[image-124]NASA's Aqua Satellite Sees System 91S Struggling
NASA's Aqua satellite provided infrared data on System 91S in the Mozambique Channel that showed a system battered by wind shear, stretched out, with broken convection.
A false-colored infrared image was created at the Naval Research Laboratory in Washington, D.C. using infrared data from the MODIS instrument aboard NASA's Aqua satellite on January 31 at 11:05 UTC/6:05 a.m. EST. The MODIS image showed the strongest thunderstorms associated with System 91S to the west-northwest of the center (over Mozambique), as a result of strong wind shear. Satellite data also revealed that the center of circulation is now elongated and that the strongest convection (rising air that forms the thunderstorms that make up a tropical cyclone) is occurring over the northwestern quadrant of the storm's center.
On January 31, System 91S had maximum sustained surface winds between 20 to 25 knots/37.0 to 46.3 kph/23.0 to 28.7 mph. Minimum sea level pressure was estimated to be near 1004 millibars.
Vertical wind shear continues to batter the tropical low, and the Joint Typhoon Warning Center expects the system to weaken as it moves south through the Mozambique Channel (between Mozambique on the African mainland and the island nation of Madagascar).
The Joint Typhoon Warning Center gives System 91S a low chance of development as it continues to deal with moderate to strong wind shear over the next couple of days.
Text credit: Rob Gutro
NASA's Goddard Space Flight Center
[image-108]Jan. 30, 2014 - NASA Satellite Sees System 91S Undeveloped in Mozambique Channel
The Tropical Rainfall Measuring Mission or TRMM satellite that observed the tropical low pressure area designated as System 91S earlier this week captured another look at a much weaker storm on January 30. Wind shear has now increased in the region, and the development chances for the tropical low pressure area have dropped.
At 800 UTC/3 a.m. EST, the center of System 91S was located near 18.2 south latitude and 39.1 east longitude, about 370 nautical miles northeast of Maputo, Mozambique (which is in the southernmost part of the country).
TRMM passed over System 91S on January 30 at 0820 UTC/3:20 a.m. EST and captured rainfall data on the low. The heaviest rainfall rates were occurring over the waters of the Mozambique Channel, where rain was falling in one area at about 1 inch/25 mm per hour. Other rainfall from the system was light. The U.S. Naval Research Laboratory overlaid TRMM rainfall imagery on top of visible imagery from Europe's METEO-7 satellite to provide a full picture of the low. The center appeared to be in the western Channel, while the heaviest rainfall was occurring in the eastern Channel.
Animated multispectral satellite imagery shows that the low-level center is elongating as a result of wind shear. A ridge of high pressure located southwest of System 91S is creating moderate wind shear (20 to 25 knots/37.0 to 46.3 kph/23.0 to 28.7 mph) hampering development.
Forecasters at the Joint Typhoon Warning Center have dropped the chances for System 91S to a low chance for potential for tropical development in the next day or two.
Text credit: Rob Gutro
NASA's Goddard Space Flight Center
[image-78][image-94]Jan. 29, 2014 - TRMM Satellite Peers at Rainfall in Developing Low Near Mozambique
The TRMM satellite flew above a System 91S, a tropical low pressure area, in the Mozambique Channel on January 28, 2014 at 1011 UTC/5:11 a.m. EST. TRMM data collected with this pass may be helpful in evaluating this low for possible tropical cyclone formation.
An analysis of rainfall from TRMM's Microwave Imager (TMI) and Precipitation Radar (PR) instruments are shown on the left overlaid on a visible/infrared image from TRMM's Visible and InfraRed Scanner (VIRS). TRMM PR measured rain falling at the rate of over 134.9 mm/~5.3 inches per hour in a band of powerful convective thunderstorms north of the center of circulation.
A 3-D view was created at NASA's Goddard Space Flight Center in Greenbelt, Md. using TRMM PR data. That image showed that some towering storms near the center of the low were reaching heights of above 16 km/9.9 miles. Towers this tall near the center of the tropical low are often an indication of tropical cyclone formation or intensification.
On January 29 at 1430 UTC/9:30 a.m. EST, the Joint Typhoon Warning Center dropped System 91S from formation alert status, but the low pressure area still has a medium chance for development in the next 24 hours. System 91S was located near 18.2 south and 39.1 east, about 585 nautical miles northeast of Maputo, Mozambique. An image from India's Oceansat satellite indicated 20 to 25 knot (37.0 to 46.3 kph/23.0 to 28.7 mph winds over the eastern semi-circle of the storm. Meanwhile the NOAA-19 polar orbiting satellite data showed weak, shallow convective banding of thunderstorms wrapping into the low-level center on January 29.
System 91S is located in an environment with moderate vertical wind shear. The Joint Typhoon Warning Center noted that dynamic computer model guidance shows System 91S should weaken as it continues moving to the southwest.
Only one named tropical cyclone called Deliwe has passed through the Mozambique Channel so far this year but this analysis found that areas of the Mozambique Channel from southeastern Mozambique through western Madagascar have already had well above normal rainfall for the past 30 days.
Text credit: Hal Pierce
SSAI/NASA Goddard Space Flight Center
[image-51]Jan. 28, 2014 - NASA Spots Developing Tropical System Affecting Mozambique's Nampala Province
NASA's Aqua satellite captured infrared data on a developing area of tropical low pressure known as System 91S that was brushing the Nampala Province of Mozambique on January 28.
Nampula is a province in northern Mozambique and its eastern coast runs along the Mozambique Channel of the Southern Indian Ocean. When NASA's Aqua satellite passed over the Mozambique Channel on January 28 at 10:35 UTC/5:35 a.m. EST the Atmospheric Infrared Sounder instrument known as AIRS captured infrared data on the clouds associated with System 91S.
AIRS showed some of the thunderstorms surrounding the low-level center of circulation had high cloud tops, where temperatures exceeded -63F/-52C, a threshold that indicates strong storms and potentially heavy rainmakers. The Joint Typhoon Warning Center noted that animated multi-spectral satellite imagery showed that the low-level center was consolidating and that there were bands of thunderstorms wrapping into the center - a sign of strengthening.
System 91S was centered near 15.4 south and 41.6 east, about 810 nautical miles northeast of Maputo, Mozambique. Maximum sustained winds are near the threshold for depression status, currently as high as 30 knots. The low is over warm enough waters to support further development.
At 11 a.m. EST on January 28, Nacala, Mozambique, located on coastal Nampula, was reporting drizzle from the fringes of System 91S with thunderstorms expected at night and on January 29.
Forecasters at the Joint Typhoon Warning Center give System 91S a high chance for becoming a tropical depression in the next day as it tracks to the southwest in the Mozambique Channel.
Text credit: Rob Gutro
NASA's Goddard Space Flight Center
