Little change to 94L; exceptional heat in Texas, record rains in California

There is not much change to report on the large, wet, and disorganized tropical disturbance (Invest 94L) in the Western Caribbean, between Jamaica and Mexico's Yucatan Peninsula. The disturbance has brought intermittent heavy rains to Jamaica over the past two days, but nearby islands have thus far escaped the deluge. Satellite-estimated rainfall amounts of 1" per hour occurred in ocean regions just east of Jamaica this morning, but the heaviest rains have missed the island so far this morning. Visible satellite loops show no increase in organization of 94L in recent hours, and the storm's low-level spiral bands and upper-level outflow are poorly defined. The storm's center of low pressure is located about 130 miles south of Grand Cayman Island, in a region with no heavy thunderstorm activity. An intense clump of thunderstorms exists on either side of this low, near Jamaica, and just east of Mexico's Yucatan Peninsula. Water vapor satellite loops show the Caribbean has moistened over the past two days, and upper air balloon soundings from the Cayman Islands continue to show much moister air at mid levels of the atmosphere (2% humidity at 500 mb on Saturday, compared to 69% last night.) Wind shear remains in the moderate range, 15 - 20 knots, and is predicted by the SHIPS model to remain below 20 knots through tonight. Water temperatures in the Central Caribbean are about 1°C above average, 28 - 28.5°C, which is 2°C above the threshold needed to support development of a tropical storm.


Figure 1. Rainfall rates of up to 1" per hour (orange colors) were estimated by the F-17 satellite for 94L at 7:03am EDT Jun 6, 2011. Image credit: Navy Research Lab, Monterey.

Since 94L is so large and poorly organized, today's mission by the Hurricane Hunters has been cancelled. A new mission is scheduled for Tuesday afternoon at 2pm EDT. This morning's 00Z and 06Z model runs were unimpressed with 94L, with most of them showing little or no development. A band of very high wind shear of 30 - 50 knots lies over Cuba and the southern Bahama Islands. The GFS and ECMWF models show 94L pushing slowly northwest at about 5 mph, hitting this shear on Tuesday and Wednesday, preventing any further development. The NOGAPS model predicts that a gap may open up in the shear sufficient for the storm to organize into a tropical depression late this week. Given 94L's current disorganization, I doubt the storm will ever develop. NHC gave 94L a 40% chance of developing into a tropical depression by Wednesday, and I believe these odds should be lower, near 20%. Regardless of development, 94L is capable of bringing very heavy rains to Jamaica, Cuba, the Cayman Islands, and Haiti through Wednesday. These rains will probably spread northwards into South Florida and the Bahama Islands by Thursday or Friday.


Figure 2. Morning satellite image of 94L.

Exceptional heat in the South
A sizzling June heat wave set record high temperatures across much of Texas, Louisiana, Alabama, Mississippi, and the Florida Panhandle on Sunday. The high temperature at the Houston, Texas airport hit 105 degrees, the warmest temperature ever recorded in the month of June (old record: 104 degrees on June 24th and June 26th, 2009.) The earliest Houston ever recorded a temperature of 105 degrees prior to Sunday was July 26th, 1954. Records for Houston date back to 1891. There have been only 15 days in which the temperature has reached or exceeded 105 degrees in Houston:

4 - 1909
1 - 1954
2 - 1962
3 - 1980
5 - 2000

So far this month, new maximum temperature records in Houston have been established on four out of the first five days. Galveston and Houston both crushed their previous record high temperature for the day (June 5th) by a remarkable seven degrees. Residents can expect another day of triple-digit heat today, thanks to the upper level ridge of high pressure parked over the state. Houston will likely break the old record of 98°F for the date.


Figure 3. An intense low pressure system moves inland over California as seen in this satellite photo taken June 4, 2011, at 2pm PDT. Image credit: NASA/GSFC.

Record rains in California
A large and unusually intense low pressure system moved inland over California over the weekend, bringing large areas of the state rains unheard of in June. According to our weather historian, Christopher C. Burt, rainfall at Mining Ridge on the Big Sur coast totaled 8.31" Sunday, which, if verified, would be California's heaviest 1-day June rainstorm on record. According to the document "Historic Rainstorms in California" Dept. of Water Resources, Aug. 1997, the previous maximum June daily rainfall was 5.83" at Forni Ridge on June 18, 1982. San Francisco had its 2nd greatest June 1-day rainfall, going back to 1850, and both the San Francisco and Oakland airport have now had their rainiest Junes on record. Rainfall at Santa Barbara Airport yesterday totaled 1.24 inches, the wettest June day there on record (previous record: 0.51" on June 5, 2009.) The 1.38"of rain so far this June has made it the wettest June in recorded history at Santa Barbara Airport, going back to 1941.

Jeff Masters