2013 Steering Pattern / Early indicators

[CrazyC83]

I think this season will be much like the last few.

But 19 storms for a 4th straight year? Who knows.

[TheStormExpert]

I still think we will have that persistent East Coast Trough again like we've had the last 3 seasons. Which is why the East Coast especially the Northeast U.S. will have a heightened storm risk like the last 2 seasons.

[cycloneye]

If the CFSv2 model is right,the Sahel region will be with plenty of moisture that helps to fuel the waves as they emerge West Africa. This forecast is for August.

[cycloneye]

Very significant difference in the March European forecast of mean sea level pressure anomaly across the Atlantic Basin vs. March of 2012. Last year, the Euro was forecasting very high pressures across the deep tropics (and most storms formed in the subtropics). This year, pressures are forecast to be nearly normal. That would suggest a greater risk of major activity in the Caribbean/Gulf.

Forecast from March of 2012 for July-September:
http://home.comcast.net/~cgh57/2012.gif

Forecast from March of This Year:
http://home.comcast.net/~cgh57/2013.gif

The ECMWF Ensemble Mean is up and also has normal pressures for July August and September and that reinforces what you said.



http://www.ecmwf.int/products/forecasts ... 0summary!/

[Hurricaneman]

Atlantic Instability March 15 2013

Gulf of Mexico: Average -8 Current -15 which is 7 below normal instability

Caribbean: Average 0 Current -4 which is 4 below normal instability

East Coast: Average -11 Current -15 which is 4 below normal instability

Tropical Atlantic: Average -6 Current -9 which is 3 below normal instability

Subtrop Atlantic: Average -9 Current -10 which is 1 below normal instability

The accumulitive nuimber around the basin below normal is 19 which is something to watch, but if this doesnt change much I may start the numbers poll with low numbers and change them if this changes

I do have a question though, how were 2005s instability numbers compared to this year to date

[TropicalAnalystwx13]

Vertical instability naturally runs below normal during this part of the year because high pressure dominates the basin and there aren't many disturbances, if any, to moisten the atmosphere.

2005:



Note it was below-average as well.

[Riptide]

[cycloneye]

Here is the latest about the instability in the Tropical Atlantic. It looks near normal in the MDR at this point.

[cycloneye]

Thanks to the negative NAO that is dominating for the past few weeks the Tropical Atlantic waters are above average. Here is a comparison from January 19 vs March 16. I have to point out that the Gulf of Mexico is cooler on March 16 than on January 19 but that is understandable because of the cooler temperatures that the GOM has been thru.

January 19



March 16

[Hurricaneman]

Atlantic Instability March 20 2013

GOM: Average -8 Current -5 which is 3 above normal instability

Caribbean: Average 0 Current -3 which is 3 below normal instability

East Coast: Average -10 Current -9 which is 1 above normal instability

Tropical Atlantic: Average -7 Current -8 which is 1 below normal instability

Subtrop Atlantic: Average -9 Current -9 which is normal instability

The accumulitive atlantic instability is right at normal

[cycloneye]

Atlantic Instability March 20 2013

GOM: Average -8 Current -5 which is 3 above normal instability

Caribbean: Average 0 Current -3 which is 3 below normal instability

East Coast: Average -10 Current -9 which is 1 above normal instability

Tropical Atlantic: Average -7 Current -8 which is 1 below normal instability

Subtrop Atlantic: Average -9 Current -9 which is normal instability

The accumulitive atlantic instability is right at normal

http://www.ssd.noaa.gov/PS/TROP/TCFP/index.html

How the Tropical Atlantic vertical instability looks in the graphic.

[TropicalAnalystwx13]

A lot of disagreement between vertical instability charts for the eastern Atlantic.

Either way, vertical instability is doing good for this time of the year. It usually starts climbing between mid-March and mid-April. We'll see if that trend starts and continues...if it does, we should see normal values this year.

[cycloneye]

The area of convection well SSE of the CV islands has persisted all day (March 21rst) but is very early for strong tropical waves to be around.For sure it will vanish in the next 6-12 hours but with the waters above average in the Eastern Atlantic,it may be a signal that may not be a surprise to see some early waves in the area.

http://www.yr.no/satellitt/afrika.html

[OuterBanker]

Poof factor positive? I looks like the waters directly off the African coast have been consistently warmer this winter into early spring. I can't remember if last year was cooler or warmer this time of year, but we all know that they were cooler during the height of the season. There were countless large well-formed waves over Africa last year that simply went poof as soon as they hit the cooler waters. If these waters stay normal to above average it will no doubt have an effect on early developing long tracking CV storms. Especially if the models that are predicting a moist Sahel region during the season come true.

BTW, thanks for that wonderful link Cycloneye. What a great site.

http://www.yr.no/satellitt/afrika.html

[TropicalAnalystwx13]

Poof factor positive? I looks like the waters directly off the African coast have been consistently warmer this winter into early spring. I can't remember if last year was cooler or warmer this time of year, but we all know that they were cooler during the height of the season. There were countless large well-formed waves over Africa last year that simply went poof as soon as they hit the cooler waters. If these waters stay normal to above average it will no doubt have an effect on early developing long tracking CV storms. Especially if the models that are predicting a moist Sahel region during the season come true.

BTW, thanks for that wonderful link Cycloneye. What a great site.

http://www.yr.no/satellitt/afrika.html

Sea surface temperatures in the eastern Atlantic this time last year were well below average:

[Hurricaneman]

The atlantic also has the tri-pole water temp profile where the tropics are above normal, subtropics are below normal and the polar regions are above normal which in most instances lead to a high concentration of storms in the MDR into the Caribbean which leads to a much higher chance of landfalling storms which is something to really keep an eye on as the spring progresses

[cycloneye]

The atlantic also has the tri-pole water temp profile where the tropics are above normal, subtropics are below normal and the polar regions are above normal which in most instances lead to a high concentration of storms in the MDR into the Caribbean which leads to a much higher chance of landfalling storms which is something to really keep an eye on as the spring progresses

Here is a good graphic that shows well the tripole.

[cycloneye]

The Tropical Atlantic is trending warmer in past few days but will it persist this way as the hurricane season arrives and gets to the peak?



http://www.tropicaltidbits.com/analysis/

[TropicalAnalystwx13]

February featured an above-average amount of precipitable water across much of the Atlantic, especially the eastern Atlantic. I think the vertical instability graphs may be a bit misleading.

[Hurricaneman]

Atlantic instability March 25 2013

GOM: Average -8 Current -18 which is 10 below normal instability

Caribbean: Average 0 Current -1 which is 1 below normal instability

East Coast: Average -11 Current -9 which is 2 above normal instability

Tropical Atlantic: Average -7 Current -7 which is normal instability

Subtrop Atlantic: Average -9 Current -10 which is 1 below normal instability

Overall instability numbers for the entire atlantic is 10 below normal instability

I know this time of year the east coast and GOM are going to be variable until May so those 2 areas are given less creedence until then