Monday, August 31, 2009

94L and Jimena


In the tropical Atlantic the tropical wave named 94L currently has intensified significantly overnight. A large mass of thunderstorms have developed directly over the broad circulation, and now looks destined to be a Tropical Depression by the end of the day. I still think this system is going to have to fight the dry air, but looking upstream to the northwest, where this system will have to go to survive, the moisture increases significantly. Additionally, a stalled out upper low is currently spinning about to the north of the system, and this will help to ventilate it as it passes to the south. So, if this system can fight off the dry air it is experiencing now, I don't see why it can't make it to a named system anymore. 10-20% chance.....bologna. The new name will be Erika.

One thing to point out though, that lingering trough and frontal boundary is still holding off of the eastern coast, and that ridge of high pressure is still supposed to build in. This could lead to three possible solutions. 1) A new low develops and consolidates, weakly (tropical or not tropical) and heads out along the boundary or stalls out...thus interfering with potential Erika as it moves east. 2) The energy is left behind as the ridge builds but does not consolidate, but is instead entrained into potential Erika to make the system stronger as she is pushed back south with the building ridge towards the west. 3) The trough is still just strong enough to leave a weakness to allow Erika to head out to sea.

These three solutions are all possible, and thus make forecasting Erika's track difficult at this time. The CMC right now believes the weakness will be strong enough to pull her north. The Euro, GFS, and HWRF all take Erika west. (The GFDL does not develop the system). Usually for track I like to believe the Euro and CMC in the Atlantic...so I am a bit split. But considering the Euro has been the best this year, I will follow that track. The one issue with the Euro....it doesn't strengthen Erika very much at all, and this could be a limiting factor of the model. The only models to forecast a stronger system are the CMC and HWRF.

Now as for the Pacific, Major Hurricane Jimena is moving north-northwest towards the Baha and is now forecast by the NHC to make landfall a little north of Cabo. This would bring the right side of the storm into the Cabo area, which tends to be the strongest side (more wind, rain, and tornadoes). Not good for the beach resorts! However, right now the track takes it far enough out to sea that the eyewall should miss Cabo directly. Any shift east however could be disastrous. Lessons learned (if the currently forecast track holds true): 1) The GFDL and HWRF were once again too far east...but did better than the Euro and CMC. 2) The models like to lose the moisture once the system makes landfall...which seems highly unlikely. A trough moving in to the northwest US should entrain the moisture from Jimena and lead to heavier rain that expected in the west and northern plains (possible also central plains later).

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