The tale of two systems – one will begin an extratropical transition today; one will likely become a storm today. Neither are expected to impact land. Ignacio looks very impressive on satellite imagery while Invest 92L looks like it is struggling with shear. At least the future of one of these storms is clear.Tropical Storm Ignacio is holding on rather impressively even though it is now over cooler waters. Ignacio looks splendid on IR imagery with good spiral bands, very good outflow in all quadrants and a good symmetric area of convection right over the center. Ignacio is likely pulling in dry air from the north which is giving it the slightly-abnormal appearance you see below. All in all, that this is a storm on the decay but still holding it’s own pretty well is rather impressive.
Tropical Storm Ignacio - Aug 25, 2009 courtesy CIMSS
Ignacio crossed the 26°c isotherm overnight – 26°c is just below 80°F, the typical minimum storm-supporting sea surface temperature(SST). As Ignacio continues forward, northwest about 14mph, water temperatures will continue to drop and Ignacio’s cloud tops should begin to warm considerably until the storm becomes a low-level low pressure system.
Tropical Storm Ignacio SST - Aug 25, 2009 courtesy CIMSS
A QuickSCAT pass late last night showed Ignacio still had a well-defined surface circulation with 40kt winds in the eastern quadrant and an elongated wind field axis with a southeast-northwest oriented axis.
Tropical Storm Ignacio QuickSCAT - Aug 25, 2009 courtesy CIMSS
The official National Hurricane Center forecast calls for Ignacio to slowly weaken throughout the next 2-3 days. However, the storm could be declared a non-tropical low as early as tomorrow.
Tropical Storm Ignacio Forecast and current wind radii
Meanwhile, Invest 92L was penetrated by hurricane reconnaissance last night. Gale-force winds were found in the northeastern quadrant of the system but the recon could not pinpoint a closed circulation indicating the system, at the surface, had a sharp wave axis. These stronger winds were located within 150nm of the center. Ideally, however, for a developing cyclone these winds will need to wrap in tighter with the axis or the surface circulation. A mid to upper-level trough sits over the lower-level wave and this is helping induce convective development so predominant in the eastern quadrant as seen on satellite imagery.
Invest 92L IR Satellite - Aug 26, 2009 courtesy CIMSS
Though development seems likely today the system is unlikely to develop rapidly with the trough overhead. It should be noted SHIPS is calling for a hurricane within 24 hours – that idea seems extremely far-fetched. SST’s support intensification, however, there aren’t really any deep pockets of warm ocean water for the storm to get a rapid burst of energy. There is, however, good atmospheric moisture all around the storm. It is possible that as the upper-level trough moves away from the system it could enhance outflow and the system could intensify. First, however, convection needs to get over the wave axis to aid the storm in closing off the surface low.
Invest 92L Shear/SST - Aug 26, 2009 courtesy CIMSS
Several GF* (insert any letter to replace the *), NOGAPS, UKMET and the NHC’s baby, HWRF, are in great agreement on a recurvature of the system before any potential landfall – nearly identical to Bill but further west.
Related posts:
- Tropical Storm Ignacio Still Weak, Invest 92L Will Struggle
- Parma leaves damage, death behind; Super Typhoon Melor to weaken before brushing Tokyo, Japan
- Flashback: Hurricane Katrina Refuses to Weaken Over South Florida
- TD 12-E Should Become TS Ignacio
- Edzani continues to strengthen to cat four; weakening immenent
