CIMSS Satellite Blog

Hurricane Bertha became the first hurricane of the season in the Atlantic Basin on 07 July 2008,  setting a new record for the furthest-east named storm formation in the tropics. GOES-12 IR images from the CIMSS Tropical Cyclones site (above) showed increasing coverage of cold cloud top temperatures and the formation of an eye; microwave imagery from the polar-orbiting SSM/I instrument (below) began to show better evidence of an eye structure a few hours before the geostationary satellite imagery.

GOES-12 visible imagery (below) showed a closer view of the forming eye of the hurricane.

A plot of the CIMSS Advanced Dvorak Technique intensity estimate (below) showed that Bertha began a period of more rapid intensification during the early morning hours of 07 July.

Bertha had been moving northwestward over increasingly warmer Sea Surface Temperatures (below), which may have played a role in the intensification of the tropical cyclone.

UPDATE: Hurricane Bertha rapidly intensified into a Category 3 storm during the afternoon hours on 07 July, with the CIMSS ADT intensity estimation technique suggesting peak wind speeds near 115 knots. During this period of rapid intensification, Bertha also displayed a nice eye on satellite imagery (QuickTime animations: GOES-12 visible | GOES-12 IR). It is interesting to note that the MIMIC Total Precipitable Water product (below) indicated that dry Saharan Air Layer (SAL) air had wrapped completely around Bertha during the 05-08 July period — the presence of such dry air in close proximity to a tropical cyclone would normally be thought of as a negative factor for rapid intensification!

AWIPS composite images of the 6.7µm GOES-11 and 6.5µm GOES-12 “water vapor” channels (above) show the eastward progression of synoptic-scale frontal systems across the US and Canada — as well as the westward motion of what could evolve into a subtropical disturbance in the eastern Gulf of Mexico — on 02 October 2007. Regions of greater middle-tropospheric moisture (blue to white enhancement) and clouds (white to green enhancement) are evident along and ahead of many of these fronts, while areas of subsidence and dry air (yellow enhancement) are seen in the wake of some of the frontal boundaries.

The CIMSS Regional Assimilation System (CRAS) numerical weather prediction model has the ability to output synthetic satellite imagery — a “forecast” of what GOES imagery might look like in the near future. AWIPS images of CRAS predictions of the GOES water vapor channel imagery (below) show the forecast covering the 02-05 October 2007 period. The CRAS imagery indicated that the pattern of alternating moist and dry features (associated with subsequent frontal passages) would continue for the next 2-3 days, while the moisture associated with the Gulf of Mexico disturbance would eventually move inland across the western and central Gulf Coast states during the forecast period.

CIMSS has been generating CRAS water vapor and IR forecast imagery since the mid-1990s, and this forecast imagery has been made available to AWIPS (via LDM subscription) since August 2006. The CRAS model forecast imagery in AWIPS has been well-received so far, being mentioned in several Area Forecast Discussions issued by the National Weather Service office at Milwaukee/Sullivan, Wisconsin. For more information, see the CRAS Forecast Imagery in AWIPS VISIT lesson.