Record Atlantic SSTs continue; very active hurricane season foreseen by CSU and TSR
Sea Surface Temperatures (SSTs) in the Atlantic's Main Development Region for hurricanes had their warmest March on record, according to an analysis of historical SST data from the UK Hadley Center. SST data goes back to 1850, though there is much missing data before 1910 and during WWI and WWII. The region between 10°N and 20°N, between the coast of Africa and Central America (20°W - 80°W), is called the Main Development Region (MDR) because virtually all African waves originate in this region. These African waves account for 85% of all Atlantic major hurricanes and 60% of all named storms. When SSTs in the MDR are much above average during hurricane season, a very active season typically results (if there is no El Niño event present.) SSTs in the Main Development Region (10°N to 20°N and 20°W to 85°W) were an eye-opening 1.26°C above average during March. This easily beats the previous record of 1.06°C set in 1969. SSTs in the Main Development Region are already warmer than they were during late June of last year, which is pretty remarkable, considering that March is one of the coldest months of the year for SSTs in the North Atlantic. Last month's anomaly of 1.26°C tied with June 2005 as the greatest monthly anomaly ever recorded in the Atlantic MDR.
Figure 1. The departure of sea surface temperature (SST) from average for April 12, 2010. Image credit: NOAA/NESDIS.
What is responsible for the high SSTs?
As I explained in detail in last month's post on record February SSTs in the Atlantic, the Arctic Oscillation (AO) and its close cousin, the North Atlantic Oscillation (NAO), are largely to blame for the record SSTs. The AO and NAO are climate patterns in the North Atlantic Ocean related to fluctuations in the difference of sea-level pressure between the Icelandic Low and the Azores-Bermuda High. If the difference in sea-level pressure between Iceland and the Azores is small (negative NAO), this creates a weak Azores-Bermuda High, which reduces the trade winds circulating around the High. During December - February, we had the most negative AO/NAO since records began in 1950, and this caused trade winds between Africa and the Lesser Antilles Islands in the hurricane Main Development Region to slow to 1 - 2 m/s (2.2 - 4.5 mph) below average. Slower trade winds mean less mixing of the surface waters with cooler waters down deep, plus less evaporational cooling of the surface water. As a result, the ocean heated up significantly, relative to normal, over the winter. This heating is superimposed on the very warm global SSTs we've been seeing over the past few decades due to global warming. Global and Northern Hemisphere SSTs were the 2nd warmest on record this past December, January, and February. We are also in the warm phase of a decades-long natural oscillation in Atlantic ocean temperatures called the Atlantic Multi-decadal Oscillation (AMO). This warm phase began in 1995, and has been partially responsible for the high levels of hurricane activity we've seen since 1995.
What does this imply for the coming hurricane season?
The high March SST anomaly does not bode well for the coming hurricane season. The three past seasons with record warm March SST anomalies all had abnormally high numbers of intense hurricanes. Past hurricane seasons that had high March SST anomalies include 1969 (1.06°C anomaly), 2005 (0.93°C anomaly), and 1958 (0.93°C anomaly). These three years had 5, 7, and 5 intense hurricanes, respectively. Just two intense hurricanes occur in an average year. The total averaged activity for the three seasons was 15 named storms, 11 hurricanes, and 6 intense hurricanes (an average hurricane season has 10, 6, and 2.) Both 1958 and 2005 saw neutral El Niño conditions, while 1969 had a weak El Niño. So, even if this year's El Niño lingers on into hurricane season, it may not protect us from a hyper-active hurricane season--the weak El Niño year of 1969 had 18 named storms, 12 hurricanes, and 5 intense hurricanes.
April forecast for the 2010 Atlantic hurricane season issued by Colorado State University
A well above-average Atlantic hurricane season is on tap for 2010, according to the latest seasonal forecast issued last week by Dr. Phil Klotzbach and Dr. Bill Gray of Colorado State University (CSU). The Klotzbach/Gray team is calling for 15 named storms, 8 hurricanes, and 4 intense hurricanes. An average season has 10 named storms, 6 hurricanes, and 2 intense hurricanes. The forecast calls for 30% above-average chance of a major hurricane hitting the U.S., both along the East Coast (45% chance, 31% chance is average) and the Gulf Coast (44% chance, 30% chance is average). The Caribbean is also forecast to have an above-average risk of a major hurricane (58%, 42% chance is average.)
The forecasters cited two main reasons for their forecast of an active season:
1) Sea surface temperature (SST) anomalies in the tropical Atlantic are at their warmest levels on record in the Main Development Region for hurricanes in the tropical Atlantic. Warmer-than-normal waters provide more heat energy for developing hurricanes. In addition, an anomalously warm tropical Atlantic is typically associated with lower sea level pressure values and weaker-than-normal trade winds, indicating a more unstable atmosphere with decreased levels of vertical wind shear, favoring hurricane development. Part of the reason for the substantial warming is because a weaker than average Bermuda-Azores High drove weak trade winds over the winter and early spring. These weaker winds acted to reduce evaporative cooling of the ocean. Weaker winds also decreased the mixing of cool waters to the surface from below.
2) Hurricane activity in the Atlantic is lowest during El Niño years and highest during La Niña or neutral years. The CSU team expects the current weak to moderate El Niño conditions to transition to neutral and perhaps weak La Niña conditions by this year's hurricane season. April and May are typically the months when the atmosphere will swing between El Niño and La Niña, which makes any seasonal forecasts of hurricane activity during April low-skill. The current computer models used to predict El Niño (Figure 2) mostly favor neutral conditions for the coming hurricane season. The models used include statistical models, which observe how previous El Niño events have evolved, and sophisticated computer-intensive dynamical models (similar to the GFS model we use to make weather forecasts). The reliability of all of these models is poor, but the CSU team believes the ECMWF model (yellow-orange squares) is the best one. The ECMWF model only goes out to JJA (June-July-August) in this plot, and is forecasting neutral conditions.
Figure 2. Computer model forecasts of El Niño/La Niña made in March. The forecasts that go above the red line at +0.5°C denote El Niño conditions; -0.5°C to +0.5°C denote neutral conditions, and below -0.5°C denote La Niña conditions. Three computer models predict El Niño conditions and three predict La Niña for the upcoming hurricane season (ASO, August-September-October). However, most of the models predict neutral conditions. Image credit: Columbia University's IRI.
Analogue years
The CSU team picked five previous years when atmospheric and oceanic conditions were similar in April to what we are seeing this year. Those five years were 2005, the most active Atlantic season in history; 1998, which had Category 5 Hurricane Mitch in the Western Caribbean; 1969, which featured Category 5 Hurricane Camille, the strongest hurricane ever to hit the U.S.; 1966, which had Category 4 Hurricane Inez that killed 1,000 people in the Caribbean and Mexico; and 1958, which had five major hurricanes. The mean activity for these five years was 16 named storms, 10 hurricanes, and 5 intense hurricanes.
How accurate are the April forecasts?
While the formulas used by CSU do well in making hindcasts--correctly modeling the behavior of past hurricane seasons--their April hurricane season forecasts have no skill in predicting the future. This year's April forecast uses the same formula as was used in 2008 and 2009. This scheme successfully predicted an active hurricane season in 2008, but failed to properly predict the relatively quiet 2009 hurricane season. A different formula was used prior to 2008, and the April forecasts using that formula showed no skill over a simple forecast using climatology. CSU maintains an Excel spreadsheet of their forecast errors (expressed as a mathematical correlation coefficient, where positive means a skilled forecast, and negative means they did worse than climatology) for their their April forecasts. For now, these April forecasts should simply be viewed as an interesting research effort that has the potential to make skillful forecasts. The next CSU forecast, due on June 2, is the one worth paying attention to. Their early June forecasts have shown considerable skill over the years.
2010 Atlantic hurricane season forecast from Tropical Storm Risk, Inc.
The British private forecasting firm Tropical Storm Risk, Inc. (TSR), issued their 2010 Atlantic hurricane season forecast last week, and they are also calling for a very active year: 16.3 named storms, 8.5 hurricanes, and 4.0 intense hurricanes. TSR predicts a 74% chance of an above-average hurricane season, 20% chance of a near-normal season, and only a 6% chance of a below normal season. They give a 77% chance that 2010 will rank in the top third of most active hurricane seasons on record.
Like the CSU April forecasts, the TSR April forecasts have little skill. I like how TSR puts their skill level right next to the forecast numbers: 12% skill above chance at forecasting the number of named storms, 7% skill for hurricanes, and 6% skill for intense hurricanes. That's not much better than flipping a coin.
TSR projects that 5.1 named storms will hit the U.S., with 2.3 of these being hurricanes. The averages from the 1950 - 2009 climatology are 3.2 named storms and 1.5 hurricanes. Their skill in making these April forecasts for U.S. landfalls is 9 - 13% above chance. In the Lesser Antilles Islands of the Caribbean, TSR projects 1.6 named storms, 0.7 of these being hurricanes. Climatology is 1.1 named storms and 0.5 hurricanes.
TSR cites two main factors for their forecast of an active season: they predict slower than normal trade winds from July - September over the Main Development Region (MDR) for hurricanes over the Atlantic (the region between 10° - 20° N from Central America to Africa, including all of the Caribbean). Trade winds are forecast to be 0.81 meters per second (about 2 mph) slower than average in this region, which would create greater spin for developing storms, and allow the oceans to heat up due to reduced evaporational cooling and reduced mixing of cooler sub-surface waters to the surface. TSR forecasts that SSTs will be 0.42°C above average in the MDR during hurricane season.
Figure 3. Accuracy of long-range forecasts of Atlantic hurricane season activity performed by Phil Klotzbach and Bill Gray of Colorado State University (colored squares) and TSR (colored lines). The CSU team's April forecast skill is not plotted, but is less than zero. The skill is measured by the Mean Square Skill Score (MSSS), which looks at the error and squares it, then compares the percent improvement the forecast has over a climatological forecast of 10 named storms, 6 hurricanes, and 2 intense hurricanes. TS=Tropical Storms, H=Hurricanes, IH=Intense Hurricanes, ACE=Accumulated Cyclone Energy, NTC=Net Tropical Cyclone Activity. Image credit: TSR.
I'll have a new post by Thursday.
Jeff Masters
Reader Comments
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If it is a tropical weather blog why is it that you are always forecasting doom and gloom from non tropical systems in Conus?
True, however I don't believe the Volcano will be enough. It might lower SSTs in the very Northern MDR. In 1980 we had Mt. Helens right? That was far more powerful than this Volcano, we had 11 storms including Allen which was an 899 mb 190 mph beast. (And this was during the inactive period, if it happened now It would be like 15 or 16)
Well i'm gonna have to disagree with you! With the current plum that continues, it will in my opinion not allow the MDR warm as much as first thought. It does not mean it won't still heat but, just not to the degree i could.
AOI
AOI
AOI
AOI
13:02:GMT den 15. april 2010
This was a severe thunderstorm or tornado, and not a tropical cyclone.
Jeff Masters
I don't disagree with your thinking but, because it is such high in latittude the particles will circle the earth near the smallest point at the top and when it comes back around is when the affects may be felt.....here is a loop to shop.
Hey i may be reaching but anything i can find to hold this years storms down would be a plus.
The journey is not as large as it seems....look at the northern hemp loop....it circles the top half much faster than the middle would.
My thinking is on this ash plum is, it will encircle the north pole and not let in as much sun light/heat and keep the summer melt to a minimum.
I'd cheer the Iceland dust as much as the shear but I don't think it will do much good after that first circumnavigation.
Good Lord Bless you and your fanily Tampa. Yours is a sad story. It pulls at the heart.
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Thousands of passengers headed to or from northern Europe are stranded this morning as ash clouds from a volcano eruption in Iceland affects aviation there. The BBC says "the huge ash cloud is drifting south, leaving airports closed and a number of passengers potentially stranded in the UK and overseas. Experts say the ash affects visibility and debris can get sucked into airplane engines, which could affect the safety of air travel."
The Associated Press reports "Britain's Civil Aviation Authority said non-emergency flights would be banned until at least 6 p.m. (1700 GMT, 1 p.m. ET). Irish authorities also closed their air space for eight hours."
With that, the shutdown of British airspace effectively suspends operations at London Heathrow, one of the world's busiest airports. AP says Heathrow, "Europe's business airport, handles upwards of 1,200 flights and 180,000 passengers per day. The closure also affected London's second- and third-largest airports, Gatwick and Stansted. It was not immediately clear when flights would resume."
AP adds that "with the major trans-Atlantic hub at Heathrow closed, dozens of flights to the United States were on hold, and cancelations spread across the continent to major hubs at Brussels,Amsterdam, Geneva and Paris, where flights heading north were canceled until midnight." The Independent of London reports "hundreds of flights across the UK were already cancelled and airports in Scotland closed indefinitely."
Ash is very different than dust. Ash will stay in the atmosphere way longer and it's so fine that it just floats around in the currents, eventually coming to rest somewhere on earth. But you cannot think of ash like dust, aerodynamic properties are so different in the way the air reacts. Dust has a rounder appearance, (i didnt say round), ash can be flat or other odds shapes, and ash can have lots of tiny holes making it even lighter.
According to a team of British and German scientists, the ash cloud should dissipate in a few days. It was a very small eruption and they do not anticipate much in the way of a health concern. At the moment I believe they are being cautious not to allow too much air traffic in the vicinity because of the elevated danger of flying into a large dust cloud. I may be wrong, but I will check with Mrs. Grothar later to see if I am. She always lets me know for sure.
There has been 4000 flights canceled so far in northern Europe
Link
The MDR is already on pair with June of last year, and its April!
Icelandic volcanic ash alert grounds UK flights
Posted on Thu, 04/15/2010 - 08:00 in World News
(BBC): All flights in and out of the UK have been suspended as ash from a volcanic eruption in Iceland moves south. Safety body Eurocontrol said up to 4,000 flights across northern Europe would be cancelled on Thursday. The air traffic control service (Nats) said no flights would be allowed in or out of UK airspace until 1800BST amid fears of engine damage. The airspace restriction was the most significant in living memory, a spokesman said. Nats suggested that the restrictions were unlikely to be lifted after 1800, saying it was "very unlikely that the situation over England will improve in the foreseeable future".
Nino 3
Nino 3.4
Nino 4
All as of yesterday show Cold-neutral / La Nina into Peak hurricane season, continuing on to January 2011.
Amazing what a pint sized ash cloud and a Polar Jet can due to N Europe. Hopefully conditions improve quickly!
NOAA’s GOES-13 spacecraft today became the official GOES-EAST satellite, perched 22,300 miles above the equator in a prime location to spot potentially life-threatening weather affecting the eastern half of the nation, including tropical storm activity in the Atlantic Ocean and Gulf of Mexico.
This is an image of what the ash cloud must look like from the inside. Should be gone in a few days. At this time, the experts say it may not have that much effect on the weather.
NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD
830 AM EDT THU APR 15 2010
ATMOSPHERIC CONDITIONS ARE NO LONGER CONSISTENT WITH EL NINO AS THEY WERE AS RECENT AS MARCH. THIS IS TRUE EVEN IN THE TROPICS.
PROGNOSTIC DISCUSSION OF SST FORECASTS
BIAS-CORRECTED FORECASTS FROM THE NCEP CLIMATE FORECAST SYSTEM (CFS) DYNAMICAL COUPLED OCEAN-ATMOSPHERE MODEL INDICATE THAT THE NINO 3.4 SST ANOMALY WILL FALL BELOW +0.5 C DURING MJJ 2010. THE CPC SST CONSOLIDATION FORECAST (AN OBJECTIVE, SKILL WEIGHTED COMBINATION OF THE CFS AND THREE STATISTICAL SST FORECASTS) ALSO TERMINATES THE PRESENT EL NINO. WHAT HAPPENS AFTER THAT IS UNCERTAIN. CFS SHOWS MILDLY COLD CONDITIONS TO DEVELOP BUT NO CLEAR LA NINA BY THE -0.5 C CRITERION. CCA AND MRK STAY ON THE WARM SIDE NEAR +0.5. ONLY THE CONSTRUCTED ANALOGUE GOES FOR A CLEAR LA NINA (10 OUT OF 12 MEMBERS DO SO) FROM LATE SUMMER ONWARD. SEVERAL OTHER MODELS RAN ELSEWHERE, SEE IRI PLUME, START TO HINT INCREASINGLY AT A LA NINA POSSIBILITY FOR NEXT WINTER. AT THIS TIME THE CPC CONSOLIDATED FORECAST IS NEAR NEUTRAL FOR THE NEXT 12 MONTHS.
Yep, supposed to be high enough altitude to cause little worries. Nice, sunny, and a little cool. Ash cloud won't go this far for a few hours yet, though.
At least it's a bit more novel of an explanation for airport closure than strikes or such else.
Earthquake Details
Magnitude
3.2
Date-Time
Thursday, April 15, 2010 at 13:22:38 UTC
Thursday, April 15, 2010 at 08:22:38 AM at epicenter
Location
34.789°N, 96.388°W
Depth
10.3 km (6.4 miles) (poorly constrained)
Region
OKLAHOMA
Distances
10 km (6 miles) SSE (168°) from Allen, OK
10 km (6 miles) WSW (240°) from Gerty, OK
19 km (12 miles) SSW (194°) from Atwood, OK
26 km (16 miles) E (84°) from Ada, OK
130 km (81 miles) SE (126°) from Oklahoma City, OK
224 km (139 miles) N (9°) from Dallas, TX
Most of the cloud is moving away from Iceland and very little ash is expected to fall. The biggest concern in Iceland is the flash-flooding because of the melting of the glaciers caused by the eruption. Hard to tell but the horse in the picture does not appear to be an Iclandic. They are usually much smaller. With most of it under water, it is hard to tell.
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