Hurricane Danielle undergoes an Eyewall Replacement Cycle

August 28th, 2010 |
Morphed Integrated Microwave Imagery at CIMSS (MIMIC) product

Morphed Integrated Microwave Imagery at CIMSS (MIMIC) product

An animation of the Morphed Integrated Microwave Imagery at CIMSS (MIMIC) product (above) revealed that Hurricane Danielle (which had intensified into a Category 4 storm) was undergoing an Eyewall Replacement Cycle (ERC) during the 27 August – 28 August 2010 period. Note how the smaller inner eyewall deteriorated and became replaced by a much larger outer eyewall during the ERC process.

Following the ERC, GOES-13 10.7 µm IR images from the CIMSS Tropical Cyclones site (below) showed Danielle beginning the recurvature process after weakening to a Category 2 storm.

GOES-13 10.7 µm IR images

GOES-13 10.7 µm IR images

Even though Hurricane Danielle was quite far from the US East Coast (below), long period ocean swells and increasing onshore winds were creating dangerous rip currents along much of the nearshore waters and beaches from Florida to the Mid-Atlantic states.

GOES-13 10.7 µm IR image

GOES-13 10.7 µm IR image

Be sure to check out the PREDICT Field Experiment Blog for additional insights on other tropical cyclone activity in the Atlantic basin.

The Active Tropical Atlantic

August 27th, 2010 |

The infrared imagery from Friday morning, 27 August, shows three separate tropical systems — in various stages of development — over the Atlantic Ocean, with a fourth system poised to move out into the tropical Atlantic from Africa. Meteosat imagery shows a fifth system moving westward over central Africa (These images are available at the University of Wisconsin SSEC‘s Geostationary Image Browser).

Hurricane Danielle, above, as seen by GOES-15 (Click here for a longer loop from GOES-13) is a mature Category IV storm over the central Atlantic, with well developed outflow in an environment characterized by warm sea-surface temperatures and small vertical wind shear. The cold cloud tops surrounding the mostly cloud-free eye have brightness temperatures in the 195-200 K range. GOES-15 IR Imagery shows similar temperatures.

Tropical Storm Earl, above, is in an environment not as conducive to development as Danielle. Analyses from the CIMSS Tropical Weather Web Page show a storm track that has recently passed over cooler ocean water. More importantly, Earl is surrounded by dry Saharan Air and that dry air is suppressing some of the convective activity needed to fuel system development. Analyses for Total Precipitable Water (taken from this site) also show Earl entraining dry air. However, the projected path of Earl is towards a warmer sea surface in a more moisture-rich environment, so intensification is forecast.

In contrast the Earl, the disturbance off the coast of Africa, above, as viewed from GOES-12, is over a region of warm water, and is south of dry air with origins over the Sahara. Shear values over the storm are low, so intensification should occur.

The next names in the list for the Atlantic are Fiona, Gaston and Hermine. For the latest on these storms, visit the National Hurricane Center website.

(Added: Dan Lindsey at CIRA notes the similarity to 1995. Here is an image from 2345 UTC on 29 August 1995 showing a similar line-up of storms across the tropical Atlantic).

Hurricane Danielle finally exhibits an eye on GOES imagery

August 26th, 2010 |
GOES-13 10.7 µm IR images

GOES-13 10.7 µm IR images

Hurricane Danielle went through another period of intensification on 26 August 2010, and GOES-13 10.7 µm IR images (above) and 0.63 µm visible images (below) from the CIMSS Tropical Cyclones site revealed the formation of a well-defined eye that was not obscured by a Central Dense Overcast (CDO) as was the case in previous days.

GOES-13 0.63 µm visible images

GOES-13 0.63 µm visible images

Tropical Storm Earl

August 25th, 2010 |
GOES-13 10.7 µm IR imagery

GOES-13 10.7 µm IR imagery

Tropical Storm Earl formed in the eastern Atlantic Ocean on 25 August 2010. GOES-13 10.7 µm IR images from the CIMSS Tropical Cyclones site (above) revealed a well-defined circulation, with the development of convective clusters and curved bands.

The environment around Earl was one that exhibited low values of 200-850 hPa deep layer wind shear (below), which was favorable for further intensification of the tropical cyclone.

GOES-13 IR image + 200-850 hPa Deep Layer Wind Shear product

GOES-13 IR image + 200-850 hPa Deep Layer Wind Shear product