1800 EDT AUG 20
97L was upgraded this afternoon 51700 EDT to tropical storm IRENE. Looking at the 5PM IR satellite it is easy to see why. over the past 24 HRS there was this hole or donut in the center of this large tropical wave with each semicircle having large area has of heavy thunderstorms. But late this afternoon the center began to fill in and when the convection reached the low level circulation center the system of upgraded– obviously finding the fly level wins a 53 knots was a real kick in the head.
The afternoon models have shifted to the east with regard to the track of Irene.
The 12z European model again remains firmly committed to the idea that IRENE is going to track over hispanola then over Eastern Cuba and turn sharply to the north move into the Florida Straits and making landfall over southwest Florida and cutting across the peninsula AUG 27… with a 2nd US landfall over southwest SC near the Georgia border. However by that time the trough over the Midwest will have moved off the northeast coast which means that the gap in the pattern over the southeastern CONUS gets “filled”. So the European model now takes this system and stalls over the southeast CONUS providing that area with several days of extremely heavy rain.
If you recall from this morning the 0Z Canadian and British models with the furthest west taking this system into the central gulf coast and threatening New Orleans but the 12z saturday no longer do that and show a system which makes a sharper turn. This results in the tropical cyclone move into the Eastern Gulf of Mexico and not threatening New Orleans.
Of course both of these models still have IRENE passing south of Jamaica which is absurd given what we are seeing on the other models and the developing atmosphere pattern.
1100 AM AUG 20
I am not going to discuss the development of 93L into the Tropical Depression which has already occurred as of early this morning. The system is clearly going to crash into Belize in Central America and is not going to be a threat to any portion of the CONUS. In addition except for some exceptionally heavy rains over the mountains of Central America this system is not even going to be a big deal for Central America. And no for the record I don’t think is going to reach hurricane status before it arrives on the coast this Saturday afternoon.
Meanwhile what WAS a very weak looking tropical wave 97L is looking much better this morning. This first image — the 12z IR satellite picture — shows what the system looked like on Friday morning 8AM EDT. It had some developing showers and thunderstorms with it but it certainly did not look all that impressive.
(note that you can also see the New TD that may become Harvey forming in the far western portions of the Caribbean headed for Belize). I am pointing out what was the weak status of tropical wave 97L on Friday morning for a particular reason . As I discussed yesterday there is another strong tropical wave in the far Eastern Atlantic Ocean… known as 98L. There has been a lot of speculation that this fairly strong looking tropical wave is either going to fall apart or track to the NW out into the open waters of the Atlantic.
98L looks far stronger now than 97L did on Thursday when it was in the same lat / Long position . However because most of the global models have been developing 97L into a major event for several days… it has became a lot easier to believe that 97L was going to hold together then intensify and and become a significant tropical cyclone.
Complicating this is the hurricane center describing a second tropical wave in close proximity to 98L… a wave they have designated as 99L . In my opinion this is a mistake …98L and 99L are the same Tropical wave and I cannot figure out for the life of me why TPC has split this tropical wave up the two portions. It is just a large organized tropical wave with two centers – not 2 different waves. What they call 99L has a center which is at 9 or 10° N latitude which is easily far enough south to ensure that it does not get turned out to sea and will become a more significant threat as it tracks westward across the tropical Atlantic…. in manner close to 97L.
Back to 97L…. The early Saturday am weather models — the 0z runs - continue to show them overall trend that we have seen for the last several days. It appears likely now from most of the hurricane models that this system will become a tropical depression and then a tropical storm called IRENE sometime over the next 36 hours. It may not happen until a system reaches the Leewards islands. However the problem is that no matter which particular long-range global model you are considering… they all take IRENE very close or over the big island’s of Hispanola and a good portion of Cuba. Even the models which don’t have it going over Hispanola and Cuba have IRENE tracking along the immediate south coast of those big island’s and their mountains. Either way it’s clear that IRENE is not likely to intensify when she is either next to or Hispanola and eastern Cuba or tracking over them.
So while it is possible that IRENE could I suppose reach hurricane status before reaching the big island of Hispaniola …. it is not likely that IRENE will not maintain hurricane status while its close to or crossing those two big islands.
The second factor that we have to deal with is the overall synoptic pattern. The overall pattern shows a very strong “Bermuda High” — which is also known as the Western Atlantic Ridge ( or W.A.R.) dominating the entire western half of the Atlantic Ocean. The periphery or edge of the Bermuda High /WAR will be actually on the eastern and southeastern CONUS next week. Over the western CONSU e have a large massive heat dome…. and it’s EASTERN edge or periphery will be located over eastern Texas into Missouri and the central Plains.
In between there will be a gap or weakness in the overall atmosphere pattern that will be over the eastern Gulf of Mexico Florida and the southeastern CONUS. To the north a fairly strong trough is going to move through the Great Lakes and the Northeast AUG 25-26-27. The passage of this trough and the gap or weakness in the atmosphere over the southeastern CONUS will allow for IRENE to turn at SOME point to the northwest and then north around AUG 28 – 29.
On this point all the models agree. But the disagreement hass to do with where IRENE will be on the map when it makes that turn to the NW…. and the strength of the trough moving through the Midwest and the northeast.
1) the further North IRENE tracks ( say over Cuba) the more likely we are to see a turn to the NW then N sooner. Conversely the further south she is the later the turn to the NW and the bigger the threat for strong central Gulf Hurricane.
2) the deeper the Midwest trough the more likely we are to see a turn to the NW then N occur sooner. Conversely the weaker the Midwest trough the later the turn to the NW and the bigger the threat for strong central Gulf Hurricane.
The 0Z GFS European model show a fairly strong trough and they have IRENE tracking over the big island of hispaniola and Cuba . Because they have IRENE this far north the Euro model turns it to the northwest sooner and as result of this model take this system into Florida then into the Southeast CONUS then up into Virginia and North Carolina AUG 30 .
These models have IRENE strengthening only into a category 1 or perhaps a category 2 hurricane because the system spend only a short period of time over the warm waters of the Florida Straits… and thew western or eastern side of FL. However the British and the Canadian models which are arguably the two worst models to use in forecasting tropical cyclones… have IRENE tracking over Jamaica and passing through the Yucatan channel. Because these models have IRENE this far to the south and west ….the interaction between the tropical cyclone and a trough over the Midwest is pretty weak so we end up with a wider turn which takes it into the Central Gulf of Mexico.
Thus the 0z Canadian and British models show a direct hit very close to New Orleans Louisiana . In my opinion this solution is crap but I am sure there are those out there who are going to try and height this scenario as a viable one. The problem with the Canadian model solution is that its resolution is not nearly as good as the European or the GFS and the tropical cyclone is at the age of the models grid so it probably does not see it very well. The British or UKMET is just a piece of crack and it needs a major upgrade. And it needed about five years ago.
1800 EDT AUG 18
If you have been following any of my posts over the past few days over at the Facebook page you know that I have been talking about the increasing threat of some sort of significant hurricane affecting some portion of the southeastern United States and or Florida sometime around August 28.
Up to this point in the hurricane season we have had seven named systems and not one of them have reached hurricane intensity. And fact none of them have even gotten close! This as you may have already heard or read has never happened before. So what does THAT mean and why?
It means that there are a lot of systems coming off Africa which are fairly vigorous but they are struggling to develop. And when they finally do begin to develop many of them have already moved out of the MDR — the main development region– of the Atlantic Basin. Some of this probably is because of the dust into portions of the eastern and central tropical Atlantic. But there is probably another reason and that is has been the lack of favorable 200 MB rising motion.
For many years we have known that the wave train of tropical ways coming off the African Coast … which of course is an intregal aprt of the Cape Verde Hurricane season … always increases during the second half of August and throughout the month of September. Then it begins to wind down OCT 1-15. But that knowledge is not enough in helping us determine which tropical waves are developing which ones are going to fall apart and why.
Many of you may know of the SAL phenomenon which is really just a fancy term we use to describe these large surges of dust which come off the African continent and move into various portions of the tropical Atlantic Ocean. This dust when it is particularly heavy or strong ….dramatically interferes with tropical wave development especially around the Cape Verde Islands.
However another feature which is often overlooked and not known by many has to do with 200 MB vertical Velocties. This again is just a fancy weather term which refers to the upper motion in the atmosphere. When there is a lot of strong vertical motion in the atmosphere… thunderstorms in tropical waves crossing the tropical Atlantic Ocean are able to develop much more rapidly. And it would follow that when you have sinking air or downward motion in the atmosphere ….thunderstorms have a great deal of difficulty developing and you end up with weakening tropical weights.
To show you what this looks like I can present you with the latest 200 MB Vertical Velocities Plots from CPC. This image as of August 17 shows a large area of GREEN (rising or positive motion) has moved into much of the tropical Atlantic and mores coming in from Africa into the entire Atlantic Basin. As you can see from the image it is not surprising their four that the entire tropical Atlantic has shown a significant increase in activity over the past several days.
Back in early August we had EMILY. Of course Emily did not actually doing anything but if you recall SOME weather models — the GFDL the GFS and the Hurircane Models — showed EMILY becoming a significant hurricane near the Florida coast. As you take a look of this image you can see that there was a another surge of GREEN or rising motion energy moving through the Caribbean Basin when Emily began to develop. Of course what Killed off EMILY was her crossing into Hispanola.
93L is finally beginning to develop in the Western Caribbean which is always a fable place for tropical systems to develop. The ocean water temperatures there are extremely warm and often there is large Ridge in the Jet stream over the southwest Atlantic Ocean which provides a favorable synoptic development area in the Western Caribbean.
However one thing I need to point out is that the satellite pictures back from August 11 showed tropical wave 93 L to be impressive looking when he came off the southwest African Coast.
However 93L was impacted by another strong tropical wave to the northwest which eventually became GERT. The close proximity of tropical storm Gert probably interfered with the development of 93L for a few days. Now that 93L is developing this afternoon it’s pretty clear that the system is going to crash into the Yucatan coast and die.
Next on the pipeline is tropical wave 97L . Again this system WAS looking fairly strong several days ago as it came off the African Coast. However over the past 36 HRS 97L has waekend SOME… probably because of the large surge of Dust to its NE in thre far eastern Atlantic which has interfere with the low level circulation.
As you can see from the satellite picture the core around the low level center of this tropical wave is now devoid of any thunderstorms. The satellite picture show there is this
“hole” in the center of the tropical wave where the surface Low should be. That being said …. It is QUITE possible that 97 L as it moves closer towards the lesser Antilles island chain … may develop into a significant.
Over the past 4 days ALL of the weather Models have been going to town with 97L and develop into a TS by the time it reaches the NE carribean … then it develops into a major hurricane that threaten some portion of the Bahamas FL and or the southeast US around August 28.
But 97L is moving away from the dust and is now entering much warmer SSTs and is now in an area of maximum vertical upward motion at 200 Mb. Not surprisingly given how strong is wave has been and is much more favorable atmosphere environment
Still given the recent model performance of over developing systems coming off Africa this is not yet a sure thing.
However there are other considerations to take into account. Recent studies have shown that there is a distinct correlation between MJO phases and tropical cyclone development in the north Atlantic.
As you can see from this table the data clearly shows that when the MJO impulse in phase 1 or 2… You are far more likely to see a significant hurricane develop in the tropical Atlantic . Likewise when the MJO is in phases 6 and 7… You are much less likely to see any tropical cyclone development and especially any hurricane evelopment .
In this next image we can clearly see the difference between the two phases of the MJO.
If this data and research is correct– and I strongly believe that it is– next question is… Given the strong tropical wave which is moved off the southwest African Coaston AUG 18 …what is the current phase of the MJO? As you can clearly see the MJO currently is in phase 2 which the research shows is extremely favorable for the development of a significant tropical cyclone. The GFS Model moves the MJO back into Phase 1 by the end of the month wehrre as the European and British MJO models show the MJO area .
When you put all this together you clearly see strong indications that 97L has a good chance developing into a major hurricane. Given the overall pattern that is expected to form over the western Atlantic and the central and eastern CONUS AUG 25-29 … The potential does exist for a significant hurricane threat.
1. 97L is moving into a much more favorable area.
2. The 200 MB vertical velocities are now extremely favorable as they show very strong pper motion over the entire tropical Atlantic Basin.
3. The MJO is quite favorable. And the Atlantic Basin is quite warm.
OK…. ANY IDEAS WHERE THIS IS GOING ?
Since 97L is weaker it is more likely to stay on a West track Longer and passes SOUTH of Puerto Rico. This means that 97L is far more to pass SOUTH of Puerto Rico and that in turn means and Bigger caribbean and Gulf of Mexico threat. What we do know is that the western Atlantic ridge ( W.A.R.) –also known as the Bermuda High –is going to build into the East coast during a period of AUG 24-28. We also know that there is going to be very strong ridge or heat dome over the western third of the nation as well extending from the west coast into the central Plains and Central Texas.
In between those two features a trough in the Jet stream will develop over the Midwest AUG 26-30. Any hurricane which is coming through the Bahamas or Florida will of course detect this Midwest trough and this will allow the potential hurricane… Potential… To begin to shift its track to the northwest and then eventually north.
In other words as the hurricane approaches the southeastern US it will depend on 1) where the western periphery or edge of the Bermuda High is located and 2) how deep or large is the Midwest and trough.
For the past several runs the European model has been taken a system close to Florida then into the South Carolina Coast and the GFS and the Canadian models have for the most part showed a similar track.
However this afternoon the 12 ZGFS European and Canadian models all shifted the track of this system to the west. They did so because they showed the system tracking over hispanola and Cuba. This means a weaker system and a weaker system means a more west track.
However that also means that once the system clears Cuba and moves into the Gulf of Mexico it will again detect the trough in the jet stream over the Midwest and turn to the northwest and then north.
One of the key benchmarks were things to look four will be where this tropical cyclone will track with relationship to Puerto Rico. Most of the time— not always that most of the time– a tropical cyclone which tracks to the north of Puerto Rico will end up affecting the southeastern US (assuming f it does not turn out to sea). On the other hand if it tracks over Puerto Rico or to the south is far more likely to move into the Gulf of Mexico or Florida. Of course there are exceptions to this general rule book and the biggest one that comes to mind is hurricane IKE back in 2008. That hurricane passed well to the north of Puerto Rico then actually turned WSW so it was forced to track over Cuba and then moved into the Gulf of Mexico .
Today a much stronger more impressive tropical wave moved off the southwest African Coast. (98L ) It is far away the most impressive tropical wave of the season and it is come off the coast at the time of maximum vertical upward motion at 200 Mb.
As you can see from the satellite picture that I use and have posted this strong tropical wave already has a very distinct curved band of clouds and probably already has a strong area of low pressure in its center. One could make a case that this feature is already close to tropical depression status right now.
Some may argue that 98L will curve out to sea… and it may. But if so it will not for several days. Models show that the HIGH over the eastern Atlantic — the AZORES HIGH as it is referred to — will slide West with 98L. This means no such early turn out to sea
By the time 98L reach 60 west Long if it has Not turned out to sea by then it wont because by then a new large Ridge– the eastern side of the Bemruda High will be in place .
But right now the Models do NOT develop 98L into a major TC. Since the tropical wave is just not coming off the coast of Africa is very difficult for any global model to figure out to ‘see” where 98 L is going to go. In other words the models are operating on an ASSUMPTION on that this feature is actually going to form even thougt until this morning of AUG 18 … it had not actually moved off the coast of Africa. ince the tropical wave is just not coming off the coast of Africa is very difficult for any global model to figure out where this feature is going to go. In other words the models are operating on an ASSUMPTION on that this feature is actually going to form even thought until this morning of AUG 18 … it had not actually moved off the coast of Africa.
The Last point has to do with WARM sea surface temperature anomalies in the Atlantic Basin. They continue to run quite warm. Once 98L reaches 40 degrees West things can really develop rapidly. When the Atlantic Basin is warm like this there is a strong correlation for significant land falling US hurricanes.