Tag: trough

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Science Tropical Weather

Tropical Storm Emily

The large tropical wave that was near the Antilles Islands has been upgraded to Tropical Storm Emily as of 7:30 PM last night by the NHC. Emily at this time is a storm with 40 MPH but should slightly increase for the next 24-48 hours. One of the reasons Emily is struggling somewhat is because there is a lot of dry air to the north of Emily and the flow from that dry air is wrapping around the storm thus making difficult for intensification. There is also a upper trough that is to the NE of Emily and that outflow is shearing the north side of the storm and again limiting the amount of intensification. This upper trough will be leaving within the next day or so and this may allow some further intensification, but this will be gradual.

A very strong trough will be diving south in the western Atlantic and soon should allow Emily to take a northwestern turn and then a turn to the north. The forecast is for Emily to possibly be a moderate strength storm with possible wind speeds of 50 – 60 MPH while heading northwest and having landfall somewhere in Hispaniola. (The trough depicted in the image below is the green to yellow to light orange pattern.)

If Emily makes landfall in the western edge of Hispaniola, Emily may or may not survive the crossing to the Atlantic due to some mountains as high as 10,000 feet. Assuming Tropical Storm Emily does cross to the Atlantic, weakened but still tropical in nature, Emily may regenerate and some strengthening may be foreseeable.

The track for Emily is very uncertain and Florida/Bahamas may be the next target. The trough will be lifting out, roughly during hours 72-96 and Emily may head a little more west-northwest heading somewhere in the vicinity of Florida or the Bahamas. Eventually a shortwave will cause a sharp turn northeastward and take Emily out to sea. If Emily stalls for a long period of time, then the track for Emily will be changed and Florida may have to deal with her. Everyone in the possible affected areas should keep an eye on this storm.

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Tropical Weather

Weakening Tropical Storm Tomas

Tropical Storm Tomas, once a category 2 storm, has been downgraded to a weak Tropical Storm and there is about another 24 hours before Tomas has any chance to restrengthen again. Tomas has been decoupled as the convection is about 100 miles to the east of the center. Westerly vertical shear is the main factor that is impacting Tomas. There is also a little dry air, but it is not as much as a factor. Both the Ships and LGEM model are forecasting that Tomas will strengthen again to a hurricane. A weakening low-mid level ridge to the north of Tomas will keep the storm on westward motion. In about 72-96 hours a large mid-tropospheric trough will be heading eastward into the Gulf of Mexico. The flow from the trough will turn Tomas north and northeast with an increase in forward speed.

Visible Satellite image of Tropical Storm Tomas
AVN Satellite image of Tropical Storm Tomas
Shear Map
Models for Tropical Storm Tomas
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Tropical Weather

Dangerous Hurricane Tomas

Hurricane Tomas in the early morning hours was found to have winds of 100MPH and Tomas is now a category 2 hurricane. With data from the reconnaissance plane and satellite imagery, Tomas is better organized but it was noted that the vertical stack of the storm is tilted northeastward with height. The tilting is probably due to the Southwesterly shear that is beginning to impact Hurricane Tomas. The shear has been forecast and further intensification will stop for about 48- 72 hours. There is the possibility Tomas may lose some strength during that forecast period. After that period, the shear will relax and further strengthening is forecast. Intensity guidance in at least the LGEM model does have Tomas strengthening and possibly be a major hurricane of at least a category 3 storm.

Hurricane Tomas is currently located south of a mid-level trough that is over the southwestern Atlantic. As this trough continues to move eastward a mid level ridge will build just north of Tomas and this will turn Tomas on a westward track for the next 2 or 3 days. Later in the forecast period, that ridge breaks down as a very large deep layer trough moves into the eastern U.S. and also digs southward. This will slow the forward speed of Tomas and also allow Tomas to gain latitude. Model guidance at days 4 and 5 is poor as far as the timing and the the sharpness of the turn to the north but there is a consensus that there will be the northern turn as Tomas will be forced north by the trough.

Visible Satellite image of Hurricane Tomas
AVN Satellite image of Hurricane Tomas
Water Vapor Satellite image of US and Western Atlantic/Tomas
Steering Layer
Models for Hurricane Tomas
Canadian Model at 108 hours
UKMET Model at 120 hours
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Tropical Weather

Hurricane Tomas

Tropical Storm Tomas has ben upgraded to Hurricane Tomas as of the 11am advisory from the NHC. Hurricane Tomas has had a very good presentation all morning. Hurricane Tomas is forecast to continue intensification and most models are forecasting that Tomas will be a major hurricane of at least category three.

The Mid-Layer trough that is taking Hurricane Shary rapidly to the NE is the same trough that is heading NE away from the Caribbean and the mid-level ridging north of Tomas has begun to build. Low to Mid level ridging is forecast by all the global models for at least the next 72-96 hours and building westward across Lesser and Greater Antilles. This will keep Tomas on a westward track for at least the next 2 days. A few days later, a broad mid-tropospheric trough that is currently located along the US west coast is forecast to move eastward into the Central US then it is forecast to dig southwestward into the Gulf of Mexico. This will erode the Western portion of the ridge and significantly weaken the steering currents in the western and central Caribbean Sea. This will force Tomas on a northward track. Exactly when the turn will happen is unclear. Some models want to wait then turn Tomas between Eastern Cuba and Haiti where other models want to turn Tomas earlier and have Tomas turn near Hispaniola.

Visible Satellite image of Hurricane Tomas
AVN Satellite image of Hurricane Tomas
Water Vapor Satellite image of Eastern US and Western Atlantic/ Tomas
Canadian Model at 120 hours
GFS Model at 160 hours
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Tropical Weather

Tropical Storm Tomas

Invest 91L has been upgraded to Tropical Storm Tomas as of the 5PM advisory from the NHC. Earlier today, the reconnaissance plane had found that a closed surface circulation was forming and on the way to becoming a tropical storm. TS Tomas is expected to continue slow strengthening and may become a hurricane by Sunday. There is the possibility that TS Tomas may become a major hurricane later in the forecast period.

The models now are forecasting that TS Tomas will continue to head WNW for at least the next 72 hours. The broad trough over the US is now expected to pull out, and this will leave a ridge to build over Tomas and all the way to Florida. Later on, a second and much deeper trough will begin to dig southward into the Southeastern U.S. and this will cause the ridge and all the steering flow to weaken. This will cause Tomas to sharply decrease the forward speed in about 120 hours. It is too early to call whether Tomas will bypass the trough and continue heading WNW or whether the trough will begin to force TS Tomas to head NW then North or not.

NO MATTER where TS Tomas heads, all interests should keep advised of the location that Tomas is heading, especially if he becomes a major hurricane.

Visible Satellite image of TS Tomas
AVN Satellite image of TS Tomas
Water Vapor Satellite image of US & Western Atlantic
Models for TS Tomas
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Tropical Weather

Invest 99L – A Possible Florida Threat??

Invest 99L which has been lingering around the Southwestern Caribbean is finally beginning to move away from the coasts of Nicaragua & Honduras. With landfall interaction, it was impossible for 99L to even try to develop. Now that it has been been heading N or NNW it has a much better chance of developing. This is the time of the year where the models have problems and this may be the case with 99L. Many of the models at this time are not seeing any type development but the GFDL and HWRF does favor development. Whether 99L will be a Florida threat or not is a forecast that is so very difficult to answer, at least for the next few days. Hopefully, with a few hours or so we may have a better idea of what might happen as the reconnaissance flight is on it’s way. Just looking at the satellite presentation, it does look like there is circulation at the mid and upper levels but not yet at the surface. I am sure this is what recon will find.

Visible Satellite image of Invest 99L
AVN Satellite image of Invest 99L
Water Vapor Satellite image of US and Invest 99L
Shear Map
Steering Layer Map
Euro Model for Invest 99L at 216 hours
GFS Model for Invest 99L at 132 hours

Below are the two models GFDL & HWRF which develop 99L into a hurricane. Only if shear abates, the high pressure system that will build after the trough has gone through and the high heads east and 99L lingers into the Southern Gulf of Mexico, then the chances for 99L to head to Florida as a tropical cyclone may increase but I doubt this will happen as there a just too many variables that have to work in unison.

GFDL Model at 144 hours
HWRF Model at 216 hours
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Tropical Weather

Hurricane Paula – A category two hurricane

Hurricane Paula, a very small but category two hurricane is now nearing the Yucatan Channel heading just east of north but Paula is expected to make a turn to the northeast then east. The forecasters at the NHC are very certain that this turn will happen but it is how much of the turn that is still unclear. Paula will become embedded in a westerly to easterly flow that is associated with the base of a deep mid-latitude trough. Some models want to take Paula on a sharp easterly track over Cuba where as other models want to take Paula on a more ENE motion.

Because of the uncertainty on both the track and the intensity, a Tropical Storm WATCH has been issued for a portion of the Florida Keys.

West Cuban Radar of Hurricane Paula
Visible Satellite image of Hurricane Paula
AVN Satellite image of Hurricane Paula
Water Vapor Satellite image of Western Atlantic / Hurricane Paula
Models for Hurricane Paula
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Tropical Weather

Tropical Storm Paula

Invest 98L has been upgraded to Tropical Storm Paula as of the 5PM advisory from the NHC. Recon earlier today found winds of 60 MPH, but that might be a little conservative. The forecast is for Tropical Storm Paula for additional strengthening and Paula is forecast to possibly become a hurricane within 24 hours according to the models SHIPS, and LGEM. Strengthening will only be possible for a few days, then slow weakening on days 4 or 5. For the next few days the track for Paula will be NW then N. The western edge of a ridge that extends across northern Caribbean is expected to weaken because of a deep-layered trough that will be moving eastward across the Southeastern US. After that forecast period most of the guidance is suggesting that the trough will move east and then leave Paula in an area of weak steering currents and Paula is expected to drift eastward for for a day or two then possibly drift southward. Model guidance after day 3 or 4 and confidence is quite low. Whether Paula will stay in the Western Caribbean and impact Nicaragua or head north and northeast unfortunately it is too difficult to forecast.

Visible Satellite image of Tropical Storm Paula
AVN Satellite image of Tropical Storm Paula
Water Vapor Satellite image of Western Atlantic/Tropical Storm Paula
Models for Tropical Storm Paula
Categories
Tropical Weather

Hurricane Otto

Tropical Storm Otto has been upgraded to Hurricane Otto as of the 11am advisory from the NHC. During the past 6 -12 hours satellite images showed that Otto had developed a well defined and large CDO – Central Dense Overcast. (This is the cirrus cloud shield that results from the thunderstorms in the eyewall of a tropical cyclone and its rain bands). Otto in an environment with light shear marginally warm waters which will allow some further intensification but gradual. This will be short lived as within 24-36 hours, southwesterly shear and cooler waters will take it’s effect on Otto and weakening if forecast. Otto will begin the transition from tropical to extra tropical within 48 hours. Otto has been heading ENE and gradually has been accelerating. Otto will stay on this track for 2 or 3 days and eventually turn to the eastward then southeastward due to a deep layered trough. Otto is expected to affect those in the Azores Islands.

Visible Satellite image of Hurricane Otto
AVN Satellite image of Hurricane Otto
Water Vapor Satellite image of Western Atlantic/Hurricane Otto
Models for Hurricane Otto
Categories
Tropical Weather

Sub Tropical Storm Otto

Sub Tropical Depression Seventeen has been upgraded to Sub Tropical Storm Otto as of the 5PM advisory from the NHC. Otto is heading northward between a weakness in a ridge in the Mid-Altlantic. A very strong mid-tropospheric trough that is located in the Eastern U.S. will be heading east and eventually turn Otto on Northeast track for 24- 36 hours. After that forecast period, Otto will accelerate very rapidly and will then be tracking ENE. Otto will be going through the transition period from Sub Tropical to Tropical within 12-18 hours or sooner due to warm SST’s and the dissipation of a upper-level low just SE of Otto. Otto is forecast to possibly reach hurricane status within 36 hours. Otto will then start to weaken due to upper level winds from the aforementioned trough. In 96 hours or so, Otto will go through transition from a tropical cyclone to a extra-tropical low.

Visible Satellite image of Sub Tropical Storm Otto
AVN Satellite image of Sub Tropical Storm Otto
Water Vapor Satellite image of Western Atlantic/Sub Tropical Storm Otto
Models for Sub Tropical Storm Otto