#930 Postby Florida1118 » Thu Jun 24, 2010 9:08 am
Blog From Jeff Masters:
The amount and intensity of heavy thunderstorm activity associated with the tropical wave (Invest 93L) located a few hundred miles south of Jamaica has increased over the past 24 hours, but the storm remains very disorganized and is not a threat to develop into a tropical depression today. The storm has not brought heavy rains to Haiti, fortunately, but heavy rains are expected today across Jamaica, where flash flood warnings have been posted. Satellite loops show a very disorganized system, with no low-level spiral bands and limited upper-level outflow. There are no signs of a surface circulation visible on satellite imagery. Pressures at the ground station nearest to the storm (Kingston) are beginning to fall, as are pressures at buoy 42057 a few hundred miles west of the storm, a sign that 93L is more organized than yesterday. Water vapor satellite loops show that moist air surrounds 93L, and there is less dry air to the storm's southwest than there was yesterday. There is an upper-level high pressure system a few hundred miles west of 93L, and the clockwise flow air around this high is bringing upper-level winds out of the northwest of about 10 knots over 93L, contributing to the 10 knots of wind shear observed in this morning's wind shear analysis from the University of Wisconsin's CIMSS group. Sea Surface Temperatures are plenty warm, a record 29 - 30°C. The Madden-Julian oscillation (MJO) currently favors upward motion over the Caribbean, which will act to increase the chances of tropical storm formation this week. The main negative for 93L continues to be the lack of spin. Last night's pass of the ASCAT satellite showed little in the way of a wind shift associated with 93L, though the pass did not completely capture the storm. The University of Wisconsin 850 mb relative vorticity analysis is showing that spin at 850 mb (roughly 5,000 feet in altitude) has increased over the past two days. The Hurricane Hunters are on call to investigate 93L Friday afternoon. Today's flight was canceled, due to 93L's lack of development.
I expect that by tomorrow, 93L should be closer to being directly underneath the upper level high pressure system to its west, which would act to lower wind shear and provide more favorable upper-level outflow. NHC is giving 93L a 40% chance of developing into a tropical depression by Saturday morning, which is a reasonable forecast. Given the storm's current lack of spin and relatively modest amount of heavy thunderstorms, the earliest I'd expect 93L to become a tropical depression would be Friday afternoon, with Friday night or Saturday morning more likely. Interaction with land will be a problem for 93L, as it will likely move over Mexico's Yucatan Peninsula or Western Cuba on Saturday. Expect 93L to bring flooding rains of 3 - 6 inches to Jamaica and eastern Cuba today through Friday. These rains will spread to the Cayman Islands, northern Honduras, and central Cuba Friday through Saturday, and western Cuba, Belize, and Mexico's Yucatan Peninsula on Saturday and Sunday. The current run of the SHIPS model has 93L slowing down late this week to a forward speed of just 7 knots (8 mph) from its current speed of about 10 mph, in response to a weakening in the steering currents. A trough of low pressure is expected to swing down over the Eastern U.S. on Monday. If this trough is strong enough and 93L develops significantly, the storm could get pulled northwards and make landfall along the northern Gulf of Mexico coast. This is the solution of the GFS, GFDL, and HWRF models. If 93L stays weak and/or the trough is not so strong, the storm would get pushed west-northwestwards across Mexico's Yucatan Peninsula and towards the Texas or Mexican coast south of Texas. This is the solution of the NOGAPS, ECMWF, and Canadian models. A likely landfall location is impossible to speculate on reliably at this point, and the storm could hit virtually anywhere along the Gulf of Mexico coast given the current uncertainty in its development. A key factor will be how far north the center of 93L eventually consolidates at.
The amount of wind shear in the Gulf of Mexico next week is highly uncertain. There is currently a band of high shear near 30 knots over the Gulf. The GFS model predicts that this band of high shear will lift northwards, keeping low wind shear over the Gulf next week. However, the ECMWF model keeps high shear entrenched over the Gulf of Mexico. I give 93L a 50% chance of eventually becoming Tropical Storm Alex, but the odds of it eventually becoming a hurricane have lessened to 10%. None of the computer models is calling for 93L to become a hurricane.
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I'm sorry, I just don't see it to the southeast of Jamaica, looks like all the ll clouds are streaming off to the NW..gif){kind=small}
