From a record-breaking extremely strong El-Nino last hurricane season, the Atlantic, the EPAC and the Central Pacific this season all were above normal. This was pretty much forecast but Mother Nature fools forecasters all the time. A short summary of the season follows:
For the Atlantic, 2012 was the last time there was an above average season. The Atlantic saw 15 named storms during Hurricane season, 2016. Out of the 15 named storms, the Atlantic basin had 7 hurricanes Alex, Earl, Gaston, Hermine, Matthew, Nicole, and Otto. What surprised many is that out of those 7 hurricanes, 3 of which were major hurricanes – Gaston, Matthew, and Nicole.
Many were wondering would Florida be spared a hurricane this year. After all these years and true to form, Florida had two Tropical Storms – Colin and Julia, and finally, Hurricane Hermine made landfall in Florida, the first since Hurricane Wilma in 2005. The Eastern coast of the US also was battered with South Carolina having landfall with Tropical Storm Bonnie and Hurricane Matthew.
Speaking of Hurricane Matthew, it was the longest-lived storm in the Atlantic and it was also the strongest with maximum sustained winds of 160 MPH, a category 5. Hurricane Matthew made landfall at Haiti, Cuba, and the Bahamas but as a category 4 storm during the trek of the Eastern Caribbean and the Atlantic.
Lest us not forget, there were other storms away from the US. Tropical Storm Danielle visited Mexico, Hurricane Earl in the Belize and lastly, very late in the season Hurricane Otto in Nicaragua.
So, how do we get a better feel of the hurricane season activity for this year? One method called [tooltip title=”ACE” content=”Accumulated Cyclone Energy” type=”info” ]ACE[/tooltip] Index. ACE Index is using a sum of the energy accumulated with all the cyclones (tropical storms, sub-tropical storms and hurricanes) that happened to form within the hurricane season. Calculating ACE is done by using the square of the the wind speed every six hours during the storm’s lifetime. Remember, a tropical depression is below 35 knots and it is not added. Hence, a cyclone that is longer lived will have a higher ACE indices verses a shorter lived cyclone which will have a lower ACE indices. ACE indices of a single cyclone is windspeed (35 knots or higher) every six hour intervals (0000, 0600, 1200, 1800 [tooltip title=”UTC” content=”Coordinated Universal Time (UTC) is the primary time standard by which the world regulates clocks and time.” type=”info” ]UTC[/tooltip]) or ACE = 104 kn2.
Total ACE:
$latex \Sigma = \frac{Vmax^2}{10^4} \ &s=2\ $
* Vmax is estimated sustained wind speed in knots. *
An average seasonal ACE in the Atlantic is between 105-115 or a mean average of 110.
2016 Atlantic ACE
Tropical Cyclone Name
Max Wind Speed (in Knots)
ACE 104 kn2
Alex *
75
4.1725
Bonnie *
40
0.1055
Colin
50
1.1350
Danielle *
40
0.4050
Earl
65
1.5450
Fiona *
45
3.0275
Gaston
105
24.2925
Hermine
70
3.0925
Ian
55
2.9575
Julia
35
1.2250
Karl
60
5.8150
Lisa
45
2.2600
Matthew
140
47.9950
Nicole
115
25.2075
Otto
95
6.1600
——–
ACE Total:
132.4350
Please note: Those with red asterisks have Tropical Cyclone Reports versus the Operational Advisories. The TCR’s are more comprehensive in detail. Those without the red asterisks will have the TCR’s in time. The ACE Index numbers may change with each TCR. I will try to update this post at that time.
The 2014 Atlantic basin hurricane season will officially end just before the stroke of midnight Sunday, November 30th.
This will be a record breaking season as it has been nine years since a major hurricane (category 3 or higher) made landfall along the U.S. coastlines. Hurricane Wilma in 2005 was the last one to do so. Not that anyone wants a major hurricane on their doorstep but it is very unusual to have a nine-year period without a major hurricane reaching the U.S. soil. This year, the Atlantic basin had eight named storms, six of them becoming hurricanes. Two became majors, Hurricane Edouard was a category 3 but far out in the Atlantic and Hurricane Gonzalo briefly became a category 4 but weakened to a category 2 as it clobbered Bermuda.
Major Hurricane Edouard
Major Hurricane Gonzalo
Hurricane Arthur was the only storm to make U.S. landfall as it hit North Carolina as a Category 2 storm and winds of 100 MPH. Hurricane Arthur was also the strongest U.S. landfall since Hurricane Ike hit Texas on 2008.
Hurricane Arthur
So what happened this season? Most tropical disturbances form as they come off the coast of Africa or in the Central Atlantic (also know as the MDR or Main Development Region). This year there were a few inhibiting factors such as dry air, strong vertical wind shear, and a lot of sinking air.
Dry air and SAL were some of the reasons development was very difficult during the beginning and middle of the season. The SAL or Saharan Air Layer inhibited development of tropical waves. The vertical wind shear causes winds blowing from opposite directions to possibly rip a storm apart or temporarily pause any further development. Sinking air or convergence will not allow thunderstorms to rise which is essential for tropical cyclone development.
In the latter portion of the season, there were a few storms that did develop, some due to the MJO. The MJO allowed upward motion allowing thunderstorms to develop.
Although early indicators did seem that a El Niño was forecast to develop but although temperatures in the Pacific were higher than the norm and the atmosphere did not follow along. The forecasted El Niño never did come to fruition and never was an inhibiting factor and had little impact in tropical cyclone development in the Atlantic.
In the Eastern Pacific (EPAC) and the Central Pacific was just the opposite and tropical cyclone activity was extremely busy. The Pacific had weak vertical shear, and unstable air, the Pacific was the busiest in several decades. The East & Central Pacific had 6 tropical storms and 16 hurricanes, nine of them majors. Mexico was hit several times, Hurricane Odile being the worst. Hurricane Odile made landfall near Cabo San Lucas with winds of 125 mph. Even Hawaii was threatened by 3 tropical cyclones, with Hurricane Ana just south of the Big Island. Hawaii was also hit by Hurricane Iselle, the first hurricane for Hawaii to have landfall since Hurricane Iniki in 1992.
Hurricane Odile in the Pacific
Not to be outdone, the Western Pacific also is having a very busy season. In fact Tropical Depression Twenty Two-W is forecast to be a Typhoon and possibly may hit the Philippines (again). As of this date, the Western Pacific has had 21 named storms, 10 Typhoons, seven of them Super Typhoons (unofficially). The strongest was Super Typhoon Vongfong with maximum sustained winds of 130 MPH. Note: Once Vongfong had moved into the are of the Philippines, PAGASA (Philippine Atmospheric, Geophysical and Astronomical Services Administration) Vongfong was now under the authority of the Phillipines and renamed Ompong.
Before the 2014 Atlantic hurricane season began, it was touted by most experts to be an “El Niño” year mostly due to some the early indicators. A few things Meteorologists monitor when it comes to tropical development in general include: Wind Shear strength, Sea Surface Temperatures/Deep Sea Temperatures, measuring of the SOI (Southern Oscillation Index) in the case of an El Niño or La Niña, and the MJO (Madden Julian Oscillation). A simplified description of an El Niño is basically an area in the Pacific Ocean that begins to warm up to more than above average sea surface temperatures. An El Niño can cause strong winds to blow eastward over Mexico and help shear off the cloud tops of thunderstorms. This helps to reduce both the number and the intensity of tropical storms and hurricanes that might be trying develop in the Atlantic. Between February-May, just before the hurricane season would begin, there were a series of Equatorial [tooltip title=”Kelvin waves” content=”Kelvin wave, in oceanography, an extremely long ocean wave that propagates eastward toward the coast of South America, where it causes the upper ocean layer of relatively warm water to thicken and sea level to rise. Kelvin waves occur toward the end of the year preceding an El Niño event when an area of unusually intense tropical storm activity over Indonesia migrates toward the equatorial Pacific west of the International Date Line. This migration brings episodes of eastward wind reversals to that region of the ocean which spawn Kelvin waves. Although such intense tropical storms of the western Pacific are associated with the development of El Niño, they may occur in other years to produce Kelvin waves that also propagate eastward but continue poleward toward Chile and California.” type=”info” ]Kelvin waves[/tooltip] in the Pacific which allowed for the possibility of a moderate to strong El Niño. While the Kelvin waves did transport the higher than normal sea surface heights, the atmosphere did not follow along with the Kelvin waves and the waves eventually faded away. Recently though, two more eastward moving Kelvin waves were seen via the Jason-2 satellite. Will these two Kelvin waves be the precursor for the El Niño? Even if they do, the El Niño would most likely be a weak to moderate one. Courtesy NASA/JPL-Caltech Another possible indicator of an El Niño is that the shift in the SOI has now been in negative territory. Although this is not a true indicator as of yet, the SOI needs to have sustained negative values below −8. Close but no cigar. Courtesy: Australia Bureau of Meteorology ******* For the math minded ******** There are a few different methods of how to calculate the SOI. The method used by the Australian Bureau of Meteorology is the Troup SOI which is the standardised anomaly of the Mean Sea Level Pressure difference between Tahiti and Darwin. It is calculated as follows:
$latex SOI = 10 \frac{(Pdiff – Pdiffav)}{SD(Pdiff)} \ $
where: Pdiff = (average Tahiti MSLP for the month) – (average Darwin MSLP for the month), Pdiffav = long term average of Pdiff for the month in question, and SD(Pdiff) = long term standard deviation of Pdiff for the month in question. The multiplication by 10 is a convention. Using this convention, the SOI ranges from about “35 to about +35, and the value of the SOI can be quoted as a whole number. The dataset the Bureau uses has 1933 to 1992 as the climatology period. The SOI is usually computed on a monthly basis, with values over longer periods such a year being sometimes used. Daily or weekly values of the SOI do not convey much in the way of useful information about the current state of the climate, and accordingly the Australian Bureau of Meteorology does not issue them. Daily values in particular can fluctuate markedly because of daily weather patterns, and should not be used for climate purposes.
*************************************
So what does this mean for this year’s Atlantic hurricane season? Probably not a whole lot. So far there is no empirical evidence either way to back up any claims of a possible El Niño. What is known is that in the Pacific, trains of Tropical cyclones in the Pacific are still developing where as in the Atlantic basin this has been a very slow hurricane season with one tropical storm and four hurricanes, with Hurricane Edouard being a major hurricane, albeit short lived as a major. As the [tooltip title=”Cape Verde” content=”A Cape Verde-type hurricane is an Atlantic hurricane that develops near the Cape Verde islands, off the west coast of Africa. The disturbances move off the western coast of Africa and may become tropical storms or tropical cyclones within 1,000 kilometres (620 mi) of the Cape Verde Islands, usually between July to September. ” type=”info” ]Cape Verde[/tooltip] season is slowly drawing to an end, the remainder of the tropical cyclone development (if any) will most likely be in the Western Caribbean and the Gulf of Mexico with the possibility of development closer to the U.S. Eastern coast. It would be foolish for me to to postulate whether the rest of the Atlantic hurricane season will continue to be as slow as it has been and whether the forecasted El Niño has been the cause (whether it is classified or not). As a stated in an earlier post:
So, how do we get a better feel of the hurricane season activity for this year? One method called [tooltip title=”ACE” content=”Accumulated Cyclone Energy” type=”info” ]ACE[/tooltip] Index. ACE Index is using a sum of the energy accumulated with all the cyclones (tropical storms, sub-tropical storms and hurricanes) that happened to form within the hurricane season. Calculating ACE is done by using the square of the the wind speed every six hours during the storm’s lifetime. Remember, a tropical depression is below 35 knots and it is not added. Hence, a cyclone that is longer lived will have a higher ACE indices verses a shorter lived cyclone which will have a lower ACE indices.  ACE indices of a single cyclone is windspeed (35 knots or higher) every six hour intervals  (0000, 0600, 1200, 1800 [tooltip title=”UTC” content=”Coordinated Universal Time (UTC) is the primary time standard by which the world regulates clocks and time.” type=”info” ]UTC[/tooltip]) or ACE = 104 kn2. Total ACE: $latex \Sigma = \frac{Vmax^2}{10^4} \ &s=2\ $ * Vmax is estimated sustained wind speed in knots. * An average seasonal ACE in the Atlantic is between 105 -115 or mean average of 110. Although technically we are in a Neutral state, this season “almost” seems more like a El Nino year. An El Niño tends to hinder tropical cyclone development in the Atlantic, due to higher amounts shear. But in a true El Niño year, you normally will have a very active season in the East Pacific (EPAC), with a few major hurricanes, and a subdued Atlantic.
In the figure below, as of this time frame, the ACE Index for this year is actually lower than last years (36.1200). That said, there is still October and November for the possibility of Tropical Cyclone development. If any Tropical Cyclones do develop, I will add them into the ACE Index accordingly. Secondly, the ACE Index numbers in the chart are from the Operational Advisories. The numbers may change when the Tropical Cyclone Reports are released. A blue asterisk will be placed next to a Storm name when a TCR has been issued. Addendum: As of 10/11/14, 0000 UTC advisory with Tropical Storm Fay, the ACE Index has now surpassed last years ACE. In addition, recently developed Hurricane Gonzalo now a category 4 hurricane, the ACE Index will continue to rise significantly. This the first time in the Atlantic basin there has been a category hurricane 4 since Ophelia in 2011.
2014 Atlantic ACE
Tropical Cyclone Name
Max Wind Speed (in Knots)
ACE 104Â kn2
Arthur *
85
6.9475
Bertha *
70
5.5175
Cristobal *
75
7.9225
Dolly
45
0.8050
Edouard *
105
15.6325
Fay *
70
3.5600
Gonzalo *
125
25.9725
Hanna *
35
.2450
——–
ACE Total:
66.6025
As always, please be sure to use the official information from the NHC or your local NWS. Although care has been taken in preparing the information supplied through the Weather or Knot blog, Weather or Knot does not and cannot guarantee the accuracy of it. I am not a professional meteorologist and this post is prepared purely for entertainment purposes.
The tropical disturbance that has been slowly moving westward and heading toward the Caribbean has been designated by the [tooltip title=”NHC” content=”National Hurricane Center” type=”info” ]NHC[/tooltip] as Invest 96L as of 08_19/1800Z. This tropical disturbance was one of the waves that came of the edge of Africa but due to the very very air and some vertical shear, 96L never had a chance to try to develop into something tropical. The dry air and shear are abating and with an ULL to the NW of 96L, increased upper divergence is now allowing 96L to ventilate and possibly have an outflow for further development. I want to make it extremely clear that although 96L is looking much better, it is still way to early to determine exactly what the track and intensity of 96L will be. There has also been some discussion as to whether or not Invest 96L(pouch P17L) and Pouch 18L which is just east of Invest 96L and will the two be two separate entities or merge into one system. Again it is still too early as both disturbances are still somewhat disorganized right at the moment albeit 96L is slowly getting organized.
Satellite imagery of 96L
Credit: NOAA Satellite Services Division
Pouch Map
Invest 96L is presently heading westward at around 15 MPH, and is being steered in the region of southern periphery of the subtropical ridge. If 96L continues the same speed, within 72-84 hours 96L should begin the feel a weakness in the ridge and head slightly WSW. This weakness in the ridge should be near or around the edge of the Bahamas or possibly a little later. Since 96L is still a tropical disturbance and has not even become a tropical depression, there are still too many variables so I want to exercise caution and not get ahead of ourselves and not make assumptions in what the forecast holds in the during the next 48-72 hours. If 96L continues to organize during the next day or so, an upper level anticyclone may park itself over 96L which should allow further intensification.
It would be unwise and irresposible for me to post any of the model forecasts, both track and intensity of 96L, at least for the time being. The different models are nothing but a tool for the hurricane specialists, nothing more, nothing less. I understand many want to see the different models, but the models change, sometimes with major shifts. People need to understand that the models have to taken with a grain of salt. Unless you have the skills in meteorology, be very careful as this inaccurate information has a snowball effect and causes a major headache for the NHC. When it looks as if the models begin to have a consensus, then I may post them. For now, will only post satellite imagery and any other graphics that might be useful.
Although care has been taken in preparing the information supplied through the Weather or Knot blog, Weather or Knot does not and cannot guarantee the accuracy of it. If you require an official forecast please contact your local National Weather Service Office or the National Hurricane Center.
A tropical wave that came off the coast of Africa a few days near the Cape Verde Islands was designated as 93L by the [tooltip title=”NHC” content=”National Hurricane Center” type=”info” ]NHC[/tooltip] yesterday afternoon. With the exception of Hurricane Arthur, this is the first significant wave with a “possibility” of development. Previous waves were pretty much not given a chance to develop due to [tooltip title=”SAL” content=”Saharan Air Layer” type=”info” ]SAL[/tooltip] and upper level winds.
During the early morning hours, 93L is somewhat disorganized but has been a slowly progressing in getting some deep convection which is extremely vital for tropical cyclone development. If fact during the day today, 93L has much better organized since earlier this morning. 93L is far enough south of the SAL and at least for the time being, is not a factor although 93L is still attached to the [tooltip title=”ITCZ” content=”Intertropical Convergence Zone – Area encircling the earth near the equator where the northeast and southeast trade winds come together.” type=”info” ]ITCZ[/tooltip]. Both the two major models, the GFS and the ECMWF model camps are forecasting to build an anti-cyclone over over 93L as it tracks westward toward the Lesser Antilles. This should allow relaxation of the upper level winds and possibly let further consolidation of the entire system.
Satellite photo of Invest 93L
Credit: American Weather Model Center
GFS Model 1800z at 135 hours
Credit: American Weather Model Center
ECMWF Model 1800z at 120 hours
Credit: American Weather Model Center
The GFS and the ECMWF seem to want to 93L to develop into at least a tropical depression some time later in the week, the ECMWF is a bit faster than the GFS and even the UKMET. Currently, 93L is tracking westward (with a slight north of west) and this movement should continue for the next 3-4 days. Although the global models may feel there is weakness in the ridge along with a trof over the east coast of the US, this should enough to allow 93L to turn WNW then NW before entering the area just east of the Northern Leeward Islands. The ECMWF though is faster and goes through the islands before turning NW. Guidance at this point in time would be sheer speculation. If factors such as shear, SAL, etc. occur, then those factors could alter the steering currents. Although this seems unlikely, anything is possible in the tropics.
All those in the Great Antilles to the Leeward Islands need to monitor 93L closely for any significant changes in both the track and the possibility of early development of a tropical cyclone.
Remember, always stick with official information such as your local WFO and the NHC.
Although the 2013 Atlantic hurricane season has not yet concluded and we still have November to contend with before the season will officially be over, all indicators are beginning to make it obvious that the end of the show is near. If you recall in my July hurricane season forecast , all signals were looking for an active season. All the criteria seemed to fit but for some unknown reason, a big piece of the puzzle has alluded forecasters as to why this years hurricane season was very, very below normal. Yes, the Atlantic basin did have a total of 13 named storms, so in one sense the season has been “active” but there were only 2 hurricanes and both were minimal category 1 hurricanes. However, 13 named storms does really cannot tell the whole story.
So, how do we get a better feel of the hurricane season activity for this year? One method called [tooltip title=”ACE” content=”Accumulated Cyclone Energy” type=”info” ]ACE[/tooltip] Index. ACE Index is using a sum of the energy accumulated with all the cyclones (tropical storms, sub-tropical storms and hurricanes) that happened to form within the hurricane season. Calculating ACE is done by using the square of the the wind speed every six hours during the storm’s lifetime. Remember, a tropical depression is below 35 knots and it is not added. Hence, a cyclone that is longer lived will have a higher ACE indices verses a shorter lived cyclone which will have a lower ACE indices.  ACE indices of a single cyclone is windspeed (35 knots or higher) every six hour intervals  (0000, 0600, 1200, 1800 [tooltip title=”UTC” content=”Coordinated Universal Time (UTC) is the primary time standard by which the world regulates clocks and time.” type=”info” ]UTC[/tooltip]) or ACE = 104 kn2.
Total ACE:
$latex \Sigma = \frac{Vmax^2}{10^4} \ &s=2\ $
* Vmax is estimated sustained wind speed in knots. *
An average seasonal ACE in the Atlantic is between 105 -115 or mean average of 110. Although technically we are in a Neutral state, this season “almost” seems more like a El Niño year. An El Niño tends to hinder tropical cyclone development in the Atlantic, due to higher amounts shear. But in a true El Niño year, you normally will have a very active season in the East Pacific (EPAC), with a few major hurricanes, and a subdued Atlantic.
2013 Atlantic ACE
Tropical Cyclone Name
Max Wind Speed (in Knots)
ACE 104Â kn2
Andrea
55
1.6175
Barry
40
0.7625
Chantal
55
2.4800
Dorian
50
2.5725
Erin
40
1.5450
Fernand
50
0.6550
Gabrielle
55
1.8150
Humberto
80
8.9375
Ingrid
75
4.9000
Jerry
45
1.9450
Karen
55
2.2675
Lorenzo
45
1.6200
Melissa
55
3.4725
No-Named Storm (AL152013)
45
1.4000
——–
ACE Total:
36.1200
As part of the post-season review, the low pressure system in December(AL152013) was classified as a subtropical cyclone and the ACE Index has been updated to reflect the ACE numbers during it’s short lived status as a subtropical cyclone.
Two notes of interest: One is that of the two hurricanes this year, Humberto was just hours from beating the record for the latest first Atlantic hurricane of the season. Secondly, this will be the 8th year in a row where the Atlantic hurricane season has not had a major hurricane (category 3 or higher). In fact, 10/24/2013 was the 8th anniversary when Hurricane Wilma made landfall on the southwestern side of Florida as a Category three hurricane and headed northeastward and the areas of the Miami-Dade, Broward, and Palm Beach counties were impacted with category two winds. If by at the end of this year hurricane season with no major hurricanes, we will tie the record.
So is there a last hurrah for one or two more storms or is it time to fold the tents and call the season over? Technically, no as the hurricane season does not oficially end until November 30. This does not mean a cyclone cannot develop. It is just that a cyclone developing after the official season is over, is a somewhat rare event, but it is not impossible. Usually any late season storms develop either in the Southwestern Atlantic or more likely in the Caribbean. The two late season cyclones late that come to mind were Sandy (2012) and Mitch (1998). As of yet, it appears that the rest of November will be quiet and although there is a chance development of in the Caribbean due to the [tooltip title=”MJO” content=”Madden Julian Oscillation – lift  or upward motion into the atmosphere allows easier development of a tropical cyclone increased convection/thunderstorms activity.” type=”info” ]MJO[/tooltip], I am somewhat skeptical on that. I won’t rule it out yet but for the moment I just am not convinced this will happen, IMHO.
As always, remember to always keep an eye to the sky and to always stick with official information, either your local [tooltip title=”WFO” content=”Weather Forecast Office” type=”info” ]WFO[/tooltip]Â or the NHC
The 2013 Hurricane season which began June 1st and both the NOAA and ENSO reports are out and the 2013 hurricane season will most likely be a much more active season than the previous years. This hurricane season may be a dangerous one for many in the East Coast of the US, especially the Florida East coast, Florida Keys and the Gulf coast of Florida and possibly even the Caribbean but we will get to that a bit later.
So lets start with the basics of why this season is expected to be different. Beginning with ENSO or El Niño Southern Oscillation. ENSO is a climate pattern in the equatorial Pacific. Many might wonder what does the equatorial Pacific have to do with storms in the Atlantic. Globally, what happens in the Pacific can induce what happens in the Atlantic. Now with ENSO, there are basically three phases. One is a cool stage, another is a warm stage and there is also a neutral stage.
To have a cool stage, abnormal SST’s (Sea Surface Temperature) must have five consecutive overlapping 3-month periods: for example – (June, July, August), (July, August, September), (August, September, October) or more and the abnormal SST’s must be -0.5 degrees Celsius or lower. This also known as an [tooltip title=”La Niña” content=”La Niña is associated with cooler than normal water temperatures in the Equatorial Pacific Ocean” type=”info” ]La Niña[/tooltip]. During an La Nina, abnormal SST’s can allow anticyclones to develop due to convergence (upward motion) which can help induce the possibility of development of a tropical cyclone.
Conversely, a warm stage must have the same five consecutive overlapping 3-month periods: or more and the abnormal SST’s must be at .05 degrees Celsius or higher. This is known as an [tooltip title=”El Niño” content=”El Niño is associated with warmer than normal water temperatures” type=”info” ]El Niño[/tooltip]. During an El Niño, storms in the Pacific will have an impact in the Atlantic. The possibility of tropical cyclones in the Atlantic developing is reduced, usually due to vertical shear. The Neutral stage is stage between the two and normally will only last a short period of time. The Neutral stage basically has no impact on the Global Weather patterns.
Next up, the Atlantic Tripole. When there is an Atlantic Tripole, basically what is happening is that in the tropical area of the Atlantic Ocean you are have warm waters to the south, and then from the tropical area to approximately 40° north latitude you now have a large of much cooler waters. From 40° north latitude northward, there would be an area of warms waters again. Since this is not the normal pattern, sometimes this can have an increase in the amount of convection and lift somewhere between Africa and the Leeward and Windward Islands. This can help the development of any tropical systems.
Hopefully, you are still with me as we talk about the NAO (North Atlantic Oscillation) and the the warm SST’s in the tropical area and the MDR (Main Development Region), MJO (Madden Julian Oscillation), and finally the PDO (Pacific Decadal Oscillation). Please note: I have purposely have left out the [tooltip title=”Indian Ocean Dipole” content=”A coupled ocean and atmosphere phenomenon in the equatorial Indian Ocean that affects the climate.” type=”info” ]IOD[/tooltip] in this discussion. Although it can a contributing factor, I felt we have enough information as is and did not want to add any further possible confusion.
The [tooltip title=”NAO” content=”North Atlantic Oscillation” type=”info” ]NAO[/tooltip] describes the strength of the surface pressure difference that is between the Azores High and the Icelandic Low. The NAO has two phases: a Positive phase and a Negative Phase. With a Positive NAO you have a stronger than average high across the Atlantic, this will increase the trade winds to the south of it. Those trade winds run across the eastern portions of the Atlantic and into the Caribbean. The stronger trade winds allow for increased evaporation cooling which then allows for cooler than average SST’s. Conversely, with a Negative NAO, the Azores High and the Icelandic Low are now weaker than average. So now with a weak high the trade winds will be much calmer allowing the SST’s to increase considerably. The NAO while it is a big player with the SST’s, the NAO also is a player in tropical cyclone development. Consider this, with quicker than average trade winds, any tropical waves will have very rapid movement as they come of the coast of Africa. The tropical waves will find it difficult to consolidate or strengthen if the forward motion is over 20 MPH or more. Not only can the tropical wave find it difficult to strengthen but this can lead to [tooltip title=”Speed Shear” content=”Speed shear is the change in wind speed with height.” type=”info” ] speed shear[/tooltip].
The NAO is also a player in the track of tropical cyclone. Recalling that during a Negative NAO, the Azores high is typically weaker but it is oriented west to east and closer to the US Southeast coastline. During a Negative NAO, any troughs on the East coast will typically be weaker and recurving of a tropical cyclone will be much more difficult to do. A Positive NAO on the other hand will allow recurvature much easier. Please note that the short term timing essentially will govern the track of a tropical cyclone, not the long term mean.
The abnormally above average [tooltip title=”SST’s” content=”Sea Surface Temperature” type=”info” ]SST’s[/tooltip] is another concern this year especially in the [tooltip title=”MDR” content=”Main Development Region” type=”info” ]MDR[/tooltip]. The MDRÂ is a very large area, extending from the Caribbean Sea to almost the coast of Africa. A warmer than normal MDR will provide the feeding fuel for the beginning of the development but also help nourish tropical cyclones. The minimum water temperature needed for a tropical cyclone to begin development is approximately 26°C or (79° F) and a depth of at least 160 feet but there also other factors needed.
Now let’s get to the [tooltip title=”MJO” content=”Madden Julian Oscillation” type=”info” ]MJO[/tooltip]. What is the MJO?  The MJO is an eastward progression of large regions of both enhanced(positive) and suppressed(negative) tropical rainfall. Simply put, there are two completely different phases with the MJO. One is a negative phase and the other is a positive phase. The MJO is different than ENSO as the MJO moves eastward at between speeds but anywhere from 8- 18 MPH across the different regions in the tropics, crossing the Earth in 30 to 60 days (with an average of 40 days). As it heads eastward and eventually into the East Pacific and then into the Atlantic the two phases are completely opposite of each other. In a Negative phase, lift is subdued and development of a cyclone is harder, but not impossible to have. In a Positive phase, now moisture and lift (upward motion) into the atmosphere allows easier development of a tropical cyclone (increased convection/thunderstorms activity).
Lastly, the [tooltip title=”PDO” content=”Pacific Decadal Oscillation” type=”info” ]PDO[/tooltip]. The PDO is a pattern of change in the Pacific Ocean’s climate. The PDO is easily recognized with cool or warm surface waters in the Pacific Ocean (north of 20° N. latitude). During a Negative or cool phase, the west Pacific  becomes warm and the eastern ocean is cool. Conversely, during a Positive or warm phase, the west Pacific becomes cool and the eastern ocean is now warm. So again you are wondering how does that affect you if you live on the US east coast? During a Negative phase and in the Atlantic basin, the rising of air helps upward lift and possibly allowing more convection which can help promote tropical cyclone development.
So now that you have had a short lesson in Meteorology 101, what does all this mean? In one sense, not a thing, but certain patterns may appear this season and may allow for possible stronger storms and also a much higher chance of landfall somewhere along the US Eastern coast. The past few years, many of the storms were recurved and they went out to sea. [tooltip title=”Trough” content=”An elongated region of relatively low atmospheric pressure, often associated with fronts” type=”info” ]Troughs[/tooltip] would develop, head east and pull the storms up and keep the storms away. This year appears to be different. A more pronounced and elongated Bermuda high will remain allowing any tropical cyclones to be caught under the [tooltip title=”Ridge” content=”A ridge is an elongated region of relatively high atmospheric pressure, the opposite of a trough” type=”info” ]ridge[/tooltip]. If the Bermuda high weakened enough, and a storm was under the ridge of the high and near the southwestern (or the periphery) of the ridge. This may allow the storm may follow around the edge of the high. This may allow a more northwestern track instead of a western track and possibly towards the East Coast of the US. Any storms much further west and if the ridge is still strong would possibly be in the Caribbean and if a system in the Caribbean and if there were a trough over the Plains of the US, this may have a storm heading toward the US Gulf Coast.
Using those different meteorological basics we talked about earlier, lets see why the possible reason why this may be a more active hurricane season.
ENSO
The ENSO is now in a neutral stage. Looking at the SST anomaly chart you must recall that for either an La Niña or El Niño ±o (either -.05° Celsius or .05° Celsius) for the last 3 months or more. Notice that is the chart both NINO 4 and NINO 3.4 have not reached the threshold needed. The short term forecast is that we will be in a neutral stage with a cold bias. Long term forecast is a bit cloudy but it is forecast that later in the season we may have a weak La Niña.
Atlantic Tripole
Now it is time again for the Atlantic Tripole. Although the chart below is not a true representative of an Atlantic Tripole, it does show the different areas. The black arrow designates the warm waters and the red arrow designates the cooler waters. In a non-Atlantic Tripole, the areas north of 40° are much cooler waters. A bit later in the season the southern Atlantic (the tropical area) is expected to be much warmer. With much warmer waters and tropical waves emerging from the coast of Africa those tropical waves have a better chance of possibly developing into something tropical.
NAO
Our attention is now focused in the NAO. All indicators reflect a Positive NAO. The Azores high is further south which can allow tropical systems to head further West or WNW. In the chart below is the latest NAO forecast both the Observed and Ensemble. The black line being the observed and the smaller lines from the different ensemble members. It you note that nearly all are indicating a Positive NAO. If you may recall from your Meteorology 101 course, a Positive NAO allows the latitudinal displacement of the Azores high further southward. For the time being the NAO is in a Positive phase but it is expected later in the season for the NAO to go into a Negative phase.
SST’s In The MDR
The abnormal high SST’s in the MDR is something I cannot emphasize enough. Recalling that a tropical system’s primary energy source is the [tooltip title=”Info ” content=”Also known as latent heat” type=”info” ]evaporation of water from the ocean surface[/tooltip], higher SST’s may allow easier development of of tropical wave, although there are other factors needed.
SST Analysis
MJO
As discussed earlier, the MJO progresses eastward with two different phases. At this time, the MJO is entering the East Pacific and Western Caribbean is a Positive phase. In the Positive phase, upward motion or lift and moisture allows easier development of convection/thunderstorms. The chart below can be a bit confusing but itself is a simple one once you comprehend how it works.
Looking at chart, you will notice that there 8 Octants with Octant 1 at the lower right and Octant 8 at the upper left. You will also notice near Octant 6 a legend for some of the different weather models with different a color for each. Next, you will notice a circle in the middle. You will also see (sometime difficult to read) numbers which correspond the different days (or index). For simplification, if the index is within the circle the MJO is considered weak. If the Index is outside the circle, then the MJO is considered a strong pulse. The MJO in the diagram moves counter-clockwise direction even though the MJO itself runs from west to east. You might have noticed the RMM1 and RMM2. Although this is something we need to worry about but the RMM1 and the RMM2 are simply mathematical methods which combine cloud amount along with winds at the upper and lower atmosphere. This provides a measure of the strength and location of the MJO.
To make things easier, we are only going to need octants 8 (East Pacific & Gulf of Mexico/Caribbean) and octant 1 which is the Atlantic basin. In the example above, near 28 in octant 1, you can see that several models (UKMET, GEFS, ECMF, CANM) all are outside the circle. Please note though, even if the MJO diagram is showing the different strong pulses within the different models, this does not always mean a development is imminent. This just means that there is usually upward motion or lift in the region and the possibility of easier thunderstorm activity.
PDO
Although not stated earlier, the  PDO is a long-term ocean fluctuation of the Pacific Ocean and wanes and waxes approximately every 20 to 30 years. When there are changes in the locations in the Pacific between the cold and warm water masses, they alter the path of the [tooltip title=”Jet Stream” content=”Fast flowing, narrow air currents found in the atmosphere.” type=”info” ]jet stream[/tooltip]. The easiest way to state this is that the jet stream in the northern hemisphere delivers the the different storms across the US. In this case the PDO is in a Negative (or cool) phase and this will will try to steer the jet stream further north over the Western portion of the US but this also allows for possible [tooltip title=”Tropical Cyclogenisis” content=”Cyclogenesis is the development or strengthening of cyclonic circulation in the atmosphere (a low pressure area).” type=”info” ]tropical cyclogenesis[/tooltip] in the Atlantic. The diagram below shows the different warm and cool phases.
Summary
Although no one (not even the Specialists at the NHC) can tell exactly what the 2013 hurricane season will be like, using some the factors I outlined in this post, it does appear that this hurricane season will be a much more active season. When you have a Negative PDO, a Neutral ENSO but with a cold bias, a Negative NAO, extremely warm SST’s in the MDR, along with a Atlantic Tripole, all these factors (along with others we have not discussed) do seem to favor a season of much higher activity. It is unrealistic to even try as to where (if any) landfall will occur but just using the above factors along with some analogue years for comparison, areas of risk for possible cyclone landfall are higher in some locations whereas other will have a lower risk. The graphic below is a generalization and is not meant to alarm those in the higher risk areas.
Okay, now that wasn’t too bad was it. Hope you enjoyed your short class of Meteorology 101 and that it hopefully paid out and I hope you learned a little in the meantime. Please note this was a generalization of what the 2013 hurricane season might like and many contributing factors may and will usually change throughout the hurricane season. If you are not sure on any of the items discussed, please feel free to Contact Me at the top of the page. Remember, I am not a trainer meteorologist. As with any storm, please check with your local WFO or the NHC>
Lastly, and most importantly, please be sure to put together your Emergency and Hurricane Survival Kit if you have not already done so. If you have pets, please be sure to have plans to care for them. Check your homeowners or renters insurance before any possible storms develop and ensure you are properly covered for property damages and I would highly recommend that you also take flood insurance.
Have you ever wondered who the hurricane specialists (forecasters) are at the National Hurricane Center (NHC) other than just their names you might see on the reports they produce during the hurricane season?
These people are the very best in their field. Not anyone can work as a specialist at the NHC. Only the best of the best were chosen. Although there will be those people who criticize every aspect of what the NHC does, thankfully those people are in the minority. These specialists do more than just view different satellite views and use some of the fantastic software they have (NAWIPS, ATCF, etc.) before they they write up the advisories, forecasts, warnings and other public products – there is a lot more behind the scenes. One thing the general public may not understand is that the specialist when writing up any of these advisory products, there are specific guidelines in how the report is written although there a few qualifiers that do allow some “freehand text” in a few of the reports. The forecaster will check on the latest model runs as this allows the specialist to help forecast where the storm might be heading. The data from the recon aircraft comes from the folks in the CARCAH (Chief Aerial Reconnaissance Coordination, All Hurricanes) office. The forecaster will have many conversations with whoever is staffing that office during the course of a recon mission – as that person is their link to the aircraft crew. The forecaster will also be checking with the TAFB (Tropical Analysis and Forecast Branch) as they provide a storm intensity estimate. The Hurricane Specialist uses the TAFB estimate as guidance but the Specialist will consider all available data in determining the intensity for the advisories.
A normal 6 hour forecast cycle;
The cycle begins, and 45 minutes later there is the reception of the fix data although that is the deadline time. The vast majority are in specialists hands 15 to 30 minutes after synoptic time. Aircraft fixes usually come right at synoptic time or even a bit earlier. An hour after the cycle started – the models are initialized. Again, that is the deadline time, usually the initialization of the models start a bit earlier. A few minutes later, the forecaster receives model guidance and starts the preparation for writing up the forecast. The primary text products in the forecast are the tropical advisory, forecast/advisory, and discussion. The second hour after the cycle started, the hotline call to both the (NWS) National Weather Service and the (DOD) Department of Defense is made. On the third hour, the forecaster has a deadline to release the tropical advisory products. Hours four and five are for possible media interviews. On hour six, the next cycle begins.
When storm watches or warnings are activated or during a landfall event the media is in the NHC building, but usually it’s the Director (Rick Knabb), Deputy Director (Ed Rappaport, PhD), or the Branch Chief (James Franklin) doing those interviews, not the Specialist on duty. There are a few times after the the advisory has been posted someone from the media may call and the forecaster on duty may answer any questions they may might have. When landfall is imminent within a stretch of shoreline, Federal and state level Emergency Managers, the NHC has someone who acts as a liaison between the EM’s and the NHC. Local EM’s are supposed to be in touch with their local WFO (Weather Forecast Office), who in turn relay their concerns to the NHC.
When hurricane season ends (officially) November 30th, the hurricane specialists remain busy outside the hurricane season. Occasionally, storms form before the official beginning of the hurricane season and also after the official end of the season, so specialists still have the responsibility with that storm too. They also have to attend some national and international hurricane conferences. The specialists do help the CPC (Climate Prediction Center), basically to prepare for the annual seasonal hurricane forecast. The specialists must also write seasonal summary articles and also participate in some applied research projects.
UPDATE: When Hurricane Sandy which become Post tropical and why the NHC and the Specialists no longer were issuing hurricane warnings as the very complex and extremely large weather system became a major issue. Basically, the NHC did not have the tools to be able to continue issuing those hurricane warnings. The old system would have caused known and unknown shutdowns within the different products and within the different vendors. Although the NHC would have loved to keep issuing the warnings, the risks were too great. For the 2013 hurricane season and beyond, the NHC now has those tools, recoding the different products and if another storm similar to Hurricane Sandy were to develop, the NHC and the Specialists now have the authority to keep issuing the warnings and other products.
So each hurricane season these specialists (and who get little recognition) are the ones that have to deal with criticism when their forecast might be off, but more times than not, they are very close in their forecast. With budget cuts and the economy the way it is, these specialists can only work with the tools they have available to them. Maybe it’s time for people to really thank the specialists for all the hard work they do.
The 2012 Atlantic Hurricane Season officially began June 1st. We have already have had two named storms before the start of the season began which is historic itself.It was over 100 years when two named storms started before the hurricane season started.
All indicators are pointing to a less active season due to El Nino/Southern Oscillation (ENSO) conditions which are forecast to be Neutral and then later during the latter half of the season there is a 50% chance of El Nino conditions. For further reading of the indicators for the ENSO, click here
For the moment, the tropics in the Atlantic hurricane basin, which includes the Caribbean and Gulf of Mexico are relatively quiet.
The GFS 06Z model run (06/11) again has begun to indicate a system that will develop into the Gulf of Mexico and possibly strengthen in to a category 1 hurricane with landfall near Texas/Louisiana in about a week or so. The 12Z found no development and 18Z run found just minor development but no closed low, but I won’t rule out possible tropical development in that area, at least for the moment.
GFS 06Z Model
GFS 12Z Model
GFS 18Z Model
GFS Ensemble 500MB Mean Anamoly
The Madden Julian Oscillation (MJO) will be heading into octants 8 and 1 which normally indicates an upward motion and pressures in that area are forecasted to be lower some time near the middle of the month. With the MJO moving into the Western Caribbean/Gulf of Mexico along with the pressures dropping, storm development may occur. With respect of model uncertainty, as the MJO moving rapidly through octants 6 and 7 and will be eventually getting to octant 8. There is a possibility that the reason the models (especially the GFS) are having a hard time pinpointing the forecast of development in the Western Caribbean may be due to the rapid movement of the MJO through the octants.
GFS
ECMWF
UK MET
While the tropics are quiet, it’s time to remember who the hurricane specialists are at the the NHC and what their duties are.
These people are the very best in their field. Not anyone can work as a specialist at the NHC. Only the best of the best were chosen. Although there will be those people who criticize every aspect of what the NHC does, thankfully those people are in the minority. These specialists do more than just view different satellite views and use some of the fantastic software they have (NAWIPS, ATCF, etc.) before they they write up the advisories, forecasts, warnings and other public products – there is a lot more behind the scenes. One thing the general public may not understand is that the specialist when writing up any of these advisory products, there are specific guidelines in how the report is written although there a few qualifiers that do allow some “freehand text” in a few of the reports. The forecaster will check on the latest model runs as this allows the specialist to help forecast where the storm might be heading. The data from the recon aircraft comes from the folks in the CARCAH (Chief Aerial Reconnaissance Coordination, All Hurricanes) office. The forecaster will have many conversations with whoever is staffing that office during the course of a recon mission – as that person is their link to the aircraft crew. The forecaster will also be checking with the TAFB (Tropical Analysis and Forecast Branch) as they provide a storm intensity estimate. The Hurricane Specialist uses the TAFB estimate as guidance but the Specialist will consider all available data in determining the intensity for the advisories.
A normal 6 hour forecast cycle;
The cycle begins, and 45 minutes later there is the reception of the fix data although that is the deadline time. The vast majority are in specialists hands 15 to 30 minutes after synoptic time. Aircraft fixes usually come right at synoptic time or even a bit earlier. An hour after the cycle started – the models are initialized. Again, that is the deadline time, usually the initialization of the models start a bit earlier. A few minutes later, the forecaster receives model guidance and starts the preparation for writing up the forecast. The primary text products in the forecast are the tropical advisory, forecast/advisory, and discussion. The second hour after the cycle started, the hotline call to both the (NWS) National Weather Service and the (DOD) Department of Defense is made. On the third hour, the forecaster has a deadline to release the tropical advisory products. Hours four and five are for possible media interviews. On hour six, the next cycle begins.
When storm watches or warnings are activated or during a landfall event the media is in the NHC building, but usually it’s the Director (Rick Knabb), Deputy Director (Ed Rappaport, PhD), or the Branch Chief (James Franklin) doing those interviews, not the Specialist on duty. There are a few times after the the advisory has been posted someone from the media may call and the forecaster on duty may answer any questions they may might have. When landfall is imminent within a stretch of shoreline, Federal and state level Emergency Managers, the NHC has someone who acts as a liaison between the EM’s and the NHC. Local EM’s are supposed to be in touch with their local WFO (Weather Forecast Office), who in turn relay their concerns to the NHC.
When hurricane season ends (officially) November 30th, the hurricane specialists remain busy outside the hurricane season. Occasionally, storms form before the official beginning of the hurricane season and also after the official end of the season, so specialists still have the responsibility with that storm too. They also have to attend some national and international hurricane conferences. The specialists do help the CPC (Climate Prediction Center), basically to prepare for the annual seasonal hurricane forecast. The specialists must also write seasonal summary articles and also participate in some applied research projects.
So each hurricane season these specialists (and who get little recognition) are the ones that have to deal with criticism when their forecast might be off, but more times than not, they are very close in their forecast. With budget cuts and the economy the way it is, these specialists can only work with the tools they have available to them. Maybe it’s time for people to really thank the specialists for all the hard work they do.
Although the 2012 hurricane season is not yet upon us, this is the time where we do need to see if any tropical systems might form. For a week or so, the GFS runs have been showing a system that might for in the western Caribbean, but lately the runs have backed off any development for now. Convection could be enhanced by a pulse from the Madden-Julian Oscillation (MJO) which should be in that area some time in very late May and into the early June time frame. Other models are calling for a much slower progression of the MJO. So for now, we will just have to see if any development were to happen.
At the moment, for several days now, several models were suggesting that a surface low would develop along the south-eastern coast of the US as a trough “splits”. The low has developed and is now over water and Invest 93L was called up. Although the models did not support any tropical development, but “surprise” Tropical Storm Alberto was declared at 5PM. There is some shear but that is forecast to abate some. TS Albero is also have a lot of dry air intrusion in the eastern and southern quadrants. As TS Alberto heads west or southwestward, some of the dry air may diminish but the biggest problem for Alberto is a new low to the northeast. This low should begin to constrict and not allow any further development. Earlier during the day, the system was tilted and the mid-levels of the circulation were being left behind but that seems to be no longer the case. TS is expected to drift SW then turn NE with just a possible close brush near North Carolina. The storm itself is very small and this should just keep the storm to as nothing but a rain event with a few areas of tropical storm winds.
This is the time to start preparing for the 2012 Hurricane season. Have all your supplies and plans ready just in case. Don’t wait till until a storm may be headed in your way.
