30 June 2010

Alex intensifying as it makes its way to the coast...

At 03Z today (11pm EDT Tuesday), Alex was upgraded to a hurricane, the first of the season.  It is the first hurricane to form in June since Allison in 1995.  At 15Z today, the intensity as measured by aircraft was 70kts and 961mb.  [if that seems like a very low pressure for that wind speed to you, you're right!... a 961mb storm would normally have winds of 95-100kts, but Alex is large and the organization has still not matured]
Further intensification is very likely today and up to landfall.

You can view a long radar loop (from Brownsville, and going back to first eyewall view):

Landfall is expected late tonight, fortunately in a very sparsely-populated area of northern Mexico.  The closest major city is San Fernando, which should experience hurricane conditions, but is inland by about 40 miles, so it won't be affected by a storm surge.  However, the storm surge will be a bigger concern further north into Texas, such as Port Isabel,
Padre Island National Seashore, Baffin Bay, and Corpus Christi Bay.  Sea levels up to 6' above normal can be expected toward Port Isabel, and gradually decreasing further north along the coast.  Even Galveston could see a surge of 2-3', and coastal areas affected by the oil spill will also see an increase in sea level, perhaps up to 1-2'.  On top of the storm surge will be larger and more violent waves than is characteristic of the Gulf.  Both coastal and inland areas in Alex's path will experience flooding as 6-20" of rain falls in the coming days (Brownsville as ALREADY received at least 3" of rain!). And of course, there is an elevated risk of tornadoes along Alex's path, particularly in the north side of the storm.

Here are observations from a coastal station in extreme southern Texas, Port Isabel:

And here are wave height observations from Gulf Shores, AL, an area representative of the oil spill region:

Please visit my tropical Atlantic headquarters.

29 June 2010

Alex getting stronger and heading for land...

Tropical Storm Alex has gotten much better organized in the past 24 hours.  The convection is becoming centralized and coalescing.  Intensity as of 15Z today is 60kts and 982mb.  It's very likely that by later today, Alex will become the season's first hurricane.  Northern Mexico and the southern tip of Texas up to Baffin Bay are under a Hurricane Warning, and a Tropical Storm Warning extends from Baffin Bay to Port O'Connor.

Landfall is expected Wednesday night just south of the US/Mexico border as a Category 1 hurricane.  Large swells of 8-10' will spread across much of the Gulf today through Thursday.  The extreme southern tip of Texas could expect a storm surge up to 5' above normal tides (smaller surge further north in Corpus Christi, etc).  Inland rainfall is always a major threat with any landfalling tropical cyclone, and northeastern Mexico and southern Texas could get 6-12" of rain.

Please visit my tropical Atlantic headquarters.

28 June 2010

Alex has entered the Gulf of Mexico...

Since my update on Friday afternoon, TD1 was upgraded to TS Alex early the following day.  It made first landfall on Belize City, Belize as a 50kt tropical storm, tracked northwest across the Yucatan Peninsula, and entered the southern Gulf of Mexico late Sunday night.  Toward the end of the trip across the peninsula, it weakened slightly to a Depression, but almost immediately regained TS strength upon entering the warm Gulf waters.  At 15Z today, the intensity was 50kts and 989mb.

As of this writing, the bulk of the deep convection is located to the east of the low-level center, and it looks fairly ragged and disorganized, as one would expect after spending nearly a full day over land.  However, Alex is forecast to become a minimal CAT2 hurricane as it approaches the western Gulf, making landfall early Thursday morning near the US/Mexico border.  One thing I'll point out is that model guidance has been gradually shifting the landfall point further and further north with each new run.  I'd suspect that the official forecast track will follow that trend and nudge slightly northward with each advisory.

In the US, coastal areas can expect a storm surge up to 6' near Brownsville and Corpus Christi, and minimal up to at least the TX/LA border.  In the coming days, larger and larger swells and waves will make their debut in the north-central Gulf; certainly a negative impact on the oil leak situation.  Instead of the typical 3-4' swells offshore of LA, MS, AL, and northwest FL, swells of 8-10' will make their way up there by Wednesday.

Please visit my tropical Atlantic headquarters.

25 June 2010

TD1 forms in west-central Caribbean...

Since last weekend, there has been an area of disturbed weather gradually making its way from the southern Windward Islands to its current location just north of Honduras.  During the past 18 hours or so, it has gotten much better organized... the convection is stronger, more persistent, and more centrally located over the low-level circulation.  Based on those indicators plus and an aircraft reconnaissance flight into it, it was upgraded to Tropical Depression 1 at 22Z today (6pm EDT).  The intensity was found to be 30kts and 1004mb and on an upward trend.

A Tropical Storm Warning has been issued for the eastern Yucatan Peninsula, and the center of the storm will move ashore late Saturday afternoon.  Although the Yucatan Peninsula is flat, it still cuts off a tropical cyclone's life support system: the warm ocean.  When the storm exits the Yucatan later this weekend, it is unknown what condition it will be in as it enters the Gulf of Mexico (anywhere from mildly weakened to severely weakened).  Regardless, the sea surface temperatures will be in the 29C ballpark, which combined with low vertical wind shear, the storm should re-intensify as it heads north across the Gulf.

TD1 will most likely become the season's first tropical storm within the next 6-12 hours, and the first name on the list is Alex.

Please visit my tropical Atlantic headquarters.

15 June 2010

Disturbance struggling in poor environment...

A combination of marginal vertical shear and decreased low-mid-level relative humidity seems to have taken a toll on the developing vortex.  Deep convection associated with the disturbance has diminished, and it's now an exposed swirl of clouds centered near 13N 46W and tracking WNW at 13kts.  It is not expected to regenerate.  See http://einstein.atmos.colostate.edu/~mcnoldy/tropics/atcf/latestATL.png for the current location and prior track.

Switching gears to the season in general, we have 4 new names in the roster to replace retired names from the historic Florida-centric 2004 season (there is a 6-year rotation of names).  Colin will replace Charley, Fiona will replace Frances, Igor will replace Ivan, and Julia will replace Jeanne.  No names were retired last season, which has only happened 4 other times in the past 20 years: 1993, 1994, 1997, and 2006.

Due to large-scale environmental factors, this season is expected to be very active.  Using a 50-year climatology, the Atlantic basin typically gets 9.6 tropical storms per year, 5.9 hurricanes, and 2.3 major hurricanes.  The CSU forecast for this season is 18 tropical storms, 10 hurricanes, and 5 major hurricanes.  See http://hurricane.atmos.colostate.edu/Forecasts/2010/june2010/jun2010.pdf for details.  The seasonal forecast from NOAA is also available here: http://www.noaanews.noaa.gov/stories2010/20100527_hurricaneoutlook.html

Please visit my tropical Atlantic headquarters.

14 June 2010

Early-season African wave getting better organized...

This is my first update of the 2010 Atlantic season, so to all of the long-time subscribers, thank you for your continued interest, and to the newcomers, welcome!  This marks the 15th consecutive year for these tropical updates, and some of you have been on the list since the beginning!  Your subscription management page is located here: http://mail.engr.colostate.edu/mailman/listinfo/ats-tropical

Back on June 9, an African easterly wave exited the western coast of Africa and has gradually gotten better organized as it trekked westward.  It's presently located near 10N 41W, or about 1400 miles east of the Windward Islands.  It's moving WNW at 12-13kts and that motion is expected to continue for the next several days.  There is a 1010mb surface Low associated with the disturbance.

Although not very organized now, it is heading into progressively warmer sea surface temperatures and higher ocean heat content,  and the vertical wind shear is expected to remain low for the next couple of days.  The satellite presentation is much more impressive today than it has been the last two days.  Should this reach tropical storm intensity, the first name of the season is Alex.

It is early in the season to get a "Cape Verde" system to develop, but this season is forecast to be extremely active, as conditions basin-wide are a candy store for tropical cyclones.  Storms in the same location as this one presently is typically end up in the Gulf of Mexico in about 1.5 weeks from now.

Please visit my tropical Atlantic headquarters.