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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(Add: drought monitor, May 22, 2012.)
Have a good one, wu weather watchers.
Here I tell ya. "1 2 3 and to the 4 Snoop doggy dog and Dr. Dre is at the door."
My mother thinks we're having a pool party barbecue Sunday over here on the ECFL coast.
When was the last time a tropical system directly hit the Southern Georgia/ Northern Florida area?
Over 100 years ago?
I don't think anyone was getting too hyped up, but yes, nothing today will give too much evidence for or against development. Everything is as predicted at this point.
The models really have a good consensus on track... The major models have been steady taking it into Jacksonville,FL.
The Dynamic models take 94l into Southern Georgia.
When ya gonna break the news to her?
For the first time in a long time, I have full confidence in the development of this system.
17.3n105.7w has been re-evaluated&altered
17.5n105.7w, 18.2w105.6 are now the most recent positions
Its vector had changed from NNEast at ~9.1mph(14.7k/h) to North at ~8.1mph(13k/h)
MaxSusWinds had decreased from ~95knots(109mph)176k/h to ~90knots(104mph)167k/h
And minimum pressure had increased from 964millibars to 970millibars
For those who like to visually track H.Bud's path...
PVR is PuertoVallarta . ZLO is Manzanillo . LZC is LazaroCardenas
The southernmost connected dot is where TropicalStormBud became HurricaneBud
The southernmost dot on the longest line-segment was H.Bud's most recent position
The longest line-segment is a straightline-projection through H.Bud's 2 most recent positions
to the coastline.
The coast-to-ZLO dumbbell was the endpoint of the 25May12amGMT straightline projection
connected to its 2nd closest airport.
The ZLO-to-coast dumbbell was the endpoint* of the 25May6amGMT* straightline projection
connected to its closest airport.
On 25May12amGMT, H.Bud was headed toward passing over the LaPrimaveraCentro in ~12hours from now
Copy&paste pvr, zlo-19.307n104.823w, zlo-19.016n104.305w, lzc,14.0n107.7w-14.6n107.5w, 14.6n107.5w-15.2n107.1w, 15.2n107.1w-16.0n106.5w, 16.0n106.5w-16.8n106.1w, 16.8n106.1w-17.5n105.7w, 17.5n105.7w-18.2n105.6w, 17.5n105.7w-19.832n105.364w into the GreatCircleMapper for more information
The previous mapping for comparison.
* 17.3n105.7w was re-evaluated&altered to 17.5n105.7w. So an incorrect vector(direction&speed) was calculated for 25May6amGMT from using the original incorrect position.
Through recalculation using the correct position, the vector has been corrected to reflect that change.
The original incorrect vector produced an incorrect straightline projection leading to an incorrect endpoint on the ZLO-to-coast dumbbell
Nonetheless I am reposting it to maintain historicity with the previous map.
I stand corrected. I was looking simply at current conditions, since those have a great impact for the next 24 hours.
Now that I've looked at everything (and made myself look stupid by jumping the gun earlier), I think development in 24 hours might be a bit premature, but the 24-48 hour period will feature a better chance. I wouldn't be shocked to see a TD at the end of 24 hours, but I'm not sure about a TS. If a TS does get going, I'm guessing it will be in the T-36 to T-48 hour period.
Great post!! That exit region of the jet is what's firing these thunderstorms on the SE Side.
I already told her and she brushed me off. Which means we're having the party whether it's raining or not.
Mom's a trooper. The fact that my sister lives in England and it's usually almost always raining there (or at least used to be) probably also has an effect because my sister is the same way. Her plans never change just because it's raining.
I'm convinced that what the models have been showing on and off of tropical cyclone formation in the NW Caribbean might happen come mid next week because energy has been left behind and it appears that a tropical wave in the eastern Caribbean might merge with this left over energy in NW Caribbean come Monday or Tuesday next week.
Everyone makes mistakes, don't sweat it.
Good luck having a Party in 35mph Winds... Lol
Some of the PWAT's east of FL are near 3" in some areas and it's this high octane tropical moisture moving in that is going to create a very wet Sunday & Monday for much of FL.
Plus you have learned to quickly move indoors and how to accomodate the quick transfer to indoors what with these summer things we have in the south, but yall might need to go on and plan the thing inside or at least on a covered patio
Just imagine if the 'C' storm formed before next Thursday (which I don't think it will), and if 92L was classified in post-season analysis (which I don't think it will be). Would give us 4 pre-season storms....
It's ok, I was just tryin to prove that I wasn't hyping anything haha... It even caught me in surprise last night when I saw a HIGH chance for development on my IPOD while at the bar... Subtropical at best first, could transition to pure Tropical. Wind shear expected to rapidly decrease in this area, which is hard to believe right now, but this is what every model is showing, and what the NHC is forecasting.
whoo hoo Jeff has a new blog!
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