CIMSS Satellite Blog

AWIPS images of the water vapor  satellite composite (above) showed the evolution of a wide variety of synoptic-scale features across the Northern Hemisphere at 3-hour intervals during the 19 May - 20 May 2008 period. Of particular interest was the water vapor signatures associated with an occluding cyclone over the North Atlantic Ocean (located south of Iceland and west of the British Isles). A closer view using Meteosat-9 images of the 6.2 µm water vapor channel at 15-minute intervals (below) revealed a great deal of interesting mesoscale structure as bands of moist and dry air wrapped into the occluding cyclone as it began to fill .

Just 11 days after deadly Cyclone Nargis made its devastating landfall in Myanmar (also known as Burma), Meteosat-7 IR imagery from the CIMSS Tropical Cyclones site (above) showed a new tropical disturbance that was moving northwestward across the Irawaddy Delta region of Myanmar on 13 May 2008. The Joint Typhoon Warning Center issued the following Tropical Cyclone Formation Alert at 20:30 UTC:

WTIO21 PGTW 132030
MSGID/GENADMIN/NAVPACMETOCCEN PEARL HARBOR HI/JTWC//
SUBJ/TROPICAL CYCLONE FORMATION ALERT//
RMKS/
1. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE WITHIN 150 NM EITHER SIDE OF A LINE FROM 16.5N 96.1E TO 19.4N 92.1E WITHIN THE NEXT 12 TO 24 HOURS. AVAILABLE DATA DOES NOT JUSTIFY ISSUANCE OF NUMBERED TROPICAL CYCLONE WARNINGS AT THIS TIME. WINDS IN THE AREA ARE ESTIMATED TO BE 25 TO 30 KNOTS. METSAT IMAGERY AT 131800Z INDICATES THAT A CIRCULATION CENTER IS LOCATED NEAR 16.7N 95.7E. THE SYSTEM IS MOVING WEST-NORTHWESTWARD AT 06 KNOTS.
2. REMARKS: RECENT ANIMATED INFRARED SATELLITE IMAGERY AND A 121210Z SSMI MICROWAVE IMAGE INDICATE PRONOUNCED LOW-LEVEL CYCLONIC TURNING OF CONVECTION AT THE WESTERN END OF THE MONSOON TROUGH. HOWEVER, MORE RECENTLY, CONVECTION HAS WANED SOMEWHAT IN RESPONSE TO LAND INTERACTION. THE CIRCULATION CENTER IS CURRENTLY TRANSITING
GENERALLY NORTHWESTWARD ACROSS THE YANGON DELTA REGION OF MYANMAR. OBSERVATIONS FROM YANGON AS OF 131300Z, SUPPORT A 25 TO 30 KNOT CIRCULATION WITH SEA LEVEL PRESSURES NEAR 1000 MB (3 MB PRESSURE FALLS OVER THE PAST 24 HOURS) AND SUSTAINED WINDS AT 10 KNOTS GUSTING TO 20 KNOTS OUT OF THE NORTHEAST. A PARTIAL 130301Z ASCAT
IMAGE ALSO INDICATES STRONG WESTERLIES TO THE SOUTH OF THE CENTER WITH SUSTAINED EASTERLIES TO THE NORTH, FURTHER PROOF OF CYCLONIC TURNING. THE CENTER CURRENTLY LIES UNDER LOW VERTICAL WIND SHEAR JUST SOUTH OF THE SUBTROPICAL RIDGE AXIS WITH FAVORABLE SOUTHWESTERLY DIFFLUENCE ALOFT. THOUGH THE DISTURBANCE IS CURRENTLY OVER LAND, MINIMAL DEGRADATION OF THE LOW LEVEL IS EXPECTED DUE TO THE LOW LYING TOPOGRAPHY AND FAIRLY QUICK TRANSIT
OVER THE LOW-LYING COASTAL REGION OF SOUTHERN MYANMAR. EMERGENCE INTO THE BAY OF BENGAL IS EXPECTED WITHIN THE NEXT 12 TO 18 HOURS. MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 25 TO 30 KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1000 MB. THE POTENTIAL FOR THE DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24 HOURS IS GOOD WITH THE ONLY LIMITATION BEING TEMPORARY LAND INTERACTION.

CIMSS satellite-derived atmospheric motion vectors and products (below) indicated that the upper-tropospheric winds, divergence, and deep layer shear were all relatively weak  over the region at that time.

If you thought that Tropical Storm Olga was the last gasp of the 2007 North Atlantic basin’s Tropical Cyclone season, think again: GOES-12 10.7 µm IR channel imagery (above; closer view) and 6.5 µm water vapor channel imagery (below) revealed a circulation southwest of the Azores on 29 December 2007 (centered near 28º North latitude, 47º West longitude) that appeared to be acquiring subtropical characteristics as it began to produce gale-force winds and some convection (evident in this 500-m resolution MODIS visible image) within the northeastern quadrant of the disturbance.

===============================================

A Meteosat-8 visible channel image (above) showed the circulation well off the coast of Africa at 12:00 UTC on 29 December. In addition, note the “hazy” appearance of the cloud-free region over and just south of the Cap-Vert region of northwestern Africa (not the larger sun glint feature seen farther south over the subtropical South Atlantic — the Saharan Air Layer (SAL) tracking product (below) suggests that this could be an area of airborne dust (yellow to orange enhancement) moving westward from the Sahara desert across the far eastern Atlantic Ocean (a good deal of the yellow-to-orange signal across the rest of the North Atlantic is a “false positive” SAL/dust signal).