Tropical weather analysis - May 24, 2012
Invest 94L
A large area of low pressure centered just north of Grand Bahama continues to become better organized. This time yesterday I wasn't enthusiastic on development, as I wanted to see how it fared against continuing westerly shear and interaction with Cuba. It has done rather well for itself though, and all indications are that it will eventually become the second named storm of the season.
Satellite and surface observations indicate that this low is becoming better organized, with large pressure falls noted over the western Bahamas this afternoon. Large scale pressure falls during the daylight hours, when oceanic convection is weakest, is usually a sign of impending development, all other things being equal. Convection is also forming nearer to the central gyre, further attesting to the valiant organization of the system.
Figure 1. Latest infrared satellite image of Invest 94L, courtesy of RAMMB imagery Colorado State University (CSU).
Vertical shear over the system is still rather strong at the moment, as evidenced by the squashed convective pattern, but is forecast to slowly diminish, and 94L could become a tropical depression or tropical storm by tomorrow evening or early Saturday. The global models unanimously predict a tropical cyclone to emerge from this, and at this point, denial will get me nowhere.
The system is sandwiched between two cold lows, one over the central Gulf of Mexico, and another over Virginia moving out into the Atlantic. The former low is forecast to dissipate by tomorrow, and the latter one is of course moving into the Atlantic. In the wake of both systems, the Atlantic subtropical ridge is forecast to rebuild and force the system back toward the west, ultimately forcing a landfall somewhere along the southeast US coast, most likely the northern Florida/southern Georgia area on Monday. Models are in excellent agreement on this.
Regardless of development, heavy rains and gusty winds will continue to impact portions of the Bahamas through at least tonight. Interests along the southeast US coast should carefully monitor the progress of this system.
Probability of genesis in the next 48 hours: 60%
Should 94L become a tropical storm, it would be the first time two tropical storms formed in May since 1887. However, early season activity does not correlate to seasonal activity as a whole, and with the oncoming El Nino, I still think this season will be only slightly above average.
Bud
Bud continues to intensify, and is now a major hurricane. This is another oddity from a historical vantage point; the last time a major hurricane occurred during the month of May was in 2002. As of the latest NHC advisory, the following was posted:
Wind: 115 mph, with higher gusts
Location: 17.1°N 105.9°W
Movement: NE at 10 mph
Pressure: 960 mb
Category: 3 (Saffir-Simpson Hurricane Scale)
The hurricane is well organized on satellite images, with a 20-25 mile wide eye that seemingly shrinks due to convection. The outflow pattern is well-defined.
Figure 2. Latest infrared satellite image of Hurricane Bud, courtesy of NOAA's Satellite Services Division (SSD).
Despite continuous forecasts of southerly shear over the last few days, there appears to be very little evidence of this on water vapor imagery. The latest SHIPS model guidance also suggests little appreciable increase in shear throughout the forecast period. The primary reason I expect Bud to weaken is cooler sea surface temperatures; the hurricane is about to reach SSTs of only 26C according to the SHIPS model. Even SSTs a couple of degrees cooler seem to have a profound negative effect on major hurricanes.
Things have changed with Bud since yesterday. The global models are now in better agreement that the hurricane will continue to accelerate, reaching the coast by early Friday evening. This is supported by real time steering analyses and water vapor imagery. Landfall should occur between Manzanillo and Puerto Vallarta. After landfall, the global model fields think that the low- and middle-tropospheric circulations will decouple, with the former lagging behind near the coast. So do I.
5-day intensity forecast
Initial 05/25 0300Z 100 KT 115 MPH
12 hour 05/25 1200Z 90 KT 105 MPH
24 hour 05/26 0000Z 80 KT 90 MPH...INLAND
36 hour 05/27 1200Z 40 KT 45 MPH...INLAND
48 hour 05/28 0000Z 30 KT 35 MPH...OVER WATER
72 hour 05/29 0000Z 25 KT 30 MPH...POST-TROPICAL/REMNANT LOW
96 hour 05/30 0000Z...DISSIPATED
5-day track forecast
Figure 3. My 5-day forecast track for Bud.
Watches and warnings
SUMMARY OF WATCHES AND WARNINGS IN EFFECT...
A HURRICANE WARNING IS IN EFFECT FOR...
* THE COAST OF MEXICO FROM MANZANILLO NORTHWESTWARD TO CABO
CORRIENTES
A TROPICAL STORM WARNING IS IN EFFECT FOR...
* THE COAST OF MEXICO FROM PUNTA SAN TELMO WESTWARD TO EAST OF
MANZANILLO
A HURRICANE WATCH IS IN EFFECT FOR...
* THE COAST OF MEXICO FROM PUNTA SAN TELMO WESTWARD TO EAST OF
MANZANILLO
A TROPICAL STORM WATCH IS IN EFFECT FOR...
* THE COAST OF MEXICO NORTH OF CABO CORRIENTES TO SAN BLAS
A HURRICANE WARNING MEANS THAT HURRICANE CONDITIONS ARE EXPECTED
SOMEWHERE WITHIN THE WARNING AREA. A WARNING IS TYPICALLY ISSUED
36 HOURS BEFORE THE ANTICIPATED FIRST OCCURRENCE OF TROPICAL-STORM-
FORCE WINDS...CONDITIONS THAT MAKE OUTSIDE PREPARATIONS DIFFICULT
OR DANGEROUS. PREPARATIONS TO PROTECT LIFE AND PROPERTY SHOULD BE
RUSHED TO COMPLETION.
A TROPICAL STORM WARNING MEANS THAT TROPICAL STORM CONDITIONS ARE
EXPECTED SOMEWHERE WITHIN THE WARNING AREA...IN THIS CASE WITHIN THE
NEXT 24 HOURS.
A HURRICANE WATCH MEANS THAT HURRICANE CONDITIONS ARE POSSIBLE
WITHIN THE WATCH AREA...IN THIS CASE WITHIN THE NEXT 24 TO 36 HOURS.
A TROPICAL STORM WATCH MEANS THAT TROPICAL STORM CONDITIONS ARE
POSSIBLE WITHIN THE WATCH AREA...GENERALLY WITHIN 48 HOURS.
FOR STORM INFORMATION SPECIFIC TO YOUR AREA OUTSIDE THE UNITED
STATES...PLEASE MONITOR PRODUCTS ISSUED BY YOUR NATIONAL
METEOROLOGICAL SERVICE.
Reader Comments
Page: 1 — Blog Index
Oops.
Viewing: 1 - 6
Page: 1 — Blog Index