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Tropical weather analysis - August 6, 2013

By: KoritheMan , 3:10 AM GMT on August 07, 2013


Hurricane Henriette continues to churn in the tropical Pacific:

Wind: 90 mph, with higher gusts
Location: 15.1°N 133.1°W
Movement: WNW at 10 mph
Pressure: 981 mb

The satellite presentation of the hurricane hasn't changed appreciably since the 2100Z advisory from the National Hurricane Center, and satellite estimates from TAFB and SAB still support an 80 kt hurricane.

Figure 1. Latest infrared satellite image of Hurricane Henriette. Image credit: NOAA's Satellite Services Division (SSD).

Recent microwave data suggest little change to the inner core structure of Henriette; a recent AMSUB pass just before 0z did not show much evidence of an eye, but that instrument tends to not detect such features unless the hurricane is particularly well-defined, at least in my experience. The intensity guidance suggests little change over the next 12 hours, although there is some potential for very slight strengthening while Henriette remains over warm water. Beyond that time, the hurricane is forecast to approach cooler water and an increasingly more stable airmass, which is expected to lead to a weakening of the cyclone. My forecast is a little higher than the National Hurricane Center forecast, and keeps Henriette a minimal tropical storm at the end of the forecast period, since the hurricane is forecast to remain over water at least in the lower range of 26C throughout most of the forecast period; in fact, waters may even warm the closer the system gets to the Hawaiian Islands.

Henriette is still moving through a weakness in the subtropical ridge extending westward to just west of 135W. As Henriette rounds the closing of this weakness, a more pronounced turn to the west-northwest is anticipated as the subtropical ridge reamplifies to the north of the hurricane. Near the end of the period, a turn to the west-southwest is expected as Henriette weakens and becomes a shallower system. The global models remain in good agreement on the track, although the ECMWF is along the northern edge of the guidance envelope, while the GFS lies along the southern edge of the guidance. My forecast is a blend of both but somewhat favoring the ECMWF, as I feel Henriette will be a little stronger at later time periods. While interests in the Hawaiian Islands should continue to monitor the progress of Henriette, confidence is increasing that the hurricane will pass well to the south of the archipelago, although it may come close enough to generate locally heavy surf on windward-facing beaches early next week.

The coordinates and track map given below are based on the 2100Z advisory. The 0300Z advisory has come out since then, but I was writing this blog while the former advisory was still active. Deal with it.

Intensity forecast and positions

INITIAL 08/06 2100Z 14.7°N 132.3°W 80 KT 90 MPH
12 hour 08/07 0600Z 15.8°N 133.7°W 80 KT 90 MPH
24 hour 08/07 1800Z 17.2°N 135.2°W 75 KT 85 MPH
36 hour 08/08 0600Z 17.5°N 137.9°W 65 KT 75 MPH
48 hour 08/08 1800Z 17.7°N 140.0°W 60 KT 70 MPH
72 hour 08/09 1800Z 17.8°N 144.8°W 45 KT 50 MPH
96 hour 08/10 1800Z 17.0°N 150.0°W 40 KT 45 MPH
120 hour 08/11 1800Z 15.5°N 157.1°W 35 KT 40 MPH

Track forecast

Figure 2. My forecast track for Henriette.


An area of low pressure is expected to form offshore the south coast of Mexico in the next few days. The GFS shows this feature eventually becoming a tropical cyclone.

The Atlantic remains quiet for now, although the GFS continues to significantly lower the wind shear over the Caribbean, which is something we have not seen much of this year. This is forecast to happen in as little as a week, which is well before the model suffers from resolution issues. The shear is forecast to decrease even more in the two week timeframe, and I imagine the models will respond to this pattern by forecasting development.

Things will wake up in the Atlantic soon enough.

The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

Reader Comments

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3. WunderAlertBot (Admin)
5:53 AM GMT on August 08, 2013
KoritheMan has created a new entry.
2. nigel20
3:20 AM GMT on August 07, 2013
Great blog update, Kori!
Member Since: December 31, 1969 Posts: Comments:
1. galvestonhurricane
3:18 AM GMT on August 07, 2013
Great update! Hoping the Atlantic lights up soon.
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Basement-dwelling pseudo-otaku with a thrill for forecasting on the side.

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