El Niño is done; Haiti at risk of heavy rains next week; oil spill update
El Niño rapidly weakened during late April and early May, with sea surface temperatures over the tropical Eastern Pacific in the area 5°N - 5°S, 120°W - 170°W, also called the "Niña 3.4 region", falling a significant 0.65°C in just one month. Temperatures in the region are now in the "neutral" range, just 0.18°C above average, and well below the 0.5°C threshold to be considered an El Niño, according to the Australian Bureau of Meteorology. The speed of the collapse of El Niño makes it likely that a La Niña event is on its way this summer. This is what happened during the last strong El Niño event, in 1998--El Niño collapsed dramatically in May, and a strong La Niña event developed by hurricane season. Six of the sixteen El Niño models (updated as of April 15) are predicting La Niña conditions for hurricane season, and I expect more models will jump on the La Niña bandwagon when the May data updates later this week. The demise of El Niño, coupled with sea surface temperatures in the tropical Atlantic that are currently at record levels, have prompted two major hurricane forecasting groups (tropicalstormrisk.com and Colorado State University) to predict a significantly above average 2010 Atlantic hurricane season. Over the full 160-year period we have records of Atlantic hurricanes, La Niña years have typically had more hurricanes, and more strong hurricanes, compared to neutral years. However, since 1995, there hasn't been any difference between neutral and La Niña years in terms of hurricane activity. La Niña conditions typically cause cool and wet conditions over the Caribbean in summer, but do not have much of an impact on U.S. temperatures or precipitation.
Figure 1. Oil spill edge over the Gulf of Mexico on Wednesday, May 19, as seen from NASA's M ODIS instrument. Note that a band of cumulus clouds formed along the edge of the oil spill. I theorize this is because the low level wind flow out of the southeast moves faster over the oil, since the oil suppresses wave action. As the winds cross the spill boundary into rougher, clean water, they slow down, forcing the air to pile up and create updrafts that then spawn cumulus clouds. See my post on what oil might do to a hurricane for more information on how oil reduces wave action.
Oil spill update
Clouds over the Gulf of Mexico have again foiled satellite imaging of the extent of the Deepwater Horizon oil spill, though through breaks in the clouds it appears that a significant amount of the oil that was pulled southwards towards the Loop Current is now caught in a counter-clockwise rotating eddy just to the north of the Loop Current. However, some oil has escaped this eddy and is on its way south towards the Florida Keys. According to the latest trajectory forecasts from NOAA, the tongue of oil flowing southwards has at most "light" concentrations. The oil will grow more dilute as it travels the 500 miles to the Florida Keys. My present expectation is that the oil entering the Loop Current this week will cause only minor problems in the Keys next week. However, there is a lot of uncertainty about what the oil may do to the fragile Keys ecosystem. See my post yesterday for answers to many of the common questions I get about the spill.
Oil spill resources
My post on the Southwest Florida "Forbidden Zone" where surface oil will rarely go
My post on what oil might do to a hurricane
NOAA trajectory forecasts
Deepwater Horizon Unified Command web site
Oil Spill Academic Task Force
University of South Florida Ocean Circulation Group oil spill forecasts
ROFFS Deepwater Horizon page
Surface current forecasts from NOAA's HYCOM model
HYCOM ocean current forecasts from LSU
Figure 2. Precipitation forecast from today's 8am EDT run of the NAVY NOGAPS model, valid 7 days from now. Precipitation amounts in excess of 70 mm (2.8") in 12 hours are predicted over Haiti, due to a tropical disturbance in the Western Caribbean. Image credit: U.S. Navy.
Potential serious rainfall threat to Haiti next week
Long-range forecasts from the GFS and NOGAPS models over the past few days have consistently been predicting an increase in moisture and decrease in wind shear over the Western Caribbean 5 - 7 days from now, and I expect that a tropical disturbance with heavy rains will develop in the Western Caribbean early next week. A strong subtropical jet stream over the southern Gulf of Mexico will steer the disturbance to the north and east, and the NOGAPS model shows heavy rains in excess of six inches impacting Haiti Wednesday through Thursday of next week. Rains of this magnitude are capable of causing a serious emergency with high loss of life in earthquake-shattered Haiti, and all interests in that nation should closely monitor the situation over the coming week. It is too early to speculate on the possibility of the disturbance becoming a tropical depression. The wunderblogs of StormW and Weather456, who are now featured bloggers for the coming hurricane season, have more information on this potential development, plus the possible development of a subtropical storm between Florida and Bermuda next week.
Major severe weather outbreak over Oklahoma expected tonight
NOAA's Storm Prediction Center has put much of Oklahoma in its High Risk region for severe weather today, warning that "The setup appears most favorable for large, relatively slow moving intense storms with large hail. A couple strong tornadoes also may occur."
I'll be back with a new post Thursday morning.
Jeff Masters
Reader Comments
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Just updated a few minutes ago...
The whole basin is above normal:
Today:
AOI
AOI
AOI
AOI
That's text book there.. No wonder the models have differed so. What a volitile moment to be trying to forecast the loop current. Wonder which side most the oil swept down that way ended up on.. Maybe we'll get a good sat pass today.
Slightly cooling Atlantic SST's due to a stronger than normal high (for the moment).
Its amazing how quickly the El Nino has collapsed, I wouldn't be surprised if by mid this year there's a moderate La Nina.
Another concern is low pressure development in the southern Caribbean. The CMC and NOGAPS show development of a strong tropical storm while the GFS and ECMWF only hint at that possibility. The GFS and CMC move it northward while the NOGAPS moves it in a more northeast fashion. I place development chances at moderate.
I would consider using the NAM since this is more of a subtropical storm
Indeed, looks that way.
Yes, the NAM was the best model for coastal storms last winter. So I guess you could consider this a variation of a coastal storm, but that may be a bit of a stretch. Either way, it should be interesting to see how it handles it in the coming runs.
Interesting
Closed low in 24 hours.
?
So it appears that a bunch of that oil now being pulled into the Loop Current may become trapped in that eddy as it breaks off and drift West to Texas beaches instead of Florida. It is looking like everyone will get to share BP's love.
Here is a discussion on the Loop Current by Dr. Masters that I found with Google... The Gulf of Mexico Loop Current: A Primer
Maybe we will get some better model support today for the "upcomming" storms.
or it could be ash... either or ...
http://www.sat24.com/Eyjafjallajokull-volcano.aspx
500 mb heights (color) vs MSLP.
Got past the colostrum, do we? could be, I suppose. (but what do I know?)
Cant see the image, close low where?
Morning...which storms are you referring to. Storms over Texas or storms in the Atlantic?
LONG TERM...SUN-WED. GFS REMAIN CONSISTENT SHOWING SFC HIGH
PRESSURE WELL NE OF THE AREA AND A LOW PRESSURE AT SFC AND ALOFT E
OF THE BAHAMAS. THIS WILL CONTINUE THE ELY LLVL FLOW FOR THE AREA.
HOWEVER...SOLUTIONS DIFFER WITH REGARD TO TIMING OF INCREASED
MEAN LAYER MOISTURE FOR THE AREA. IN GENERAL...EXPECT RAIN CHANCES
TO GRADUALLY INCREASE EACH DAY AS THE ASSOCD MID AND UPPER LEVEL LOW
NE OF THE BAHAMAS RETROGRADES TOWARD THE SE U.S. COAST BUT WILL KEEP
POPS CAPPED AT 30%. TSTMS CHANCES MAY BE ONLY SLIGHT GIVEN COOLER
AFTERNOON HIGHS IN THE LOWER TO MID 80S. AT THE LEAST...BREEZY
COASTAL NE WINDS WILL DEVELOP TUE AND WED IF MODELS SOLUTIONS ARE
CORRECT.
here
NE of Bahamas
The STS off te SE coast and the Carrib low. Looks as if the STS may have more model support.
I'm doing well. Better than ever...and busier than a bee here at home.
tornadodude and his friend, last I heard, had decided to end their chase mission which is roundly viewed as a total success...and head for home.
They should get home today.
Well done, young men! Your work out in the field this past week has been stellar! :)
Assuming they do actually stop the oil fairly soon, any oil that gets "trapped" by the loop current eddy would not make it to Texas for months...likely nothing left to foul TX beaches...
Excerpts:
CFS PREDICTS COLD CONDITIONS TO DEVELOP, REACHING THE NOMINAL -0.5 C CRITERION FOR LA NINA CONDITIONS JUST AFTER MJJ 2010. CFS PREDICTS NINO 3.4 SST ANOMALIES TO HOLD AT ABOUT -0.6 C THROUGH ASO 2010, AND THEN COOL TO BELOW -1.0 C JUST AFTER SON 2010.
THE TEMPERATURE OUTLOOK FOR JJA 2010 INDICATES THAT THE CHANCES OF BELOW NORMAL TEMPERATURES ARE ELEVATED OVER THEIR CLIMATOLOGICAL PROBABILITY FOR MUCH OF THE GREAT PLAINS AND GREAT LAKES REGIONS. ABOVE NORMAL TEMPERATURES ARE FAVORED FOR CENTRAL AND SOUTHERN SECTIONS OF THE INTERIOR WEST, INTERIOR ALASKA, THE GULF COAST, AND SECTIONS OF THE SOUTHEAST.
THE PRECIPITATION OUTLOOK FOR JJA 2010 INDICATES INCREASED CHANCES FOR ABOVE-MEDIAN PRECIPITATION FROM OKLAHOMA THROUGH THE DAKOTAS, THE GULF COAST, AND FLORIDA (BASED ON THE CAS). THE PREDICTION OF ENHANCED LIKELIHOOD OF ABOVE MEDIAN PRECIPITATION IN THE CENTRAL PLAINS HAS SOME SUPPORT FROM CON, CFS, IRI, ECP, AND CAS. THE DRY SIGNAL IN THE NORTHWEST IS BASED ON CON, WHICH IS DOMINATED BY TREND THERE.
Feeling a bit more confident in a hybrid low in the SW Atlantic this morning. Whether it gets named or not is anyone's guess, but the Euro appears to be showing it deepening due to convective processes.
SST's in the area are in the mid-upper 70s.
Correct. And more models foresee something along the lines of 60 mph or greater.
I do not think the SW Carib disturbance will surpass 50 mph.
Predicting below normal activity in the Central Pacific, likely due to La Nina.
That is unfortunately a very big assumption at this point.
TWOs now to the nearest 10%
The genesis forecasts for the risk of tropical cyclone development will be provided to nearest 10 percent, in both the text and graphical Tropical Weather Outlooks. In previous years, only risk categories (low/medium/high) were given.
Thanks!
I hope all the rain starved people along the east coast get some much needed rain but nothing worse.
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