June 6, 2013: Andrea's Remnants To Produce Heavy Rain

Forecast Highlights:

The first tropical storm of the year, Andrea, formed in the Gulf of Mexico yesterday, and has since strengthened into a strong tropical storm. Andrea will make landfall in Florida later today, gradually losing tropical characteristics as it tracks up the East Coast, with its remnants producing widespread heavy rain between 1.5 and 3 inches, locally up to 4 inches, on Friday and Friday night. A drier and warmer weekend is expected behind Andrea, with rain to return on Monday again.

**Updated at 4:45 PM with a rain map**

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Tropical Storm Andrea Outlook

Since last night, tropical storm Andrea has somewhat improved in organization, and has intensified early this morning to a strong tropical storm with sustained winds of 60 mph and a minimum pressure of 997 mb. Andrea is still struggling with moderate wind shear, however, with the majority of the wind and rain focused to the east of the storm center. As Andrea continues to approach Florida along with continued moderate wind shear, Andrea should maintain its intensity or slightly weaken prior to landfall this evening, with a continued NNE track as it merges with another low pressure to produce widespread heavy rainfall along the East Coast. Andrea will lose tropical characteristics over the southeastern US, with the extratropical low moving up the coast relatively quickly, producing heavy rain in the Northeast US on Friday into Friday night while moving out overnight.

Outlook for NYC area: Last night's update noted the main uncertainty was regarding the location of the axis of heavy rain. The GFS was the easternmost model, keeping the axis of heavy rain offshore with the area near or under 1 inch, while the ECM and CMC were further west, with 2-3 inches of rain in the area. This morning's 6z GFS run trended towards that direction as well, with a track just off the coast. Andrea will be a relatively compact storm, with the heaviest rain confined mostly to the north and NE of the storm center. Regarding the storm track, with a generally consistent model consensus, the track is expected to remain right along or just off the coast.

Rain from the initial low pressure in the Ohio Valley will spread into the region this afternoon and evening, reaching the area tonight. Light to moderate rain is expected, with 1/4 to 1/2 inch west of NYC and less than 1/4 inch east of NYC. As Andrea continues to track up the coast as an extratropical low, moderate to heavy rain will spread in from the SSW, affecting the area throughout the afternoon and evening hours. The heaviest rainfall rates are expected as the low pressure passes through the area, mainly between 8 PM and 2 AM, with lighter rain expected afterwards mostly ending by the early morning hours on Saturday.

Significant moisture will be available, with precipitable water values over 2 inches. Taking into consideration the heavy rainfall rates and relatively quick motion of the storm, 2 to 3 inches of rain are expected across the area, with locally higher totals up to 4-5 inches possible. Storm updates will be posted on Friday, especially during the evening and early overnight hours.


Longer Range: Warmer Weekend, Cooler/Rainy Next Week

Behind Andrea's remnants, drier conditions are expected for Saturday and Sunday, although scattered showers can't be ruled out, especially on Saturday afternoon/evening. Warmer temperatures are expected as well, peaking in the mid to upper 70s on Saturday and the upper 70s to low 80s on Sunday. By Monday, an upper level low will approach the region; widespread showers and thunderstorms are expected, followed by cooler temperatures on Tuesday and Wednesday, likely peaking in the mid 60s to low 70s for highs, with a risk of additional showers with the cutoff low slow to exit. The outlook for early-mid next week is still subject to change, and more information will be posted over the next few days.