."
3) An El Niño event may occur this year: "Another climate factor known to significantly impact Atlantic hurricane activity is the El Niño-Southern Oscillation (ENSO.) The three phases of ENSO are El Niño, La Niña, and ENSO-Neutral. El Niño events tend to suppress Atlantic hurricane activity, while La Niña events tend to enhance it (Gray 1984). If El Niño fails to develop, the probability of an above-normal Atlantic hurricane season will be higher and the actual seasonal activity will likely be toward the upper end of our predicted ranges." There is currently of lot of uncertainty whether or not an El Niño event will develop in time for the August - September - October peak of hurricane season--the latest NOAA El Niño discussion is giving a 41% chance of an El Niño event during hurricane season, and a 48% chance of neutral conditions.
4) NOAA is increasingly using output from ultra-long range runs of the computer forecast models we rely on to make day-to-day weather forecasts, for their seasonal hurricane forecasts: "The outlook also takes into account dynamical model predictions from the NOAA Climate Forecast System (CFS), the European Centre for Medium Range Weather Forecasting (ECMWF), the United Kingdom Meteorology (UKMET) office, and the EUROpean Seasonal to Inter-annual Prediction (EUROSIP) ensemble. These models show large spreads in the ENSO forecasts for ASO, ranging from ENSO-Neutral to a moderate-strength El Niño episode. As a result, their forecasts for the Atlantic hurricane season also show a considerable spread, ranging from slightly above normal to slightly below normal."
How accurate are the NOAA seasonal hurricane forecasts?
A talk presented by NHC's Eric Blake at the 2010 29th Annual AMS Conference on Hurricanes and Tropical Meteorology studied the accuracy of NOAA's late May seasonal Atlantic hurricane forecasts, using the mid-point of the range given for the number of named storms, hurricanes, intense hurricanes, and ACE index. Over the past twelve years, a forecast made using climatology was in error, on average, by 3.6 named storms, 2.5 hurricanes, and 1.7 intense hurricanes. NOAA's May forecast was not significantly better than climatology for these quantities, with average errors of 3.5 named storms, 2.3 hurricanes, and 1.4 intense hurricanes. Only NOAA's May ACE forecast was significantly better than climatology, averaging 58 ACE units off, compared to the 74 for climatology. Using another way to measure skill, the Mean Squared Error, May NOAA forecasts for named storms, hurricanes, and intense hurricanes had a skill of between 5% and 21% over a climatology forecast. Not surprisingly, NOAA's August forecasts were much better than the May forecasts, and did significantly better than a climatology forecast.
Figure 2. Mean absolute error for the May and August NOAA seasonal hurricane forecasts (1999 - 2009 for May, 1998 - 2009 for August), and for forecasts made using climatology from the past five years. A forecast made using climatology was in error, on average, by 3.6 named storms, 2.5 hurricanes, and 1.7 intense hurricanes. NOAA's May forecast was not significantly better than climatology for these quantities, with average errors of 3.5 named storms, 2.3 hurricanes, and 1.4 intense hurricanes. Only NOAA's May ACE forecast was significantly better than climatology, averaging 58 ACE units off, compared to the 74 for climatology. Image credit: Verification of 12 years of NOAA seasonal hurricane forecasts, National Hurricane Center.
I'll have an update on Hurricane Bud and Invest 94L Friday morning.
Jeff Masters
Reader Comments
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I have to say that i do hope this storm forms because i am anxious to see just what it will do! And i also know it is NOT forecast to become a hurricane, is it?
The models have been hinting at a low developing in this area around mid week next week. I do not know the forward speed of the wave but they sometimes provide the spark needed for something to spin up. Usually the waves are pretty subdued in the Eastern Caribbean, especially this early in the year.
The GFS tracks the wave to our area quite nicely but does not do much with it except more rain. The 18UTC run shows good rotation with the wave all the way into the NW Caribbean. Just have to watch it.
EDIT
From the discussion
A tropical wave extends from 12n57w to 8n60w moving W near 15
kt. The wave lies embedded within a broad area of enhanced
moisture present in total precipitable water imagery. Due to
interaction with an upper level trough earlier in the week...the
exact location of the wave has been difficult to discern.
Scattered moderate convection is E of the axis from 9n-11n
between 56w-59w...and W of the wave axis from 12n-15n between
60w-66w.
I hope mexico doesnt have a bunch of mudslides because of Bud. Storms can really devastate them down there.
Thanks, this year is bit unusual already :), now the sky is a funny light yellow, I guess a reflection the sun trying to break through rain clouds!
A lot of stuff happening out there...
Yeah, weird colour outside. See my edit to the post where I inserted the Twave info. They have it just east of the islands but position stated to be unsure. Given that position it would seem the timing would put it here early next week as progged by the GFS
That would have to be a 50-60 mph tropical storm, so that probably will not happen :/
didn't happen....
You mean Beryl?
Nope. It's really close though.
crap!
The eye is contracting...
FORECAST POSITIONS AND MAX WINDS
INIT 24/2100Z 16.4N 106.4W 95 KT 110 MPH
12H 25/0600Z 17.4N 105.9W 100 KT 115 MPH
24H 25/1800Z 18.6N 105.4W 85 KT 100 MPH
36H 27/1800Z 19.5N 105.5W 30 KT 35 MPH...OVER WATER
48H 28/1800Z 19.0N 105.5W 20 KT 25 MPH...POST-TROP/REMNT LOW
72H 26/0600Z 19.8N 105.2W 65 KT 75 MPH...INLAND
96H 26/1800Z 20.5N 105.1W 45 KT 50 MPH...INLAND
LOL!!!
The latter "Hurricane 2" was responsible for the greatest flood in South Louisiana history. My town of Crowley, Louisiana received 33" of rain in a 2 day period
the SE Us could see rain.
What radar you using to view that, what location.
it has good speed 50mph, but i dont see it lasting.
Which also means the Euro's Set up of the storm is more likely. This means there's a better chance of seeing Beryl out of 94L. The GFS was stronger with the trough which was prohibiting the storm as seen by models, but if the Euro's is more accurate, that means Beryl is more likely.
PINHOOOOOOOOLE!!!!!!!!!
Magnitude 6.2 - NORWEGIAN SEA
What do you mean?
GRLevel 3, central Wisconsin near Merril and Brokaw, a new warning was just issued, tornado still on the ground and moving at 65mph.
Not really the North Pole...
You can clearly seethe "I" right over the Southern Tip of Florida.
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