Tropical weather analysis - July 4, 2012
Tropical Depression Four-E
The area of low pressure we were previously tracking developed into the a tropical depression today. As of the latest NHC advisory, the following information was posted on the cyclone:
Wind: 35 mph, with higher gusts
Location: 13.6°N 108.9°W
Movement: WNW at 12 mph
Pressure: 1005 mb
Category: Tropical depression (Saffir-Simpson Hurricane Scale)
The storm is still not well-organized, but relative to earlier it is looking a little healthier. Given the current structure, it is likely that the diurnal convective maximum period this morning will be sufficient to bring the system up to a tropical storm.
Figure 1. Latest infrared satellite image of Tropical Depression Four-E. Image credit: NOAA
There still appears to be some northeasterly shear lingering in the area, but satellite images suggest that the depression is outrunning these negativities. The potential exists for strengthening through about 48 hours, and my forecast shows it becoming a hurricane. Thereafter, the cyclone is likely to cross a sharp sea surface temperature gradient, then encounter dry air and northwesterly shear. Most of the global models retain a circulation for the next five days, and I will consciously follow suit. Howver, the system is expected to be weakening over cool water at such times. It is improbable that this system will be able to hold together as a viable tropical cyclone long enough to impact the Hawaiian Islands. However, local rainfall enhancement can be expected along windward facing beaches in the middle of next week.
The cyclone is currently situated to the south of a well-established ridge. Little change to this pattern is expected in the global model forecast fields, and water vapor imagery corroborates this. Many Pacific tropical cyclones move west to west-northwest without ever threatening land. A continued generally west-northwest motion is expected for the next day or so, followed by a turn to the west as the storm finds itself sliding underneath the small weakness to the north, into a more uniform easterly flow.
My forecast track is in good agreement with the GFS and ECMWF consensus, albeit slower.
5-day intensity forecast
INITIAL 0300Z 07/05 30 KT 35 MPH
12 hour 1200Z 07/05 35 KT 40 MPH
24 hour 0000Z 07/06 45 KT 50 MPH
36 hour 1200Z 07/06 55 KT 65 MPH
48 hour 0000Z 07/07 65 KT 75 MPH
72 hour 0000Z 07/08 55 KT 65 MPH
96 hour 0000Z 07/09 45 KT 50 MPH
120 hour 0000Z 07/10 35 KT 40 MPH
5-day forecast track
Figure 2. My 5-day forecast track for Tropical Depression Four-E.
Another disturbance lies behind TD4-E
I am tracking another disturbance moving into the Gulf of Tehuantepec. Shower activity with this low is disorganized, and environmental conditions are only conducive for slow development over the next few days as it moves slowly westward.
Probability of development in 48 hours: 20%
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