Steady rains fall across Rio Grande Valley, November 30-December 1 (click to enlarge)
A Full Serving of Winter, Valley Style
Cold Rains Start It, Widespread Frost Finishes It, November 30–December 4, 2009

Into the Cool Rain: November 30–December 1
A vigorous upper level disturbance moved through South and Central Texas along an active subtropical jet stream from November 30th through December 1st. The disturbance transferred some of its energy to the Lower Texas coast, where low pressure developed along the cold front which had cleared the coast early on November 30th – dropping temperatures up to 30 degrees in some locations from the balmy 80s during the afternoon of the 29th into the 50s by afternoon of the 30th. Lift provided by these systems translated into abundant rainfall for Deep South Texas, with the Lower Rio Grande Valley northward into southern Kenedy County seeing 2 to 3 inches. The following are preliminary rainfall totals across Deep South Texas for the period November 30 through December 1:

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE BROWNSVILLE TX
118 PM CST WED DEC 2 2009

...PRELIMINARY RAINFALL TOTALS FOR NOVEMBER 30TH THROUGH DECEMBER 1ST...

THE FOLLOWING ARE PRELIMINARY RAINFALL TOTALS FOR DEEP SOUTH TEXAS
FOR NOVEMBER 30TH THROUGH DECEMBER 1ST. THESE VALUES WILL BE UPDATED
AS NEEDED.

AIRPORTS                    AMOUNT
====================================
BROWNSVILLE                  2.11"
PORT ISABEL-CAMERON CO       2.11"
MCALLEN                      1.86"
HARLINGEN                    1.52"


NWS COOPERATIVE OBSERVERS   AMOUNT
====================================
ARMSTRONG                    3.03"
WESLACO                      2.68"
SANTA ROSA                   2.65"
LA JOYA                      2.35"
ISALA BLANCA/S PADRE ISLAND  2.28"
EDINBURG                     2.24"
PORT ISABEL                  2.17"
HARLINGEN                    2.12"
SAN MANUEL                   2.09"
MERCEDES                     1.97"
RIO GRANDE CITY              1.84"
PORT MANSFIELD               1.78"
HEBBRONVILLE                 1.76"
FALFURRIAS                   1.70"
SARITA                       1.64"
FALCON DAM                   1.50"


VOLUNTEER COCORAHS          AMOUNT
====================================
BAYVIEW 2.9 N                3.09"
HARLINGEN 4.7 WSW            2.62"
BROWNSVILLE 2.2 W            2.59"
RANCHO VIEJO 3.0 SE          2.47"
HARLINGEN 4.3 WSW            2.46"
LA JOYA 11.1 N               2.36"
RANCHO VIEJO 0.7 E           2.35"
LOS FRESNOS 0.3 NE           2.33"
BROWNSVILLE 4.5 NNW          2.32"
BROWNSVILLE 4.1 E            2.27"
BROWNSVILLE 4.4 NE           2.22"
BROWNSVILLE 4.2 NE           2.19"
ALAMO 1.5 NNE                2.18"
BROWNSVILLE 4.1 NNE          2.15"
PALM VALLEY 2.2 SSW          2.15"
BROWNSVILLE 3.5 N            2.10"
PHARR 5.1 N                  1.98"
ALTON 4.7 N                  1.92"
MISSION 1.9 ENE              1.90"
BROWNSVILLE 4.1 ENE          1.82"
BROWNSVILLE 4.6 NNW          1.80"
MCALLEN 2.6 NE               1.66"
MCALLEN 1.7 SSE              1.62"
SAN BENITO 5.0 SSE           0.53"*
HARLINGEN 2.6 ESE            0.44"*

*DENOTES INCOMPLETE DATA

 

Rimey frost in North Brownsville, December 5, 2009 (click to enlarge) Frost on grass in North Brownsville, December 5, 2009 (click to enlarge)

Winter’s Bluster, Then Frost: December 4–5
Temperature recovery behind the rainfall to open the month was short lived, as the tail of a second upper level disturbance, this time originating in Canada, dropped a modified arctic air mass into the eastern Rockies and front range on December 3rd. Energy from this disturbance lifted residual moisture near the Gulf into another round of precipitation early on the 4th along and just west of the Southeast and South Texas coast. Enough cold air reached into locations from Corpus Christi to Victoria into the Houston area to mix snow with the rain; accumulating snow of 1 to 4 inches fell mainly between Victoria and Houston.

While a repeat of 2004’s White Christmas did not occur, some of the coldest feeling air in years invaded the region, as afternoon temperatures on the 4th plummeted into the upper 30s to lower 40s and, when combined with persistent 25 mph and gusty winds, left wind chill values in the upper 20s to lower 30s across the Lower Rio Grande Valley. Soon after nightfall, skies rapidly cleared and winds diminished quickly as the cold high pressure center built overhead, leading to a widespread frosty freeze across all of Deep South Texas. Low temperatures (below) ranged through the 20s in most areas, with rural areas of Deep South Texas seeing more than 6 hours of temperatures below freezing. In fact, these were the coldest temperatures to be recorded, area–wide, since the White Christmas event in 2004.

Data on any crop and plant damage have not been received as of this writing. It is hoped that the light freeze and frost may actually benefit some crops, particularly citrus, where cool early winter temperatures help to eradicate pests and bring out sweetness in the fruit. Only time will tell.

A frosty start to December 5th, 2009 (click to enlarge)

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