Monday, November 9, 2009

Making Some Changes to the Forecast...The Latest on Ida

Monday, November 9, 2009

Based on current model and radar data, it is necessary to make some changes to the previous forecast for today. The Flood Watch that had been issued by the National Weather Service last night has been canceled.The anticipated rainfall has had a hard time moving onshore from the Gulf. This is most likely because of some dry air on the back side of Ida. We are on the subsident side of the storm, and this is likely allowing for dry air to entrain into the are of Gulf moisture over our area. A shield of rain hovers just offshore, and extends inland over parts of Acadiana through Baton Rouge. It's raining along and East of a line from Marsh Island to New Iberia to Port Allen. Some scattered light rain is developing near the Sabine River from near Johnson Bayou up into Calcasieu Parish between the state line and Sulphur, mainly south of I-10. The highest chances of rain for today will be along and south of I-10 and over Acadiana. Up to 1" of rain is still possible in some areas closer to the coast, and perhaps 2" for Acadiana. No severe weather is expected, and very little in the way of thunderstorm activity is expected. Rain chances will be less for SE Texas and up across Central Louisiana. All rain chances will come to an end tonight as the cold front moves through and a very dry and cool air mass is ushered in. Beautiful weather is expected through the weekend. I will include a new set of preliminary numbers at the conclusion of this blog.

Windy conditions are expected to continue for the next couple of days due to pressure differences between Ida to our East, and building high pressure behind the front. East winds of 15-25 mph with higher gusts are expected throughout the day today, and winds of about the same speed are expected tomorrow, but from a Northerly direction in the wake of the front. Winds will subside by the middle of the week as Ida pulls away and spins down over the SE U.S., and high pressure builds in from the Great Plains.

Now, for the latest on Ida. Ida has begun the expected weakening trend, and transition to an extratropical system. All of the discussed ingredients over the weekend have come together, and are taking effect on the storm. Ida is no longer a hurricane, and it is accelerating in response to strong upper level winds over the Gulf. As of 9a.m., Ida is now a strong tropical storm with 70 mph winds. Ida's forward speed has increased to 17 mph, and it should speed up a bit more later today. It is still moving on a NNW heading, and is located some 185 miles SSE of the Mouth of the Mississippi River. A turn towards the North is expected later today, before taking a NE turn on Tuesday. Ida will come very close to the Mouth of the Mississippi River later today, before approaching the Northern Gulf Coast likely between the Mississippi/Alabama border and Pensacola, FL on Tuesday. Tropical storm conditions will be experienced across SE Louisiana beginning this afternoon through early Tuesday, and across the rest of the Northern Gulf coast from late tonight through Tuesday. Heavy rain, high winds, and flooding will be the main threats across the Gulf Coast with 5-10" of rain expected along to the right of the center of circulation. 4-8" of expected across SE Louisiana, and some flooding is expected mainly outside the levee protection system. Winds of 40-50 mph are possible across a good portion of SE Louisiana including New Orleans and the Northshore. Winds of 50-60 mph will be expected from South Mississippi Eastward to the Florida Panhandle. The strongest winds will be confined to a small area right near the center where 60-70 mph winds are expected. The current forecast takes the transitining Ida inland near Mobile, AL around 6a.m. (12Z) Tuesday morning. The weakening trend will continue through the day as Ida morphs into an extratropical entity.

Tropical Storm Ida

Latitude:     26.5 N
Longitude:  88.3 W
This is 185 SSE of the Mouth of the Mississippi River and about 285 miles SSW of Pensacola, Florida (PNS).

Maximum Sustained Winds: 70 mph w/ higher gusts. Tropical Storm fore winds extend outward 200 miles from the center. Additional weakening is expected today.

Movement: NNW @ 17 mph. A turn to the North is expected to commence later today, followed by a turn to the NNE on Tuesday. On this track Ida will be approaching the Northern Gulf Coast around sunrise Tuesday.

Pressure: 29.41" or 996 mb.

Watches/Warnings: All Hurricane Watches and Warnings have been discontinued, and replaced with a Tropical Storm Warning. A Tropical Storm Warning is in effect for the Gulf Coast from Grand Isle, LA to the Aucilla River, FL. This includes New Orleans and Lake Pontchartrain.








Here's some spot reports from the threat area:

Louisiana

New Orleans Cloudy  70    NE12G25
Slidell            Cloudy  71    NE8
Belle Chasse  Cloudy  69   NE18G25
Boothville       Cloudy  72   E20G36

Mississippi

Biloxi            Cloudy  71   NE15
Pascagoula   Cloudy  70    E16G25
Gulfport        Cloudy  74   E15G26

Alabama

Gulf Shores   Light Rain  69  E16G26
Mobile          Cloudy  68    E10G25

Florida

Pensacola       Rain  69   E18G26
Panama City  Light Rain  68  E9
Apalachicola  Cloudy  71   E16G22
Tallahassee    Cloudy  71   E7


 That's the latest on Ida. Check back for more later this afternoon. I will have a link that will allow to watch the center of the circulation move toward the coast once it comes into radar range.

Here's an updated forecast----No 7 Day...The complete forecast package will still be issued at its normal time tonight.

Preliminary Numbers & Zone Forecast:

LCH  74   57/71   47/67   60 30 0 0 0
LFT   72   58/72   46/67   70 50 0 0 0
BPT   72   59/73   49/68   40 20 0 0 0
AEX  71   55/67   44/65   40 30 0 0 0
POE  71   56/67   44/65   40 30 0 0 0
ARA  72   60/73  48/69    80 60 0 0 0


*Lake Wind Advisory in Effect through Midnight.*

This Afternoon...Cloudy and Windy with off and on showers. High 74. East wind 15-25 mph and gusty. Chance of rain 60%.

Tonight...Cloudy and Windy with a 30% chance of showers before midnight. Skies clearing overnight. Cooler. Low 57. East wind 15-25 mph and gusty, becoming NNW at 15-25 mph overnight.

Tuesday...Sunny and Windy. High 71. North wind 15-25 mph and gusty.

Tuesday Night...Clear. Low 47. North wind 10-15 mph.

Wednesday...Sunny. High 67. North wind 10 mph.

-DM-

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