Monthly Archives: September 2010

Invest 97L

A couple waves in the atlantic (PGI48L, PGI49L) merged as Invest 97L. PGI49L was the dominant wave and eventually merged into one large system. There are two trains of thought on this system. One of the problems is that 97L is close to the ITCZ, but will probably gather some latitude soon. If not, then this system will be headed toward the Caribbean. So far, some of the models favor a WNW then NW track. The large trough off the East coast of the US will be headed NNE and this will weaken the ridge over the Mid-Atlantic and allow 97L to turn to the NW. The Euro and Canadian Model are forecasting that turn which will keep 97L away from the US coast. There might be a problem with those model runs as they were initialized with the two separate (PGI48L & PGI49L) systems. There is also a TUTT (Tropical Upper Tropospheric Trough) retrograding westward that is to the NW of 97L along with some dry air. If the TUTT doesn’t weaken, then this may keep 97L in check and continue the westward movement for a little longer. 97L is forecast possibly become TS Otto in a few days.

The problem is if the westward movement continues, this may allow 97L to slide under the ridge allowing the Northern Leeward Islands to be affected. This will also tend to keep the U.S. East Coast under the gun or possibly go through the Florida Straights and then a new trough pick up 97L anywhere from the Gulf States to Florida. Until the models can get a better grip on this system and have a more consensus between the models and since this is the peak of hurricane season, everyone should keep an eye on the tropics.


Ex-Tropical Storm Nicole

Tropical Storm Nicole which was poorly organized has been degraded to nothing but an elongated area of low pressure. This low pressure system will continue to have plenty of rain and there are some area of strong winds. A new strong non- tropical low pressure system with gale force winds is expected to develop to the Southeast U.S. Coast sometime tonight. The new low is not considered to be the remnants of Ex-Nicole. The heavy rainfall that is associated with the remnants of ex-Nicole are going to continue affecting portions of Eastern Cuba, and also Central & Northwestern Bahamas. Florida will see a gradual decrease in the rainfall tonight.


Tropical Storm Nicole

Tropical Depression Sixteen has been upgraded to Tropical Storm Nicole as of the 11am Advisory. Although there has been an increase in the convection with bands of thunderstorms that are closer to the center of circulation in the southeastern quadrant, Nicole is not that organized. All warnings and watches for Florida have been discontinued. As it was discussed yesterday, all the strongest winds and convection are east of the center of circulation. Nicole is forecast to become extratropical within 24 hours and head northeastward along the U.S. East coast. Heavy rains will be the dominant event over Cuba, and also in the mountainous areas of Jamaica. Florida will continue to get some rain, but most of the rain will be offshore.

There are a few models that are forecasting a new system will develop in the western Caribbean, but there is no genesis for this at this time.


TD Sixteen – a ragged system.

After the Hurricane Hunter recon plane went through TD Sixteen, it was found that the LLC was very broad with light winds of 20 knots or so (about 23 MPH) and the pressure was uniform over a long range. A normal system would have lower pressure within the center. Definitely not a typical cyclone. The forecast is that TD Sixteen may become a Tropical Storm either tonight or tomorrow. After 36 hours or so, the window will be closed for any further intensification as a large mid – to upper level trough that is digging down the southeastern US coast will keep intensification down. Some models are forecasting that TD Sixteen will become extratropical within 36-48 hours. The track of TD Sixteen has been shifted slightly to the west. UNLESS the structure of TD Sixteen improves and starts to tighten up, most of the strongest winds and rain will be east of the center and will be offshore away from the coast of Florida.


Tropical Depression Sixteen

Invest 96L has been upgraded to Tropical Depression Sixteen as of the 11am Advisory from the NHC. The forecast is for TD sixteen to become a Tropical storm before it gets to South Florida BUT it will most likely begin the transition to a subtropical storm. I will try to explain the difference between a Tropical Storm and a Sub Tropical storm. In a normal tropical storm – the central portion or the “center” of a storm it is a “warm core” meaning all the strongest winds will be in the center. In a “cold core” system all the winds are displaced away from the center. Also in a cold core system – all the circulation is at all levels. In a warm core system such as a hurricane, this has a pool of warm air aloft generated by latent heating. The thermal wind changes direction at some altitude aloft due to the change in the temperature gradient and you get an anticyclonic circulation at high levels above the hurricane which you see as the wispy cirrus clouds that “push away” from the center.

I believe that South Florida will be ok as most of the convection is to the east of the center and will probably be offshore BUT everyone should keep tabs on this system as with any tropical system, things can change very quickly.


Invest 96L

During the day today Invest 96L had been designated. This is the system from the monsoonal low that is starting to get together as we speak. This system at the moment is off the coast of Belize with pressures dropping. Cyclonic turning is beginning to slowly wrap up, but at the moment there is no LLC. Most models believe this will head north across Cuba and into South Florida. Until there is an actual LLC, it will be very difficult to give any accurate estimate of rain and wind. Will this be a tropical system or will this be a subtropic system. A lot of questions yet very hard to answer. The one problems is that there is a not a lot of time to prepare if this will be a Tropical storm or hurricane. Therefore, all those in middle to south Florida and also those along the East coast of the U.S. should monitor this system even if it ends up just being a rain event.

The advancing front that is headed toward Florida will have some dry air along with some shear will this be a major factor – it all depends on the timing and the structure of Invest 96L. There is also a possibility that a second storm later in the week that might actually be stronger than 96L. Will this affect Florida or will shift east and go over the Bahamas. Again, a lot of questions with few answers.


Remnant Low Matthew, PGI48L

Tropical Depression Matthew has been downgraded to a remnant low. Although Matthew has been downgraded  and is just a low pressure system, Matthew along with a very large cyclonic gyre will continue to bring large amount of rain in Eastern Mexico and Central America.  The remains of Matthew is forecast to turn clockwise and either  be embedded into the gyre or dissipate. This monsoonal low is forecast to form somewhere in the western Caribbean and possibly head north to Jamaica, Cuba and Florida. With respect of the intensity if and when the new system forms is still unclear. Since the forecast is somewhat cloudy, all those in the Gulf States, Cuba, Jamaica, Florida, and the East coast of the U.S. need to keep and eye of this system. I will update this blog later today with some of the latest model runs.

Below are three different model runs. Until forecasters can see where any storm may form – the model runs are just that – models. I have to discount the GFS run as it won’t to create two or three different tropical storms each running north over Cuba and then into south Florida but I am including it.

Pre-invest PGI48L is a new system in the Atlantic at roughly 12N – 34W. This is a system that has potential and may develop in in the next 3-5 days.


TD Matthew…

Tropical Storm Matthew which made landfall yesterday with 50mph winds has continued to trek W- WNW. As of the 2PM advisory, Matthew has been downgraded to a Tropical Depression. There is pretty much a consensus that Matthew will slow down and dissipate over Central America in the next two days. Copious amounts of rain has already made a bad situation worse in Honduras and it is expected to do the same in Belize, Guatemala and possibly Eastern Mexico. Although it is forecast for Matthew to dissipate, almost all the models are forecasting a new system to develop in the western Caribbean as the entire area is under the influence of a monsoonal low. If this forecast pans out, then there is the chance that the Gulf States, Florida, or the Eastern US may be impacted. These forecasts are very unpredictable at the moment as the fluid dynamics involved in the atmosphere are very complex. The few models below are for the next system (if any) and if named it would be Nicole.

Latest Satellite images of TD Matthew


Tropical Depression Lisa, Tropical Depression Fifteen, Ex-Julia

Tropical Storm Lisa has been downgraded to a Tropical Depression. Although the deep convection has increased and has been better organized, and shear is still low – the dry air around Lisa is still a problem. Within 24-36 hours, Lisa should be in cooler SST’s along with an increase in shear. Lisa is forecast to continue the weakening trend and is forecast to be a post-tropical/remnant low in 120 hours.

ADDENDUM: as of the 5PM advisory from the NHC – Lisa has been upgraded to Tropical Storm Lisa.

A very bullish remnant low Julia has redeveloped but chances of it becoming anything tropical are very slim.

Invest 95L which will probably be Tropical Depression Fifteen as I speak as the first recon report is finding 39 MPH winds at flight level but you have to adjust for the surface winds which is roughly 32 MPH. A special Advisory from the NHC will be issued at 2:00PM. By later today or early tomorrow I am sure Tropical Depression Fifteen will be upgraded to Tropical Storm Matthew. Where this storm will have landfall is a big question mark. Some models still want it to make landfall closer to Honduras or Belize or will the other models want it make landfall somewhere further north in the Yucatan. To complicate things even more there is a possibility a new system might develop east of TD Fifteen and might be a part of the same gyre only to confuse the models even further. For the next 48 hours most do believe a W to WNW track is forecast for TD Fifteen. This a system that needs to be watched by all in the western Caribbean and all those in the Gulf states and especially Florida.

ADDENDUM: As of the 5PM advisory Tropical Depression Fifteen has been upgraded to Tropical Storm Matthew.


Tropical Storm Lisa & Invest 95L

Tropical Storm Lisa way out in the Eastern Atlantic has been somewhat stationary or has drifted southeastward and the low-level center has been exposed. Tropical Storm Lisa is in an area of weak steering currents and is forecast to be drifting for the next 24-48 hours. Lisa is located within a COL which is an area between two high- and two low-pressure centers. After 48 hours a trough is expected to lift up northeastward and another ridge will build westward. This will allow Lisa to slowly move westward. At the moment shear over Lisa is light, but here is a lot of dry air around Lisa which is inhibiting or slowing further intensification. Since the shear is still low, there is the slight possibility of some intensification during the next 48 hours, but any intensification will be slow, if any. After the 48 hours, increasing shear is forecast. The forecast is for Lisa to weaken and there is the possibility it will just become an open wave.

Invest 95L is very disorganized and this will probably be this way until the system heads westward and gets to longitude 75W where there will be less interaction with South American coast. Shear will be light at that time and further development is forecast. There are two camps divided on where the system may head. A few models believe the Invest 95L will head due west and landfall will be near Nicaragua and possibly Honduras and dissipate. The other models like the Euro and the GFS believe 95L will slowdown and head WNW to NW and landfall will be around the Yucatan. With a strong trough coming down from the US this may pick this system up and the implications with that is this may be a strong tropical system that may head anywhere from Texas to the west coast of Florida. This is a system that needs to be watched carefully for the next 7 – 10 days. By then a much better forecast can be made.