Category: Tropical Weather

Tropical Weather

Invest 91L and ex-Gaston

Ex-Gaston who seems to have been around forever has lost most of it’s cyclonic spin is now just under Puerto Rico and the last satellite imagery of Gaston was showing the best convection it has had in a long time. The only problem with Gaston is that he will soon be headed right into Hispaniola. The mountain range there can be very high and has many a time either disrupted a storm or killed it. If Gaston only clips the mountains, Gaston may survive and possibly may develop while in the the western Caribbean.

A tropical wave that has just come off Africa has been designated as Invest 91L. This tropical wave does have some decent cyclonic turning but there is some wind shear of about 20-30 knots just north and northwest of it. The shear will relax within the next 24-48 hours. Some on the models have just been initialized thus there may be errors or bias within them. Several models are suggesting this will be our next tropical cyclone.

Tags models

Tropical Weather

Tropical Storm Hermine

What was Invest 90L then updated to TD Ten has now been upgraded to Tropical Storm Hermine. Overnight, TS Hermine started to head N which did give it a little more breathing space to develop. It is still forecast to make the turn toward the NW but when that turn will happen is still unclear. The track for Hermine has shifted right from the previous one and this places TS Hermine right again the Mexico/Texas border. TS Hermine has a very ragged CDO(Central Dense Overcast), but unless it start to make the turn to the NW, the CDO should begin to have a better overall appearance. Additional strengthening is forecast but I don’t think it will have enough time to become a minimal hurricane even though the SST’s are in the 30Â°C-31CÂ° range. I do believe the forecast track will need to be adjusted slightly to the right again as the ridging over the northern Gulf has been slow in coming.

vis — Visible Satellite image of TS Hermine

Tags CDO, models, SST's

Tropical Weather

Tropical Depression Ten

Invest 90L has now been upgraded to a depression this evening with the 11PM advisory. TD Ten is favorable for some intensification till land interaction will restrict further development. At the moment TD Ten in headed NW to NNW. There is some disagreement between the models as to when the left turn will occur. A ridging will be developing over the northern Gulf of Mexico. All models are in agreement on this scenario.

Tags models

Tropical Weather

Invest 90L, Ex-Gaston

An area of disturbed weather in the BOC has now been designated as Invest 90L. This system was basically a part of the energy from the system in the Pacific TD-11-E. 90L is trying very hard to become something tropical in nature and it may become a tropical depression but there are some factors which are keeping it from developing quickly. In the last couple frames of the satellite loop, there is an area trying to rotate. If thus system can stay out in the waters for about 24-36 hours, it might have a chance to develop. If it starts to get close to the shore then the interaction with the land will just keep as an area of disturbed weather. In either case, the track is pretty simple, and because there is a high over Central Texas, this will be a system for Mexico.

vis — Visible Satellite image of Invest 90L

This morning satellite imagery of Ex- Gaston did seem to indicate that Gaston was having problems but later satellite imagery is now seeing a much better system. Gaston is slowly pulling away from the dry air around it and convection has been trying to wrap around the west and south. Cyclonic turning is also much better improved. The TUTT near PR/Hispanolia is visibly far enough away from Gaston it does loop like a high between the two is beginning to form. If Gaston continues to improve during the day and the convection begins to wrap around the center, Gaston may be like the Phoenix, and regeneration may occur with Gaston within 24-48 hours. The models are showing that Gaston may be headed toward the Leeward Islands although there a few there are further south. If Gaston stays to the north , then the Bahamas and Florida may have to keep an eye out. If it goes south, then it may go through Hispanolia and possibly dissipate there due to the high mountain range.

Tags BOC, land interaction

Tropical Weather

Earl, Ex-Gaston, Invest 99Lâ€¦

Post author By Admin
Post date 09/04/2010
No Comments on Earl, Ex-Gaston, Invest 99Lâ€¦

Tropical Storm Earl has been bearing down on Nova Scotia with winds of 70 MPH, and the center is now inland and within 24-36 hours will be a post-tropical/extratropical system.

Ex-Gaston has continued to look somewhat healthy although the convection is west of the center but it is trying to redevelop back to a tropical cyclone. With the exception of some dry air, the environment will be favorable for continuing development and the forecast for Gaston is to become at least a Tropical Storm if not a Hurricane within the next few days. There is a TUTT in the area of PR and will continue to head SW and that will help develop an anticyclone that will possible be over Gaston – thus Gaston will be able to gather more strength and vent out. The direction for Gaston is simple, it will continue it’s westward drive. I feel it will stay that way till after it has passed through the Lee/Windward islands but later on it may want to take a more WNW- to NW direction. The forecast after that is still unclear.

Using the Shear map you can see the TUTT.

Invest 99L is disorganized system as it is very elongated from SW to NE. There is the possibility that the “center” could be within the ITCZ. If this were the case the models are going to incorrect. At the moment the models are forecasting a NW movement and away from everyone. If the convection is near that “center” within the ITCZ – we have a new ballgame. Until there is a better grasp on something that does not even have a LLC – an “accurate” forecast cannot be made.

20100904.1400.msg2.x.vis1km_high.99LINVEST.25kts-1006mb-167N-210W.100pc — Satellite image of Invest 99L

In the BOC – there an area of disturbed weather. This looks to be some energy from the system in the Pacific – TD11-E. The shear in that area is very light (5-10 knots) and is conducive for some limited development. Is may start to head NW or NNW. Within 36-48 hours, shear will increase and interaction with the land masses will hinder further development.

visBOC — Visible Satellite image of the BOC

Tags ITCZ, LLC

Tropical Weather

Invest 99L

Post author By Admin
Post date 09/03/2010
No Comments on Invest 99L

A large tropical wave that just came off of Africa has been designated as Invest 99L. Although there isn’t much of any cyclonic turning, conditions are favorable for slow development. At the moment, the NHC is giving a 30% chance of becoming a tropical cyclone in within 48 hours. Most of the models are forecasting that Invest 99L will be turning NW and hopefully nothing we will ever have to worry about (unless you are a fish). This system has just been initialized and bias and errors are possible.

An update of ex-Gaston, conditions will be improving in the next few days and Gaston may regenerate. Gaston will be heading into an area where an anticylone will be over it which will allow strengthening to possible be a tropical storm in about 4 or 5 days.

Tags tropical wave

Tropical Weather

Earl, Fiona, and downgraded Gaston

Post author By Admin
Post date 09/02/2010
No Comments on Earl, Fiona, and downgraded Gaston

Hurricane Earl is the big story now as it looks to threaten the Outer Banks with now category 3 winds. Earl is beginning to feel some affects of W and SW dry air entrainment. Earl, with winds now at 125 MPH, is still a large and dangerous storm. If the center as forecast stays just offshore, then they will not get the dirty side of the storm and hopefully it will not be as bad as expected. The center of Earl should pass the Outer Banks later tonight.

Tropical Storm Fiona continues to to move toward the NNW with a forward speed of 17 MPH with highest winds of 50 MPH. A turn to the N is expected later tonight. Sometime late Friday night or early Saturday night Fiona will pass close to Bermuda. I would expect Fiona to lose some strength by the time it passes by Bermuda.

Gaston has been downgraded at least temporarily now as a Tropical Depression as Gaston lost most of its convection and the structure of the storm is poor. Gaston, as expected, lost a lot due to a lot of dry air and subsidence this morning. If Gaston can survive, which I believe it will, it will be brought up to a tropical storm in a day or two. The forecast for Gaston is that it will most likely will become at least a minimal hurricane possibly by Monday morning. Due to the ridging – Gaston will continue the W or WNW track. If this track continues, Gaston will be in the area of the Leeward Islands or possibly further south to the Windward Islands.

Addendum: As of the 5:00PM Advisory – Gaston has been downgraded even further and is now a remnant low. Advisories discontinued unless regeneration occurs. This very possible if conditions improve in a day or so.

Tags dry air, subsidence

Tropical Weather

Tropical Storm Gaston

What a day! This morning the wave that was designated as Invest 98L then later in the morning it was then upgraded to Tropical Depression Nine has now been upgraded to Tropical Storm Gaston. I still believe that there will not be too much more intensification because of the the dry air to the north and west though there is little shear – it may but very little. See my previous post about TD Nine.

Tags models, shear

Tropical Weather

Hurricane Earl, TS Fiona, and now TD Nine

Post author By Admin
Post date 09/01/2010
No Comments on Hurricane Earl, TS Fiona, and now TD Nine

Since this is the peak of the Hurricane season the tropics are hot and the trains of storm keep coming off the coast of Africa.
Hurricane Earl is now down to a Category 3 storm and the east coast from NC to Nova Scotia may get some effects from Earl. Earl is over very warm waters and also has a very good Cirrus outflow in a directions with the exception of the south, but Earl is now experiencing some SW vertical shear of 15-20 knots. There is also some mid to upper level dry air which is wrapping around portions of the storm. This should continue for 36 to 48 hours, but after that Earl will be over some cooler SST’s and this should begin to drop the intensity levels. The forecast is for Earl to be extratropical within 96 hours.

Tropical Fiona has become better organized today. Fiona looks much better with the exception of mid level dry air in the northern quadrant. The forecast for Fiona also better than yesterday which has Fiona dissipating in 48 hours. Most of the latest guidance now believe that Fiona will be a hurricane short term – possibly as soon a late tomorrow even though Fiona is going though some moderate shear. Soon after, there will strong northeasterly shear, mostly due to strong upper level winds associated from Earl. The pattern in a few days has Fiona rapidly weakening.

LATEST

The tropical wave that came off Africa yesterday and was designated as Invest 98L this morning has now been classified as Tropical Depression Nine. A deep-layered subtropical ridge will keep TD Nine on W track for the next few days. By days 2-3, the ridge will weaken slightly and this will slow down the storm and also let the storm track WNW. Later, by days 4-5 the ridge is expected to strengthen again., and the storm is forecast to accelerate some. The intensity is problematic as although TD Nine will be over very warm SST’s, TD Nine will be experiencing Moderate to Strong vertical shear along with a large SAL to the North and west which should inhibit some of the convection.
Models are having a very hard time trying to get a grasp on the storm so there will be some bias and error – wait a day or two to see what happens at that time.

Tags Cirrus, outflow, SAL, SST's, vertical shear

Tropical Weather

Hurricane Earl & Tropical Storm Diona

Post author By Admin
Post date 08/30/2010
No Comments on Hurricane Earl & Tropical Storm Diona

Hurricane Earl has been in an environment for continuing intensification and has blown up today and is now a Category 4 storm. There will probably be times where there will be an ERC (Eyewall Replacement Cycle) which is normal with a storm this strong. The intensification will be short term, probably 36-48 hours.

What was Invest 97L has been upgraded to Tropical Storm Fiona. Diona lack organization and the wind field is very large. The overall structure of Fiona is very poor and intensification will be slow. Most models are forecasting that Fiona may be a hurricane in 36-48 hours although the GFS model wants to dissipate Fiona is 2 or 3 days. The Models are still forecasting that Fiona will turn NW then N but there is a chance that the subtropical ridge will build back in and that will keep Diona from recurving. This is something forecasters will have to keep an eye on.

Tags ERC, GFS, recurve