Thursday, July 6, 2017

TROPICAL DEPRESSION 4 UPDATE JULY 6 2017 0500 PM EDT

As of 0500 PM EDT Tropical Depression Four remains disorganized as it tracks through dry air and speeds across the Atlantic near 23 mph forward speed.  This speed for tropical cyclone does not help in the development process and the storm produces its own wind shear of over the cloud structure.

The depression is tracking almost due west, however, according to 18z model XTRP the direction of travel is west of due north while the Invest previous and present track is directly westward.

Not much change is expected unless it slows down but that does not look likely, as a 1029 mb High pressure system near 35° N. Long. and 35° W. Lat. is helping to steer this system quickly across the Central Atlantic.

Remember what I mentioned yesterday a weak system always tends to track west to west-northwest. A tropical cyclones path are governed by trough and low pressure weakening the High pressures ridge.  As the High pressure ridge is weaken it opens a passage way for a well organized tropical cyclone to move into.  However, in the case of an Andrew storm the High pressure got stronger and the ridge built westward over the cyclone strengthening it and turning it westward.  There was no strong low pressure system or trough to prevent that westward track.  So this depression could remain on the westward or west-northwest track until it weakens further and dissipates.

RTW  http://ralphstropicalweather.myfreesites.net 







TROPICAL WEATHER OUTLOOK JULY 6, 2017 0416 PM EDT

Other than weak tropical depression four the tropical Atlantic remains quiet for now.  Sahara dust and dry air over off the African coast affecting wave number one and wave number three is also being affected by dry and African dust that has made its way toward the Lesser Antilles.  This dry air limits the development of thunderstorms along these waves axis.  Some wind shear is also present over the west Caribbean that is also affecting tropical wave number 4.  Elsewhere all remains quiet.

I will have an update on TD Four as soon as the data is released.

RTW http://ralphstropicalweather.myfreesites.net

TROPICAL UPDATE JULY 6, 2017 1100 AM EDT

RTW:  Ralph's Tropical Weather
TROPICAL DEPRESSION FOUR LOOKING ILL DEFINE THIS MORNING.  MOST OF THE CONVECTION (THUNDERSTORMS) HAVE DIMINISHED.  


THE DEPRESSION IS MOVING THROUGH DRY AIR AND IS PRESENTLY MOVING TO FAST 21 MPH FORWARD SPEED.  

THIS PRODUCES SHEAR OVER THE THUNDERSTORMS AND THEY BEGIN TO LOSE THEIR INTENSITY.  ON VISIBLE SATELLITE YOU CAN SEE FEATHERING OF THE CLOUD SURROUNDING THE DEPRESSION.  THAT IS WIND SHEAR OVER THE STORM.

IF THIS TREND CONTINUES IT MAY HAVE TO BE DOWNGRADED TO AN OPEN WAVE AGAIN...RTW

http://ralphstropicalweather.myfreesites.net