Monday, June 01, 2015

Andres Continues To Surprise

Andres has continued to strengthen and is now a Category 4 hurricane. The images above and below are for 6:30 am MST, with the top view focused on Andres and the wider-view below showing both Andres and Two E off to east-southeast of the hurricane. 

From NHC this morning:

200 AM PDT MON JUN 01 2015

The satellite appearance of Andres has changed little overnight.
The hurricane is exhibiting characteristics of an annular hurricane
with a well-defined 25 to 30 n mi wide eye, a symmetric mass of deep
convection, and a lack of outer banding features.  A blend of the
subjective and objective Dvorak intensity estimates support an
initial intensity of 125 kt.

Unfortunately, the NHC glossary does not provide the user with a definition of what an "annular hurricane" is. As per Knaff, Kossin, and DeMaria (Weather and Forecasting, April 2003) the definition is:

The IR imagery is the visual means by which we determine whether a storm is an annular hurricane. An annular hurricane is identified if the hurricane persists for at least 3 h in an axisymmetric state defined by the following: 1) the hurricane has a normal-to-large-sized circular eye surrounded by a single band of deep convection containing the inner-core region and 2) the hurricane has little or no convective activity beyond this annulus of convection.

Andreas has also demonstrated how difficult forecasting intensity of hurricanes remains. The forecast below is from NHC at 15 UTC on May 30th:

FORECAST VALID 01/1200Z 16.8N 120.6W
50 KT... 50NE  40SE  30SW  50NW.
34 KT...100NE  90SE  70SW  90NW.

Finally, graphic below shows the current NHC forecast for Two E - after very slow movement, the TD is forecast to head north-northwestward as another major hurricane (Category 3 or stronger) by the later part of the week. The GFS forecasts take Hurricane Blanca toward the south end of Baja, just as the model did with Andreas. Certainly an interesting start to the eastern Pacific hurricane season.

1 comment:

  1. Bob,

    The GFS at 144 hrs has a really interesting set up with lots of deep moisture heading our way...

    A long way off and I suspect will change, but interesting for June none the less!

    Mike C